Intensification, optimization and economic evaluations of the CO2-capturing oxy-combustion CO2 power system integrated with the utilization of liquefied natural gas cold energy

Abstract

This work focuses on the investigation of CO2-capturing oxy-combustion CO2 power system integrated with the utilization of liquefied natural gas (LNG) cold energy. Working fluid CO2 is compressed and combusted with high purity oxygen and natural gas and is then expanded by the gas turbine to atmospheric pressure for driving the electricity generator. After recuperating the residual heat in the exhaust stream, the concentration of water is reduced to the standard of less than 1 ppm, to avoid the corrosion caused by the formation of ice in the following cryogenic process. Next, CO2 is compressed to its condensation pressure and condensed by using LNG cold energy. Liquid CO2 is then pumped to high pressure for recirculation where excess CO2 is captured. Besides, reheating procedure is applied to two-stage turbine expansion to increase energy efficiency, and an additional natural gas turbine is installed to generate more electricity. On the basis of 100 kg/s for both recirculating CO2 and LNG, this LNG enhanced CO2 power system shows its superiority in the net power output of 134.61 MW, the annual profit of 52.58 MUSD, the energy efficiency of 66.94%, CO2 recovery of 98.60% and the CO2 captured purity of 99.94 mol%. Furthermore, when turbine outlet pressure is adjusted to CO2 condensation pressure, higher energy efficiency can be achieved at 69.01%, but the net power output will decrease to 53.54 MW.