Energy Efficiency Analysis of Oxy-Fuel Circulating Fluidized Bed Combustion System with High Oxygen Concentration

The low net efficiency of oxy-fuel circulating fluidized bed (CFB) combustion is mainly due to the addition of air separation unit (ASU) and carbon dioxide compression and purification unit (CPU). High oxygen concentration is one of the effective methods to improve the net efficiency of oxy-fuel combustion technology in CFB. In this research, a series of calculation and simulation were carried out based on Aspen Plus platform to provide valuable information for further investigation on the CFB oxy-fuel combustion system with high oxygen concentration (40%, 50%). A CFB oxy-fuel combustion system model with high oxygen concentration was established including ASU, CPU and CFB oxy-fuel combustion and heat exchange unit. Based on the simulation data, energy and exergy efficiency were analyzed to obtain the following results. The cross-sectional area of furnace and tail flue of 50% CFB oxy-fuel combustion boiler are 43% and 56% of the original size respectively, reducing the construction and investment cost effectively. With the increase of oxygen concentration, the net efficiency of power generation increased significantly, reaching 24.85% and increasing by 6.09% under the condition of 50% oxy-fuel combustion. The total exergy loss increases with the increase of oxygen concentration. In addition, the exergy loss of radiation heat transfer is far higher than convection heat transfer.