Simulation and Exergy Analysis of a 600 MWe Oxy-Combustion Pulverized Coal-Fired Power Plant

Abstract

CO2 emission from pulverized coal-fired power plants (PC) can be efficiently controlled by adopting the oxy-combustion technology, which adds a cryogenic air separation process (ASU) and a flue gas treatment process (FGU) to the conventional combustion process. To understand the thermodynamic properties of the oxy-combustion process, a simulation study and an exergy analysis of a 600 MWe oxy-combustion PC were conducted. The commercial flowsheet software Aspen Plus was used to simulate the process and the simulation results are the basis to perform the exergy analysis. The simulation results show that the CO2 concentration in the flue gas from the oxy-combustion boiler can be more than 80 mol% and the CO2 purity from the FGU can reach 99 mol%; the net efficiency of the oxy-combustion system is 10.84% (lower heating value) lower because of the power consumptions of the ASU and FGU processes; the unit power consumption for the oxygen production in the ASU is 0.247 kWh/kg-O2. The exergy analysis focused on the boiler models (oxy-combustion and conventional) and each of them was divided to be several parts, such as furnace, heat exchanger. The exergy analysis results show that the exergy efficiency of the oxy-combustion boiler is 0.8% higher than that of the conventional combustion boiler, the primary reason for this is the exergy efficiency of the combustion process in the oxy-combustion boiler is about 4% higher. In addition, water wall and air heater in any boiler model have very low exergy efficiencies.