GB861946A - Improvements relating to ion-exchange processes and apparatus - Google Patents

Abstract

A conventional cylindrical vessel 1 has upper and lower collecting and distributing devices 2 and 3 extending transversely across it enclosing an ion-exchange bed. A pipe 4 with two-valve-controlled branches 5 and 6 is connected to the space 7 in the top of the vessel 1 above the device 2, and a similar pipe 8 with two valve-controlled branches 9 and 10 is connected to the space 11 below the device 3. An apertured plate 12 spans the vessel transversely. To start service flow from the position shown in Fig. 1, the liquid under treatment is introduced through the pipes 9 and 8 and the device 3 at a high rate and drives the bed upwards as a <PICT:0861946/III/1> <PICT:0861946/III/2> whole into the position shown in Fig. 2, the space 14 being filled by granules. The rate is then reduced, while treated liquid flows to service through the pipes 4 and 5 until the bed needs regeneration. The bed is of greater volume than the space between the device 2 and the plate 12, so some of it does not pass through the plate and this part drops downwards at the decreased rate of liquid flow to leave a space 15 below the plate 12. Regenerant (or eluant) is introduced through the pipes 6 and 14, and its downward flow causes the bed of granules to move downwards as a whole, so that the space 15 below the plate 12 is completely filled with granules, as shown in Fig. 1. The effluent liquid leaves through the pipes 8 and 10. After regeneration has been completed by rinsing away the excess regenerant by a flow of water in a downward direction, upward flow of the liquid to be treated begins again. Such disturbance of the bed as is caused by the passage of granules through the plate 12 can be minimized by putting the plate at only a short distance, say 10 or 12 inches, above the device 3. The minimum upward velocity through the apertures in the plate 12 necessary to ensure that the bed is continuously pressed against the device 2 varies with the nature of the ion-exchange granules in question.