Application of optimization method based on discretized thermal energy in condensing heat recovery system of combined heat and power plant

Abstract

Recovering waste heat can improve the energy efficiency of a combined heat and power plant. The pinch method is widely used in heat recovery systems; however, the minimum energy grade of the remaining heat demand cannot be determined using this method. In this study, a method for discretizing thermal energy for the heat sources and demands is proposed and illustrated with a detailed description. The proposed method can maximize heat recovery and minimize energy grade requirements. Different heat transfer temperature differences could be considered in the proposed method. Two different optimized heat recovery systems for a combined heat and power plant are developed based on the novel and pinch methods. The amount of heat recovered using the optimized systems are the same, with values 2.08% higher than that of the conventional heat recovery systems. Compared with the pinch method based optimized system, the energy grade of the remaining heat demand could be reduced from 61.9 °C to 58.2 °C using the proposed method.