关键词: 提升管, 循环流化床, 循环回路, 压降, 压力平衡

Abstract: A riser with varying diameter and dual-loop is set up to study the fluid catalytic cracking (FCC) process of maximizing iso-paraffins (MIP). The riser is composed of a bottom pneumatic transport region with smaller diameter and higher gas velocity and a top fast fluidization region with larger diameter and lower gas velocity. Particles are added to the riser at both the bottom and the middle positions, and two solids circulating loops named main-loop and sub-loop are formed. The pressure balance of the two solids circulating loops and the effects of operating conditions on pressure drops of the riser were investigated in experiment. The pressure drops of both main-loop and sub-loop of the riser decrease with increasing gas velocity. The total solids circulating rate and the pressure drop of the two solids circulating loops increase with increase in the either solids circulating rate, although the increase of one solids circulating rate leads to the decrease of the other. Two circulating loops are influenced by each other, and the prerequisite for normal operation is that pressure balances of both loops are maintained and the pressure of downcomer side is higher than that of riser side at each solids circulating rate control valve. The increase in inventory, downcomer diameter and downcomer height is helpful to maintain the normal operation of system.

Key words: riser, circulating fluidized bed, circulating loop, pressure drop, pressure balance