GB1279008A - Layered ion exchange process - Google Patents

Abstract

1279008 Regeneration of ion exchange resins ILLINOIS WATER TREATMENT CO 16 July 1969 [2 Aug 1968] 35743/69 Heading B1J In the removal of different ions having the same ionic polarity from an aqueous solution by passing the solution in succession through two beds of ion exchange resin disposed in an upright tank and stratified therein one above the other below an upper free-board space, the type of resin constituting one bed differing from the type of resin constituting the other bed, the resin of the beds is regenerated by a process which comprises the sequential steps of (a) discontinuing passage of solution through the beds, (b) introducing water into the tank at a level between the upper bed and the lower bed, the water flowing upwardly through the upper bed to expand the upper bed into the upper free-board space without disturbing the lower bed and to wash from the upper bed and the tank matter accumulated in the upper bed during passage therethrough of the aqueous solution, (c) discontinuing passage of water to allow the resin which originally formed the upper bed to settle and reform the upper bed and (d) introducing into the tank at a level below the lower bed a concentrated solution of a regenerant suitable for regenerating the resin of both of the beds, the regenerant solution flowing upwardly in succession through both of the beds and introducing water into the tank at a level between the upper bed and the lower bed thereby to dilute the regenerant solution flowing into and upwardly through the upper bed. The beds may be in contact with each other whence the level between the upper bed and the lower bed is defined by the interface between the beds; alternatively, the beds may be separated one from the other. As disclosed with reference to Figs. 1 to 4 (not shown), an aqueous solution, for example "raw" water, passes in succession downwardly through a first tank containing an upper bed of weekly acidic cation exchange resin in contact with a lower bed of strongly acidic cation exchange resin and downwardly through a second tank containing an upper bed of weekly basic anion exchange resin in contact with a lower bed of strongly basic anion exchange resin, backwashing of only the upper bed of resin and dilution of regenerant solution passing into the upper bed of resin being effected in respect of each of the tanks in the manner described; as an alternative to diluting the regenerant solution passing into the upper bed of resin in the tank containing anion exchange resins, any desired amount of such regenerant solution may be removed from the tank after passing through the lower bed of resin and without contacting the upper bed of resin. During passage of regenerant solution through either or both of the tanks, the beds of resin may be held in a compacted state either by passing water downwardly through the free-board space above the upper bed of resin or by maintaining the free-board space filled with air under pressure.