Effect of Jet Gas on Solid Hold-up Profile in the Feed Injection Section of the Riser
喷嘴进料对提升管进料段内颗粒浓度分布的影响

The effect of jet gas on the radial solid hold-up profile in the feedstock injection section of a FCC riser is investigated in a cold-model FCC riser. The experimental results demonstrate that three types of solid hold-up profiles can be used to describe the effect intensities of jet gas on solid flow in the feed injection zone of the riser. The three types have a distinct W-shaped distribution for very strong effect at the axial locations near the nozzle exits, an annular-core one for very weak effect in the axial positions further from the nozzle exits, and an indistinct W-shaped one for stronger effect between the two areas. Changes of solid hold-up from a W-shaped profile to an annular-core one indicate the lowered effect of jet gas on solid flow when increasing the jet gas velocity or decreasing the pre-lift gas velocity. Furthermore, the momentum ratio of jet gas to pre-lift two-phase mixture, Mj/Mr, is introduced to describe the effects of physical properties of gas and solid, operating conditions, and equipment configuration on solid hold-up distribution. With increasing Mj/Mr, the radial solid hold-up profile turns gradually from a W-shaped to an annular-core. The effects of operating conditions and equipment dimensions on solid flow are dependent on the momentum ratio, They are about 0.675-1.075 m when the momentum ratio is smaller than 4.21, and about 0.375-0.675 m when the momentum ratio is greater than 4.21.