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Show to state that a high boiling liquid fuel probably will produce higher NO^ emission than low boiling ones. The results of Haebig and co-workers (6) agree with this relationship. They fired coal liquids of differing boiling range in a residential boiler. The distillate fraction (130-364°C), which was obtained from the full range liquid, produced about 40 percent lower NO than the full range liquid. x The distillate coal liquid contained only 60 percent as much nitrogen as in the full range liquid. Half of the nitrogen compounds in the full range liquid boiled at about 350°C,while all the nitrogeneous components of the distillate fuel boiled below 350°C. The data in Figures 7, 8 and 9 show a somewhat dramatic relationship between the capacity of a fuel to produce NO and a primary fuel property, i.e., boiling range. Figure 7 is a plot of all data calculated from references (4-22). Figure 8 represents a plot of averaged data from all the references while Figure 9 shows the same plot for fuels containing same percent fuel bound nitrogen to eliminate the effect of variation in concentration of fuel nitrogen. The data in these figures allow a distinction to be made between volatile and refractory fuel-bound-nitrogen, as has been done for residual oils (2) and coal (11 ). This distinction has permitted past researchers (2,11) to gain a somewhat better understanding of the mechanism and effectiveness of NO control via staged combustion for these fuels. It will now be applied, for the first time, to coal-derived liquid fuels. Data from these figures indicate that conversion efficiency of fuel-bound nitrogen to NO during combustion of coal liquids is a complex relationship with the boiling range. The conversion efficiency exhibits an initial increase at low boiling range, passes through a maximum, and subsequently decreases at the high boiling range. The data obtained by Haebig and co-workers (6) agree with this relationship. They found a conversion efficiency of 52 percent for distillate coal liquids(boiling range 130-364°C) and 32-40 percent for the full range coal /C -19- |