Waste materials are classified into industrial wastes from industrial activities (4 billion t/y) and municipal wastes (50 million t/y). In 2003, electricity power generation from industrial waste was about 200,000 kW which was about one-sixth of that from municipal waste. However, since industrial wastes are composed of high calorie refuses, such as waste woods, sewage sludge, used oil, medical waste, they could be a prospective energy resource in the near future. Water-quenched step-wise mechanical stoker incinerators have been successfully utilized for high calorie refuses, while rotary kiln type is generally used for the incineration of used oil and medical wastes. Heat from incineration of wastes is recovered as hot water, hot air or steam. Steam boilers which are in practical use for municipal waste incineration do not meet economic requirement for incineration of industrial waste on a small scale (less than 100 t/d) because of fouling and erosion of heat exchanger. Recently, the author has revealed that there exists an optimum temperature range which gives effective heat recovery with heat exchanger though detailed observations and precise chemical analyses. The most promising methods of heat recovery from industrial wastes could be a heat container, which stores heat in an incineration site and transports it to heat utilization sites and a thermoelectric generator which converts temperature differences directly to electricity. Conversion efficiency of the thermoelectric generator is 4~5% at present, but it is a potential heat recovery method for small scale incinerators.
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