Computational study of solid circulation in chemical-looping combustion reactor model

• 3-D Eulerian models on solid circulation in CLC DCFB model have been developed.
• Cross-sectional solid distribution and velocity field were numerically studied.
• Coefficient of variation was used to evaluate circulation stability.
• Effects of FR flow rate on circulation fluctuation strength and stability were studied.
• Global and internal circulation stability was weakened by growth in LLS flow rate.

A three-dimensional computational fluid dynamic (CFD) model has been developed for simulating full-loop solid circulation in a dual circulating fluidized bed (DCFB) chemical loop combustion (CLC) reactor model. The standard k-ε turbulence model and kinetic theory of granular theory based Eulerian multiphase model were used to describe the gas and solid motions, respectively. The simulations focused on the investigation of solid circulation in a CLC reactor model which consists of an air reactor (AR, height of 1.36 m, diameter of 0.05 m) and a fuel reactor (FR, height of 0.97 m, diameter of 0.054 m). Key gas–solid flow behaviors related to gas–solid circulation behaviors, e.g. the transient flow regime, solid velocity, solid distribution and circulation characteristics, were numerically investigated. It was found that a core–annulus flow structure appeared in FR. The influences of FR and LLS fluidization flow rate on global and internal circulation rate were studied separately. With FR fluidization flow rate increasing, the time-averaged axial solid volume fraction in the top region of FR first increased and then decreased. The influences of FR and LLS fluidization rate on circulation dynamic characteristics, including circulation fluctuation strength and circulation stability, were also numerically investigated in this work.

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