Abstract: Total site heat integration (TSHI) providesmore opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid circuits, i.e., steam, dowtherms and hotwater, have been proposed during last fewdecades. Indirect heat integration is preferredwhen the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and performance of heat integration. This work presents a new methodology for indirect heat integration in low temperature range using hot water circuit as intermediate-fluidmedium. The new methodology enables the targeting of indirect heat integration across plants considering the factorsmentioned earlier. AnMINLPmodelwith economic objective is established and solved. The optimization results give themass flow rate of intermediate-fluid, diameter of pipeline, the temperature of the circuits and the matches of heat exchanger networks (HENS) automatically. Finally, the application of this proposed methodology is illustrated with a case study.

Key words: Indirect integration, Intermediate-fluid, Across plants, Pipeline, Optimization

摘要： Total site heat integration (TSHI) providesmore opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid circuits, i.e., steam, dowtherms and hotwater, have been proposed during last fewdecades. Indirect heat integration is preferredwhen the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and performance of heat integration. This work presents a new methodology for indirect heat integration in low temperature range using hot water circuit as intermediate-fluidmedium. The new methodology enables the targeting of indirect heat integration across plants considering the factorsmentioned earlier. AnMINLPmodelwith economic objective is established and solved. The optimization results give themass flow rate of intermediate-fluid, diameter of pipeline, the temperature of the circuits and the matches of heat exchanger networks (HENS) automatically. Finally, the application of this proposed methodology is illustrated with a case study.

关键词: Indirect integration, Intermediate-fluid, Across plants, Pipeline, Optimization