OCR Text |
Show The results show that N0X decreased slowly with a decreasing NH3 concentration at high fuel NH3 levels and rapidly at low fuel NH3 levels. An 80% reduction in the fuel NH3 concentration (from 0.5 to 0.1%) reduced N0X by 40%. The S02 emissions decreased slowly with a decreasing NH3 concentration. The CO emissions remained independent of fuel NH3. NH3 Conversion to N0r Figure 10 shows the effects of excess air and of NH3 concentration in fuel on percent NH3 converted to N0X. The NH3 conversion to N0X increased with excess air in the range tested, as would be expected because of the increased 02 availability. However, at the same excess air level, NH3 conversion decreased rapidly with an increasing NH3 concentration in the fuel. At an NH3 concentration of 0.1% in the fuel, about 40% NH3 was converted to N0X, but with 0.5% only 13% was converted. N0y Emissions per 106 Btu Fuel Input Figure 11 shows the effects of excess air and fuel NH3 concentration on N0X emissions per 106 Btu fuel input. Fuel input excludes the sensible heats in the combustion air and in the fuel. As shown in the figure, to operate the combustor below 0.7 lb/106 Btu fuel input, either the excess air should be kept below about 7% for the average gas containing 0.56% NH3 or the NH3 concentration in the average gas should be less than 0.1% at an excess air level of 15%. With 7% excess air, however, the CO concentration in the flue gases was about 300 ppra. Effect of H2S Concentration in Fuel on Emissions Figure 12 shows the effect of H2S concentration in fuel on emissions. As in the case of the NH3 tests, the loss in fuel heating value at a reduced H2S concentration was made up by adding natural gas. As shown in the figure, the S02 concentration in the flue products increased with an increasing H2S concentration in the fuel, as would be expected but the NO and CO emissions were relatively independent of fuel H2S concentration. Effects of Turndown and Fuel Moisture Content on Flame Stability The average heating value gas flame was stable down to a 4.3:1 turndown ratio with 8.5% moisture in the fuel. The front wall temperature increased 5.7.16. INSTITUTE OF GAS TECHNOLOGY |