1 CHAPTER 1 INTRODUCTION 1.1 GENERAL Industrialization and globalization have increased the automobile population in the recent years. This has led to the rapid depletion of fossil fuel resources, leading to a worldwide fuel crisis. During the 1970 s, the Organization of Petroleum Exports Countries (OPEC) implemented a series of price hikes leading to a demand for fuel. The ever-increasing demand due to an increase in vehicle population increased the cost of fuel. In addition the vehicles have to meet the increasingly stringent emissions norms. These factors have made the researchers to focus their attention on alternative renewable and eco-friendly fuels that would help to reduce the import of crude oil, which will also the reduce the emissions significantly. Diesel engines are widely used in light, medium and heavy duty vehicles, load carriers, tractors, power generation and in heavy machinery. Because of higher fuel efficiency and the ability for lean burn operation, diesel engines are widely used. Further, the lean burn capability helps to lower the carbon-monoxide and hydrocarbon emissions compared to those of gasoline engines. However, the emission of oxides of nitrogen and particulate matter is higher in diesel engines.
2 1.2 BIO-MASS Bio-mass is a renewable energy resource derived from carbonaceous waste. Carbonaceous waste is derived from numerous sources, which include by-products from the timber industry, agricultural crops, raw materials from the forest and also from household wastes. Bio-mass has been a source of fuel used traditionally for many centuries in under-developed countries. In the developed world, the application of bio-mass as an important source for combined heat and power generation is increasing significantly. In addition, bio-mass energy is gaining significance as a source of clean heat for domestic and community applications. In countries like Finland, USA and Sweden, the per capita use of bio-mass energy is higher than that in India, China or Asia. India accounts for one third of the total bio-mass consumption in the world. Bio-mass is used as a fuel in over 90 % of the rural households and about 15 % of the urban households. Indian sugar mills are rapidly turning to bagasse, the leftover of the crushed cane to generate electricity. This is mainly done to clean the environment, cut down power costs and earn additional revenue. According to current estimates, about 3500 MW of power could be generated from bagasse in the existing 430 sugar mills in India. Around 270 MW capacity power plants have already been commissioned and some more are under construction. 1.3 BIO-OIL Bio-oil is formed by a process called pyrolysis wherein plant material (bio-mass), such as sawdust or bagasse from sugar cane, is exposed to 400-500 o C in an oxygen-free environment. It is a dark brown, free flowing
3 liquid fuel with a smoky odour reminiscent of the plant from which it is derived. 1.4 BIO-FUELS Bio-fuel is any fuel that is derived from bio-mass such as waste fruits, vegetables, living organisms or their metabolic byproducts, such as dung from cows. It is a renewable energy source, unlike other natural resources such as petroleum, coal and nuclear fuels. Bio-mass to liquid (BTL) is a multi-step process to produce liquid fuels out of biomass. The two steps are Extracting the liquid from the bio-mass. Condensation to produce synfuels out of gasified biomass. While bio-diesel and bio-ethanol production so far use only the parts of a plant, i.e. oil, sugar or starch, BTL production uses the whole plant which is gasified or converted enzymatically. The result is that for BTL, less land area is required per unit of energy produced compared to bio-diesel or bio-ethanol. Bio-fuels namely ethanol, methanol, vegetable oils and bio-gas are being used as an alternative to fossil fuels partially or fully. 1.4.1 Ethanol Ethanol is the most commonly used bio-fuel worldwide. It can be produced from wheat, corn, sugarcane and many other biomass stocks. The production methods used are fermentation of sugar, distillation and drying. Ethanol can be used in petrol engines as a replacement to gasoline; it can be
4 mixed with gasoline upto 85 %. However, cars would need to have their engines modified. 1.4.2 Methanol Methanol, which is currently produced from natural gas, can also be produced from biomass, although this is not economically viable at present. Methanol can be considered as a prime alternative to diesel fuel. There are a few techniques by which methanol can partially or completely replace diesel fuel. Methanol is also called as oxygenated fuel, because it contains oxygen structurally. 1.4.3 Bio-Diesel Bio-diesel the derivatives of vegetable oil is the most common biofuel used in Europe. The main drawbacks of vegetable oil are high viscosity and low volatility, which cause poor combustion in diesel engine. Hence vegetable oils are transesterified to reduce the viscosity. Transesterification is the process of removing the glycerides and combining oil esters of vegetable oil with alcohol. This process brings the viscosity of the ester equal to that of diesel and improves the combustion. It can be produced from any oil or fat using the transesterification process to get a liquid similar to mineral diesel. It can be mixed with mineral diesel and used in a diesel engine. In most European countries, and the USA, 5 % bio-diesel blend is widely used (Rickeard and Thompson 1993). 1.4.4 Bio-Gas Bio-gas is produced by a process of anaerobic digestion of organic material by anaerobes. It can be produced either from bio-degradable waste
5 materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields. The solid byproduct, digestate, can also be used as a bio-fuel. Bio-gas contains methane which can be recovered in industrial anaerobic digesters and mechanical biological treatment systems. Landfill gas is a less clean form of bio-gas which is produced in landfills through naturally occurring anaerobic digestion. If it escapes into the atmosphere it is a potent greenhouse gas. 1.5 ORANGE SKIN AS BIOMASS Citrus fruit has been produced in the world continuously during the last decades of the 20 th century. The total annual citrus production from 140 countries was over 166 million tonnes during the period 2000-2004. 30-35 % of peels are obtained from the total citrus fruits were available in the year 2004. Most citrus fruits are grown in the Northern Hemisphere, accounting for around 70 % of the total citrus production. The production of oranges was half the total production of citrus fruits in the world in the year 2004 (Mishra et al 2005 and Wolford et al 1971). The world citrus fruit production and geographical distribution of fresh citrus fruit production are given in Appendix 1. Orange skin, which is a bio-waste, is available in large quantity from fruit shops, restaurants and hotels. It can be used as a biomass derived fuel which will also solve the problem of its disposal. Shankpal and Lakshminarayan (1998) concluded that a considerable amount of groundnut husk, coconut shell, and coffee husk are available as ingredients for bio-mass. Just as coal is pulverized, these husks can be pulverized and mixed with either fuel oil, water or methanol to form a slurry. The slurry can be filtered in the
6 form of a solution and it can be used as an alternative fuel in compression ignition engines (Udayakumar and Venkatachalapathy 2000). Similarly, orange skin powder mixed with diesel in the form of a slurry or in the form of a solution can be used as an alternative fuel to diesel. 1.6 ORANGE OIL AS BIO-FUEL Orange oil can be extracted from the peel of orange. The main ingredient of orange oil is d-limonene (C 10 H 16 ). When citrus fruits are juiced, the oil is pressed out of the rind. This oil is separated from the juice, and distilled to recover certain flavour and fragrance compounds. The bulk of the oil is left behind and collected; which is a food grade d- Limonene. After the juicing process, the peels are conveyed to a steam extractor which extracts more oil from the peel. When the steam is condensed, a layer of oil floats on the surface of the condensed water; which is a technical grade d-limonene. India has a huge potential for producing approximately 27600 tonnes per annum (based on 0.6 % recovery of oil from 46 lakhs ton fruits by cold press process) of oil from the orange fruits (Mishra et al 2005). At present, the production of orange oil is very limited, to meet the needs of the food (flavours) and soft drink, perfumes and chemicals industries, hence the cost is high. However, the price of orange oil can be brought down in future by increasing the cultivation of oranges. The physical properties of orange oil are similar to gasoline in nature and they are miscible with gasoline without any phase separation. They can be used in the form of a blend with gasoline in spark ignition engines with minor engine modifications. Orange oil can also be used in compression ignition engines in the dual fuel mode. The fuel economics of orange oil calculated and compared with diesel fuel are given in Appendix 2.
7 1.7 PRESENT WORK In the present work the following techniques were adopted to use orange skin powder and orange oil in a diesel engine: i) Orange skin powder diesel solution (OSPDS) in different percentages. ii) Optimum OSPDS at different nozzle opening pressures. iii) Neat orange oil blended with diesel fuel. iv) Neat orange oil with DEE as an ignition improver. One of the major advantages of the present work is that, total replacement of diesel fuel with 100 % orange oil is possible, which is very essential especially in the transportation sector. The objectives of the present work are: 1. To study the performance, emission and combustion characteristics of orange skin powder diesel solution in a diesel engine. 2. To study the effect of nozzle opening pressure on the performance, emission and combustion characteristics of orange skin powder diesel solution in a diesel engine. 3. To study the performance, emission and combustion characteristics of neat orange oil and orange oil-diesel fuel (DF) blend in a diesel engine. 4. To study the effect of diethyl ether on orange oil combustion.
8 1.8 ORGANISATION OF THE THESIS Chapter 1 gives the introduction to various Bio-related fuels with a focus on orange skin powder as biomass and orange oil as a bio-fuel in diesel engines. Chapter 2 presents the previous experimental work reported on biomass fuel in internal combustion engine operation. Chapter 3 discusses the objectives and methodology of the present work and the different techniques adopted such as operation with orange skin powder diesel solution, the effect of nozzle opening pressure, neat orange oil, its blends and diethyl ether as a fumigated fuel to study the performance, emissions and combustion characteristics. The details of the experimental setup and various instruments like pressure sensor, crankangle encoder and five gas analyzers used, are also discussed. Chapter 4 presents the results and discussion of all the techniques adopted in the present work. The parameters discussed include, brake thermal efficiency, unburnt hydrocarbon, carbon monoxide, oxides of nitrogen, smoke and exhaust gas temperature. In addition, the results of combustion parameters including firing pressure, heat release rate, maximum rate of pressure rise and peak heat release rate are also discussed. Chapter 5 presents the conclusions based on the experimental studies, namely OSPDS as fuel, optimum OSPDS at different nozzle opening pressures, blending of orange oil with diesel fuel and neat orange oil with DEE as an ignition improver.