Performance Investigation Of Chemical Looping Air Separation Based Oxy-Fuel Power Plant

Observation of the increasing CO2 concentration in the atmosphere and the thereto connected global warming effects has made prevention of CO2 emission from fossil fuel utilization an important field of research. Chemical looping air separation (CLAS) technology, as a novel oxygen generation technology, can effectively separate oxygen from air. Preparing O2/CO2 mixture gas, combined with conventional coal-fired power plant, can efficiently produce power with zero carbon dioxide emissions.Based on Aspen Plus software, the work in this dissertation includes:1) The CLAS system, the coal-fired boiler system and flue gas cooling and compression system are integrated to produce power with carbon capture, and the integrated system is simulated.2) The CLAS O2/CO2 combustion system is discussed and optimized. The optimum operation parameters are found. Energy consumption and efficiency are examined and compared with the conventional power plants.3) Based on the limitations existed in the O2/CO2 combustion system,a novel CLAS oxy-fuel system is proposed. And the performance is simulated, and the operation parameters are discussed.The existing 1000MW coal-fired plant intergrated with CLAS is simulated. Using oxygen carrier Mn3O4-Mn2O3, the operation conditions of CLAS reactors are optimized, and oxidation reactor temperature is 787℃, while the reduction reactor temperature is 762.4℃. The oxygen concentration in O2/CO2 mixture gases is 12.2%. After cooling and compression, the CO2 concentration in exhaust flue gas exceeds 97%, and the flue gas is ready for large-scale transport and storage to achieve zero carbon emissions. The net efficiency of CLAS oxy-fuel system is 38.92%, close to that of the conventional power plants, only 3.28 percentage points lower.CLAS systems, boiler and turbine system and flue gas cooling and compression system are coupled and optimized. After optimization, the net efficiency of CLAS oxy-fuel system is 40.44%, increased by 1.52 percentage points. The effects of CLAS system reactor temperature, excess air ratio and the different oxygen carriers on the performance of CLAS oxy-fuel system are simulated. The results show that under the oxidation reactor temperature of 790℃, the reduction reactor temperature of 765℃, the excess air ratio of 1%, and the oxygen carrier of Mn3O4-Mn2O3, the system achieves the optimum performance.Single-pressure reheat CLAS oxy-fuel system is proposed in this work. The simulation results show that the net efficiency is 43.32%. By comparisons with other CCS technologies, such as IGCC-CCS, oxy-fuel combustion with ASU, etc, CLAS single-pressure reheat oxy-fuel system has the highest thermal efficiency and is more advantageous. Therefore, Single-pressure reheat CLAS oxy-fuel system is of the potential for further research and development.