Research ArticleExperimental Investigation of Thermal Characteristics of KiwiraCoal Waste with Rice Husk Blends for Gasification
Deodatus Kazawadi1 Geoffrey R John2 and Cecil K Kingrsquoondu1
1 Department of Sustainable Energy Science and Engineering The Nelson Mandela African Institution of Science and TechnologyPO Box 447 Arusha Tanzania
2Department of Mechanical and Industrial Engineering The University of Dar es Salaam PO Box 35131 Dar es Salaam Tanzania
Correspondence should be addressed to Deodatus Kazawadi kazawadidnm-aistactz
Received 30 July 2014 Revised 9 November 2014 Accepted 9 November 2014 Published 19 November 2014
Academic Editor S Venkata Mohan
Copyright copy 2014 Deodatus Kazawadi et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
Eminent depletion of fossil fuels and environmental pollution are the key forces driving the implementation cofiring of fossil fuelsand biomass Cogasification as a technology is known to have advantages of low cost high energy recovery and environmentalfriendliness The performanceefficiency of this energy recovery process substantially depends on thermal properties of the fuelThis paper presents experimental study of thermal behavior of Kiwira coal wasterice husks blends Compositions of 0 20 4060 80 and 100 weight percentage rice husk were studied using thermogravimetric analyzer at the heating rate of 10 Kmin to1273K Specifically degradation rate conversion rate and kinetic parameters have been studiedThermal stability of coal waste wasfound to be higher than that of rice husks In addition thermal stability of coal wasterice husk blend was found to decrease withan increase of rice husks In contrast both the degradation and devolatilization rates increased with the amount of rice husk Onthe other hand the activation energy dramatically reduced from 131 kJmol at 0 rice husks to 75 kJmol at 100 rice husks Thereduction of activation energy is advantageous as it can be used to design efficient performance and cost effective cogasificationprocess
1 Introduction
The ever increasing need for clean energy environmentalprotection and alternative use of fossil fuel has necessitatedthe recovery of energy from waste fossil energy resourcesEfficient ways to recover damped coal waste are on recordand range from circulating fluidized bed combustor togasification and pyrolysis [1]
Tanzania has approximately 15 billion metric tons ofproven coal [2] with Kiwira coal mine having a provendeposit of 4 million metric tons [3] It has an annual coalwaste production of 17374 tons [4] and has damped over500000 metric tons of waste for the 2 million metric tonsof coal already mined Although Tanzania has reasonablyenough unutilized fresh coal effective use of coal waste canprovide sustainable profile of fossil fuel use
Tanzania has a wide range of biomass including forestryand agricultural residue Rice husk in Tanzania is not used
efficiently and as suchmost of it is wasted For exampleMhiluestimated 326220 tons of rice husks are wasted annuallycompared to 10400 tons of coffee husks [5]
Direct combustion of coal waste has a wide range of con-straints from environmental pollution low energy recoveryand high cost [1] Proven cheap and environmental friendlytechnologies such as gasificationcogasification [6] are suit-able for the utilization of these materials The technology toincorporate renewable resources into fossil fuels especiallybiomass for energy recovery is on increase Researches oncogasification of coal and biomass have shown advantagesranging from economic benefit to environmental friendlyand increased energy recovery [7 8] The utilization of thesetechnologies in Tanzania can be an alternative for sustainableenergy supply especially for the utilization of coal waste
It has been shown that coalcoal waste-biomass blendsnot only reduce pollution especially carbon dioxide butalso increase the recovery during gasification due to
Hindawi Publishing CorporationJournal of EnergyVolume 2014 Article ID 562382 8 pageshttpdxdoiorg1011552014562382
2 Journal of Energy
the catalytic nature of inorganic minerals in the biomassand reduction in operating temperature [8 9] Althoughcogasification of coal and biomass has not been put in placeat large scale [10] it is nevertheless a promising technology[11]
Biomass is a promising energy source due to its abun-dance [12] The report on biomass potential in Africa pre-dicted that in 2020 up to 13900 PJyr from crops 5400 PJyrfrom forests and 5254 PJyr from wastes will be available[13] Utilizing biomass with coal waste will increase thedownstream use of renewable energy sources in the energysystems
Biomass and coal waste however have different chemicaland physical properties such as volatile matter ash con-tent composition density and calorific value [14] Thesedifferences in the properties lead to different reactivity andthermal characteristics during thermochemical processesFor example biomass gasification occurs at low temperaturethan coal thus reducing heat loss emission and materialproblems associated with high temperature [15] Blending ofcoal waste and biomass can reduce gasification temperature[7]
Earlier studies on thermal behavior of biomass andcoal are on record Bhagavatula et al [16] studied thermalperformance of Montana coal and corn stover blends andfound that increasing biomass reduced reaction temperatureThe study done by Magdziarz and Wilk [17] on coal sewageand biomass indicated that the temperature of maximumloss increased with addition of 90 of coal Furthermoreother studies have shown coal biomass blends to have higherreactivity compared to coal alone due to high volatile matter[18]
Thermal behavior of Tanzanian coal waste and biomassis not on record to date [19] This coupled with the hugeabundance of coal waste and biomass in Tanzania providesthe stimulus to undertake studies related to thermal char-acteristics of coal wastebiomass blends for energy recoveryThe aim of this paper is therefore to provide data that can beused for the design of an effective and environment friendlycogasification process for the recovery of energy from coalwastesrice husk blends To achieve this it is imperativeto determine the reaction rate conditions and maximumgasification temperature and to understand thermal decom-position mechanisms [20]
2 Methodology
21 Sample Collection and Preparation Coal waste sampleswere randomly sampled from Kiwira coal waste dump Ricehusk samples were randomly obtained from rice mill wastesin Dodoma
The samples were ground to less than 2mm in order tolimit the effect of interparticle heat transfer [16] The samplesmass were measured on beam balance to make the blendswith composition by weight percent of 0 20 40 60 80and 100 rice husk Homogeneity was obtained by thoroughmixing The selection of the above blends was to ensure thatthe study covered a reasonable range of blend
22 Experiment Carryout Each sample was analyzed in trip-licate and standard errors are calculated using (2)
119878119903= radic
1
(119899 minus 1)
119899
sum
119894=1
(119909119894minus 119909)2
(1)
Se =119878119903
radic119899 (2)
where 119909119894is experiment 119894 data 119909 is mean 119899 is the number
of experiments 119878119903is standard deviation and Se is standard
error
23 Proximate andUltimate Analysis Proximate analysis wasdone by standard method ASTM 3172 in the furnace Thecalorific values were determined by ASTM D4809 standardmethod in a bomb calorimeter
Determination of carbon hydrogen nitrogen and sulfurwas done by ASTM (E775 E777 and E778) standards meth-ods Oxygen was determined by difference where the sum ofash carbon hydrogen sulphur and nitrogen was subtractedfrom 100 [21]
24 Thermogravimetric Analysis Thermogravimetric (TG)analysis is one of the thermal analysis techniques usedto measure the mass change thermal decomposition andthermal stability of materials Overall kinetics can be easilyobtained by measuring the change in mass of a sample withtime based on isothermal or nonisothermal thermogravimet-ric data [22]
Thermal stability of blends was studied under inertnitrogen condition using a simultaneous thermal gravimetricanalyzer typeNETZSCHSTAPCLuxxTGNitrogen (9995purity) was used as the carrier gas controlled by gas flowmeter at a flow rate of 60mLmin and pressure of 05 barsto avoid unwanted oxidation In the STA 409 PC Luxx TGPreteus software was used to acquire store and analyze datain desktop computer
The samples were dried at 100∘C temperature for 24 h toremove moisture 30mg of the samples of particle size lessthan 2mm were placed on a crucible and heated from 35 to1000∘C at constant heating rate of 10 Kmin The low heatingrate was used in expectations of allowing the reactions toreach equilibrium [23]
25 Kinetics of Thermal Degradation Parameters that de-scribe kinetics considered were activation energy and preex-ponential factor Activation energy is defined as the heightof energy barrier which has to be overcome by relativetranslation motion of the reactants for a reaction to occur[24] The activation energy indicates how much energy mustbe absorbed by reactant to start the reaction [25] Higheractivation means the rate of reaction depends strongly ontemperature
251 Theoretical Approach Pyrolysis process of a solid cangenerally be described as
119860 solid 997888rarr 119861solid + 119862volatile (3)where volatile is the sum of gas and tar
Journal of Energy 3
The degree of conversion 120572 of a material is defined as
120572 =119882119900minus119882119905
119882119900minus119882119891
(4)
where119882119900is the original mass119882
119891is the final mass and119882
119905is
the mass at time 119905Rate of degradation of a material is expressed by a way of
[26]
119889120572
119889119905= 119896 (119879) lowast (1 minus 120572)
119899
(5)
where 119899 is the order of reaction 120572 is the degree of conversionand 119896(119879) is the rate constant of reaction whose temperaturedependence is expressed by the Arrhenius equation
119896 (119879) = 119860Exp(minus119864119877119879) (6)
where 119864 is the activation energy in kJmole 119879 is temperaturein K 119877 is the universal gas constant (8314 JKmol) and 119860 isthe preexponential factor (minminus1)
For pyrolysis and oxidation reactions under nonisother-mal conditions the heating rate plays a very important role indetermining the kinetic parameters Low heating rate meansthat a reaction is closer to equilibrium and vice versa [26 27]
Many authors have approximated the overall process asa first-order decomposition occurring uniformly throughoutthe coal and biomass particles [28ndash30] For a first-orderreaction at constant heating rate
120573 =119889119879
119889119905 (7)
Equation (5) is transformed to
119889120572
119889119879= [119860
(1 minus 120572)
120573] exp(minus119864
119877119879) (8)
Integration of the above equation subject to the condition thatconversion is zero at initial temperature 119879
0 leads to
ln [1 minus 120572] = minus119860120573int
119879
119879119900
Exp(minus119864119877119879)119889119879 (9)
Since there is no conversion at initial temperature 1198790 the
limits of the integral become
int
119879
0
Exp(minus119864119877119879
) (10)
Introducing a new function
119891 (119910) = int
infin
119910
119890minus119910
1199102119889119910 (11)
where 119910 is minus119864119877119879 (9) becomes
ln (1 minus 120572) = minus119860
120573119891 (119910) (12)
0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
Zone III
Zone II
Zone I
minus5
minus45
minus4
minus35
minus3
minus25
minus2
minus15
minus1
minus05
0
Temperature (∘C)
Figure 1 DTG results showing reaction steps of rice husk
The Coats-Redfern approximation method was deployed inthis study to determine the approximate value of temperatureintegralThis method was chosen because it provides the bestlinearity of the data as opposed to other analytical model-fitting methods [27 31 32]
When this method is used (11) yields
119891 (119910) asymp119890minus119910
1199102(1 minus 119910) (13)
Equation (8) is rearranged to result in
ln [minus ln (1 minus 120572)1198792
] = ln [119860119877119867119864
(1 minus2119877119879
119864)] minus
119864
119877119879 (14)
Equation (13) is written in the form 119910 = 119886119909 + 119887 where
119886 = minus119864
119877 119887 = ln [119860119877
119867119864(1 minus
2119877119879
119864)] (15)
The temperature in the intercept value ldquo119887rdquo is obtained byaveraging the initial and final mass remaining for a specificreaction step The obtained value corresponds to the temper-ature value to be used
119882119879=
(119882119900+119882119891)
2 (16)
Reaction steps considered are moisture removal (Zone I)volatile removal (Zone II) and char pyrolysis (Zone III)as indicated in Figure 1 In each reaction step degree ofconversion is recalculation For each step of reaction 119864 and119860 can be calculated using (14)
3 Results and Discussion
31 Proximate andUltimateAnalysis Proximate andultimateresults are shown in Table 1 Coal waste was found to havehigh ash content and low volatile matter compared to ricehusks and their corresponding blends High ash content ofcoal waste leads to high thermal stability
4 Journal of Energy
Table 1 Proximate and ultimate results
Sample Kiwira coal waste Rice husksMoisture content () 326 plusmn 004 72 plusmn 002
Proximate dry basisVM 1684 plusmn 021 5959 plusmn 043FC 1923 plusmn 077 1729 plusmn 045Ash 6393 plusmn 057 2312 plusmn 006
Proximate dry basis
C 1968 plusmn 033 3813 plusmn 012H 207 plusmn 003 459 plusmn 0005O 1289 plusmn 036 3310 plusmn 008Cl NIL 031 plusmn 0002S 100 plusmn 004 006 plusmn 0003N 043 plusmn 001 068 plusmn 0032
HHVMJkg daf 220 plusmn 035 196 plusmn 004
0102030405060708090
100
0 100 200 300 400 500 600 700 800 900 1000
Mas
s rem
aini
ng (
)
100 KCW20 KCW60 KCW
80 KCWRH40 KCW
Temperature (∘C)
Figure 2 TG analysis results of Kiwira coal wasterice husk blends
32Thermogravimetric (TG) Analysis Results TheTGweightloss curves of the blends in a nonisothermal heating at heatingrate of 10 Kmin are shown in Figure 2
Weight loss profiles of blends are between the two profilesof coal waste and rice husk The results showed that ricehusk is more reactive than coal waste This is in agreementwith the work of Zakaria et al [33] which showed thatrice husk is more reactive than coal during pyrolysis andcombustionThis is due to the fact that coal waste unlike ricehusk has high ash contents since it contains thermally stablecomponents like silica
The results also showed that as rice husk contentincreased temperature of pyrolysis decreased For examplefor pure coal waste the pyrolysis temperature was about760∘C while that of 40 coal wasterice husk blend and purerice husk was about 690 and 650∘C respectively as shown inFigures 3 4 and 5
Coal is considered as a complex polymer network con-sisting of aromatic clusters of aliphatic bridge [16] Durationof evolution of volatiles (that end up producing CO H
2 CH4
and H2O) is relatively shorter for biomass than coal [34 35]
The decrease in thermal stability with increase in rice huskcontent could be useful in designing cheap thermochemicalconversion (eg gasification) processes
00 100 200 300 400 500 600 700 800 900 1000 1100 1200
DTG
(m
in)
Temperature (deg)
minus14
minus12
minus1
minus08
minus06
minus04
minus02
Figure 3 DTG results of Kiwira coal waste
0000 100 200 300 400 500 600 700 800 900 100011001200
DTG
(m
in)
Temperature (deg)
minus500
minus450
minus400
minus350
minus300
minus250
minus200
minus150
minus100
minus050
Figure 4 DTG results of rice husk
Temperature (∘C)
0 0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
100 KCW20 KCW40 KCW
60 KCW80 KCWRH
minus5
minus45
minus4
minus35
minus25
minus2
minus3
minus15
minus05
minus1
Figure 5 DTG profiles of Kiwira coal wasterice husk blends
33 Differential Thermogravimetric (DTG) Analysis ResultsFigures 3ndash5 show the DTG profiles of coal waste rice huskand their corresponding blends at heating rate of 10 Kmin innonisothermal conditions Three clear zones were observedthat can be grouped as shown in Figure 1 These zonesare useful for comparing different materials in terms of
Journal of Energy 5
Table 2 Zones of reactions of blends
Blend
Devolatilization Char combustion
Temperaturerange (∘C)
Maximumpeak
(min)
Temperaturerange (∘C)
Maximumpeak
(min)Coal waste 300ndash560 12 560ndash760 1220 160ndash390 33 390ndash670 1340 160ndash400 31 400ndash690 1360 160ndash400 19 400ndash720 1280 170ndash400 09 400ndash730 12Rice husk 160ndash380 48 400ndash650 14
composition and measuring the fuel reactivity [36 37] Forexample the material with high range of char degradationmeans that thematerial has high fixed carbon Coal waste hasbeen shown to have high fixed carbon by proximate analysis
Each sample showed a first peak which corresponds tomoisture removal [38]This peak occurred at temperature lessthan 200∘C Second and third profiles represent devolatiliza-tion and char combustion respectively Devolatilization incoal waste occurred at higher temperature than that inrice husk and coal wasterice husk blends For coal wastedevolatilization and char combustion profiles occurred closeto each other Gil et al observed only one profile for bothdevolatilization and char combustion on coal [39]
Table 2 reports temperature ranges for devolatilizationand char pyrolysis stages Rice husk devolatilization occurredbetween 160 and 380∘C This range is similar to the onereported for the pyrolysis of rice husk hemicelluloses andcellulose [33] Coal waste devolatilization occurred at tem-peratures (300ndash560∘C) higher than those of rice husk Thecoal waste devolatilization temperature range obtained wascomparable to that of coal (415ndash520∘C) reported by Zakariaet al [33] Char combustion for coal waste has been seen tobe higher than rice [33] This is attributed to the high fixedcarbon context in coal wastes In our study rice husk charwas completely degraded at 650∘C while coal waste degradedat 760∘C Rice husk char degradation temperature (650∘C)obtained in our work is comparable to 600∘C reported ricehusk char by Sonobe et al [40]
Degradation rate increased with increase in rice huskThis was attributed to reactivity of rice husk (biomass) Thepresence of rice husks promotes the production of volatilesin coal wasterice husk blends This phenomenon was alsoreported by Haykiri-Acma and Yaman [41] Devolatilizationand char combustion temperatures decreased with increasein rice husk Degradation peak values increased with anincrease in rice huskThis is attributed to the reactivity of ricehusk which is higher than that of coal waste due to increasein volatile matter in biomass [16]
The temperature band width of reaction decreased withincrease in rice husk due to the increase in volatile matter anddecrease in fixed carbon leading to increased reactivity of theblendThebond strength of coal waste can also be a reason forincreased reaction temperature bandwidthwith increasing incoal waste Coal has been reported to have a high bond energy
0
001
002
003
004
005
006
007
40 140 240 340 440 540 640 740 840 940Temperature (deg)
100 coal20 coal80
40600
Reac
tion
rate
(d120572d
t)
Figure 6 Conversion rates of Kiwira coal wasterice husk biomassblends
of about 1000 kJmol [42] compared to biomass with bondenergy around 380ndash420 kJmol [43]This means degradationrate will increase with increase in rice husk content
34 Conversion Rate Figure 6 shows the rate of conversionof different blends It can be observed that at devolatilizationstage the rate of conversion increased with increase in ricehusk content This is attributed to the reactivity of volatilematter in rice husk content Conversion rate of char increasedwith increase in coal waste This is attributed to the increasein fixed carbon with increasing coal waste
Devolatilization rate increased with increase in rice huskcontent It is known that volatilematter leads to production oftarwhich is not needed in the syngas [35] Blending coalwasteand rice huskmay reduce production of tar however thismaybe accompanied by the reduction in the rate of conversion
High conversion rate of devolatilization occurred ataround 320∘C while for char degradation it occurs at 500∘CHigh reaction rate of devolatilization with increase in ricehusk content can be explained by devolatilization behaviorofmost biomass fuels Biomass contains reactive componentsresponsible for initial steps of devolatilization Final tail ofdevolatilization which is the decomposition of lignin andmainly produces char is suggested to be caused by the lessreactive structure of the remaining solid after main pyrolysis[44]
35 Kinetics Parameters Results The kinetic properties acti-vation energy and preexponential factor have been calculatedusing (14) Table 3 shows the calculated results of kineticparameters of the blends
The activation energy for devolatilization was found toincrease with increase in rice husk The results indicated thatactivation increased from 51 to 85 for 100 coal to 0 coalrespectively This was due to the increase in volatile matters
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
2 Journal of Energy
the catalytic nature of inorganic minerals in the biomassand reduction in operating temperature [8 9] Althoughcogasification of coal and biomass has not been put in placeat large scale [10] it is nevertheless a promising technology[11]
Biomass is a promising energy source due to its abun-dance [12] The report on biomass potential in Africa pre-dicted that in 2020 up to 13900 PJyr from crops 5400 PJyrfrom forests and 5254 PJyr from wastes will be available[13] Utilizing biomass with coal waste will increase thedownstream use of renewable energy sources in the energysystems
Biomass and coal waste however have different chemicaland physical properties such as volatile matter ash con-tent composition density and calorific value [14] Thesedifferences in the properties lead to different reactivity andthermal characteristics during thermochemical processesFor example biomass gasification occurs at low temperaturethan coal thus reducing heat loss emission and materialproblems associated with high temperature [15] Blending ofcoal waste and biomass can reduce gasification temperature[7]
Earlier studies on thermal behavior of biomass andcoal are on record Bhagavatula et al [16] studied thermalperformance of Montana coal and corn stover blends andfound that increasing biomass reduced reaction temperatureThe study done by Magdziarz and Wilk [17] on coal sewageand biomass indicated that the temperature of maximumloss increased with addition of 90 of coal Furthermoreother studies have shown coal biomass blends to have higherreactivity compared to coal alone due to high volatile matter[18]
Thermal behavior of Tanzanian coal waste and biomassis not on record to date [19] This coupled with the hugeabundance of coal waste and biomass in Tanzania providesthe stimulus to undertake studies related to thermal char-acteristics of coal wastebiomass blends for energy recoveryThe aim of this paper is therefore to provide data that can beused for the design of an effective and environment friendlycogasification process for the recovery of energy from coalwastesrice husk blends To achieve this it is imperativeto determine the reaction rate conditions and maximumgasification temperature and to understand thermal decom-position mechanisms [20]
2 Methodology
21 Sample Collection and Preparation Coal waste sampleswere randomly sampled from Kiwira coal waste dump Ricehusk samples were randomly obtained from rice mill wastesin Dodoma
The samples were ground to less than 2mm in order tolimit the effect of interparticle heat transfer [16] The samplesmass were measured on beam balance to make the blendswith composition by weight percent of 0 20 40 60 80and 100 rice husk Homogeneity was obtained by thoroughmixing The selection of the above blends was to ensure thatthe study covered a reasonable range of blend
22 Experiment Carryout Each sample was analyzed in trip-licate and standard errors are calculated using (2)
119878119903= radic
1
(119899 minus 1)
119899
sum
119894=1
(119909119894minus 119909)2
(1)
Se =119878119903
radic119899 (2)
where 119909119894is experiment 119894 data 119909 is mean 119899 is the number
of experiments 119878119903is standard deviation and Se is standard
error
23 Proximate andUltimate Analysis Proximate analysis wasdone by standard method ASTM 3172 in the furnace Thecalorific values were determined by ASTM D4809 standardmethod in a bomb calorimeter
Determination of carbon hydrogen nitrogen and sulfurwas done by ASTM (E775 E777 and E778) standards meth-ods Oxygen was determined by difference where the sum ofash carbon hydrogen sulphur and nitrogen was subtractedfrom 100 [21]
24 Thermogravimetric Analysis Thermogravimetric (TG)analysis is one of the thermal analysis techniques usedto measure the mass change thermal decomposition andthermal stability of materials Overall kinetics can be easilyobtained by measuring the change in mass of a sample withtime based on isothermal or nonisothermal thermogravimet-ric data [22]
Thermal stability of blends was studied under inertnitrogen condition using a simultaneous thermal gravimetricanalyzer typeNETZSCHSTAPCLuxxTGNitrogen (9995purity) was used as the carrier gas controlled by gas flowmeter at a flow rate of 60mLmin and pressure of 05 barsto avoid unwanted oxidation In the STA 409 PC Luxx TGPreteus software was used to acquire store and analyze datain desktop computer
The samples were dried at 100∘C temperature for 24 h toremove moisture 30mg of the samples of particle size lessthan 2mm were placed on a crucible and heated from 35 to1000∘C at constant heating rate of 10 Kmin The low heatingrate was used in expectations of allowing the reactions toreach equilibrium [23]
25 Kinetics of Thermal Degradation Parameters that de-scribe kinetics considered were activation energy and preex-ponential factor Activation energy is defined as the heightof energy barrier which has to be overcome by relativetranslation motion of the reactants for a reaction to occur[24] The activation energy indicates how much energy mustbe absorbed by reactant to start the reaction [25] Higheractivation means the rate of reaction depends strongly ontemperature
251 Theoretical Approach Pyrolysis process of a solid cangenerally be described as
119860 solid 997888rarr 119861solid + 119862volatile (3)where volatile is the sum of gas and tar
Journal of Energy 3
The degree of conversion 120572 of a material is defined as
120572 =119882119900minus119882119905
119882119900minus119882119891
(4)
where119882119900is the original mass119882
119891is the final mass and119882
119905is
the mass at time 119905Rate of degradation of a material is expressed by a way of
[26]
119889120572
119889119905= 119896 (119879) lowast (1 minus 120572)
119899
(5)
where 119899 is the order of reaction 120572 is the degree of conversionand 119896(119879) is the rate constant of reaction whose temperaturedependence is expressed by the Arrhenius equation
119896 (119879) = 119860Exp(minus119864119877119879) (6)
where 119864 is the activation energy in kJmole 119879 is temperaturein K 119877 is the universal gas constant (8314 JKmol) and 119860 isthe preexponential factor (minminus1)
For pyrolysis and oxidation reactions under nonisother-mal conditions the heating rate plays a very important role indetermining the kinetic parameters Low heating rate meansthat a reaction is closer to equilibrium and vice versa [26 27]
Many authors have approximated the overall process asa first-order decomposition occurring uniformly throughoutthe coal and biomass particles [28ndash30] For a first-orderreaction at constant heating rate
120573 =119889119879
119889119905 (7)
Equation (5) is transformed to
119889120572
119889119879= [119860
(1 minus 120572)
120573] exp(minus119864
119877119879) (8)
Integration of the above equation subject to the condition thatconversion is zero at initial temperature 119879
0 leads to
ln [1 minus 120572] = minus119860120573int
119879
119879119900
Exp(minus119864119877119879)119889119879 (9)
Since there is no conversion at initial temperature 1198790 the
limits of the integral become
int
119879
0
Exp(minus119864119877119879
) (10)
Introducing a new function
119891 (119910) = int
infin
119910
119890minus119910
1199102119889119910 (11)
where 119910 is minus119864119877119879 (9) becomes
ln (1 minus 120572) = minus119860
120573119891 (119910) (12)
0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
Zone III
Zone II
Zone I
minus5
minus45
minus4
minus35
minus3
minus25
minus2
minus15
minus1
minus05
0
Temperature (∘C)
Figure 1 DTG results showing reaction steps of rice husk
The Coats-Redfern approximation method was deployed inthis study to determine the approximate value of temperatureintegralThis method was chosen because it provides the bestlinearity of the data as opposed to other analytical model-fitting methods [27 31 32]
When this method is used (11) yields
119891 (119910) asymp119890minus119910
1199102(1 minus 119910) (13)
Equation (8) is rearranged to result in
ln [minus ln (1 minus 120572)1198792
] = ln [119860119877119867119864
(1 minus2119877119879
119864)] minus
119864
119877119879 (14)
Equation (13) is written in the form 119910 = 119886119909 + 119887 where
119886 = minus119864
119877 119887 = ln [119860119877
119867119864(1 minus
2119877119879
119864)] (15)
The temperature in the intercept value ldquo119887rdquo is obtained byaveraging the initial and final mass remaining for a specificreaction step The obtained value corresponds to the temper-ature value to be used
119882119879=
(119882119900+119882119891)
2 (16)
Reaction steps considered are moisture removal (Zone I)volatile removal (Zone II) and char pyrolysis (Zone III)as indicated in Figure 1 In each reaction step degree ofconversion is recalculation For each step of reaction 119864 and119860 can be calculated using (14)
3 Results and Discussion
31 Proximate andUltimateAnalysis Proximate andultimateresults are shown in Table 1 Coal waste was found to havehigh ash content and low volatile matter compared to ricehusks and their corresponding blends High ash content ofcoal waste leads to high thermal stability
4 Journal of Energy
Table 1 Proximate and ultimate results
Sample Kiwira coal waste Rice husksMoisture content () 326 plusmn 004 72 plusmn 002
Proximate dry basisVM 1684 plusmn 021 5959 plusmn 043FC 1923 plusmn 077 1729 plusmn 045Ash 6393 plusmn 057 2312 plusmn 006
Proximate dry basis
C 1968 plusmn 033 3813 plusmn 012H 207 plusmn 003 459 plusmn 0005O 1289 plusmn 036 3310 plusmn 008Cl NIL 031 plusmn 0002S 100 plusmn 004 006 plusmn 0003N 043 plusmn 001 068 plusmn 0032
HHVMJkg daf 220 plusmn 035 196 plusmn 004
0102030405060708090
100
0 100 200 300 400 500 600 700 800 900 1000
Mas
s rem
aini
ng (
)
100 KCW20 KCW60 KCW
80 KCWRH40 KCW
Temperature (∘C)
Figure 2 TG analysis results of Kiwira coal wasterice husk blends
32Thermogravimetric (TG) Analysis Results TheTGweightloss curves of the blends in a nonisothermal heating at heatingrate of 10 Kmin are shown in Figure 2
Weight loss profiles of blends are between the two profilesof coal waste and rice husk The results showed that ricehusk is more reactive than coal waste This is in agreementwith the work of Zakaria et al [33] which showed thatrice husk is more reactive than coal during pyrolysis andcombustionThis is due to the fact that coal waste unlike ricehusk has high ash contents since it contains thermally stablecomponents like silica
The results also showed that as rice husk contentincreased temperature of pyrolysis decreased For examplefor pure coal waste the pyrolysis temperature was about760∘C while that of 40 coal wasterice husk blend and purerice husk was about 690 and 650∘C respectively as shown inFigures 3 4 and 5
Coal is considered as a complex polymer network con-sisting of aromatic clusters of aliphatic bridge [16] Durationof evolution of volatiles (that end up producing CO H
2 CH4
and H2O) is relatively shorter for biomass than coal [34 35]
The decrease in thermal stability with increase in rice huskcontent could be useful in designing cheap thermochemicalconversion (eg gasification) processes
00 100 200 300 400 500 600 700 800 900 1000 1100 1200
DTG
(m
in)
Temperature (deg)
minus14
minus12
minus1
minus08
minus06
minus04
minus02
Figure 3 DTG results of Kiwira coal waste
0000 100 200 300 400 500 600 700 800 900 100011001200
DTG
(m
in)
Temperature (deg)
minus500
minus450
minus400
minus350
minus300
minus250
minus200
minus150
minus100
minus050
Figure 4 DTG results of rice husk
Temperature (∘C)
0 0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
100 KCW20 KCW40 KCW
60 KCW80 KCWRH
minus5
minus45
minus4
minus35
minus25
minus2
minus3
minus15
minus05
minus1
Figure 5 DTG profiles of Kiwira coal wasterice husk blends
33 Differential Thermogravimetric (DTG) Analysis ResultsFigures 3ndash5 show the DTG profiles of coal waste rice huskand their corresponding blends at heating rate of 10 Kmin innonisothermal conditions Three clear zones were observedthat can be grouped as shown in Figure 1 These zonesare useful for comparing different materials in terms of
Journal of Energy 5
Table 2 Zones of reactions of blends
Blend
Devolatilization Char combustion
Temperaturerange (∘C)
Maximumpeak
(min)
Temperaturerange (∘C)
Maximumpeak
(min)Coal waste 300ndash560 12 560ndash760 1220 160ndash390 33 390ndash670 1340 160ndash400 31 400ndash690 1360 160ndash400 19 400ndash720 1280 170ndash400 09 400ndash730 12Rice husk 160ndash380 48 400ndash650 14
composition and measuring the fuel reactivity [36 37] Forexample the material with high range of char degradationmeans that thematerial has high fixed carbon Coal waste hasbeen shown to have high fixed carbon by proximate analysis
Each sample showed a first peak which corresponds tomoisture removal [38]This peak occurred at temperature lessthan 200∘C Second and third profiles represent devolatiliza-tion and char combustion respectively Devolatilization incoal waste occurred at higher temperature than that inrice husk and coal wasterice husk blends For coal wastedevolatilization and char combustion profiles occurred closeto each other Gil et al observed only one profile for bothdevolatilization and char combustion on coal [39]
Table 2 reports temperature ranges for devolatilizationand char pyrolysis stages Rice husk devolatilization occurredbetween 160 and 380∘C This range is similar to the onereported for the pyrolysis of rice husk hemicelluloses andcellulose [33] Coal waste devolatilization occurred at tem-peratures (300ndash560∘C) higher than those of rice husk Thecoal waste devolatilization temperature range obtained wascomparable to that of coal (415ndash520∘C) reported by Zakariaet al [33] Char combustion for coal waste has been seen tobe higher than rice [33] This is attributed to the high fixedcarbon context in coal wastes In our study rice husk charwas completely degraded at 650∘C while coal waste degradedat 760∘C Rice husk char degradation temperature (650∘C)obtained in our work is comparable to 600∘C reported ricehusk char by Sonobe et al [40]
Degradation rate increased with increase in rice huskThis was attributed to reactivity of rice husk (biomass) Thepresence of rice husks promotes the production of volatilesin coal wasterice husk blends This phenomenon was alsoreported by Haykiri-Acma and Yaman [41] Devolatilizationand char combustion temperatures decreased with increasein rice husk Degradation peak values increased with anincrease in rice huskThis is attributed to the reactivity of ricehusk which is higher than that of coal waste due to increasein volatile matter in biomass [16]
The temperature band width of reaction decreased withincrease in rice husk due to the increase in volatile matter anddecrease in fixed carbon leading to increased reactivity of theblendThebond strength of coal waste can also be a reason forincreased reaction temperature bandwidthwith increasing incoal waste Coal has been reported to have a high bond energy
0
001
002
003
004
005
006
007
40 140 240 340 440 540 640 740 840 940Temperature (deg)
100 coal20 coal80
40600
Reac
tion
rate
(d120572d
t)
Figure 6 Conversion rates of Kiwira coal wasterice husk biomassblends
of about 1000 kJmol [42] compared to biomass with bondenergy around 380ndash420 kJmol [43]This means degradationrate will increase with increase in rice husk content
34 Conversion Rate Figure 6 shows the rate of conversionof different blends It can be observed that at devolatilizationstage the rate of conversion increased with increase in ricehusk content This is attributed to the reactivity of volatilematter in rice husk content Conversion rate of char increasedwith increase in coal waste This is attributed to the increasein fixed carbon with increasing coal waste
Devolatilization rate increased with increase in rice huskcontent It is known that volatilematter leads to production oftarwhich is not needed in the syngas [35] Blending coalwasteand rice huskmay reduce production of tar however thismaybe accompanied by the reduction in the rate of conversion
High conversion rate of devolatilization occurred ataround 320∘C while for char degradation it occurs at 500∘CHigh reaction rate of devolatilization with increase in ricehusk content can be explained by devolatilization behaviorofmost biomass fuels Biomass contains reactive componentsresponsible for initial steps of devolatilization Final tail ofdevolatilization which is the decomposition of lignin andmainly produces char is suggested to be caused by the lessreactive structure of the remaining solid after main pyrolysis[44]
35 Kinetics Parameters Results The kinetic properties acti-vation energy and preexponential factor have been calculatedusing (14) Table 3 shows the calculated results of kineticparameters of the blends
The activation energy for devolatilization was found toincrease with increase in rice husk The results indicated thatactivation increased from 51 to 85 for 100 coal to 0 coalrespectively This was due to the increase in volatile matters
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Energy 3
The degree of conversion 120572 of a material is defined as
120572 =119882119900minus119882119905
119882119900minus119882119891
(4)
where119882119900is the original mass119882
119891is the final mass and119882
119905is
the mass at time 119905Rate of degradation of a material is expressed by a way of
[26]
119889120572
119889119905= 119896 (119879) lowast (1 minus 120572)
119899
(5)
where 119899 is the order of reaction 120572 is the degree of conversionand 119896(119879) is the rate constant of reaction whose temperaturedependence is expressed by the Arrhenius equation
119896 (119879) = 119860Exp(minus119864119877119879) (6)
where 119864 is the activation energy in kJmole 119879 is temperaturein K 119877 is the universal gas constant (8314 JKmol) and 119860 isthe preexponential factor (minminus1)
For pyrolysis and oxidation reactions under nonisother-mal conditions the heating rate plays a very important role indetermining the kinetic parameters Low heating rate meansthat a reaction is closer to equilibrium and vice versa [26 27]
Many authors have approximated the overall process asa first-order decomposition occurring uniformly throughoutthe coal and biomass particles [28ndash30] For a first-orderreaction at constant heating rate
120573 =119889119879
119889119905 (7)
Equation (5) is transformed to
119889120572
119889119879= [119860
(1 minus 120572)
120573] exp(minus119864
119877119879) (8)
Integration of the above equation subject to the condition thatconversion is zero at initial temperature 119879
0 leads to
ln [1 minus 120572] = minus119860120573int
119879
119879119900
Exp(minus119864119877119879)119889119879 (9)
Since there is no conversion at initial temperature 1198790 the
limits of the integral become
int
119879
0
Exp(minus119864119877119879
) (10)
Introducing a new function
119891 (119910) = int
infin
119910
119890minus119910
1199102119889119910 (11)
where 119910 is minus119864119877119879 (9) becomes
ln (1 minus 120572) = minus119860
120573119891 (119910) (12)
0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
Zone III
Zone II
Zone I
minus5
minus45
minus4
minus35
minus3
minus25
minus2
minus15
minus1
minus05
0
Temperature (∘C)
Figure 1 DTG results showing reaction steps of rice husk
The Coats-Redfern approximation method was deployed inthis study to determine the approximate value of temperatureintegralThis method was chosen because it provides the bestlinearity of the data as opposed to other analytical model-fitting methods [27 31 32]
When this method is used (11) yields
119891 (119910) asymp119890minus119910
1199102(1 minus 119910) (13)
Equation (8) is rearranged to result in
ln [minus ln (1 minus 120572)1198792
] = ln [119860119877119867119864
(1 minus2119877119879
119864)] minus
119864
119877119879 (14)
Equation (13) is written in the form 119910 = 119886119909 + 119887 where
119886 = minus119864
119877 119887 = ln [119860119877
119867119864(1 minus
2119877119879
119864)] (15)
The temperature in the intercept value ldquo119887rdquo is obtained byaveraging the initial and final mass remaining for a specificreaction step The obtained value corresponds to the temper-ature value to be used
119882119879=
(119882119900+119882119891)
2 (16)
Reaction steps considered are moisture removal (Zone I)volatile removal (Zone II) and char pyrolysis (Zone III)as indicated in Figure 1 In each reaction step degree ofconversion is recalculation For each step of reaction 119864 and119860 can be calculated using (14)
3 Results and Discussion
31 Proximate andUltimateAnalysis Proximate andultimateresults are shown in Table 1 Coal waste was found to havehigh ash content and low volatile matter compared to ricehusks and their corresponding blends High ash content ofcoal waste leads to high thermal stability
4 Journal of Energy
Table 1 Proximate and ultimate results
Sample Kiwira coal waste Rice husksMoisture content () 326 plusmn 004 72 plusmn 002
Proximate dry basisVM 1684 plusmn 021 5959 plusmn 043FC 1923 plusmn 077 1729 plusmn 045Ash 6393 plusmn 057 2312 plusmn 006
Proximate dry basis
C 1968 plusmn 033 3813 plusmn 012H 207 plusmn 003 459 plusmn 0005O 1289 plusmn 036 3310 plusmn 008Cl NIL 031 plusmn 0002S 100 plusmn 004 006 plusmn 0003N 043 plusmn 001 068 plusmn 0032
HHVMJkg daf 220 plusmn 035 196 plusmn 004
0102030405060708090
100
0 100 200 300 400 500 600 700 800 900 1000
Mas
s rem
aini
ng (
)
100 KCW20 KCW60 KCW
80 KCWRH40 KCW
Temperature (∘C)
Figure 2 TG analysis results of Kiwira coal wasterice husk blends
32Thermogravimetric (TG) Analysis Results TheTGweightloss curves of the blends in a nonisothermal heating at heatingrate of 10 Kmin are shown in Figure 2
Weight loss profiles of blends are between the two profilesof coal waste and rice husk The results showed that ricehusk is more reactive than coal waste This is in agreementwith the work of Zakaria et al [33] which showed thatrice husk is more reactive than coal during pyrolysis andcombustionThis is due to the fact that coal waste unlike ricehusk has high ash contents since it contains thermally stablecomponents like silica
The results also showed that as rice husk contentincreased temperature of pyrolysis decreased For examplefor pure coal waste the pyrolysis temperature was about760∘C while that of 40 coal wasterice husk blend and purerice husk was about 690 and 650∘C respectively as shown inFigures 3 4 and 5
Coal is considered as a complex polymer network con-sisting of aromatic clusters of aliphatic bridge [16] Durationof evolution of volatiles (that end up producing CO H
2 CH4
and H2O) is relatively shorter for biomass than coal [34 35]
The decrease in thermal stability with increase in rice huskcontent could be useful in designing cheap thermochemicalconversion (eg gasification) processes
00 100 200 300 400 500 600 700 800 900 1000 1100 1200
DTG
(m
in)
Temperature (deg)
minus14
minus12
minus1
minus08
minus06
minus04
minus02
Figure 3 DTG results of Kiwira coal waste
0000 100 200 300 400 500 600 700 800 900 100011001200
DTG
(m
in)
Temperature (deg)
minus500
minus450
minus400
minus350
minus300
minus250
minus200
minus150
minus100
minus050
Figure 4 DTG results of rice husk
Temperature (∘C)
0 0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
100 KCW20 KCW40 KCW
60 KCW80 KCWRH
minus5
minus45
minus4
minus35
minus25
minus2
minus3
minus15
minus05
minus1
Figure 5 DTG profiles of Kiwira coal wasterice husk blends
33 Differential Thermogravimetric (DTG) Analysis ResultsFigures 3ndash5 show the DTG profiles of coal waste rice huskand their corresponding blends at heating rate of 10 Kmin innonisothermal conditions Three clear zones were observedthat can be grouped as shown in Figure 1 These zonesare useful for comparing different materials in terms of
Journal of Energy 5
Table 2 Zones of reactions of blends
Blend
Devolatilization Char combustion
Temperaturerange (∘C)
Maximumpeak
(min)
Temperaturerange (∘C)
Maximumpeak
(min)Coal waste 300ndash560 12 560ndash760 1220 160ndash390 33 390ndash670 1340 160ndash400 31 400ndash690 1360 160ndash400 19 400ndash720 1280 170ndash400 09 400ndash730 12Rice husk 160ndash380 48 400ndash650 14
composition and measuring the fuel reactivity [36 37] Forexample the material with high range of char degradationmeans that thematerial has high fixed carbon Coal waste hasbeen shown to have high fixed carbon by proximate analysis
Each sample showed a first peak which corresponds tomoisture removal [38]This peak occurred at temperature lessthan 200∘C Second and third profiles represent devolatiliza-tion and char combustion respectively Devolatilization incoal waste occurred at higher temperature than that inrice husk and coal wasterice husk blends For coal wastedevolatilization and char combustion profiles occurred closeto each other Gil et al observed only one profile for bothdevolatilization and char combustion on coal [39]
Table 2 reports temperature ranges for devolatilizationand char pyrolysis stages Rice husk devolatilization occurredbetween 160 and 380∘C This range is similar to the onereported for the pyrolysis of rice husk hemicelluloses andcellulose [33] Coal waste devolatilization occurred at tem-peratures (300ndash560∘C) higher than those of rice husk Thecoal waste devolatilization temperature range obtained wascomparable to that of coal (415ndash520∘C) reported by Zakariaet al [33] Char combustion for coal waste has been seen tobe higher than rice [33] This is attributed to the high fixedcarbon context in coal wastes In our study rice husk charwas completely degraded at 650∘C while coal waste degradedat 760∘C Rice husk char degradation temperature (650∘C)obtained in our work is comparable to 600∘C reported ricehusk char by Sonobe et al [40]
Degradation rate increased with increase in rice huskThis was attributed to reactivity of rice husk (biomass) Thepresence of rice husks promotes the production of volatilesin coal wasterice husk blends This phenomenon was alsoreported by Haykiri-Acma and Yaman [41] Devolatilizationand char combustion temperatures decreased with increasein rice husk Degradation peak values increased with anincrease in rice huskThis is attributed to the reactivity of ricehusk which is higher than that of coal waste due to increasein volatile matter in biomass [16]
The temperature band width of reaction decreased withincrease in rice husk due to the increase in volatile matter anddecrease in fixed carbon leading to increased reactivity of theblendThebond strength of coal waste can also be a reason forincreased reaction temperature bandwidthwith increasing incoal waste Coal has been reported to have a high bond energy
0
001
002
003
004
005
006
007
40 140 240 340 440 540 640 740 840 940Temperature (deg)
100 coal20 coal80
40600
Reac
tion
rate
(d120572d
t)
Figure 6 Conversion rates of Kiwira coal wasterice husk biomassblends
of about 1000 kJmol [42] compared to biomass with bondenergy around 380ndash420 kJmol [43]This means degradationrate will increase with increase in rice husk content
34 Conversion Rate Figure 6 shows the rate of conversionof different blends It can be observed that at devolatilizationstage the rate of conversion increased with increase in ricehusk content This is attributed to the reactivity of volatilematter in rice husk content Conversion rate of char increasedwith increase in coal waste This is attributed to the increasein fixed carbon with increasing coal waste
Devolatilization rate increased with increase in rice huskcontent It is known that volatilematter leads to production oftarwhich is not needed in the syngas [35] Blending coalwasteand rice huskmay reduce production of tar however thismaybe accompanied by the reduction in the rate of conversion
High conversion rate of devolatilization occurred ataround 320∘C while for char degradation it occurs at 500∘CHigh reaction rate of devolatilization with increase in ricehusk content can be explained by devolatilization behaviorofmost biomass fuels Biomass contains reactive componentsresponsible for initial steps of devolatilization Final tail ofdevolatilization which is the decomposition of lignin andmainly produces char is suggested to be caused by the lessreactive structure of the remaining solid after main pyrolysis[44]
35 Kinetics Parameters Results The kinetic properties acti-vation energy and preexponential factor have been calculatedusing (14) Table 3 shows the calculated results of kineticparameters of the blends
The activation energy for devolatilization was found toincrease with increase in rice husk The results indicated thatactivation increased from 51 to 85 for 100 coal to 0 coalrespectively This was due to the increase in volatile matters
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
4 Journal of Energy
Table 1 Proximate and ultimate results
Sample Kiwira coal waste Rice husksMoisture content () 326 plusmn 004 72 plusmn 002
Proximate dry basisVM 1684 plusmn 021 5959 plusmn 043FC 1923 plusmn 077 1729 plusmn 045Ash 6393 plusmn 057 2312 plusmn 006
Proximate dry basis
C 1968 plusmn 033 3813 plusmn 012H 207 plusmn 003 459 plusmn 0005O 1289 plusmn 036 3310 plusmn 008Cl NIL 031 plusmn 0002S 100 plusmn 004 006 plusmn 0003N 043 plusmn 001 068 plusmn 0032
HHVMJkg daf 220 plusmn 035 196 plusmn 004
0102030405060708090
100
0 100 200 300 400 500 600 700 800 900 1000
Mas
s rem
aini
ng (
)
100 KCW20 KCW60 KCW
80 KCWRH40 KCW
Temperature (∘C)
Figure 2 TG analysis results of Kiwira coal wasterice husk blends
32Thermogravimetric (TG) Analysis Results TheTGweightloss curves of the blends in a nonisothermal heating at heatingrate of 10 Kmin are shown in Figure 2
Weight loss profiles of blends are between the two profilesof coal waste and rice husk The results showed that ricehusk is more reactive than coal waste This is in agreementwith the work of Zakaria et al [33] which showed thatrice husk is more reactive than coal during pyrolysis andcombustionThis is due to the fact that coal waste unlike ricehusk has high ash contents since it contains thermally stablecomponents like silica
The results also showed that as rice husk contentincreased temperature of pyrolysis decreased For examplefor pure coal waste the pyrolysis temperature was about760∘C while that of 40 coal wasterice husk blend and purerice husk was about 690 and 650∘C respectively as shown inFigures 3 4 and 5
Coal is considered as a complex polymer network con-sisting of aromatic clusters of aliphatic bridge [16] Durationof evolution of volatiles (that end up producing CO H
2 CH4
and H2O) is relatively shorter for biomass than coal [34 35]
The decrease in thermal stability with increase in rice huskcontent could be useful in designing cheap thermochemicalconversion (eg gasification) processes
00 100 200 300 400 500 600 700 800 900 1000 1100 1200
DTG
(m
in)
Temperature (deg)
minus14
minus12
minus1
minus08
minus06
minus04
minus02
Figure 3 DTG results of Kiwira coal waste
0000 100 200 300 400 500 600 700 800 900 100011001200
DTG
(m
in)
Temperature (deg)
minus500
minus450
minus400
minus350
minus300
minus250
minus200
minus150
minus100
minus050
Figure 4 DTG results of rice husk
Temperature (∘C)
0 0 100 200 300 400 500 600 700 800 900 1000
DTG
(m
in)
100 KCW20 KCW40 KCW
60 KCW80 KCWRH
minus5
minus45
minus4
minus35
minus25
minus2
minus3
minus15
minus05
minus1
Figure 5 DTG profiles of Kiwira coal wasterice husk blends
33 Differential Thermogravimetric (DTG) Analysis ResultsFigures 3ndash5 show the DTG profiles of coal waste rice huskand their corresponding blends at heating rate of 10 Kmin innonisothermal conditions Three clear zones were observedthat can be grouped as shown in Figure 1 These zonesare useful for comparing different materials in terms of
Journal of Energy 5
Table 2 Zones of reactions of blends
Blend
Devolatilization Char combustion
Temperaturerange (∘C)
Maximumpeak
(min)
Temperaturerange (∘C)
Maximumpeak
(min)Coal waste 300ndash560 12 560ndash760 1220 160ndash390 33 390ndash670 1340 160ndash400 31 400ndash690 1360 160ndash400 19 400ndash720 1280 170ndash400 09 400ndash730 12Rice husk 160ndash380 48 400ndash650 14
composition and measuring the fuel reactivity [36 37] Forexample the material with high range of char degradationmeans that thematerial has high fixed carbon Coal waste hasbeen shown to have high fixed carbon by proximate analysis
Each sample showed a first peak which corresponds tomoisture removal [38]This peak occurred at temperature lessthan 200∘C Second and third profiles represent devolatiliza-tion and char combustion respectively Devolatilization incoal waste occurred at higher temperature than that inrice husk and coal wasterice husk blends For coal wastedevolatilization and char combustion profiles occurred closeto each other Gil et al observed only one profile for bothdevolatilization and char combustion on coal [39]
Table 2 reports temperature ranges for devolatilizationand char pyrolysis stages Rice husk devolatilization occurredbetween 160 and 380∘C This range is similar to the onereported for the pyrolysis of rice husk hemicelluloses andcellulose [33] Coal waste devolatilization occurred at tem-peratures (300ndash560∘C) higher than those of rice husk Thecoal waste devolatilization temperature range obtained wascomparable to that of coal (415ndash520∘C) reported by Zakariaet al [33] Char combustion for coal waste has been seen tobe higher than rice [33] This is attributed to the high fixedcarbon context in coal wastes In our study rice husk charwas completely degraded at 650∘C while coal waste degradedat 760∘C Rice husk char degradation temperature (650∘C)obtained in our work is comparable to 600∘C reported ricehusk char by Sonobe et al [40]
Degradation rate increased with increase in rice huskThis was attributed to reactivity of rice husk (biomass) Thepresence of rice husks promotes the production of volatilesin coal wasterice husk blends This phenomenon was alsoreported by Haykiri-Acma and Yaman [41] Devolatilizationand char combustion temperatures decreased with increasein rice husk Degradation peak values increased with anincrease in rice huskThis is attributed to the reactivity of ricehusk which is higher than that of coal waste due to increasein volatile matter in biomass [16]
The temperature band width of reaction decreased withincrease in rice husk due to the increase in volatile matter anddecrease in fixed carbon leading to increased reactivity of theblendThebond strength of coal waste can also be a reason forincreased reaction temperature bandwidthwith increasing incoal waste Coal has been reported to have a high bond energy
0
001
002
003
004
005
006
007
40 140 240 340 440 540 640 740 840 940Temperature (deg)
100 coal20 coal80
40600
Reac
tion
rate
(d120572d
t)
Figure 6 Conversion rates of Kiwira coal wasterice husk biomassblends
of about 1000 kJmol [42] compared to biomass with bondenergy around 380ndash420 kJmol [43]This means degradationrate will increase with increase in rice husk content
34 Conversion Rate Figure 6 shows the rate of conversionof different blends It can be observed that at devolatilizationstage the rate of conversion increased with increase in ricehusk content This is attributed to the reactivity of volatilematter in rice husk content Conversion rate of char increasedwith increase in coal waste This is attributed to the increasein fixed carbon with increasing coal waste
Devolatilization rate increased with increase in rice huskcontent It is known that volatilematter leads to production oftarwhich is not needed in the syngas [35] Blending coalwasteand rice huskmay reduce production of tar however thismaybe accompanied by the reduction in the rate of conversion
High conversion rate of devolatilization occurred ataround 320∘C while for char degradation it occurs at 500∘CHigh reaction rate of devolatilization with increase in ricehusk content can be explained by devolatilization behaviorofmost biomass fuels Biomass contains reactive componentsresponsible for initial steps of devolatilization Final tail ofdevolatilization which is the decomposition of lignin andmainly produces char is suggested to be caused by the lessreactive structure of the remaining solid after main pyrolysis[44]
35 Kinetics Parameters Results The kinetic properties acti-vation energy and preexponential factor have been calculatedusing (14) Table 3 shows the calculated results of kineticparameters of the blends
The activation energy for devolatilization was found toincrease with increase in rice husk The results indicated thatactivation increased from 51 to 85 for 100 coal to 0 coalrespectively This was due to the increase in volatile matters
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Energy 5
Table 2 Zones of reactions of blends
Blend
Devolatilization Char combustion
Temperaturerange (∘C)
Maximumpeak
(min)
Temperaturerange (∘C)
Maximumpeak
(min)Coal waste 300ndash560 12 560ndash760 1220 160ndash390 33 390ndash670 1340 160ndash400 31 400ndash690 1360 160ndash400 19 400ndash720 1280 170ndash400 09 400ndash730 12Rice husk 160ndash380 48 400ndash650 14
composition and measuring the fuel reactivity [36 37] Forexample the material with high range of char degradationmeans that thematerial has high fixed carbon Coal waste hasbeen shown to have high fixed carbon by proximate analysis
Each sample showed a first peak which corresponds tomoisture removal [38]This peak occurred at temperature lessthan 200∘C Second and third profiles represent devolatiliza-tion and char combustion respectively Devolatilization incoal waste occurred at higher temperature than that inrice husk and coal wasterice husk blends For coal wastedevolatilization and char combustion profiles occurred closeto each other Gil et al observed only one profile for bothdevolatilization and char combustion on coal [39]
Table 2 reports temperature ranges for devolatilizationand char pyrolysis stages Rice husk devolatilization occurredbetween 160 and 380∘C This range is similar to the onereported for the pyrolysis of rice husk hemicelluloses andcellulose [33] Coal waste devolatilization occurred at tem-peratures (300ndash560∘C) higher than those of rice husk Thecoal waste devolatilization temperature range obtained wascomparable to that of coal (415ndash520∘C) reported by Zakariaet al [33] Char combustion for coal waste has been seen tobe higher than rice [33] This is attributed to the high fixedcarbon context in coal wastes In our study rice husk charwas completely degraded at 650∘C while coal waste degradedat 760∘C Rice husk char degradation temperature (650∘C)obtained in our work is comparable to 600∘C reported ricehusk char by Sonobe et al [40]
Degradation rate increased with increase in rice huskThis was attributed to reactivity of rice husk (biomass) Thepresence of rice husks promotes the production of volatilesin coal wasterice husk blends This phenomenon was alsoreported by Haykiri-Acma and Yaman [41] Devolatilizationand char combustion temperatures decreased with increasein rice husk Degradation peak values increased with anincrease in rice huskThis is attributed to the reactivity of ricehusk which is higher than that of coal waste due to increasein volatile matter in biomass [16]
The temperature band width of reaction decreased withincrease in rice husk due to the increase in volatile matter anddecrease in fixed carbon leading to increased reactivity of theblendThebond strength of coal waste can also be a reason forincreased reaction temperature bandwidthwith increasing incoal waste Coal has been reported to have a high bond energy
0
001
002
003
004
005
006
007
40 140 240 340 440 540 640 740 840 940Temperature (deg)
100 coal20 coal80
40600
Reac
tion
rate
(d120572d
t)
Figure 6 Conversion rates of Kiwira coal wasterice husk biomassblends
of about 1000 kJmol [42] compared to biomass with bondenergy around 380ndash420 kJmol [43]This means degradationrate will increase with increase in rice husk content
34 Conversion Rate Figure 6 shows the rate of conversionof different blends It can be observed that at devolatilizationstage the rate of conversion increased with increase in ricehusk content This is attributed to the reactivity of volatilematter in rice husk content Conversion rate of char increasedwith increase in coal waste This is attributed to the increasein fixed carbon with increasing coal waste
Devolatilization rate increased with increase in rice huskcontent It is known that volatilematter leads to production oftarwhich is not needed in the syngas [35] Blending coalwasteand rice huskmay reduce production of tar however thismaybe accompanied by the reduction in the rate of conversion
High conversion rate of devolatilization occurred ataround 320∘C while for char degradation it occurs at 500∘CHigh reaction rate of devolatilization with increase in ricehusk content can be explained by devolatilization behaviorofmost biomass fuels Biomass contains reactive componentsresponsible for initial steps of devolatilization Final tail ofdevolatilization which is the decomposition of lignin andmainly produces char is suggested to be caused by the lessreactive structure of the remaining solid after main pyrolysis[44]
35 Kinetics Parameters Results The kinetic properties acti-vation energy and preexponential factor have been calculatedusing (14) Table 3 shows the calculated results of kineticparameters of the blends
The activation energy for devolatilization was found toincrease with increase in rice husk The results indicated thatactivation increased from 51 to 85 for 100 coal to 0 coalrespectively This was due to the increase in volatile matters
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
6 Journal of Energy
Table 3 Kinetic properties of Kiwira coal wasterice husk blends
Blend( coal)
Degradation stepVolatilization Char combustion
119864 (kJmol) 119860 (minminus1) 119864 (kJmol) 119860 (minminus1)100 5134 plusmn 075 347 plusmn 70 13102 plusmn 16 77 plusmn 02E680 5889 plusmn 044 28 plusmn 012E4 8335 plusmn 027 39 plusmn 09E460 5943 plusmn 019 38 plusmn 045E4 8109 plusmn 025 34 plusmn 1E440 6060 plusmn 020 39 plusmn 012E4 7863 plusmn 067 54 plusmn 28E420 6370 plusmn 09 88 plusmn 07E4 7651 plusmn 07 66 plusmn 12E40 849 plusmn 05 15 plusmn 02E4 7514 plusmn 092 12 plusmn 075E4
In char combustion step the activation energy wasobserved to increase with increase in coal waste rangingfrom 131 to 75 kJmol for 100 coal to 0 coal respectivelyThis was attributed to the high content of fixed carbon incoal waste than that in rice husk Smaller values of averageactivation energy mean a more reactive solid while largervalues mean a less reactive solid [20] This means coal wasteshave char which is less reactive
Overall activation energy at char combustion stagedecreasedwith increase in rice huskThis is attributed toweakbonds in rice husk than that in coal waste [45] This showsthat rice huskcoal waste blends proceed at low energy thancoal waste alone This favors gasification of blends than thatof coal waste alone
4 Conclusions
Thermogravimetric analysis has been performed on Kiwiracoal wasterice husk blends aiming at establishing data forcogasification for syngas production The kinetic parametershave been calculated using multistep first-order reaction at10 Kmin heating rate The following information has beenobtained which is essential to design cogasification process
(1) Thermal stability of coal waste is high and decreaseswith increase in rice husk Blending of coal waste andrice husk may reduce thermal stability of coal wasteand thus offer designing economic and environmen-tal friendly thermochemical recovery method
(2) Increase in degradation rate with increases in ricehusk shows the reactivity of rice huskThis also favorsthermochemical process to recover energy from coalwaste
(3) Activation energy in char pyrolysis zone hasdecreased with increase in rice husk 131ndash75 kJmolThis is associated with decrease in the fixed carbon ofblend with increase in rice husk
(4) The overall activation energy of pyrolysis of blendshas decreased with increase in rice husk 131ndash85 kJmole Decrease in activation indicates that oper-ating temperature also decreases This shows thatgasification of blends occurs at low temperature thanis coal waste alone This is advantageous to reduce
pollutants production that depends on high tempera-ture such as NO
119909
(5) Cogasification to recover energy from coal waste isa breakthrough technology favoured by decreasingoperating temperature with blending technique
The study has shown that using blending technique thermalstability and activation energy properties of coal wastericehusk blends have been reduced by increasing rice huskThermochemical energy recovery process can be undertakenat low temperature compared to coal waste alone The useof low temperature process minimizes construction materialcost and reduces pollutants formation With these dataobtained it is expected that cogasification of coal waste andrice husk is less costly and releases less pollutants whencompared to coal waste gasification alone
Nomenclature
KCW Kiwira coal wasteRH Rice huskTG ThermogravimetricDTG Differential thermogravimetric
NM-AIST Nelson Mandela African Institution ofScience and Technology
COSTECH Commission for Science andTechnology
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
The authors sincerely appreciate the support provided byNM-AIST and COSTECH Appreciation is also extended tothe Administration of Kiwira Coal Mine for providing accessin obtaining the samples Sincere thanks are also extended tothe University of Dar es Salaam for allowing the access of itslaboratories and providing necessary support
References
[1] S Su Y G Jin X X Yu and R Worrall ldquoPreliminaryexperimental studies of waste coal gasificationrdquo in CleanerCombustion and Sustainable World pp 719ndash723 Springer 2013
[2] TMAA ldquoMinerals Found in Tanzania-Coalrdquo 2014httpwwwtmaagotzmineralsviewcoal
[3] Ministry of Energy and Minerals Power System Master Plan2012 Update Ministry of Energy and Minerals Dar es SalaamTanzania 2012
[4] D A Mwakipesile P L Mtui I S N Mkilaha and M HMkumbwa ldquoBehaviour of trace metals in gasification of Kiwiracoal wastesrdquo in Proceedings of the International ConferenceMechanical and Industrial Engineering pp 269ndash273 ArushaTanzania 2012
[5] C FMhilu ldquoAnalysis of energy characteristics of rice and coffeehusks blendsrdquo ISRN Chemical Engineering vol 2014 Article ID196103 6 pages 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Energy 7
[6] M H Lapuerta J J Hernandez A Pazo and J LopezldquoGasification and co-gasification of biomass wastes effect ofthe biomass origin and the gasifier operating conditionsrdquo FuelProcessing Technology vol 89 no 9 pp 828ndash837 2008
[7] Y G Pan E Velo X Roca J J Manya and L PuigjanerldquoFluidized-bed co-gasification of residual biomasspoor coalblends for fuel gas productionrdquo Fuel vol 79 no 11 pp 1317ndash1326 2000
[8] J J Hernandez G Aranda-Almansa and C Serrano ldquoCo-gasification of biomass wastes and coal-coke blends in anentrained flow gasifier an experimental studyrdquo Energy andFuels vol 24 no 4 pp 2479ndash2488 2010
[9] M W Seo J H Goo S D Kim S H Lee and Y C ChoildquoGasification characteristics of coalbiomass blend in a dualcirculating fluidized bed reactorrdquo Energy and Fuels vol 24 no5 pp 3108ndash3118 2010
[10] G Gordillo K Annamalai and N Carlin ldquoAdiabatic fixed-bedgasification of coal dairy biomass and feedlot biomass using anair-steammixture as an oxidizing agentrdquoRenewable Energy vol34 no 12 pp 2789ndash2797 2009
[11] N Koukouzas A Katsiadakis E Karlopoulos and E KakarasldquoCo-gasification of solid waste and lignitemdasha case study forWestern Macedoniardquo Waste Management vol 28 no 7 pp1263ndash1275 2008
[12] C B Field J E Campbell and D B Lobell ldquoBiomass energythe scale of the potential resourcerdquo Trends in Ecology andEvolution vol 23 no 2 pp 65ndash72 2008
[13] K Stecher A Brosowski and D Thran Biomass Potential inAfrica IRENA-DBFZ Abu Dhabi United Arab Emirates 2013
[14] P Molcan G Lu T L Bris Y Yan B Taupin and S CaillatldquoCharacterisation of biomass and coal co-firing on a 3 MWthCombustion Test Facility using flame imaging and gasashsampling techniquesrdquo Fuel vol 88 no 12 pp 2328ndash2334 2009
[15] A Kumar D D Jones and M A Hanna ldquoThermochemicalbiomass gasification a review of the current status of thetechnologyrdquo Energies vol 2 no 3 pp 556ndash581 2009
[16] A Bhagavatula G Huffman N Shah and R Honaker ldquoEval-uation of thermal evolution profiles and estimation of kineticparameters for pyrolysis of coalcorn stover blends using ther-mogravimetric analysisrdquo Journal of Fuels vol 2014 Article ID914856 12 pages 2014
[17] A Magdziarz and M Wilk ldquoThermal characteristics of thecombustion process of biomass and sewage sludgerdquo Journal ofThermal Analysis and Calorimetry vol 114 no 2 pp 519ndash5292013
[18] P Wang S Hedges K Casleton and C Guenther ldquoThermalbehavior of coal and biomass blends in inert and oxidizinggaseous environmentsrdquo International Journal of Clean Coal andEnergy vol 1 pp 35ndash42 2012
[19] L Wilson and H Iddi Scientific and Technical Cooperationbetween Tanzania Industrial Research and Development Orga-nization (TIRDO) of Tanzania and the Council of Science andIndustrial Research (CSIR) of India TIRDO 2014
[20] E Biagini A Fantei and L Tognotti ldquoEffect of the heatingrate on the devolatilization of biomass residuesrdquoThermochimicaActa vol 472 no 1-2 pp 55ndash63 2008
[21] A Volborth G E Miller C K Garner and P A JerabekldquoOxygen determination and stoichiometry of some coalsrdquo inProceedings of the American Chemical Society Meeting Divisionof Fuel Chemistry Chicago Ill USA 1977
[22] S C Turmanova S D Genieva A S Dimitrova and L T VlaevldquoNon-isothermal degradation kinetics of filled with rise huskash polypropene compositesrdquoExpress Polymer Letters vol 2 no2 pp 133ndash146 2008
[23] P J Haines Principles ofThermal Analysis and Calorimetry vol30 Royal Society of Chemistry 2002
[24] M Menzinger and R Wolfgang ldquoThe meaning and use of theArrhenius activation energyrdquoAngewandte Chemie InternationalEdition vol 8 no 6 pp 438ndash444 1969
[25] G Raj Chemical Kinetics Krishna Prakashan Media UttarPradesh India 8th edition 2010
[26] L Zhou Y Wang Q Huang and J Cai ldquoThermogravimetriccharacteristics and kinetic of plastic and biomass blends co-pyrolysisrdquo Fuel Processing Technology vol 87 no 11 pp 963ndash969 2006
[27] A W Coats and J P Redfern ldquoKinetic parameters fromthermogravimetric datardquo Nature vol 201 no 4914 pp 68ndash691964
[28] C Di Blasi ldquoModeling chemical and physical processes of woodand biomass pyrolysisrdquo Progress in Energy and CombustionScience vol 34 no 1 pp 47ndash90 2008
[29] A K Sadhukhan P Gupta and R K Saha ldquoModelling andexperimental studies on pyrolysis of biomass particlesrdquo Journalof Analytical and Applied Pyrolysis vol 81 no 2 pp 183ndash1922008
[30] Y G Pan E Velo and L Puigjaner ldquoPyrolysis of blends ofbiomass with poor coalsrdquo Fuel vol 75 no 4 pp 412ndash418 1996
[31] E Sima-Ella G Yuan and T Mays ldquoA simple kinetic analysisto determine the intrinsic reactivity of coal charsrdquo Fuel vol 84no 14-15 pp 1920ndash1925 2005
[32] J Fermoso B AriasM V Gil et al ldquoCo-gasification of differentrank coals with biomass and petroleum coke in a high-pressurereactor forH
2-rich gas productionrdquoBioresource Technology vol
101 no 9 pp 3230ndash3235 2010[33] Z M Zakaria M A Mohd Ishak M F Abdullah and K
Ismail ldquoThermal decomposition study of coals rice husk ricehusk char and their blends during pyrolysis and combustion viathermogravimetric analysisrdquo International Journal of ChemicalTechnology vol 2 no 3 pp 78ndash87 2010
[34] A K Sadhukhan P Gupta T Goyal and R K Saha ldquoModellingof pyrolysis of coal-biomass blends using thermogravimetricanalysisrdquo Bioresource Technology vol 99 no 17 pp 8022ndash80262008
[35] C Higman andM van der BurgtGasification Elsevier ScienceNew York NY USA 2003
[36] P T Williams and S Besler ldquoThe pyrolysis of rice husks in athermogravimetric analyser and static batch reactorrdquo Fuel vol72 no 2 pp 151ndash159 1993
[37] K Raveendran A Ganesh and K C Khilar ldquoPyrolysis charac-teristics of biomass and biomass componentsrdquo Fuel vol 75 no8 pp 987ndash998 1996
[38] S S Idris NA RahmanK Ismail A B Alias Z A Rashid andM J Aris ldquoInvestigation on thermochemical behaviour of lowrank Malaysian coal oil palm biomass and their blends duringpyrolysis via thermogravimetric analysis (TGA)rdquo BioresourceTechnology vol 101 no 12 pp 4584ndash4592 2010
[39] M V Gil D Casal C Pevida J J Pis and F Rubiera ldquoThermalbehaviour and kinetics of coalbiomass blends during co-combustionrdquo Bioresource Technology vol 101 no 14 pp 5601ndash5608 2010
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
8 Journal of Energy
[40] T Sonobe P Suneerat and N Worasuwannarak ldquoPyrolysischaracteristics of Thai-agricultural residues of rice straw ricehusk and corncob by TG-MS technique and kinetic analysisrdquoin Proceedings of the 2nd Joint International Conference onldquoSustainable Energy and Environment (SEE rsquo06)rdquo BangkokThailand November 2006
[41] H Haykiri-Acma and S Yaman ldquoInteraction between biomassand different rank coals during co-pyrolysisrdquoRenewable Energyvol 35 no 1 pp 288ndash292 2010
[42] J Cai Y Wang L Zhou and Q Huang ldquoThermogravimetricanalysis and kinetics of coalplastic blends during co-pyrolysisin nitrogen atmosphererdquo Fuel Processing Technology vol 89 no1 pp 21ndash27 2008
[43] H B Vuthaluru ldquoInvestigations into the pyrolytic behaviour ofcoalbiomass blends using thermogravimetric analysisrdquo Biore-source Technology vol 92 no 2 pp 187ndash195 2004
[44] M Zhang and F Min ldquoPyrolysis characteristics and kinetics offresh biomass with different initial moisturerdquo in Proceedings ofthe 41st Annual Conference Bowling Green Ky USA August2013
[45] E A Evans andK Ritchie ldquoStrength of a weak bond connectingflexible polymer chainsrdquo Biophysical Journal vol 76 no 5 pp2439ndash2447 1999
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Top Related