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Show Session VIII, In-Furnace NOx Reduction "Demonstration of Reburning Technology on an MSW Furnace" 1. Introduction Yasujiro Wakamura Managing Director and Engineer-in-Chief Takuma Co., Ltd., Osaka, Japan. At the AFRC/ JFRC joint conference held at Maui, Hawaii in October 1994, I submitted a report on the result of the de-NOx operational test carried out in USA using natural-gas reburning technology. Since the test was successful in achieving stable de-NOx under low CO environment, its effectiveness in reducing dioxin emission was anticipated. Today, I wish to report on another test carried out, this time in Japan, for the reduction of NOx and dioxin, using Japanese municipal solid waste (MSW) which has higher moisture content and lower heat value US waste. Since fossil fuel is used for this operation and heat recovery is very important, a separately-fired superheater using natural gas was installed, and its exhaust gas was used as the carrier of the natural gas for reburning, improving the heat efficiency. 2. MSW from USA and Japan Table 1 shows the analyses' results of raw MSW and processed RDF from USA and raw MSW from Japan. As shown, US waste has lower moisture and higher ash content, or incombustible, as the kitchen waste is usually disposed into the sewer system. For this reason, drying grate is not required in the stoker. However, it is difficult to control combustion because refuse ignites immediately after it is fed into the furnace. In Japan, while ash content is lower due to higher degree of source separation practiced at home, kitchen waste is collected as part of MSW, raising moisture content. In rural areas, in particular, waste of farm produces end up in MSW, lowering the overall heat value. . For this reason, incineration takes place after MSW goes through drying process, and the whole grate area is used for relatively slow combustion, making control easier. Table 2 lists the comparison of test results from USA and Japan. 1 |
