OCR Text |
Show boilers. In fact, this behavior can be deduced by examination of the temperatuare dependant 00 burn-out characteristics shown in Figures 3 or 7. Lastly, when using SNCR, there is a "coupling" between the combustion process and the reagent injection process. This occurs not only because of the flue gas temperature resulting from the burner performance, but also chemically due to the co. This coupling effects the location and width of the temperature window, N20 emissions, NH3 emissions, etc. This may be especially important for low NOx burner systems where, as is well known, there are frequently trade-offs between the NOx reduction and co levels. CONCLUSIONS Introduction of even small amounts of co into the SNCR process resulted in significantly altered behavior for urea and ammonia. In the case of urea: o co shifts and broadens the effective process temperature removal efficiency range. In addition, the peak removal efficiency decreases as co increases. o Increases N20 as co levels increase In contrast, ammonia reagent yielded the following results: o 10 to 30 point higher removal efficiency than urea, depending on 00 level. o Peak removal efficiency remains constant as co is increased. o co shifts the removal efficiency temperature window to a lower region, but no broadening of the window is observed. o Increasing 00 yields an increase in N20 levels. The absolute N20 concentrations are somewhat below those of urea. 12 |