Recovery and utilization of waste energy is an excellent method to solve environmental. In Japan, steel industry releases almost half from the energy requirement in the process. The wasted energy is emitted into the atmosphere together with molten materials and off gas without any recovery. In this paper, we discuss a possibility of using the waste heat in steelworks as heat source in chemical reaction process. Two heat recovery systems of hydrogen production and blast furnace (BF) cement process using waste heat of molten slag and off gas are proposed. The amount of CO_2 emitted by the combustion of carbon is calculated by dividing the recovered heat of wastes by the combustion heat of carbon. When the heat of molten slag is recovered to produce hydrogen, the amount of CO_2 emission decreases by 1.39 million tons per year. In BF cement process, both heats of molten slag and off gas are utilized for endothermic reaction. The process will cut 33 percent of CO_2 based on the emission from conventional process. In conclusion, to save energy and minimize CO_2 emission, it is imperative that the hydrogen production and cement process be improved with the recovery of the high temperature waste heat.
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