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Show 0.50 n 0.45 •- 0.25 -- 0.20 -I • Low Load • Higfi Load 10 Gas Cofire, % 15 20 Figure 7. Lilly N O x Emissions Results. Purdue recognized the capability of cofire to allow derate recovery with acceptable opacity and particulate emissions, and to allow smokeless startup. Accordingly, dual Coen CoFyr burners were retrofit to Boiler No. 1 in December 1998, and to Boiler No. 2 in M a y 1999. The combined firing capacity of the gas burners for both systems was 70 MMBtu/hr. The installation on Boiler No. 1 was tested during February 1999. Measurements included continuous monitoring of 02, C O , N O x , and S02 , E P A Method 5 for particulate, and grab samples of fuel and ash. Figure 8 shows the effect of cofire on stack opacity (6-minute average) for three loads tested. The figure shows that stack gas opacity decreased from nominally 17 percent to just over 10 percent with 10-percent gas cofiring at 180-kpph load. Similarly, opacity decreased from 19 percent to 11 percent with 10-percent gas cofiring, and 9 percent with 20-percent gas cofiring, at 160-kpph load tests. Of course, all these are below the Purdue permit limit of 40 percent, 6-minute average. At 190 kpph load, opacity with 10 percent cofire was uniformly less than 20 percent. However, without cofire, opacity was 27 percent for one test and 54 percent for another. This higher value, more in keeping with past Purdue experience, exceeded Purdue's permit limitation. Thus, 10 percent cofire would indeed allow recovery of lost capacity, and allow boiler operation at 190 kpph load or higher with acceptable opacity. Figure 9 shows the effect of cofire on boiler particulate emissions at 180-kpph load. The figure shows that 10 percent cofire reduced particulate emissions 50 percent at this load. Figure 10 shows corresponding data at 190 kpph load. This figure shows that particulate emissions at the 190-kpph load at 10-percent cofire were 0.08 lb/MMBtu. This represents an approximate 90-percent reduction from the 0.73 lb/MMBtu level measured for one test with no cofire, and even a 35-percent reduction from another test with no cofire, a test not considered reflective of typical operation at this load. Again, 10-percent gas cofire clearly allowed operation at a 190-kpph or even higher load in compliance with the Purdue particulate emissions limitation of 0.7 lb/MMBtu, a situation not reliably possible without gas cofire. 10 |