What are the characteristics of the internal circulation of a circulating fluidized bed boiler?

　　The internal circulation of the circulating fluidized bed boiler is accompanied by particle clusters. Due to the increase in mass and volume of the particle clusters, the free sedimentation rate is relatively high. It cannot move upwards at a certain airflow speed, but sinks downwards against the airflow. During the process, the gas-solid phases will have a relatively large relative velocity. The particle clusters are easily broken up into fine particles by the updraft. The fine particles are driven by the airflow to move upward from the center of the furnace, and then gather into particle clusters during the ascent, settling down along the surrounding walls.