The energy-saving mechanism of coal-fired power plant with S–CO2 cycle compared to steam-Rankine cycle

Abstract

S–CO2 (Supercritical-CO2) coal-fired power plant is a promising technology for efficient and clean utilization of coal for power generation. The comparative study between the S–CO2 coal-fired power plant and the power plant with steam Rankine cycle from aspects of energy and exergy balances is conducted. The conversion and transfer of the energy and exergy in the power plants are revealed. With the main gas parameters of 32MPa/620 °C and double-reheat process, the power generation efficiencies of the S–CO2 coal-fired power plant and the power plant with steam Rankine cycle are 49.06% and 48.12%, respectively. The corresponding exergy efficiencies are 48.02% and 47.10%, respectively. The energy-saving mechanism of the S–CO2 coal-fired power plant is revealed: the smaller boiler efficiency and larger exergy efficiency of the boiler system in the S–CO2 coal-fired power plant make the energy level of the energy being transferred to the S–CO2 cycle is higher than that of the energy being transported to the Rankine cycle. The CO2 absorbs the high-level energy and produces more mechanical power through the S–CO2 cycle to obtain higher power efficiency.