OCR Text |
Show pressure, operates on either gas or light oil, and has an energy output of 890 MJ/hr (840,000 Btu/hr). The as-received boiler was tested on natural gas over a range of stoichiometrics at four load conditions. Excess air ranged from 0 to 80 percent. The four loads were 50, 64, 81, and 97 percent of full load. At 64 to 100 percent load and 20 percent excess air, the NO emissions were approximately 60 A to 70 ppmv, CO and UCH were about 15 ppmv, and the efficiency (calculated by the ASME Heat Loss Method) was 82 percent. Figure 3 shows the NO emissions relatively constant across the range of excess air levels. The data are discussed further below in comparison to preliminary Fiber Burner A test results conducted to date. Retrofit hardware was required to adapt the fiber burner to the York- Shipley boiler. Figure 4 shows the fiber burner assembly, as fit into the firetube. Minimal changes to the boiler were required. With the high pressure drop through Fiber Burner A of 1000 to 1250 Pa (4 to 5 inches w.g.), a larger blower was also needed. The front burner flange with refractory ring was replaced, and port holes were added for thermocouples and igniter. The boiler and burner assembly are shown in Figure 5. In operation, combustion air is premixed with gas injected into four ports upstream of the burner. The reactants enter the burner, pass through the fiber matrix, and are ignited with a standing pilot. Internally, a center body reduces the cross-sectional flow area to minimize the premixed gas volume and maintain the gas and air mixture at a high velocity should flashback occur. A perforated metal cylinder supports the fiber matrix burner. Testing was conducted on natural gas at 64 to 100 percent load at stoi-chiometries from 10 to 80 percent excess air. N0X emissions, shown in Figure 3, were approximately 80 percent lower than the baseline NO at loads above 85 percent. Table 2 shows the results of both Burner A and the conventional burner at 64 percent load and 20 percent excess air. CO emissions were comparable for both burners. Efficiency was improved by 1 percentage point with the fiber matrix burner. Exhaust gas temperature 3-7 |