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Show shown. th~t both NOx and CO are reduced by more than 50%, and also shown vast reductIon In dioxin density. From the success of the test, it can be concluded that by adopting reburning system, NOx can be kept under the regulated value without additional deNOx facility, and dioxin can be controlled to remain below the guideline, when combined with the use of furnace gas constituency simulation which would determine the appropriate locations of gas injection nozzles and the optimum gas volume. 7. Refuse Incineration with High-Efficiency Power Generation MSW incineration plants must be built within a reasonable distance from population centers for the ease of handling and transportation. In order to placate the local residents, smoke from the stack must be kept invisible, and even the white plume should be avoided. For this reason, exhaust-gas reheaters are installed. Water vapor from the cooling tower is not acceptable for the same reason, and air-cooled corr densers are usually preferred. This forces to increase the exhaust steam pressure from the steam turbine. In order to prevent the high-temperature corrosion of steal parts by HC f in the exhaust gas, the temperature of super-heated steam has been capped at approximately 300°C in Japan. This has kept our power-generation eff~ ciency below 20% Recently, studies are being conducted for raising steam pressure and temperature, starting with the use of corrosion-resistant materials for superheater tubes. Adoption of gas turbine is also considered for the overall improvement of power gerr eration efficiency. In this article, total of four sample systems have been configured for calculations. They are: (A) conventional system(Figure 6), (B) addition of separately-fired superheater, and two combinations of separately-fired superheater and reburning technology; (C) exhaust gas from the separately-fired superheater goes through heat recovery process independent of the furnace, (Fig ure 7), and (D) exhaust gas is used as the assist gas for reburning(Figure 8). The results are shown on Table 8 and Table 9. The power generation efficiency of the conventional system remained at the low figure of 1 6.4%, whereas the addition of separately-fired superheater improved-it to 21 .5",24%. It should be noted that under system (D) where superheater exhaust was used as the assist gas for reburning, the natural gas utilization rate exceeded 50%. This is due to the fact that the oxygen content in the gas is lower compared to system (C), reducing natural gas consumption. 10 |