Experimental study of the effect of internals on optimizing gas–solid flow in a circulating fluidized bed

The solids concentration in a circulating fluidized bed of flue gas desulfurization (CFB-FGD) is low, and the gas–solid mixing needs to be strengthened to improve the reaction efficiency. The addition of internals in a square CFB-FGD is studied here. Different sizes of wedge-shaped internals were set in the middle of the riser on opposite sides of the bed, at same height or at different heights. By comparing the concentration distributions, we found that positioning the internals at different heights is more effective in increasing the density of the center region. By observing the radial distribution of the fractal dimension, we found that a strong degree of turbulence can improve the gas–solid mixing. A larger upper/smaller lower arrangement of the internals with a moderate apparent gas velocity provided the best flow field, with increased concentration gradients and improved gas–solid mixing.