Mass transfer model based on the spatial superposition assumption for simulating the catalytic ozone decomposition in downer reactor

Abstract

A mass transfer model based on the spatial superposition assumption is proposed in this work to better reflect the effect of heterogeneous structure on the mass transfer behavior of the downer. Attributing to the special assumption of this model, fewer concentration parameters are required compared with the classic multi-scale method, which largely saves the calculation consumption. The simulation results of this model also could be in good agreement with the experimental data. Additionally, the calculated mass transfer coefficients are in the range from 10−3 to 10−1, which are approximately three orders of magnitude lower than that of the homogeneous structure. It is proved that the existence of clusters would seriously affect the gas-solid mass transfer effectiveness, thereby deteriorating the reaction rate. By simulating the distribution of ozone concentration in the catalytic ozone decomposition, it can be found that the mass transfer near the inlet region plays the dominant role while along the flow direction, the influence of reaction process becomes stronger than that of the mass transfer process and gradually turns to control the whole decomposition process. These results indicate that the present model is useful and could be applied for the simulation of mass transfer process in other gas-solid fluidized systems with heterogeneous structures.