Research on the Operating Characteristics of Low-Temperature Return-Water Cogeneration Heating Systems

This paper introduces the composition of the combined heat and power (CHP) generation system with low-temperature return water. Focusing on the Gujiao–Taiyuan heating system, it systematically analyzes the effects of key operational parameters, such as supply–return-water temperatures, circulating water flow, maximum back-pressure, and minimum supply-water temperature, on overall system energy consumption. The results indicate that lowering supply and return-water temperatures, increasing circulating water flow, raising the maximum back-pressure, and reducing the minimum supply temperature generally contribute to a decrease in the heating equivalent electricity. Furthermore, the study compares several operation regulation modes of the heating system, including two-stage quality regulation, two-stage quantity regulation, and staged quality–quantity regulation. It is concluded that staged quality–quantity regulation achieves the lowest energy consumption. The impacts of heating steam allocation and variable back-pressure under different heating loads are also examined. Based on these findings, an extraction steam reduction sequence is proposed following the principle of minimizing the system’s heating equivalent electricity, along with a strategy to lower the back-pressure of selected units during the early and late heating periods. Finally, an economic operation strategy for the CHP system with low-temperature return water is developed, integrating recommendations on circulating water flow, temperature settings, steam allocation, and back-pressure regulation across different heating loads, leading to improved energy efficiency and economic performance.