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Show suspension. The mineral matter melts, exits the cyclone furnace from a tap at the cyclone throat, and is dropped into a water-filled slag tank. The flue gases and remaining ash leave the cyclone and enter the main furnace. SLAG SPOUT OPENING Figure 1. Cyclone furnace COAL CHUTE CRUSHED COAL 1/4" SCREEN MESH TERTIARY ~AIRINLET IUIt:#t:;::~ SCROLL BURNER No commercially-demonstrated combustion modifications have significantly reduced NOx emissions without adversely affecting cyclone operation. Past tests with combustion air staging achieved 15 - 30% reductions. Cyclone tube corrosion concerns due to the resulting reducing conditions were not fully addressed because of the short duration of these tests. Further investigation of staging for cyclone NOx control was halted due to utility corrosion concern. Additionally, since no mandatory Federal/State NOx emission regulation was enforced, no alternative technologies were pursued. The recent emergence of the reburning technology offers a promising alternative to conventional combustion controls and SCR systems. During the early 1980s, Tokyo Electric Power Company (Japan) and Babcock-Hitachi K.K. (BHK) jointly developed a technology known as in-furnace NOx reduction (IFNR) to reduce NOx emissions from natural gas-, oil-, and coal-fIred furnaces. Babcock & Wilcox is the exclusive licensee of BHK's IFNR process. The technology, a version of the process widely known in the industry as reburning, is based upon extensive laboratory research and has been proven in subsequent pilot- and full-scale operation in Japan. BHK has applied IFNR as a retrofit technology to 10 wall-fITed utility boilers in Japan. The retrofit units are natural gas, oil, and coal fired ranging from 175 to 700 MW in size. BHK's pilot- and full-scale experience has demonstrated typical NOx emission levels shown in Table 1. Adapting this technology to the inherent characteristics of cyclone boilers was reviewed/determined during the aforementioned B& W engineering feasibility study. Based on the results of the study, it is estimated that a nominal 60% NOx emissions reduction could be achieved from cyclone boilers with the use of reburning. Table 1 identifies these anticipated levels. 3 |