Utilizing Vegetable Oils for Biofuel Generation

Utilizing Vegetable Oils for Biofuel Generation

By

Alexandra Davis

TABLE OF CONTENTS

CHAPTER

TITLE PAGE

  Important properties of fuels used in compression ignition engines as per ASTM standards

First generation biodiesel 24

Second generation biofuels 26

India 2030 automotive energy scenario 26

References 28

LITERATURE REVIEW AND SCOPE OF THE PRESENT

WORK

Biodiesel production methods 32

Transesterification  process 34

Homogenous catalyzed transesterification processes 36

Heterogeneous catalyzed transesterification processes 42

Enzyme catalyzed transesterification processes 58

  Non catalytic biodiesel production-Supercritical transesterification process

  Biodiesel production by two-step process – Esterification followed by transesterification

2.3  Outcome of the literature review 68

2.4  Merits and demerits of the existing  biodiesel  production  process

2.5  Need for a new process 74

2.6  Scope of the present work- 74

References 76

3  MATERIALS AND EXPERIMENTAL METHODS

3.1  Feedstock procurement for biodiesel production 88

3.2  Chemicals procured for production of biodiesel, analysis of product and feedstock

3.3  Experimental methods 89

3.4  Methodology for determination of biodiesel yield from the production process

3.5  Proposed new method for biodiesel production methods and experimental setup

3.6  Experimental methods for engine performance and emission testing of produced biodiesel

3.7  Engine testing parameters and methods 98

3.8  Experimental procedure 98

3.9  Samples to be tested in engine 98

3.10  Methodology for engine performance studies 99

Methodology for testing the brake thermal efficiency (BTE) of

3.11  

the fuel at specific loads (25, 50, 75 and 100 % load),  for  various blends, biodiesel and diesel.

100

Reference 101

4  A NEW METHOD FOR THE PRODUCING BIODIESEL FROM USED PALM OIL

4.1  Introduction 103

4.2  Palm oil and sunflower oil - the most used vegetable oil for cooking

103

4.3  Types of process used for producing biodiesel from waste vegetable oil

4.4  Production of biodiesel from used vegetable oil using the  existing process

4.5  Production of biodiesel using the proposed new process from used palm oil as feedstock

4.6  Calculation of yield of biodiesel obtained by the new process  rom used palm oil

4.7  Analysis of the palm oil biodiesel produced using the new process

105

105

111

114

116

4.8  Results and discussions 117

4.8.1  Physical  properties  of  the  biodiesel  produced  from  used  palm oil

118

4.8.2 FT-IR spectral studies 119

4.9 Gas chromatography  mass  spectral  studies  of  palm  oil  biodiesel

123

4.10   Conclusion 124

References 126

7.9 Composition of samples to be tested for performance  and  emission characteristics

211

7.10 Results and discussion 213

7.10.1 Engine performance and emission test for used sunflower oil biodiesel and its blends

213

7.11 Palm Oil 222

7.11.1 Engine performance and emission test  for  used  palm  oil biodiesel and its blends

222

7.12 Neem Oil 230

7.12.1 Engine performance and emission  test  for  neem  oil  biodiesel and its blends

230

7.13 Jatropha Oil 238

7.13.1 Engine performance and emission test for jatropha oil biodiesel and its blends

238

7.14

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8

9

Conclusion References

SUMMARY AND CONCLUSION FUTURE SCOPE OF STUDY

247

248

253

260

1  INTRODUCTION

1.1  HISTORY OF DIESEL ENGINES

The first fuel used in a compression ignition engine invented (1890) by Rudolf Diesel was pure vegetable oil. The triglycerides present in the peanut oil were the first biofuel used in a compression ignition engine in the history of mankind. Rudolf diesel set up his first workshop at Paris (1885) to develop a full-fledged compression  ignition engine. He patented [1-4] (1890) many of his work for developing a highly efficient slow speed compression-ignition internal combustion engines. Many of his first attempts were unsuccessful, after many improvement and test he successfully tested the engine (Figure 1.1) on February 17 (1897) working at an efficiency of 26.2% under load, attaining this efficiency was a remarkable achievement at that point of time because the most popularly used steam engines were working at an efficiency of 10 %.

Figure 1.1-Rudalof diesel’s successfully tested diesel engine.

Rudolf diesel tested the engine (1897) with the following specification, Single cylinder, four-stroke, air-cooled, air injection of fuel, having a fuel consumption  of  317g/KWh, with a displacement volume of 19.6L.

1.1.1 Internal combustion engines:

Internal combustion engines are the one, which consists of a fixed cylinder and a moving piston and the oxidation of fuel takes place inside the cylinder of the engine. The combustion products of the fuel which will be in the form of gases mostly carbon dioxide and water having an enormous amount of kinetic energy, part of this energy is used to  push the piston by expansion to the bottom dead centre  (BDC). The piston with the help  of flywheel will move to the top dead centre (TDC) to push the exhaust gases out of the cylinder completing a cycle in a linear fashion. This reciprocating motion of the piston is converted into a circulatory motion with the help of crankshaft. The power from the crankshaft is transferred to the wheels of the vehicles through a gear system in  a  controlled manner which sets the vehicle in motion.

1.2  COMPRESSION IGNITION ENGINES

Major components:  The  major  components  of  a  compression  ignition  engines (Figure 1.2) are

a)  Combustion chamber: This is the chamber where the air is compressed and the combustion of the injected fuel takes place.

b)  Inlet valve: The air to be compressed is admitted through this valve during the suction stroke.

c)  Injector: To inject the fuel into the combustion chamber, which contains the compressed air.

d)  Exhaust valve: The product of combustion is sent out of the combustion chamber through this valve.

e)  Piston: It is the reciprocating part present inside the cylinder of the engine, which converts the expansion of the combusted products of the fuel into thrust forces during the power stroke.

f)  Crankshaft: It is the part which converts the reciprocating motion of the piston into rotatory motion through the connecting rod.

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Figure 1.2-Major components of compression ignition engines.

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1.2.1  Working mechanism:

A single cycle of a compression ignition engine is based on the four steps of operation (Figure 1.3) or strokes namely

1)  Suction stroke.

2)  Compression stroke

3)  Power stroke

4)  Exhaust stroke

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Figure 1.3-Four strokes of operations of compression ignition engine.

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Suction stroke: In the suction stroke, the atmospheric air is sucked into the combustion chamber through the inlet valve when the piston moves from the top dead centre (TDC)  to the bottom dead centre (BDC) and therefore, a definite amount of air which also contains oxygen is present inside the cylinder.

Compression stroke: The definite amount of air that is present inside the combustion chamber is compressed to 1/15th of the volume so that, the temperature and pressure of  the compressed air reach 500oC and 15.2 atm. respectively.

Power stroke: At the end of the compression stroke the fuel diesel is injected into the combustion chamber, where the fuel and the oxygen present in the compressed air get

ignited into gaseous products resulting in the development of high pressure of about 100 atm. and temperature of 1500oC.

Exhaust stroke: In this stroke, the product of combustion mostly carbon dioxide and  water are ejected out of the combustion chamber by the movement of the piston from the bottom dead centre to the top dead centre through the exhaust valve which gets opened during this stroke.

1.3  CLASSIFICATION OF DIESEL ENGINES

Diesel engines are classified high speed, medium speed and low-speed engine based on their rotational speeds (i.e.) the rotation per minute of the crankshaft. If the rotation per minute is more than 1000, it is classified under high-speed diesel engines, these engines are used to power cars, buses, trucks, compressors and small electric generators the maximum output of a high-speed diesel engine is around 5 MW [5]. These engines can run either on diesel or biodiesel.

Engines having a rotation per minute between 300-1000 comes under medium speed diesel engines, these engines are used to run large electrical generators, large compressors and ship propulsion systems using diesel fuel or heavy oil or biodiesel and  the efficiency of such engines could be 47 - 48 % [6].

Slow speed diesel engines are those engines which have rotation per minute of  less than 300, these engines are usually large in size used to power ships and water pumping application.  It is classified into two types based on the number of stokes, such  as two-stroke and four-stroke. The fuels used for these types of engines are primarily  heavy oil or raw vegetable oil and it can have efficiency up to 55% [7].

1.4  PETROLEUM CRUDE OIL –DIESEL

Petroleum is a naturally occurring mineral oil found under the earth crust such as  in sedimentary rocks formed as a result of slow decomposition of the organic matter. The first petrochemical industry [8] started during the 1850’s produced kerosene  for  oil  lamps, artificial asphalt, machine oil and lubricants. Since only a fraction of crude oil  could be converted into kerosene, a lot of unused byproducts such as diesel which is cheaper than vegetable oil, at that point of time attracted the attention of Rudolf diesel to design the compression ignition engine.

The crude oil is a mixture of organic compounds containing hydrogen and carbon; it is separated into various fractions based on the boiling range which also depends on the number of carbon atoms in the chain. The fuel diesel is the fraction that is separated from crude oil at a boiling temperature range of 150-380⁰C [9] containing 16 to 20 carbon atoms.

The most important properties of diesel fuel are

Calorific value.

Cetane rating.

Flash point

Cloud point

Pour point.

Viscosity.

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Calorific value: Calorific value of diesel can be determined by using an oxygen bomb calorimeter. A definite amount of fuel is taken and the heat released from the complete

combustion of the fuel is calculated from the rise in temperature of the calorimeter. The approximate calorific value of diesel fuel is about 45.5 MJ/Kg. [10]

Cetane rating: Cetane rating of the fuel is the rate at which the diesel fuel ignites after injection into the cylinder of the combustion chamber, which is also called an ignition delay. Saturated straight-chain hexadecane is called cetane, which ignites and gets combusted easily on compression without any delay and is given a rating of 100. While alpha-methyl naphthalene, a cyclic aromatic hydrocarbon is assigned to a cetane rating of 0.All the other hydrocarbon within the diesel range are indexed within the 0-100  depending on how well they get ignited under compression. Higher the cetane number lower will be the ignition delay.  Generally, the cetane number should be between 48 to  50 for the smooth operation of the diesel engines, but high-speed diesel engines require diesel fuel with high cetane number.

Flash point: It is the lowest temperature at which the diesel fuel when heated produces enough vapours so that it gives a flash when a flame is introduced into it. It can be measured either using an open cup or a closed cup apparatus, generally, the flash point of diesel fuel is between 53oC and 96oC [11]. The flash point of fuel describes whether the nature of fuel is flammable or combustible. If fuel has a flash point of 37.8oC or below, it  is flammable, if it is above 37.8oC, the fuel is combustible in nature.

Cloud point: Cloud point of diesel is the temperature at which a cloudy or haziness of  the fuel appears. At this temperature, the wax crystals present in the fuel starts to solidify and decreases the flow of the fuel. The cloud point temperature generally ranges from - 28oC to 4oC.

Pour point: Pour point of diesel is the temperature at which the liquid ceases to flow due to the crystallization of the alkyl chain. The pour point of any fuel is  an  important physical property which gives an idea about the fuel that can be used in a particular  climate or country. It generally ranges from -15 to 16oC.

Viscosity: Viscosity of any fluid or fuel is the measure of the resistance to the flow in a given rate. The viscosity of diesel fuel is an important property concerning  the  combustion of fuel in a compression ignition engine because the spray characteristics of the fuel injection can vary much depending on the viscosity of the fuel. The normal viscosity range of diesel fuel is 1.9 to 6.0 mm²/s.

1.5  CHEMISTRY OF VEGETABLE OIL

Rudolf diesel stated that in 1911 "The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in the course of time as important as petroleum and the coal tar products of the present time."

Most of the seed-bearing crops can produce oil when the seeds are removed, dried and compressed mechanically by an expeller. These crops which can produce oil are classified into edible oil and non-edible oil. The edible oils are mass-produced for human consumption and used for frying and other activities in cooking. Widely used cooking  oils are palm oil, sunflower oil, soybean oil, peanut oil, coconut oil, olive oil, mustard oil, cottonseed oil, canola oil, Sesame oil and rapeseed oil. The non-edible oils widely available in India are neem oil, Jatropha oil, pongamia oil, paradise oil and castor oil.

1.5.1  Chemical structure of vegetable oils

All these vegetable oils both edible and non-edible oils are generally called triglycerides which have the same backbone of the glycerol [12] forming esters with the long chain of fatty acid depending upon the vegetable oil. Hence the difference between different vegetable oils is based on the difference in the fatty acid chains.

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Figure 1.4-Structure of triglycerides of vegetable oil.

The major composition of almost all the vegetable oil is triglycerides (Figure 1.4) and the remaining 0-5 % will be made up of some unsaponifiable matters. The  triglycerides present in the oil may also be converted into monoglycerides, diglycerides and free fatty acids (Figure1.5) [13] which depends upon the nature of the vegetable oil,  its mode of extraction and storage conditions.

Figure 1.5-Structure of monoglyceride, diglyceride and free fatty acid.

1.5.2  Types of fatty acids present in vegetable oils

The fatty acids that are present in different vegetable oils are both saturated and unsaturated and are given in the (Table 1.1)

Table 1.1- Different types of free fatty acids.

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1.5.3  STRUCTURE OF FATTY ACIDS PRESENT IN THE VEGETABLE OILS

The fatty acid present in the vegetable oil consists of carbon chain  starting from  six carbons to twenty carbon, containing carbon-carbon single bond for saturated fatty  acid and one or more carbon-carbon double bond for unsaturated fatty acids. The chain

length and the unsaturation of bonds present in the fatty acid play an important role in deciding the properties such as viscosity, density, calorific value, cetane number, cloud point, pour point and