Simulation of a Supercritical CO2 Recompression Cycle with Zero Emissions

The NET power cycle (NPC) offers an alternative way to inherently capture combustion derived CO2 with low efficiency penalty. This manuscript improves the NPC by recompressing a portion of the recycled CO2 stream to the exit of low temperate regenerator, forming a recompression NET power cycle (RNPC). The RNPC further enhances cycle recuperation and no longer needs to input extra heat to cover the heat gap between low pressure and high pressure CO2 streams in the regenerator. The model of internal convection cooling for the turbine in sCO(2) cycle is also accomplished according to the semiempirical formula, aiming to investigate the effect of coolant flow. This manuscript respectively conducts the system multiparameter optimization for uncertain boundary parameters and the sensitivity analysis for definite boundary parameters. The simulation results show that RNPC can output 27.2 MWe more NEP than NPC without extra heat input, leading to 3.54% of the increase in net electric efficiency. RNPC's efficiency increases monotonically with not only turbine inlet temperature but inlet pressure, which indicates that RNPC has the potentiality to further improve its efficiency at higher turbine inlet temperature and inlet pressure. However, turbine outlet pressure has a nonmonotonic effect on the cycle performance, and the optimal turbine outlet pressure corresponding to the maximum cycle efficiency is about 38-42 bar. The multiparameter optimization indicates that the global optimal cycle efficiency is approximately 53.55% within the ranges of investigated parameters. The RNPC's efficiency is considerably influenced by the minimum cycle temperature (0.234%/degrees C), compressor efficiency (0.08%/%), turbine efficiency (0.355%/%), and regenerator temperature differences (0.083%/degrees C for HTR and 0.080%/degrees C for LTR). (c) 2020 American Society of Civil Engineers.