化学链燃烧中赤泥载氧体的体相氧迁移动力学

Kinetics of Bulk Oxygen Migration in Red Mud Oxygen Carriers in Chemical Looping Combustion

体相氧迁移过程被认为是化学链反应中的限速步骤,对体相氧迁移过程的研究有助于载氧体的开发与反应器的设计。然而,气固两相反应受到气体在固体产物层内扩散的影响,很难获得准确的本征体相氧迁移动力学结果。本文提出了一种排除气体扩散影响的方法,使用YSZ氧传导膜抑制还原性气体的内扩散,将气体扩散过程与体相氧迁移过程解耦。基于质量守恒定律和菲克第二定律构建赤泥载氧体体相氧迁移过程的数学模型,并通过模型求解得到体相氧迁移过程的动力学方程。研究结果表明:YSZ氧传导膜能将还原性气体的内扩散和载氧体体相氧迁移过程解耦,赤泥载氧体本征体相氧迁移过程的活化能为77.32kJ/mol,指前因子为7.98×10^(-7)m^(2)·s。

The bulk oxygen migration process is considered to be the rate-limiting step in the chemical looping reaction. The research of the bulk oxygen migration process is helpful to the design of oxygen carriers and reactors. However, the gas-solid two-phase reaction is affected by the diffusion of gas in the solid product layer, and it is difficult to obtain accurate kinetic results of intrinsic oxygen migration. This paper proposes a method to eliminate the influence of gas diffusion,using YSZ thin oxygen conductive film to suppress the internal diffusion of reducing gas, and decouple the gas diffusion process from the bulk oxygen migration process. Based on the law of conservation of mass and Fick’s second law, a mathematical model of the red mud oxygen-carrying bulk oxygen migration process is constructed, and the kinetic equation of the bulk oxygen migration process is obtained by solving the model. The results of the study show that the method of loading YSZ oxygen ion conductive membrane can decouple the internal diffusion of the reducing gas and the oxygen transport of the oxygen carrier body. The activation energy of the red mud oxygen carrier’s intrinsic oxygen migration process is 77.32 kJ/mol, and the pre-exponential factor is 7.98×10^(-7)m^(2)·s.