Chapter 3

FUEL DEVELOPMENT AND CHARACTERIZATION

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Chapter 3 FUEL DEVELOPMENT AND CHARACTERIZATION

3.1 Introduction

It is the primary and most important part of any experimental activity involving engine

research. A slightly change in composition or quantity of any specific fuel present or both in

the test fuel affects directly the performance and emission characteristic of the test engine.

Therefore, to obtain the true nature of research, the mechanism of development and

characterization of fuel has to be studied in depth and also the experiment has to be carried

both precisely and judiciously. The economic growth of our country depends upon self

reliance in energy. It is highly essential to search for alternative sources of energy, which are

renewable, safe and non-polluting. Alternative fuel selection for the experiment depends upon

its availability and suitable fuel properties. Bio-origin liquid fuels because of its

environmental compatibility have been selected to use as pilot fuel in dual fuel engine.

Vegetable oils or blends with diesel and its biodiesel can be directly used in diesel engines as

their cetane number and calorific value are closer to diesel. Similarly, the producer gas

because of its non fossil and renewable origin is being selected to use as primary fuel in dual

fuel engine. The producer gas mainly generated from variety of biomass sources. These

biomass sources are woody based obtained from different fire woods like Babul, Acacia, and

eucaly ptus and agricultural and forest waste based (coir-pith, rice husk, saw dust, coconut

shell, ground nut husk and cereal straw etc).

3.2 Karanja (Pongamia pinnata) oil as a fuel for diesel engine

Karanja is a non-edible vegetable oil which is available plentily in northern and eastern states

of India. It is a medium sized tree, yielding fruits after 4-6 years. Its production rate in India is

135,000 metric tons per year. Seeds are light brown coloured and contain 30-40% oil. This

oil contains high amount of triglyceride and has a bitter taste and odour due to the presence of

falconoid composition i.e. pongamiin and karanjin. Due to this bitter in taste, it is not

considered for edible purpose. It is extensively used as a lubricant, medicine and pesticide.

The presence of oxygen bonding in this oil reduces its calorific value as compared to diesel. It

has been tested as a fuel in diesel engine and shows good thermal efficiency [25]. The

constituents of this oil are 27.5% fatty oil, 19% moisture, 17.4% protein and 6.6% starch [54].

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3.3 Extraction of Karanja oil

The oil seeds were mechanically processed using expeller as shown in Figure 3.1 to produce

vegetable oil. The raw vegetable oil was then filtered using oil filter as shown in Figure 3.2.

Figure 3.1 Photograph of mechanical expeller

Figure 3.2 Photograph of oil filter

3.4 Development of Karanja bio-diesel as a fuel for diesel engine

Firstly, the crude Karanja oil was collected from the crusher mill, which is a clear, viscous and

dark brown in colour. Then it was filter with a nylon mesh cloth filter. After filtration, the

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phosphorus in the crude oil was removed by a chemical process called degumming. In this

process the oil was treated with 1% v/v phosphoric acid. After degumming, The Karanja oil is

processed for biodiesel production by transesterification method. The first step of biodiesel

production i.e. esterification of crude oil, in which degummed Karanja oil was mixed with

22% volume/volume (v/v) ratio methanol and1% v/v ratio sulphuric acid. The mixture was

then heated in a constant temperature bath for one hour with continuous stirring at 65 °C. This

esterified mixture was then transesterified. In this process, acid esterified Karanja oil was

taken in transestrification unit in which a reagent mixture is mixed with this esterified oil. A

reagent mixture was prepared with anhydrous methanol (22% v/v) and base catalyst (0.5% v/v

ratio) of potassium hydroxide (KOH). The total mixture was then continuously stirred at a

constant speed below a temperature of 65 °C (i.e. the boiling point of methanol) for about 2.0

hours. Then the stirring and heating was stopped and the mixture was allowed to settle down

for about 24 hours. After settling, glycerol which is dark in colour was obtained in the lower

layer and separated through separating valve. The upper layer which is Karanja methyl ester

was collected separately. Then water washing of methyl ester was performed 2-3 times to

remove extra esters and KOH if any. It was then heated above 65 °C to remove additional

methanol to obtained pure Karanja bio-diesel. The photographs of different stages of bio-

diesel production are shown in Figure 3.3(a-f).

(a) Crude Karanja oil (b) Esterification processes

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(c) Transetrification processes (d) Separation processes

(e) Heating after water washing (f) Bio-diesel

Figure 3.3(a-f) Stages of bio-diesel production

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3.5 Blend oils preparation method and Property Analysis of Test fuels

In the present work, the blends used are K10, K20, B10 and B20. The blend K10 is prepared by

mixing 10% Karanja oil with 90% diesel by weight basis followed by the preparation of other

blends.

Firstly, the sample of various concentrations of this oil and diesel are weighed and taken in a

container. The mixture formed is stirred for one hour by a stirring unit. After preparation of

the above blends, some of the important properties of the test fuels are carried out before use

in engine. Fuel properties like density, kinematic viscosity, acid value, free fatty acid (FFA),

flash point, fire point, cetane number and calorific value etc are calculated using various

ASTM methods and instruments. The various ASTM methods and instruments used for

measurement of fuel properties are given in Table 3.1.

Table 3.1 Various ASTM methods and instruments used for measurement of fuel properties

Properties ASTM Methods

Instruments

Density at 25 °C (kg/m3) D 1298 Hydrometer

Kinematic viscosity at 40 oC (cSt.) D 445 Kinematic Viscometer

Calorific value (MJ/kg) D 240 Bomb Calorimeter

Cetane number D 613 Ignition Quality Tester

Flash point (°C) D 93 Pensky-Martens closed cup tester

Fire point (°C) D 93 Pensky-Martens closed cup tester 3.6 Physico-chemical properties of Karanja oil and its bio-diesel

From various literatures review, it is found that vegetable oil blend with diesel fuel would

bring the viscosity to satisfy the engine specification range. Therefore, by blending the neat

Karanja oil with diesel oil in varying proportion, reduce its viscosity close to that of

conventional diesel. Similarly, usage of 100% biodiesel in engine is not cost effective and also

enhances the NOx emission. Hence to avoid these problems, blending of bio-diesel is needed.

The physical and chemical properties of all the test fuels are tested at the Renewable Energy

laboratory of ‘SOA’, University, Bhubaneswar, India. The photographs of various samples of

test fuels are shown in Figure 3.4(a-f).

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(a) Sample of Karanja oil. (b) Sample of Diesel oil.

(c) Sample of blend K10. (d) Sample of blend B10

(e) Sample of blend K20. (f) Sample of blend B20.

Figure 3.4(a-f) Photograph of various samples of test fuels.

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3.6.1 Density

Density is the mass per unit volume. The weight of a fixed volume of fuel was measured

using a precision balance to measure the density. The measurements are made at 25°C

temperatures as specified in the ASTM D1298. The density of different fuel blends with

diesel, bio-diesel and vegetable oil are measured and then compared with that of diesel fuel.

The photograph of density measuring instrument is shown in Figure 3.5

Figure 3.5 Density bath with hydrometer apparatus

3.6.2 Viscosity

Viscosity is the important property of a fluid which resists the fluid motion when it is

subjected to flow due to internal resistance. Viscosity is a measure of internal resistance force.

The viscosity of vegetable oil affects its atomization and fuel delivery rates. The reason being

if its value is too low and too high, then its atomization, mixing with air in combustion

chamber gets affected. Viscosity studies are conducted for different fuel blends of diesel, bio-

diesel and vegetable oil. Absolute viscosity sometimes called dynamic or simple viscosity is

the product of fluid density and kinematic viscosity. Kinematic viscosity of liquid fuel

samples are measured using the Viscometer at 40 °C as per specification given in ASTM

D445. The photograph of measuring unit is shown in Figure 3.6.

Density bath with Hydrometer

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Figure 3.6 Kinematic viscometer bath apparatus

3.3.3 Flash and Fire point

Flash point is the minimum temperature at which oil gives so much of vapor, which when

mixed with air forms combustible mixtures and gives a momentary flash on application of a

small pilot flame. The flash and fire point of the fuel blends were measured as per standard of

ASTM D93. The sample is heated in a test cup at a slow and constant rate of stirring. A small

pilot flame is directed into the cup at the regular intervals with simultaneous interruption of

stirring. Fire point is an extension of flash point in a way that it reflects the conditions at

which vapor burn continuously for at least 5 seconds. Fire point is generally higher than the

flash point. A Pensky-Martens apparatus is used in the study for determination of flash point

as well as fire point as shown in Figure 3.7.

Kinematic Viscometer

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Figure 3.7 Pensky- Martens flash point apparatus

3.6.4 Calorific value

The calorific value is defined in terms of the number of heat units liberated in kJ/kg. All fuels

containing mainly hydrogen, carbon, sulphur and other oxidizable element along with

moisture. The moisture in the available form will combine with oxygen and form steam

during the process of combustion. If the products of combustion are cooled to its initial

temperature, the steam formed as a result will condense and thus maximum heat is extracted.

This heat value is called the higher calorific value. The calorific value of the fuel is

determined with the help of Isothermal Bomb Calorimeter shown in Figure 3.8 as per the

specification ASTM D240. The combustion of fuel takes place at a constant volume in a

totally enclosed vessel in the presence of oxygen. The sample of fuel is ignited electrically.

The water equivalent of bomb calorimeter is determined by burning a known quantity of

benzoic acid and heat liberated is absorbed by a known mass of water. Then the fuel samples

are burnt in bomb calorimeter and the calorific value of all samples are calculated. The heat of

combustion of the fuel samples is calculated with the help of equation 3.1 given below:

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Hc = (Wc. ∆T) / Ms (3.1)

Hc = Heat of combustion of the fuel sample in kJ/kg

Wc = Water Equivalent of the calorimeter assembly in kJ/ °C

∆T = Rise in temperature in °C

Ms = Mass of sample burnt in kg

Figure 3.8 Bomb calorimeter

3.6.5 Cloud and Pour point

The cloud point is the temperature at which wax formation starts when the fuel is cooled. This

value is higher than conventional diesel. The pour point is the lowest temperature above

which the fuel can flow. It is measured by cloud point & pour point apparatus as shown in

Figure 3.9. Its temperature range varies from ambient to - 40°C.

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Figure 3.9 Cloud point & pour point apparatus

3.7 RESULT & DISCUSSION

3.7.1 Performance of Karanja oil and its blends as fuel for diesel engine

The properties like kinetic viscosity, density, calorific value, flash point, fire point, cloud

point and pour point of Karanja oil, diesel and their blends are tested as per the ASTM

standards and results are shown in Table 3.2. Kinematic viscosity, density, flash point, fire

point, cloud point and pour point are found to be higher in neat Karanja oil and its blends. The

flash point and fire point of Karanja oil are found 219 ºC and 235 ºC respectively which is

higher than diesel. The high flash point of oil is a beneficial safety feature as the fuel can be

safely stored and transported at the room temperature. The calorific value of Karanja oil is

found to be 34700 kJ/kg and for blended oil it increases with the addition of the oil to pure

diesel fuel. Kinematic viscosity of Karanja oil is found 28.69 cSt at 40 ºC. The relatively high

viscosities of vegetable oils cause problems like coking of injectors, oil ring sticking and

thickening of lubricating oil. However, the viscosity of blended fuels is close to diesel. Due to

this reason this blended fuels are suitable for diesel engine application. This high viscosity

results from the higher molar masses of the oils and the presence of unsaturated fatty acids.

Diesel has more number of double bonds than vegetable oils.

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Table 3.2 Properties of diesel, Karanja oil & its blends (K10, K20)

Properties Diesel Karanja oil K10 K20

Density at 25 °C(Kg/m3) 825 925 832 837

Kinematic viscosity at 40 °C (cSt.) 2.76 28.69 3.7 4.36

Calorific value (MJ/kg) 42.5 34.7 41.72 40.91

Flash point (°C) 73 219 89 109

Fire point (°C) 103 235 119 135

Cloud point (°C) -12 3.5 - 4 -6

Pour point (°C) -16 -3 -10 -14

3.7.2 Performance of Karanja bio-diesel and its blends as fuel for diesel engine

The properties like kinetic viscosity, density, calorific value, flash point and fire point of

Karanja bio-diesel, diesel and their blends are analyzed as per the ASTM standard and results

are shown in Table 3.3. Kinematic viscosity, density, flash point and fire point are found to be

higher values in Karanja bio-diesel and its blends. The flash point and fire point of Karanja

bio-diesel are found 161 ºC and 189 ºC respectively which are higher than diesel. The high

flash point of oil is a beneficial safety feature as the fuel can be safely stored and transported

at the room temperature. The calorific value of Karanja bio-diesel is found to be 37500 kJ/kg

and for blended oil it increases with the addition of the oil to pure diesel fuel. Kinematic

viscosity of Karanja bio-diesel, B10 and B20 are found to be 5.12 cSt, 2.92 cSt and 3.88 cSt

respectively at 40 ºC which are very close to diesel. Hence due to this comparable viscosity of

bio-diesel and its blends with diesel, these are suitable for diesel engine application without

any engine modification.

Table 3.3 Properties of Diesel, Karanja bio-diesel and its blends (B10, B20)

Properties Diesel Karanja bio-diesel B10 B20

Density at 25 °C (kg/m3) 825 885 827 831

Kinematic viscosity at 40 °C (cSt.) 2.76 5.12 2.92 3.88

Calorific value (MJ/kg) 42.5 37.5 42 41.5

Flash point (°C) 73 161 79 81

Fire point (°C) 103 189 102 109

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3.8 Babul wood (biomass feed stock) as producer gas resource

Woody biomass is a well known fuel in India and has been traditionally used for generation of

heat due to its higher calorific value and low ash content. In the present experiment for

gasifier feedstock, small pieces of Babul wood with an approximate size of 25 mm length and

25 mm diameter is generated in author’s laboratory and suitably used. The photograph of the

Babul wood chips is shown Figure 3.10. Babul wood (Prosopis juliflora) is abundantly

available in the northern part of India as well as in Odisha. It is a medium sized tree, yielding

fruits after 5-7 years. It has higher calorific value and density as compared to other available

timber woods in India. During the process of gasification, Babul wood does not produce any

tar. Production of tar during gasification may cause the problem of gasifier. Hence, producer

gas generated from Babul wood is of better quality and higher calorific value with a

reasonable moisture content of less than 20%. The ultimate and proximate analysis of Babul

wood under wet basis (wb) and dry basis (db) is shown in Table 3.4

Figure 3.10 Photograph of Babul wood chips

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Table 3.4 Ultimate and proximate analysis of Babul wood [101]

Sl. No. Characteristics Corresponding values 01 Size (mm) 25x25 02 Bulk density (kg/m3) 395 03 Moisture content (%wb) 10.2 04 Volatile mater (%db) 83.42 05 Ash content (%db) 1.05 06 Fixed carbon (%db) 15.53 07 Calorific values (kJ kg-1) 16304

3.8.1 Generation of producer gas using downdraft gasifier

Gasification is the thermo-chemical conversion of solid biomass to gaseous fuel in a gasifier

by pyrolysis process at a higher temperature. Producer gas is generated through gasification

process in a downdraft type biomass gasifier. The downdraft gasifier has been selected for the

present research work because of its low tar concentration in the product. Since the produced

gas is used as fuel in a dual fuel engine whose performance is greatly affected by tar

concentration in producer gas. The downdraft gasifier used in this research has been procured

from Ankur Scientific Energy Technology Pvt. Ltd., Baroda. The biomass gasifier consists of

a reactor, gas cooling unit, two sets of gas filters. The detailed specification of the downdraft

woody biomass gasifier is given in Table 3.5. The photograph of the biomass gasifier and

cooling unit are shown in Figure 3.11(a) and (b) respectively.

Table 3.5 Specification of the downdraft woody biomass gasifier.

Model WBG-10 in scrubbed, clean gas mode Rated gas flow 25 Nm3/hr Gasifier type Downdraft Average gas calorific value 1000 Kcal/Nm3 Gasification temperature 1050-1100 °C Fuel storage capacity 100 kg Ash removal Manually, Dry ash discharge Start up Through scrubber pump Permissible moisture Less than 20% (wet basis) Rated hourly consumption 8-9 kg Rated hourly ash discharge 5-6 %

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(a) Photograph of biomass gasifier. (b) Photograph of gas cooling unit.

Figure 3.11(a-b) Photograph of gasification unit

The biomass is loaded from the top of the gasifier and ash is removed after a regular interval.

The partial combustion of biomass in the gasifier reactor is converted in to high temperature

producer gas, which enter in to the gas cooler. The temperature of combustion gas before

enter in to the cooling system is measured by the help of thermocouple and found to be 458

°C and after cooling and cleaning, it is found to be about 40 °C. During trial run, the

indicative pressure drop in the nozzle at rated flow is found to be 20 mm of water column and

indicative pressure drop in the gasifier is found to be 40-45 mm of water column at rated gas

flow rate. The moisture, tar and dust particle is removed by passing through two set of filters.

Some properties of producer gas are collected from published literature and shown in Table

3.6. The compositions of producer gas are measured by the help of the gas chromatograph as

shown Figure 3.12.

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Table 3.6 Properties of producer gas

Sl. No. Properties Reference Corresponding values 1 Density [89] 1.287 kg/m3 2 Calorific value 3771 kJ/kg 3 Octane number 100 �105 4 Laminar burning velocity [89] 0.5 ± 0.05 m/s 5 Stoichiometric air/fuel ratio [89] 1.12:1 6 Energy density [89] 1.26 MJ/m3

7 Adiabatic flame temperature [89] 1546 ± 25K

Figure 3.12 Photograph of gas Chromatograph

3.8.2 Performance of producer gas as fuel for diesel engine

The typical compositions of producer gas generated from Babul wood are measured in

Author’s laboratory by the help of a microprocessor based gas chromatograph (model No

2010) supplied by Chromatography and instruments company Pvt. Ltd. Baroda. The

compositions of producer gas are shown in Table 3.7. The calorific value of producer gas is

found to be 3771 kJ/kg. The higher percentage of nitrogen in composition of producer gas

acts as a knock suppressor [92].

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Table 3.7 Composition of producer gas

Carbon monoxide 19±3%

Carbon dioxide 10±3%

Nitrogen 50%

Hydrogen 18±2%

Methane Up to 3%

3.9 Conclusion

Experiments were conducted as per ASTM specified standards and the different physico-

chemical properties of liquid fuels such as viscosity, density, calorific value, flash point, fire

point, cloud point, pour point of diesel, Karanja oil and its blends, Karanja biodiesel and its

blends were measured. Similarly the compositions and calorific value of producer gas were

obtained using gas chromatograph. Because of availability of limited experimental facility the

other properties of producer gas have been collected from the published article and shown in

table 3.6. From the above fuel properties it has observed that the fuel samples are suitable as a

diesel substitute and selected for engine testing. The fuel samples of fossil diesel, 10%

Karanja oil blend, 20% Karanja oil blend, 10% Karanja bio-diesel blend and 20% Karanja

bio-diesel blend were prepared for the test engine.

Chapter Summary

This chapter describes the selection of materials and its development as test fuels and the

methods employed to carry out the investigations. It presents the details of the physical,

chemical and thermal characterization of the test fuels by using the standard ASTM methods.