Solids holdups of gas-solid two-phase upward flow in fully developed region of CFB riser

Systematic experiments were conducted with FCC particles in a 16 m high CFB riser to investigate the solids holdup in a fully developed section of the riser, with superficial gas velocity U_g from 2.0 to 10.3 m·s^-1 and solids circulating rate G_s from 5.4 to 230 kg·m^-2·s^-1. Of 134 sets of operation conditions employed in the experiments, there were 113 sets of operation conditions under which the gas-solids two-phase flow became fully developed in the upper or even the whole section of the riser. It is found that in a fully developed section of the riser, the average solids holdup ε_s increases linearly with the increase of solids circulating rate G_s and decreases with the increase of superficial gas velocity U_g, with a trend rather different from that reported in literature. The correlation for solids holdup in a fully developed section of CFB riser is in good agreement with the experimental data and also explains the differences among the predicted results of other authors, delineating more clearly the variations of solids holdup in a fully developed section with operation parameters.