CFD investigation on the effect of ring-type internals on oxy-fuel combustion in pilot-scale circulating fluidized bed

Abstract

The effect of internals in the riser of circulating fluidized bed on the oxy-fuel combustion is in lack. Consequently, the multiphase particle-in-cell (MP-PIC) method, which belongs to the Eulerian-Lagrangian framework, is used to investigate the influence of ring-type internals on the particle-scale characteristics, including particle velocity, temperature, heat transfer coefficient (HTC), slip velocity, and Reynolds number. The results show that the incorporation of ring-type internals significantly affects the distribution and motion of gas and particles. Increasing the internal number or reducing the aperture ratio slightly improve the sand temperature in the riser by facilitating improved interphase momentum exchange and heat transfer. Increasing internal number from two to six improves the sand temperature and HTC in the riser of about 13 K and 61 W/m2·K. While increasing the aperture ratio from 0.7 to 0.9 decreases the sand temperature of about 17 K. The incorporation of internals within the riser also induces fluctuations in particle variables nearby. The horizontal feeder of coal leads to asymmetrical distribution of local particle HTC. Sand and coal particles exhibit similar distributions in key parameters such as size, temperature, HTC and Reynolds number. The consistent trend in Reynolds number and HTC between sand and coal particles can be attributed to the primary factors influencing these parameters, such as interphase momentum exchange and heat transfer.