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Show Finally, referring to Figures 4 and 5, it may be observed that even though the West Virginia parent coal fuel mixtures tend to support the existance of an optimum coal particle size, the data of the North Dakota lignite mixtures indicates that fixed carbon in the parent coal overrides the effects of coal size. This is evidenced by the fact that the coal size used in the North Dakota lignite mixtures is 75pm, well above the 15pm or 44pm used in either of the West Virginia fuel mixtures. Visual data observed through the rear viewport in the chamber indicated that the North Dakota lignite flame was the least luminous of all the flames. The flames generated by all other fuel mixtures were highly luminous. With the exception of the lignite flame, the other fuel mixture flames were very similar in luminosity to the No. 2 fuel oil flame. All flames generated were stable, compact and characteristic of a No. 2 fuel oil flame. Even though CO levels approached high values, no visible smoking was observed. The firing rate for all flames was maintained in the range of lxl06kJ (9.1xl05Btu) to 1.5kJ (1.4x10 Btu) per hour. Furnace temperatures were maintained in the range of 760-815°C (1400-1500°F). All mixtures were successfully fired at the 50 percent by weight coal loading. CONCLUSIONS The conclusions of this work are: 1. Fuel mixtures of 50 weight percent coal and No. 2 fuel oil are readily fired in existing combustors originally designed to fire fuel oil or natural gas. Sonic burner systems similar to that used in this study are highly recommended when firing these fuel mixtures. 2. Fixed carbon content of the parent coal used in fuel mixtures containing coal and No. 2 fuel oil is a critical parameter when considering combustion effi( Lency. In this respect, the lignite coal which was studied m this research is highly recommended for use in No. 2 I lie I oil-coa] mixtures as compared to the other high rank coals investigated. 3. Although fixed carbon is the dominant parameter to be considered in mixtures of No. 2 fuel oil and coal, coal particle size is of interest as well. The study showed that as particle 17 |