Effects of particle type on the particle fluidization and distribution in a liquid–solid circulating fluidized bed boiler

Abstract

• Circulating fluidized bed technology is combined with boiler. • Effects of particle type on particle fluidization and distribution are investigated. • Particles accumulation exists at the bottom of the drum for all types of particles. • Particle properties obviously affect the fluidization and distribution of particles. • The non-uniform degree decreases with increased feedwater flow rate. A liquid–solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can’t be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally, the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes. Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.