GB724003A - Improvements relating to hydrogen-ion-exchange processes for the treatment of water - Google Patents

Abstract

724,003. Purifying water. PERMUTIT CO., Ltd. April 9, 1953. [April 23, 1952 ; April 8, 1953] Nos. 10244/52 and 9556/53. Class 46. Water is treated by passage through two beds of hydrogen-ion-exchange materials, one bed containing strong groups and few or weak groups, and the other weak groups and few or no strong groups, the water under treatment flowing first through the bed containing the weak groups and then through the bed containing the strong groups, and the beds are regenerated by an amount of acid in excess of that required for regeneration of the strong groups, all the regenerating acid flowing through the bed containing the strong groups and either all or all but an initial fraction of the effluent acid from this bed flowing through the bed containing the weak groups. The exchange materials are preferably synthetic resins, that containing the weak groups having a smaller specific gravity than, or smaller. particle size than, that containing the strong groups, a bed of the former resting upon a bed of the latter. Water to be treated is passed downwards through the beds in succession. After backwashing prior to regeneration the beds re-settle as before. Regenerating acid is then passed upwards through the beds in succession, excess from the strong group bed regenerating the weak group bed. Remaining acid is washed from the strong to the weak bed by upflowing wash water where it effects further regeneration. Ordinary water, used for washing, leaves metallic cations in the bottom part of the strong bed which would in turn be taken up by downflowing water in the subsequent service run, such water having become acidic by contact with the preceding part of the beds. This may be avoided by putting the beds in separate containers. Fig. 4, and passing regenerant downwards, first through the lower bed and then the upper ; the washing water follows the same path. The beds may be in one container with an additional distributing device A, Fig. 5. Regenerant from the bed S alone is collected in a tank T, Fig. 5, thence pumped to the top of the bed W, Fig. 6, from which it is removed by the device A, now (after appropriate alteration of valves) acting as a collecting device. Where the water contains much calcium permanent hardness, and sulphuric acid is the the regenerant, the deposition of calcium sulphate in the bed W may be avoided by passing to waste at P, Figs. 4 to 6, that portion of effluent regenerant from the bed S having a high calcium content. Specification 684,848 is referred to.