CFD study of nonuniformity of gas-solid flow through a chemical looping combustion system with symmetrical series loops

Abstract

Multiple identical paths are usually connected to form circulating loops in many industrial reactors including chemical looping combustion (CLC), however the flow pattern may be highly nonuniform in these identical paths, compromising the stable operation. In this study, by using the Eulerian multifluid model, the nonuniformity in a CLC apparatus is studied. First, the symmetry of computational domain is verified by simulation and the model setting is validated by experimental data. Then the typical nonuniformity phenomenon is discussed and evaluated in terms of bed inventory evolution and gas-solid distribution in symmetrical parts. The effects of key operating parameters including total bed inventory, gas aeration rate, and wall roughness on nonuniformity degree are then studied. The simulating results show that the nonuniformity degree between the two symmetrical parts increases with the increase of total bed inventory and gas aeration rate and this trend will be intensified in the predictable short-term future. And through the analysis of pressure fluctuation, the instability of the system is aggravated. However, wall roughness shows an indefinite influence and tendency. This work provides an insightful understanding of nonuniformity and will help further optimise symmetrical CLC systems.