Patent GB-1268421-A (GB)
Title: Water purification process
IPC: B01J49/00
Filed: 1969-03-31
Abstract: 1,268,421. Ion exchange. CRANE CO. 31 March, 1969 [25 Sept., 1968], No. 16720/69. Heading B1J. In a process for the purification of water for example condensate which is used in a steam turbine power plant, by contacting the water with a mixture of granules of cation exchange resin and granules of anion exchange resin, the granules of cation exchange resin having a different specific gravity from the granules of anion exchange resin, the resins are regenerated by a method which comprises the steps of (a) separating the mixture of granules into a first bed containing a major proportion of granules of anion exchange resin and a minor proportion of granules of cation exchange resin and a second bed containing the majority of the granules of cation exchange resin present in the mixture, (b) regenerating with alkali, for example caustic soda, the anion exchange resin present in the first bed but not any anion exchange resin present in the second bed, (c) removing residual alkali regenerant from the first bed, (d) circulating and recirculating ammonia through both beds in series in order to transfer, from the granules of cation exchange resin present in the first bed to the granules of cation exchange resin present in the second bed, alkali metal which may have been derived, at least impart, from the alkali regenerant, (e) regenerating with acid, for example sulphuric acid, the cation exchange resin present in the second bed, (f) removing residual acid regenerant from the second bed and (g) remixing the granules of the first bed and the granules of the second bed. As described, the granules of cation exchange resin have a higher specific gravity than the granules of anion exchange resin so that the separation of the mixture of granules, for example by conventional backwashing and settling procedures, is such that the first bed lies above the second bed but is separated therefrom by an intermediate layer containing at least the majority of the granules of cation exchange resin which are not present in the second bed; the subsequent treatment with alkali regenerant, ammonia and acid regenerant may be effected either while the first bed is isolated from the intermediate layer, for example after the first bed has been transferred from the vessel in which the separation of the mixture of granules was effected to a separate vessel, see Figure 1 (not shown), or while the first bed is resting on the intermediate layer, see Figure 2 (not shown). The apparatus illustrated in Figure 1 essentially is that apparatus illustrated in Figure 1 of Specification 1,225,273 and Figure 2 of Specification 1,224,793 except that a line, incorporating a pump, interconnects the bottom of the separator and cation regenerator to the top of the anion regenerator and a line interconnects the bottom of the anion regenerator to the top of the separator and cation regenerator; the apparatus illustrated in Figure 2 essentially is that apparatus illustrated in Figure 2 of Specification 1,225,273 except that a line, incorporating a pump, interconnects the bottom of the separator and regenerator vessel to the top of the separator and regenerator vessel. Reference also is made to Specifications 1,261,042 and 1,261,074.