Optimal dispatch of the cascade heating CHP plants integrating with the high back-pressure technology

Abstract

High back-pressure (HBP) retrofit is a satisfactory approach to enhance the heat-supply capacity of combined heat and power (CHP) units via waste heat recovery. In this study, focusing on economic operation, the problems regarding the plant-level dispatch of a cascade heating CHP plant with the HBP technology are addressed. In consideration of the operation region (OR) and load balancing constraints, the optimal dispatch strategies are proposed. It is found that the optimal heat load sharing ratio of the HBP unit can be predicted via the real-time temperatures of supply water, return water, preheat water, and heat load. For the extraction-condensing (EC) units, the uneven distribution of heat-power loads is a preferable coal-saving option. A case study is then performed to show the favorable outcomes quantitatively. Results show that the heat load sharing ratio of the HBP unit would be increased by about 8.01% overall. Moreover, the optimal heat-power loads of the EC units present a clear law. From the plant-level perspective, the average coal saving ratio is 0.76%. Besides, the reduction of standard coal consumption of the case plant is about 607,829 tons during the heating season, which means that 1.59 million tons of CO2 would be accordingly reduced.

Keywords

• CHP
• Cascade heating
• High back-pressure
• Optimal dispatch
• Coal saving