CFD-DEM study of the effect of ring baffles on system performance of a full-loop circulating fluidized bed

Abstract

Gas-solid distribution is non-uniform in the circulating fluidized bed (CFB), which deteriorates gas and solid mixing, causing a lower system performance. In this work, the effect of ring baffles on system performance of a full-loop CFB is comprehensively studied using the computational fluid dynamics-discrete element method (CFD-DEM). Detailed information (i.e., solid velocity, solid flux, solid circulation rate, solid inventory height, solid residence time, and solid dispersion) are obtained and analyzed. Meaningful results include: (i) ring baffles improve the inter-particle and inter-phase interactions, and solid particles become more uniformly dispersed in the riser; (ii) introduction of ring baffles increases the solid holdup in local regions of the riser while has a slight influence on pressure drop; (iii) increasing the number of ring baffles and the spacing between ring baffles increases the solid circulation rate and solid inventory height, decreases solid cycle time in the system and SRT in the riser, increases SRT in the dipleg, and has a slight impact on SRT in the cyclone; (iv) the average solid dispersion coefficients in the riser along three directions are 0.675 × 10−3, 0.522 × 10−3, and 8.415 × 10−3 m2/s, and the insertion of ring baffles decreases the overall dispersion intensity in the axial direction while has a slight influence in the radial direction.