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Show Flue gas temperatures were measured with a suction pyrometer near the flue opening 355 cm (140 in.) from the burner. The temperature of the flue gas was slightly higher when larger coal particles were burned, but these temperatures could also be affected by the firing rates and wall losses. Furnace temperatures were measured with a ceramic shielded type "R" thermocouple located in the roof and in the sidewall opposite to the removable doors. The positions of the thermocouples along the furnace axis are 120, 220, and 310 cm (47, 86, and 121 in.) from the burner and denoted as front, middle, and rear in Table 3. The flue gas temperature was higher than the rear wall temperature, which is to be expected. Flue gas analyses for the trials are listed in Table 4 and show no great variation from one trial to the next. Oxygen and carbon dioxide levels indicate an amount of excess air close to 20% in all trials. Nitrogen oxides and carbon monoxides concentrations showed no trend with the coal particle size. The conversion of fuel nitrogen to nitrogen oxides was calculated by dividing the fuel nitrogen oxides by the maximum fuel nitrogen oxides that would occur assuming that all of the nitrogen in the coal was converted to nitrogen oxides in the flue gas. Flame Size and Shape The carbon monoxide concentration was measured to determine the size and shape of the flame for Trials 1, 2, and 3. The furnace was operated with a slightly positive interior pressure to halt the flow of atmospheric air into the furnace. The flame shape boundaries were determined where the concentration of carbon monoxide indicated 99% of the fuel consumed. Figure 14 shows the flame shape for the finest coal (Trial 1) with a short regular shape and length of 50 cm (20 in.). In Trial 5, the same coal (6.6 urn) was fired at a higher firing rate (700 kW, 2.4 X 106 Btu/h) and the flame measured 60 cm (24 in.) long. The flame in Trial 2 (Figure 15) was regularly shaped, 90 cm (35 in.) long. Trial 3 used the coarsest coal and produced a slightly asymmetrical flame shape (Figure 16), 140 cm (55 in.) long. Some slag 25 |