GB725660A - Improvements in or relating to the loading and regeneration of ion exchangers used in ion exchange processes - Google Patents

Abstract

<PICT:0725660/III/1> <PICT:0725660/III/2> A method of loading and regenerating an ion exchange system comprising a set of columns arranged in a series packed with ion exchanger to be loaded and another series of columns containing ion exchanger to be regenerated, is characterized in that the series to be loaded is divided into two groups, the loading solution is passed through the two groups in succession, the solution discharged from the last column of the second group is freed by crystallization from a large part of the compound formed during loading, the mother lye is concentrated and returned to the first column of the second group. The regenerating solution passes through the regenerating series of columns in such amount that regeneration is incomplete but a virtually pure regenerated solution leaves the last column. In Fig. 1 the columns C1 to Cm and D1 to Dn constitute the first and second groups of the loading series. The loading solution B2A2 is passed through the columns in succession and the solution leaving the last column of the second group is freed from the B1A2 compounds formed, by crystallization at Cr, and the residual lye is evaporated at Ev and returned to the first column of the second group, that is, D1. The regeneration is shown in Fig. 2 where columns E1 to Ep are arranged in series and are transversed by the regenerating solution B1A1 the amount thereof being such that a virtually pure B2A1 solution leaves the last column. Periodically the columns are disconnected and switched over so that the first column E1 in the regenerating group becomes the last column of the first loading group; at the same time column C1 is added to the end of the regeneration group and column D1 becomes column Cm, the cycle is then repeated. The invention is illustrated by the production of potassium nitrate crystals and calcium chloride solution from calcium nitrate solution and potassium chloride solution, six columns in two groups of three being employed for loading and a single group of three for regenerating. During loading the columns, saturated with potassium ions, are treated with a calcium nitrate solution passed therethrough, until the final column of the first group is 100 per cent. saturated with calcium ions. After leaving the last column potassium nitrate is crystallized out and the residual lye returned to column D1. Regeneration is effected with potassium chloride solution to such an extent that the regenerated column is only 80 per cent. saturated with potassium ions.