关键词: Circulating fluidized bed, Pure-oxygen combustion, Gas-solid flow characteristics, Simulation, CO₂ capture

Abstract: Under the pressure of carbon neutrality, many carbon capture, utilization and storage technologies have witnessed rapid development in the recent years, including oxy-fuel combustion (OFC) technology. However, the conventional OFC technology usually depends on the flue gas recirculation system, which faces significant investment, high energy consumption, and potential low-temperature corrosion problem. Considering these deficiencies, the direct utilization of pure oxygen to achieve particle fluidization and fuel combustion may reduce the overall energy consumption and CO₂-capture costs. In this paper, the fundamental structure of a self-designed 130 t·h^-1 pure-oxygen combustion circulating fluidized bed (CFB) boiler was provided, and the computational particle fluid dynamics method was used to analyze the gas-solid flow characteristics of this new-concept boiler under different working conditions. The results indicate that through the careful selection of design or operational parameters, such as average bed-material size and fluidization velocity, the pure-oxygen combustion CFB system can maintain the ideal fluidization state, namely significant internal and external particle circulation. Besides, the contraction section of the boiler leads to the particle backflow in the lower furnace, resulting in the particle suspension concentration near the wall region being higher than that in the center region. Conversely, the upper furnace still retains the classic core-annulus flow structure. In addition to increasing solid circulation rate by reducing the average bed-material size, altering primary gas ratio and bed inventory can also exert varying degrees of influence on the gas-solid flow characteristics of the pure-oxygen combustion CFB boiler.

Key words: Circulating fluidized bed, Pure-oxygen combustion, Gas-solid flow characteristics, Simulation, CO₂ capture