GB783483A - Contacting liquids with solids - Google Patents

Abstract

<PICT:0783483/III/1> <PICT:0783483/III/2> A mass of solids (e.g. ion-exchange resin) is confined between two liquid-pervious walls, liquid (from which an undesirable ion is to be removed or a valuable ion recovered) is caused to flow from one wall to the other through the mass, contacted solids are withdrawn from the mass adjacent the first wall while flow of material from the space at other points is prevented, and the mass is replenished by introducing solids adjacent the second wall. Liquid to be treated is pumped (7, 18) to a distributor 19, Fig. 1, located at the bottom of a gravel bed 3 constituting the "first wall" and flows upwards through a bed 4 of ion-exchange resin and through a filter element 9 (the "second wall") comprising a coarse-mesh screen bearing a coco matting, a jute filter cloth and a fine-mesh screen, and flows out through a valve 14. After a time valve 14 is closed and a valve 6 is opened, whereupon the portion of the bed 4 adjacent the gravel bed 3 is "undercut" and conveyed by the liquid flow along the pipe 13 and through the valve 6. The valve 6 is then closed, valve 18 is closed, and a valve 16 leading from a resin slurry tank 5 and a drain valve 8 are opened. Thereupon resin slurry flows in at 15 to replenish the bed, displacing liquid through the valve 8. On completion of this stage the valves are re-set as before. To prevent channelling of the bed 4 during solids removal a "wall" which will allow the passage of solids may be interposed between the gravel bed 3 and the second wall 9. The interposed wall in that case constitutes the "first wall" and the gravel bed is designated the "third wall". The interposed wall may consist of two perforated plates whose apertures do not overlap, or of three grizzly screens, the upper pair having the spaces between the bars parallel but out of alignment and the lower screen having the bars perpendicular to those of the upper pair. In this embodiment, during solids removal the portion of the bed above the "first wall" is retained there by the wall itself and by the upward liquid pressure of the undercutting liquid flow so that the portion of the bed formerly between the third and first walls is wholly removed. On opening of the valves 8 and 16 to permit bed replenishment, solids will pass through the first wall, and the bed added to, from above, until the whole of the space between the second and third walls is filled once more. A modification of this embodiment is shown in Fig. 6, wherein during normal operation liquid to be treated passes from pump 7 through valve 64, distributer 61 and "first wall" 30 into solids 66. For removal of solids, valves 65 and 6 are opened while valve 14 is closed. Liquid passing through distributer 64a, gravel bed 3 (the "third wall") and out through the valve 6 removes solids from the transfer chamber 63 only. Thereupon valves 64, 65 and 6 are closed and valves 16 and 8 opened, so that solids pass from the space 67 through a constriction 62 into the transfer chamber 63, solids pass through the wall 30 to replenish the space 67 and the bed is replenished at the top from the tank 5. In Fig. 7 (not shown) three containers are arranged in series: in the first, ion-exchange of a liquid to be treated takes place, and solids periodically removed from that container are fed to the slurry tank of the second container, up which regenerating liquid is passed. Solids are passed from the second container to the third, where they are rinsed, the used rinsing water being used to make up fresh regenerating solution. The solids are fed in slurry form back to the first container.