Heat integration and optimization of direct-fired supercritical CO2 power cycle coupled to coal gasification process

Abstract

Supercritical carbon dioxide (sCO2) power cycle is a promising power cycle that has drawn much attention in recent years. Among various layouts, the direct-fired sCO2 power cycle achieves not only high efficiency but also near zero emission. Coal gasification and air separation process are indispensable processes when coal is used as fuel. To explore the best cycle performance, the above two processes have to be tightly integrated with the sCO2 power cycle in both mass and energy. Key parameters that govern the heat integration should also be optimized to achieve better performance. A two-stage method is applied for simultaneous optimization and heat integration of a direct-fired sCO2 power cycle coupled to coal gasification process. First, boundary parameters of the heat integration process are optimized. Then the heat exchanger network, which reveals viable heat integration scheme, is designed to fulfill the optimized target. The result shows that the net efficiency reaches 39.29% when heat integration of ASU is not considered. If heat integration of ASU is considered, the net efficiency increases to 40.97%, showing an efficiency increment of 1.68%. When the CO2 turbine pressure ratio is also optimized, the net efficiency increases further to 41.41%.