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Show INTRODUCTION Coal conversion technology, with its manifold process variations, can produce substitute liquid fuels for petroleum-derived ones. One common problem associated with coal liquefaction methods is that during them nitrogen in the parent feedstock coal is usually concentrated into the coal-derived liquid. Fuel-bound nitrogen concentrations in coal liquids can be from a factor of 3 to an order-of-magnitude higher than those of refined petroleum crudes. The coal liquids, therefore, have the potential for producing increased nitrogen oxides (NO ) emissions during combustion unless abatement procedures are taken. The challenge of complying with NO air-pollution regulations when burning these nitrogen-rich fuels has been the focus of considerable research (1-24), which is summarized in Table 1. Nitrogen oxides are primarily formed during the combustion process by three basic mechanisms: (a) the thermal fixation of atmospheric nitrogen at elevated temperatures within the flame zone, (b) the oxidation of organically-bound nitrogen and (c) the attack on the strong N bond by hydrocarbon fragments in the reaction zone. The last, proposed by Fenimore (26) and called prompt NO, has only just recently been accepted (39). NO formation by thermal fixation, normally referred to as thermal NO , is essentially dependent upon the flame temperature and the concentration of atmospheric oxygen and nitrogen within the flame zone. The conversion of organically-bound nitrogen to NO , however, is a complex function of fuel properties and burner design and operating variables. Several studies have been carried out on rich laminar premixed and diffusion flames (1,3,26,27,32-34) to investigate some of the factors affecting NO emission and control during combustion. Turbulent diffusion flames are more complicated, however, and have not been studied as extensively (30,35,36). /tf-2- |