J.T. Kuo

Velocity profiles of granules in moving bed filters

The velocity fields in three symmetric and two asymmetric louver-walled moving bed systems were studied experimentally. The horizontal and vertical velocity distributions at five levels of the louver section were plotted. The results indicate that the velocity profiles of filter granules are influenced by the louver geometry. When the louver angle is steep, the velocity profile of filter granules is close to plug flow. When the louver section is shallow, the quasi-stagnant zones exist along the louver walls. The kinematic model for predicting the granule velocity distribution is used for analyzing the three symmetric louver configurations at different height levels.

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.

Flow patterns and stresses on the wall in a moving granular bed with eccentric discharge

The flow patterns and stresses on the wall in a moving granular bed with eccentric discharge were investigated experimentally. The flow pattern histories of granular solids in the moving bed were recorded using a digital camcorder. The image processing system included a frame grabber. A new pressure gauge for simultaneously measuring the normal and shear stresses of granular solids was used. During filling the granular material, the variations in stresses acting on the side walls with time in a granular bed were observed. Also, the dynamic wall stresses were obtained during the eccentric discharge. Employing the results obtained by stress measurements and image processing, the pressure pulsation phenomena in a moving granular bed may be understood further.

Numerical simulation of flow patterns of disks in the asymmetric louvered-wall moving granular filter bed

Abstract Using the Discrete Element Method (DEM) model [P.A. Cundall, O. Strack, Geotechnique, 29 (1979) 47.], the granular solid flow pattern histories, velocity field and quasi-stagnant zone development close to the louvered walls of six kinds of 2-D asymmetrical moving granular filter beds were studied numerically. The numerical results reported here and the experimental results [J.T. Kuo, J. Smid, S.S. Hsiau, C.Y. Wang, C.S. Chou, Filtr. Sep., 35(6) (1998) 529.] provide fundamental and important information for designing moving granular bed high-temperature flue gas cleanup filters.

Flow patterns and velocity fields of granules in Dorfan Impingo filters for gas cleanup

Inside a two-dimensional model of the louvered Dorfan Impingo panel with transparent front and rear walls the flow regions of filter granules without gas the cross-flow were observed. The white PE beads were used as filter granules. Colored PE beads served as tracers. Filter granules were discharged and circulated to the bed. The flow rate of filter medium was controlled by the belt conveyor. The image processing system was used to record the granular flow. The flow patterns and the quasi-stagnant zones history in the moving granular bed were evaluated. The experiment showed that there exists a fast central moving region (flowing core) of filter granules and two quasi-stagnant zones along the louver walls. The velocity fields in the moving bed in the Dorfan Impingo filter systems were also measured and analyzed. The results indicate that the velocity profiles of filter granules are influenced by the louver geometry.

Numerical simulation of flow patterns of disks in the symmetric louvered-wall moving granular filter bed

Abstract Employing the stack disk method in the louvered-wall configuration described in the Appendix, the initial coordinates of the disks center and the filter boundary were defined. The flow pattern histories of granular solids, velocity field and development of quasi-stagnant zones close to the louvered walls of three kinds of two-dimensional (2D) symmetrical moving granular filter beds and 2D hybrid moving granular filter beds were studied numerically. The discrete element method was used in this study. The numerical results reported here and experimental results provide fundamental and important information for designing moving granular bed for high-temperature flue gas clean-up filters.

The flow patterns and stresses on the wall in a symmetric louvered-wall moving granular filter bed

Abstract The flow patterns and stresses on the wall in a symmetric two-dimensional louvered-wall moving granular filter bed were investigated. The static wall stress distributions produced by the granular solids were measured and compared with the theoretical prediction using the differential slice and Runge–Kutta (order four) methods. The variations in the dynamic wall stresses with time in a moving granular filter bed were obtained. In addition, the effect of the louver angle upon the flow patterns and wall stresses was investigated. Four different flow regions were observed in a moving granular filter bed. As the angle of the louver decreases, the quasi-stagnant zone area adjacent to the side wall becomes smaller and the static normal stress acting on the convergent section of the side wall becomes larger. The magnitude of the static normal stress acting on the convergent section is approximately 10 times as large as that acting on the vertical section. When the normal stress measured by pressure gauge installed on the upper stage decreases to zero, the normal wall stress measured by pressure gauge installed on the adjacent lower stage then begins to descend and fluctuate under the static normal wall stress during granular material withdrawal. Employing the results obtained using stress measurements and image processing, the pressure pulsation phenomenon in a symmetric two-dimensional louvered-wall moving granular filter bed may be further understood.