| OCR Text |
Show Emission Reductions Figure 6 contains the test results for opacity plotted as a function of boiler load both with and without the SGR system. These opacity data were taken before the overfire air system had been modified and before the sidewall overfire air modifications had been installed. These additional modifications combined to reduce the opacity even further than shown in Figure 6. The "before" data shown in Figure 6 indicates that the boiler had a fairly narrow operating window within the opacity regulation of 40 percent. The boiler exceeded this 40 percent limit at 40,000 pph and again at 80,000 ppm steam. After the SGR system was installed the opacity was below the 40 percent regulation at all steaming loads. In fact the maximum steaming rate was extended to 120,000 pph, thus providing the owner with a 40,000 pph increase in the available capacity of the boiler. The reduction in excess air required to fire the boiler resulted in a reduction of the NO emission. Figure 7 contains the NO emission data plotted as a function of excess oxygen in the flue gas. Emissions approaching 100 ppm were measured at the lowest excess oxygen levels. The N0X data taken with the SGR modification in place fell below the unmodified data. It is speculated that this is the result of a degree of "natural staging" that takes place when low fuel bed stoichiometries are achieved. Further work is underway to exploit these low fuel bed stoichiometries in a staged firing configuration to achieve even lower NO emissions from stoker boilers. Significant particulate emission reductions were measured in back-to-back tests over a forty-hour test period each with and without the use of the SGR system. The average of five Method 5 particulate tests at two boiler loads are given in Table 2. At 60,000 pph with a 30 percent flue gas recirculation rate the average stack particulate emission rate was 0.145 lb/10 Btu heat input. This represented a 42 percent reduction over the unmodified average emission rate. At 80,000 pph with a 20 percent flue gas recirculation 23-13 |
