Abstract

An ever increasing demand of fuels has been a challenge for today's scientific workers. The fossil fuel resources are dwindling day by day. Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources and seems to be a solution for future. Food consumption around the world produces large amounts of waste vegetable oils and fats that, in many world regions, are disposed of in harmful ways. Consequently, this study intended to investigate the feasibility of utilizing this renewable and low cost fuel raw material as a diesel fuel replacement in small scale applications such as in residential heating boilers. Specifically, the study examined the aspects of combustion performance and emissions of biodiesel relative to the baseline diesel fuel in a water-cooled furnace. The combustion efficiency, ?c, and exhaust temperature, Texh, as well as the common pollutants and emissions were tested over a wide range of air/fuel ratio ranging from very lean to very rich. All tests were conducted at two different levels of energy inputs for the fuels. The findings showed that at the tested levels of input energy, biodiesel combustion efficiency was a little inferior to that of diesel fuel due to its higher density and lower heating value while on the other hand, from emissions view points, biodiesel emitted less pollutants at the whole range of A/F ratio considered.

Introduction

The increasing demand of fuels has been a challenge for today's researchers. The fossil fuel resources are decreasing day by day. Iran is one of the top countries that have many natural resources such as crude oil. However, the utilization of these natural resources is getting limited in near future. So it is necessary to utilize renewable resources energy beside of fossil energy. It is believed that, one third of Iran's total land area can be utilized to produce crops if sufficient water is provided. At the moment only 12% of the total land area is utilized for crop growing. It seems that agricultural waste materials can be used for production of biofuels such as bioethanol and biodiesel. The researches indicate that about 17-20% of total produced crops in Iran are available as the agricultural residues which could be converted to biofuels (Najafi et al. 2008). Recently biodiesel has become more attractive because of its environmental benefits and the fact that it is made from renewable resources. The advantages of using biofuels as an alternative fuel are (1) reducing the greenhouse gas emissions, (2) reducing the fossil fuel use, (3)increasing national energy security, (4)increasing rural development, and (5) sustainable fuel supply for the future. Biodiesel, an alternative diesel fuel, is made from renewable biological sources such as vegetable oils and animal fats. This fuel is biodegradable and non-toxic and has low emission profiles as compared to petroleum diesel. Biodiesel is produced through a reaction known as transesterification. In a transesterification or alcoholysis reaction, stoichiometry show that one mole of triglyceride reacts with three moles of alcohol (molar ratio of methanol to vegetable oil of 3:1) to form one mole of glycerol and three moles of the respective fatty acid alkyl esters. Several types of vegetable oils, with a varied composition in fatty acids, can be used for the preparation of biodiesel. While there is much research on the use of biodiesel in diesel engines (Lapuertaet al. 2008) research on the use of biodiesel in boilers are rare. The objective of this study is to check if the overall performance for biodiesel is comparable with that of diesel or not. Besides, measurements of exhaust gases pollutants emitted from the combustion of biodiesel relative to diesel are also examined.

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