Method for integrating low-grade industrial waste heat into district heating network

Low-grade industrial waste heat could be a considerable potential energy source for district heating, on the condition that the heat from different industrial waste heat sources is integrated properly. This study considers a method for integrating low-grade industrial waste heat into a district heating system and focuses on how to improve the outlet temperature of heat-collecting water by optimizing the heat exchange flow for process integration. The pinch analysis concept is considered, and a newly developed thermal theory called entransy analysis is introduced. By using entransy dissipation to describe the energy quality loss during the heat integration, this study analyzes how heat exchange flows influence the final outlet water temperature and attempts to provide an efficient method to optimize the heat exchange flow. Finally, the effectiveness of the proposed methodology is demonstrated by testing it in a project involving the recovery of waste heat from a copper plant for district heating.