Construction of Environmentally Benign Regional Energy System by Cascade Use of Waste Energy

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The purpose of this research is to investigate the potential of cascade use of waste heat among energy intensive industries : iron & steel, cement, paper & pulp and ethylene. Firstly, regional energy-saving potential by heat cascading was evaluated in the actual local industrial structure in Japan. Secondly, spatial constrains of industries were introduced in the conbinat model to facilitate the evaluation of regional energy-saving. Thirdly,from the viewpoints of cost-saving potential as well as the energy-saving potential, new economic incentives, referred to as "energy tax" and "energy-tax refund", were proposed in consideration of the quality of energy use. Main results obtained in this paper are summarized as follows :1. Energy-saving potential by heat cascading highly depends on local industrial structure.2. Cascading between high temperature waste heat supply of ethylene and middle & low temperature heat and electricity demand of paper & pulp can provide high energy-saving.3. Oil consumption of steam boilers for the energy balance in a combinat can be reduced by more than about 90% by optimizing the industrial structure.4. Heat transmission loss will give little influence to the energy-saving potential in the optimized combinat.5. The conversion of waste energy into electricity is preferable, when considerable heat transmission loss is unavoidable.6. Economic incentives are effective to increase the energy-saving potential in the combinat optimized from the viewpoint of cost-saving potential.7. "Energy tax" in consideration of the quality of energy use promotes the introduction of heat cascading more economically than energy tax.8. "Energy-tax refund" based on exergy efficiency is more practical than "Energy tax", which can accomplish almost the same cost and oil consumption optimized from the cost-saving viewpoint as those optimized from the energy-saving viewpoint.