OCR Text |
Show The results of tests with the 40-hp burner demonstrated the ability of the cyclonic burner to operate with 20 ppm NOx with combustion air staging and with even lower NOx levels with excess air firing. The flame was very stable in both configurations, and the CO emissions were about 50 ppm or lower. Significantly lower CO levels can be expected on actual boilers because of the additional residence time at high temperatures. As discussed earlier, the excess air tests also demonstrate the potential for similar NOx reductions using other diluents, such as FGR. 200-hp TEST BURNER The 40-hp test burner demonstrated excellent combustion/emission capabilities; however, it was not certain whether similar performance could be achieved on larger burners because of 1) the potential decrease in swirl and, consequently, internal combustion products recirculation and 2) the reduced heat transfer surface area per unit heat input. In early 1990, with internal funding, IGT decided to continue the development effort on a scale that is consistent with industrial boiler sizes. IGT also decided to direct the initial development toward firetube boiler retrofits because an immediate market exists in the southern California area and the cyclonic burner adopts itself well to the firetube boiler. A 200-hp burner size was selec ted for this development because it represents a typical indus trial firetube boiler and would fit both the existing 24-inch-diameter boiler simulator as well as the 24-inch-diameter Morison tube of the firetube boiler at IGT. The emission goals set for the retrofit burner when firing natural gas are - • ~15 ppm NOx • ~50 ppm CO • ~10 ppm THe with minimal loss in boiler thermal efficiency or increase in electricity consumption. Similar to the 40-hp burner, the 200-hp burner was designed to provide a wide variation in the critical parameters such as - • Burner length • Design, number, size, and orientation of combustion air/natural gas injectors • Provisions for water injection and FGR. As with the smaller test burner, the 200-hp test burner was watercooled to provide flexibility in design and testing. The first commercial burner for firetube boiler retrofit and even the commercial prototype that we plan to develop will not be water-cooled. Figure 9 shows the test |