| OCR Text |
Show urea, these figures are for an initial NOx level of 125 ppm, NINO of 2 and a range of 00 from 0 to 2000 ppm. NO Re.oval Bfficiency Important differences in the removal efficiency behavior between urea and ammonia are readily seen in Figure 8. In contrast to urea, addition of CO to the ammonia SNCR system results in a major shift of the entire NO removal efficiency vs. temperature dependance to a lower temperature regime; further, the temperature "window" for ammonia i8 not widened a8 in the case of urea. Perhaps of greatest interest is the increased production of NO--up to 70\ increase--as CO increases from 0 to 2000 ppm. Note that this phenomenon occurs at a lower temperature and to a greater extent as the CO is increased. Lastly, unlike urea, it appear8 that the peak NOx removal efficiency does not decrease as CO levels increase. CO Baiaaiona CO byproduct emissions for the case of ammonia reagent are shown in Figure 9. Unlike the removal efficiency, CO emissions for the two reagents behave very similarly. As the initial CO level is raised, final CO levels are higher at the low end of the process temperature range; however, CO levels rapidly converge to a low level--irrespective of initial CO--once the temperature exceeds about 8500C. HB3 Baiaaiona As with 00, slip ammonia levels using ammonia as reagent follow a behavior similar to that of urea. The well-known increase in slip ammonia at the low end of the process temperature window is seen. Of greater interest is the large decrease in leak ammonia levels as the initial CO level increases. At the 2000 ppm level, NH3 emissions are less than 5 ppm over the entire temperature range investigated. Similar behavior is also noted for urea (Figure 3). A comparison of the results for N20 emissions using ammonia as the SNCR reagent show several different features compared to urea: N20 levels with ammonia are lower in all comparable cases. The highest N20 level observed for ammonia reagent was 17 ppm. For urea, the highest value was 28 ppm. N20 levels are significantly lower for ammonia in the temperature range above 9000C. N20 levels for ammonia reagent appear to peak in temperature range of 750-9000C as CO increases. the highest N20 levels for urea tend to occur at portion of the window (ca. 10000C). 10 the lower In contrast, the high temperature |
