Optimization and analysis of combined heat and water production system based on a coal-fired power plant

Abstract

The combined heat and water (CHW) system has been studied by many scholars since it was proposed, and a project has been implemented in Shandong, China in 2021. However, there have been few studies on optimization and comparisons of cases on the heat source side of CHW. Taking a coal-fired thermal power plant as an example, through the reasonable matching of steam flows and analysis of thermal economic parameters, the effect number and heat source steam temperature of a multi-effect distillation (MED) + multi-stage flash (MSF) combined heat and water production (CHWP) system were optimized. The optimal MED heat source temperature was found to be 70 °C, and the optimal MED and MSF effect numbers were 10 and 5, respectively. Finally, the waste heat in the power plant was utilized as much as possible throughout the year. Compared with two cases of the separate heat and water production (SHWP) system, the CHWP system easily achieved better water quality and economy under the condition of almost equal exergy efficiency, and it was easier to realize than the first case of the SHWP system.