| OCR Text |
Show arrangement. The simulator is constructed from seven, l6-inch-long, 24-inch-diameter, bare water-cooled rings that are joined to simulate a 110-inch-long by 24-inch-diameter corrugated firetube. Each ring is equipped with a rotameter to measure the flow rate of cooling water and a thermocouple to measure its temperature rise. This allows the measurement of the heat flux along the length of the combustor. The large ring around the test burner is the primary air plenum and the two large hoses downstream of the test burner are for the secondary air. Because of the limited amount of internal funding, only proof-of-concept testing is being undertaken. If the results of these tests are encouraging, further development, optimization, and commercialization will be carried out with burnerfboiler manufacturers and with funding support from external sources. Currently, the test burner is undergoing proof-of-concept testing. Preliminary tests with combustion air staging and with high excess air firing have already been carried out, and tests with water inj ection are planned for the near future. The first series of tests on the 200-hp test burner were carried out to investigate the effectiveness of staged air combustion, which had provided ~20 ppm NOx levels on the 40-hp burner. The test configuration used was, however, different (in terms of orifice placement and secondary air injection strategy) from that used with the 40-hp burner. Figure 10 compares the results of combustion air staging from the two test burners. The overall excess air for the data shown was in the range of 8% to 15% for the 200-hp burner and 5% to 7% for the 40-hp burner. The data show that, at comparable stoichiometric ratios above 0.7, the NOx emission level was higher for the 200-hp burner; however, it appears to converge at about 15 ppm between primary stoichiometry ratios of 0.5 to 0.6. These s to ichiome tric conditions could not be achieved in the firs t tes t series due to operating constraints. We believe that, with some refinements to the design configuration, it will be possible to operate the burner at the lower primary stoichiometric ratios and further decrease the NOx level. The CO emission level during these tests was fairly low. At the maximum firing rate of 8.5 X 106 Btu/h, the CO level was comparable to the level with the 40-hp burner. At the reduced firing rate of 4 X 106 Btu/h, the CO level was even lower and remained relatively unaffected with a decreasing primary stoichiometric ratio. It must be noted that these emission levels were measured at the exit of the combustor. While the NOx levels are expected to be stable, the CO levels are expected to continue to decrease in a real boiler because of the additional residence time and turbulence at high temperatures. The second series of tests were carried out with single-stage combustion to evaluate the impacts of high excess air firing. Figure 11 shows the effect of excess air on NOx and CO emissions for different firing rates and for two different firing configurations. Directionally, the results are similar to those with the 40-hp burner. The NOx emissions decrease rapidly with increasing excess air. With the first configuration, the CO emissions were similar for firing rates of 2.2 X 106 to 5.5 X 106 Btu/h. The NOx emissions at comparable excess air levels were also similar |
