Particle distribution and pressure drop in a horizontal two-pass liquid-solid circulating fluidized bed heat exchanger

A horizontal two-pass liquid-solid circulating fluidized bed heat exchanger is designed and built to investigate particle distribution and pressure drop by visualization research. The selected working media include water and three types of particles with different densities and settling velocities. The influence of operating parameters, such as circulation flow rate, amount of added particles, and particle type, on the hydrodynamics of liquid-solid two-phase flow is studied using a charge couple device and differential pressure transmitter. The results show uniform and uneven particle distributions in the upper and lower tube pass, respectively. The non-uniform de-gree in the lower tube pass generally decreases with the increase in circulation flow rate, increases with the increase in particle settling velocity, and fluctuates with the increased amount of added particles. The pressure drop ratio fluctuates with the changes in operating parameters. The pressure drop ratio reaches negative values at high circulation flow rates, and the maximum pressure drop ratio range amounts to 11.0% when circulation flow is 4.9 m3/h, the amount of added particles is 0.8%, and particle type is PC1. Three-dimensional diagrams are established to display the effect of operating parameters on particle distribution and pressure drop.