OCR Text |
Show operating at 75 percent of its full capacity. Additional tests are being performed to acquire information on carbon burnout and boiler performance at different firing rates, combustion air temperatures, and flue gas oxygen levels. Boiler Performance The preliminary results of the CWM combustion tests in the 100-hp boiler indicated that at full load, the carbon conversion efficiencies ranged from 81 to 85 percent, and the boiler efficiencies ranged from 66 to 69 percent (in comparison with 82.4 percent using No. 6 fuel oil). Both carbon conversion and boiler efficiencies were higher at a higher combustion air temperature and/or with a higher flue gas oxygen level. Of the total thermal input, 5.3 to 5.9 percent was consumed in evaporating the water in the CWM. At half load, the carbon conversion efficiency was about 5 percent higher than that at full load; the boiler efficiency was about 2 percent higher than at full load. At a 75 percent firing rate and with the maximum available combustion air (approximately 1 percent flue gas oxygen) at 510 F, the 700-hp boiler operated with 95 and 78 percent carbon conversion and boiler efficiencies, respectively. The heat loss due to evaporation of the water in the CWM was about 5.7 percent of the total thermal input. Pollutant Emissions Preliminary data from the CWM tests in the 100-hp boiler indicate that at full load, the NOx emissions ranged from 576 to 712 ppm, or 0.62 to 0.85 lb/MBtu, as compared to 235 ppm, or 0.294 lb/MBtu, when burning No. 6 oil at a flue gas oxygen level of 2.5 percent. The SO2 emissions corresponded to the sulfur content in the CWM. The uncontrolled fly ash emissions ranged from 15.7 to 20.0 lb/MBtu; the carbon content of the fly ash ranged from 48 to 51 percent. In the CWM tests conducted in the 14-16 |