Effect of baffle on hydrodynamics in the air reactor of dual circulating fluidized bed for chemical looping process

The air reactor plays an important role in a dual circulating fluidized bed system for chemical looping process while the non-uniformity of solid distribution in the riser leads to a poor gas-solid contact and decreases the operation stability of the system. The aim of the study was to propose a novel baffle consisting of a ring-type baffle and a convergent pipe to improve the flow pattern and enhance the gas-solid contact. The effect of baffle on the system hydrodynamics was investigated based on CFD simulations. Three configuration parameters were studied: baffle opening ratio, baffle thickness and baffle number. The effect of baffle on radial solid distribution was evaluated through the standard deviation. Additionally, the radial non-uniformity index (RNI) of radial solid volume fraction was introduced to describe the axial change of radial solid distribution. The results showed that the baffle significantly affected the system hydrodynamics. The baffle opening ratio and the number of baffles were the key factors to decrease the standard deviation of radial solid volume fraction. The axial RNI profile showed that medium baffle thickness can effectively maintain a uniform radial solid distribution in the region away from baffle. Analysis of the simulation results revealed that the baffle increased the gas and solid velocities and it created turbulent eddies to eliminate the solid back-mixing near the wall. (C) 2018 Elsevier B.V. All rights reserved.