Particle Velocity and Solids Holdup Characteristics and the Flow Development in a High Density Circulating Fluidized Bed Riser
1. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China;
2. School of Chemical and Chemical Engineering, Yantai University, Yantai 264005, China
Abstract：High density circulating fluidized bed riser is a good reactor for maximizing light olefins by catalytic pyrolysis of oils which is an important technology for refining-chemical integration. An 18 m high riser circulating fluidized bed system is built and experiments are carried out under wide operating conditions with solids flux up to 600 kg/(m2·s) for systematical study of gas-solids flow characteristics and its flow development. Axially, solids holdup decreases monotonously from the riser bottom and keeps constant above 3 m of the riser when solids flux is lower. With high solids flux/density operations, solids holdup increases first with decreasing at the riser bottom and then remain nearly constant at the top of the riser. Radially, solids holdup is lower near the center with fast flow development and relatively higher near the wall region with slow flow development. Particle velocity distribution axially is affected by superficial gas velocity. Particle velocity shows exponential type along the riser and develops fast into constant value when superficial gas velocity is smaller than 5 m/s. It shows inverse “C” shape along the riser when superficial gas velocity is higher. Radial development of particle velocity shows the same trend as the development of solids holdup. Flow structure would be affected by both inlet and outlet showing multi-staged flow characteristics when flowing in a small riser without fully development. In such a tall riser with 18 m in height, gas-solids flow shows fully development with an exponential flow structure.
WANG Chengxiu1,PEI Huajian1,SU Xin1 et al. Particle Velocity and Solids Holdup Characteristics and the Flow Development in a High Density Circulating Fluidized Bed Riser[J]. 化学反应工程与工艺, 2020, 36(1): 8-16.
