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 (508Kb)
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14,809,000 Yen (FY1997;5,034,000 Yen)
Emission control technology of the nitrous oxide (N2O), which is one of the green house gases, from the combustion processes was studied. Sewage sludge combustion, one of the major source of N2O, was examined with a Jab-scale circulating fluidized bed combustor in order to investigate an effective control technique at the first year of this research program. N2O emission level had exceeded 1000 ppm in the flue gas. However, conversion ratio of nitrogen to N2O during sewage sludge combustion was 15-20% compared with 30% when coal was burnt with the same combustor. From the detail studies, it is understood that N2O in the sewage sludge combustion was mainly formed from the volatile matters.
Practical mitigation methods were studied from the second year. Catalytic decomposition of N2O in flue gas, enhancement of the N2O destruction reaction by injection of supplemental fuel gas to make hot spot in the combustor, were tried as practical methods. It was found that Rh/ZnO catalyst had high N2O decomposition reactivity in pure system. It easily lost, however, its reactivity in the existence of SO2 which was very common gas in the combustion processes. N2O decomposition by making the high temperature spot in the furnace by injecting supplementary fuel gases was able to decrease N2O emission about 40% without additional NO emission. This method seems to be an effective control technique for practical use. In the final year, tried the mitigation method by the preprocessing of the fuel to omit the volatile matter as a further decreasing method. By using this method, about 40% of N2O emission could be decreased
N2O from the combustion process may be controlled by about 80% or less by combining the control methods shown in the above-mentioned.
Nitrous Oxide, Combustion, Mitigation methods