Effect of exit structure on the particle velocity distribution in the dilute region of a rectangular circulating fluidized bed riser

In order to study the effect of exit deflecting arrangement and hanging screen arrangement on the particle velocity distribution under different operation parameters,the left wall and front wall in the dilute region were tested by using a high-speed video camera,in a plexiglas rectangular CFB cold model.The particle velocity profile were analyzed through combining with particle image velocimetry(PIV) technology.The results showed that the distribution of flow field was dramatically affected by exit deflecting arrangement.Under the action of exit gravity,a core-annulus distribution of flow zone near the left wall side was no longer presented,with the complete lateral velocity hardly,and severe erosion below the exit.Because of the blocking of the hanging screen and wall friction,the direction of the particle motion was changed,and a particle re-distribution appeared in the flow zone between the hanging screen and wall,showing the parabola profile of the particle axis velocity similar to the whole cross-section of the furnace.As the furnace outlet effects were weakened by hanging screen arrangement,the particle distribution near the right wall were mainly restrained by the flow and wall friction.