A novel coal-fired chp system integrated with steam ejectors to realize heat-power decoupling and energy saving

Traditional combined heat and power (CHP) units should run in the heat-controlled mode. The adjustable range of power load is restricted by the heat load, and the minimum power load increases with the heat load. Because of high penetration of intermittent renewable power, operational flexibility of CHP units is highly required. It is necessary to adopt some technical solutions to realize heat-power decoupling for CHP units. To find a heat-power decoupling method with low investment and high energy efficiency, the steam ejectors, simple in structure and low in cost, are applied to design a novel heat-power decoupling system in this study. Steam ejectors can recover the waste heat of exhaust steam of steam turbines. Therefore, the integration of steam ejector may realize heat-power decoupling and energy saving simultaneously. Three heat-power decoupling systems with steam ejectors are designed. The heat-power decoupling performance and energy consumption characteristics of these systems are investigated with a reference 330 MW coal-fired CHP unit. Results show that all three modified systems can realize heat-power decoupling. The heat-power decoupling performance of improved system III is the best, and improved system I has the least coal consumption rate for power generation.