Flow of filter granules in moving granular beds with louvers and sublouvers

It is important to develop the technology of high-temperature gas cleanup for some advanced power generation systems based on the gasification or combustion of coal or biomass. The moving granular bed filter has great potential to be developed for the hot gas cleanup. However the existence of stagnant zones in granular moving bed systems with louvered walls cause major technical problems, especially in filtration and adsorption processes. With the existence of stagnant zones, the dust particulates and fly ash coining with flue gas may plug the system and the filtration efficiency decreases remarkably. We propose a new design by placing sublouvers into the convergent channel between louvers to diminish the stagnant zones. This paper presents the results of a study of the flow patterns in a quasi two-dimensional cross-flow moving granular bed with systems of louvers and sublouvers. Silica sands were used as filter granules which were discharged from an upper hopper and circulated to the bed. An image processing system was used to record the granular flow for the investigations in flow patterns of filter granules. The velocity field and velocity distributions of filter granules are also evaluated and discussed. In this study, the design of sublouver-system moving bed has been optimized to almost completely eliminate the stagnant zones. (C) 2007 Elsevier B.V. All rights reserved.