Study On The Flow Characteristics In Horizontal Liquid-solid Circulating Fluidized Bed

As a novel on-line self-cleaning and heat transfer technology,circulating fluidized bed heat exchange is favorable to the heat transfer enhancement and fouling prevention.In order to investigate the hydrodynamic performance of the liquid-solid circulating fluidized bed heat exchanger,a cold horizontal liquid–solid circulating fluidized bed is designed and built.The effects of the operating parameters,such as the circulation flow rate,the amount of added particles,particle types and so on,are systematically investigated by using the image measurement and acquisition system of a charge-coupled device(CCD)and pressure measurement system.Based on the tube bundle experiment,a distributor is designed and joined to improve the particle distribution.Firstly,the effects of the circulation flow rate,the amount of added particles and particle types on particle distribution and pressure drop in horizontal multi-tube circulating fluidized bed were investigated.The results showed that the pressure drop increases with the increase in the amount of added particles,circulation flow rate,but fluctuates with the increase in the sediment velocity of the particle.The pressure drop ratio increases with the increase in the amount of added particles.The pressure drop ratio initially decreases and then increases slightly with the increase in the circulation flow rate,but fluctuates with the increase in the sediment velocity of the particle.Secondly,the effects of the fluid velocity,the amount of added particles,particle types and pipe diameter on particle distribution and pressure drop in horizontal single-pipe circulating fluidized bed were investigated.The results showed that the solid holdup increases with the increase in the fluid velocity,the amount of added particles and pipe diameter,but decreases with the increase in the sediment velocity of the particle.The non-uniform degree of the particle distribution decreases with the increase in the fluid velocity,but increases with the sediment velocity of the particle.The non-uniform degree increases initially and then decreases with the increase in the pipe diameter,but slightly fluctuates with the increase in the amount of added particles.The pressure drop of the liquid-solid two-phase flow of the horizontal single pipe is not greater than that of the single-liquid phase;the pressure drop ratio decreases with the increase in the fluid velocity,but fluctuates with the increase in the amount of added particles and the sediment velocity of the particle.Finally,the addition of the distributor can improve the uniformity of the particle distribution,especially when the angle of the distributor is 27°.According to the results of the study,the phase diagrams are established to display the variation ranges of the operating parameters for particle distribution and pressure drop and used to guide industrial production practice.