Industrial Application of Rice Husk

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com ( ISSN 2250-2459 , Volume 2, Issue 10,October 2012)

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Rice husk is unusually high in ash compared to other

biomass fuels in the range 10-20%. The ash is 87-97%silica [7], highly porous and light weight, with a very highexternal surface area. Presence of high amount of silicamakes it a valuable material for use in industrialapplication. Other constituents of RHA, such as K 2O,Al2O3., CaO, MgO, Na 2O, Fe 2O3 are available in less than1 %ref. Various factors which influence ash properties areincinerating conditions (temperature and duration), rate of heating, burning technique, crop variety and fertilizer used.[8] The silica in the ash undergoes structuraltransformations depending on the conditions of combustionsuch as time and temperature.

III. APPLICATION OF HUSK Suitability of RH to be used for different applications

depends upon the physical and chemical properties of thehusk such as ash content, silica content etc. Direct use of rice husk as fuel has been seen in power plants. Apart fromits use as fuel, RH finds its use as source raw material for synthesis and development of new phases and compounds.A detailed description related to application of rice husk inindustrial sectors as well as other fields has been given

below. A. As a Fuel in Power Plant [9]

Rice husk is mostly used as fuel in boilers for processing paddy and generation of process steam. Heat energy is produced through direct combustion and/or by gasification.Small sector process industries use fixed low capacity

boilers, which are manually fired using rice husk as a fuel.Partial and uneven fuel combustion lead to smoke emissionand decrease the fuel efficiency. As husks are availablevirtually for free, the boiler efficiency and the degree of combustion were the issues of receiving the latest attention.Plants with capacity 2-10 MW range can becomecommercially viable and this biomass resource can beutilized to a much greater extent than at present. It has beenseen that to produce 1MWh, approximately 1 tonne of ricehusk is required. So, the technical and economic factorsdecide the effective use of rice huck as fuel for power

generation. Also, rice husk has been used as an useful andalternative fuel for household energy. [10] RH is also usedas fuel in brick kilns, in furnaces etc [11].

B. Formation of Activated Carbon [12]Due to presence of large amount of hydrocarbon such as

cellulose and lignin content, rice husk can be used as a rawmaterial to prepare activated carbons which are complex

porous structures.

They are obtained by two different processes: the

―physical‖ or ―thermal‖ activation and the ―chemical‖activation. In the former carbonization is followed by char activation; in the second one, carbonization and activationare performed in a single step, using a chemical agent.Physical activation of rice husk produces activated carbonthat exhibits very low specific area. Activated carbons areeffective adsorbents due to their microporous structure.C. As a source of Silica and Silicon Compounds [13, 14]

Apart from organic component, presence of up to 20%silica makes rice husk a promising raw material source for a number of silicon compounds such as silicon carbide,silicon nitride, silicon tetrachloride, zeolite, silica, and puresilicon. The applications of such materials derived fromrice husks are very comprehensive. The above compounds

prepared in powder form are characterized by high purityand fine dispersity [15].

D. Porous SiO 2 /C composite from RH During heat treatment of RH in inert atmosphere,

organic compounds decompose and partly change to H 2O,CO, CO 2, and volatile compounds, remaining carbon andSiO 2[16]. The porous SiO 2/C composites with a highsurface area have been fabricated by heating the pellets ininert atmosphere. Porous SiO 2/C composite was able to befabricated through a simple one-step firing process. The

pore characteristics of the products could be controlled bychanging the molding pressure, raw RH particle size, andheat treatment temperature. Heating at 1000º C displayedthe optimal properties such as 87% porosity and 450 m 2/ gspecific surface area. Larger RH particles resulted in

products with higher strength. [17]. E. Insulating fire brick using RH [18]

Bricks made using rice husk develop plenty of poresduring heat treatment due to burning out of organicmaterial. The more the percentage of rice husk in a brick,the more porous would be the brick and better thermalinsulation. Presences of entrapped air in pores have thermalinsulating characteristics and thus make the porous fire

brick structure suitable for back up insulation.

F. Other usesRH is used as a raw material for production of xylitol,

furfural, ethanol, acetic acid, lingo sulphonic acids. It isused as cleaning or polishing agent in metal and machineindustry, in manufacturing of building materials etc [19].RH has been used as an industrial raw material e.g , as aninsulating board material, fillers in plastics, filling material,

building materials, for making panel board, activatedcarbon etc[20].





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Little effort has been made to manufacture composite

products based on two surface structure of rice husk [21].Despite so many well established uses, little portion of

rice husk produced is utilized in a meaningful way,remaining part is allowed to burn in open piles or dumpedas a solid waste. Rice Husk ash finds large number of industrial applications which are described below.

IV. APPLICATIONS OF R ICE HUSK ASH

Rice husk ash has been widely used in various industrialapplications such as processing of steel, cement, refractoryindustry etc. [19]. Suitability of RHA mainly depends onthe chemical composition of ash, predominantly silicacontent in it. RHA is found to be superior to other supplementary materials like slag, silica fume and fly ash[22].

A. RHA in Steel industry [23]RHA is used during the production of high quality flat

steel. The ash also finds application as an excellentinsulator, having fine insulating properties including lowthermal conductivity, a high melting point, low bulk density and high porosity. It is used as "tundish powder" toinsulate the tundish container, prevent rapid cooling of steeland ensure uniform solidification in casting process. RHAis also used as a coating over the molten metal in thetundish and in ladle which acts as a very good insulator anddoes not allow quick cooling of metal.

B. Use in Ceramic and refractory industry [24]Rice husk ash is used in the manufacture of refractory

bricks because of its insulating properties. It has been usedin the manufacture of low-cost, lightweight insulating

boards. RHA has been used as silica source for cordierite production. Replacement of kaolinite with rice husk silicain the mixture composition, yields higher cordierites with alower crystallize temperature and decrease in activationenergy of crystallization.C. Use of RHA as Silica Source [25]

Due to presence of large silica content in ash, extractionof silica is economical. Silica is also precipitated incustomized forms to meet the requirements of various uses.Some of the uses of silica are in rubber industry asreinforcing agent, in cosmetics, in toothpastes as acleansing agent and in the food industry as an anti-cakingagent [26]. There is a growing demand for fine amorphoussilica in the production of high performance cement andconcrete, use in bridges, marine environments, nuclear

power plants etc.

Silica aerogels prepared from RHA finds application in

super thermal insulators, catalyst supports and dielectricmaterials [27]. RHA can be an economically viable rawmaterial for the production of silicates and silica.

D. RHA in cement and construction industriesThe increasing need for stronger and durable building

materials has been to some extent fulfilled by a newconcept i.e, blended cement. Blending of reactive rice husk ash in cement has become a common recommendationalmost in all the international building codes. Extensiveresearch has been carried out on application of RHA asmineral additive to improve performance of concrete.Reports indicated RHA as a highly reactive pozzolan [28] .RHA is mainly used a replacement of silica fume or as anadmixture in manufacturing of low cost concrete block.

E. Other applicationsBasha, et al [29] examined the possibilities of improving

residual soil properties by mixing RHA and cement insuitable proportions as stabilizing agents. Indian SpaceResearch Organization has successfully developed atechnology for producing high purity silica from RHA thatcan be used in manufacturing of silicon chip in industry ref.Saha, et al [30] studied the possibility of using RHA inwater purification. Attempts have been made to utilizeRHA in vulcanizing rubber [31]. H Ismail et al [32] studieduse of Rice Husk to synthesize High-PerformancePhosphors. Other uses of RH are in control of insect pestsin Stored Food Stuffs, in the water purification, invulcanizing rubber, as flue gas desulphurization absorbents.RHA has been found to be effective as an oil spillabsorbent, and for use in waterproofing chemicals, flameretardants, and as a carrier for pesticides and insecticides. Its absorbent and insulating properties are useful to manyindustrial applications.

V. MARKETS W ITH POTENTIAL I N THE FUTURE

As already described above, RH and its ash are suitablematerials for a wide range of industrial as well as researchapplications. In consideration with its low cost and easy

availability, application of RH and RHA is still limited andthere is tremendous potential of this material for use inupcoming industrial processing and technology. Potentialfuture markets include manufacturing of silicon chip,synthesis of activated carbon, production of light weightconstruction materials and insulation etc. Small marketsexist for RHA in the manufacture of refractory bricks andas oil absorbent whish can be expanded in to a largevolume market.





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Though RHA finds largest and most commercially

viable markets in cement, concrete and steel industries,constraints to the expansion of this market is due to thehealth issues associated with using crystalline ash andhence there is a great potential for use of amorphous RHAin these area.

VI. CONCLUSIONS

Rice husk has been used directly or in the form of asheither as a value added material for manufacturing andsynthesizing new materials or as a low cost substitutematerial for modifying the properties of existing products.Presence of silica is an additional advantage in comparisonto other byproduct materials which makes RH an importantmaterial for a wide range of manufacturing and applicationoriented processes. Easy availability and low price of ricehusk in rice producing countries is an extra benefit towardsthe use of this material. Despite having high potential andsuitability in so many well established uses, use of ricehusk has been limited. In the competitive market, proper utilization of rice husk and its ash will benefit industrialsectors. The use of rice husk as fuel/electricity generationin efficient manner is likely to transform this agriculturalwaste material in to a valuable fuel for industrial sectors. Asystematic approach to this material can give birth to a newindustrial sector of rice husk.

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in India a Literature Review. International Conference on Cleaner Technologies and Environmental Management PEC, Pondicherry,India. January 4-6,2007.

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[3 ] Koteswara Rao. D and Pranav,Stabilization of expansive soil withrice husk ash, lime and gypsum – an experimental study InternationalJournal of Engineering Science and Technology (IJEST)

[4 ] Madhumita Sarangi S. Bhattacharyya and R. C. BeheraRice Effectof temperature on morphology and phase transformations of nanocrystalline silica obtained from rice husk , 82: 5, 377 — 386

[5 ] Agus setyo muntohar ,Utilization of uncontrolled burnt rice husk ashin soil improvement dimensi teknik sipil, vol. 4, no. 2, 100 - 105,september 2002Issn 1410-9530

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[9 ] Assureira Estela, Rice husk – an alternative fuel in Peru.universtaria

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[11 ] Shabbir H. Gheewala, and Suthum Patumsawad EmissionAssessment of Husk Combustion for Power Production WorldAcademy of Science, Engineering and Technology 53 2009.

[12 ] Cristina Dolly Granados, Rosa Venturini. Activated CarbonsObtained from Rice Husk: Influence of Leaching on TexturalParameters Ind. Eng. Chem. Res. 2008, 47, 4754 – 4757

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behaviour and bioactivity of sol – gel synthesized bioglass-ceramicsusing rice husk ash as a silica source Department of CeramicEngineering, National Institute of Technology, Rourkela, Odisha769008, India

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[23 ] The UK Steel Association: Www.Uksteel.org

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[26 ] Rama Rao G.A. Sastry R.K and Rohatgi Bull P.K.,Nature andreactivity of silica available in rice husk and its ashes Mater. Sci.vol12, no.5, dec 1989, pp. 469-479

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http://www.uksteel.org/






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[29 ] Basha E A, Hashim R, Mahmud H B and Muntohar A

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Industrial Application of Rice Husk

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