Stagnant zones in granular moving bed filters for flue gas cleanup

The flow patterns in three symmetric and two asymmetric louver-walled granular moving bed systems are studied experimentally. The flow pattern histories of granular solids in moving beds were recorded by videocamera throughout the whole test period. The image processing system including a frame grabber was used. Selected discrete images showing the flow pattern development were digitized and stored in files. Individual granular flow frames show a development of quasi-stagnant zones close to the louvered walls, the shear zones and a central flow region with width depending on the louver angle. The vertical shift of one or the other louvered wall in asymmetric configuration considerably influences the history of quasi-stagnant zones.