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Show 1.3.2 INTRODUCTION Because of the abundance of their feedstock, synthetic fuels manufactured from coal are recognized as the potential substitutes for petroleum derived fuels [1]. As the physical and chemical properties of synthetic fuels depend on the nature and source of the raw material and the conditions of the process employed in their manufacture, their properties span a wide spectrum. Furthermore, because of the inherent differences in the chemical structure of coals and petroleum crude, the combustion properties of coal-derived oils are markedly different from their petroleum-derived counterparts, unless expensive refining processes are employed to upgrade them. Some large-scale combustor studies [2,3] and bench-scale laboratory studies [4,5,6] have identified the problems that need to be resolved before synthetic liquids can be commercially used as environmentally acceptable fuels. The emissions of large amounts of nitrogen oxides, carbon monoxide, and particulate matter are considered as serious factors. A method that has received a great deal of attention in the last decade with regard to the modification of the combustion characteristics of heavy petroleum fuels is their emulsification with water. Some of the studies on the combustion of emulsified fuels are presented in [7-13]. In general, the results of these studies indicate that emulsification of petroleum fuels with water decreases particulates, but its effects on the emissions of NO , CO, and unburnt hydrocarbons are complex functions of the operating conditions of the burner. Since the chemical structure of coal-derived synthetic fuels is different from that of petroleum fuels, * The numbers in brackets indicate the references listed at the end. |
