GB1137679A - Procedures and apparatus for electrodialytic treatment of liquids - Google Patents

Abstract

1,137,679. Electrodialysis cells. WALLACE & TIERNAN Inc. Feb.23, 1966 [Feb.24, 1965], No. 8030/66. Heading C7B. An electrodialysis cell comprises an inner electrode 23, a hollow outer electrode 24 concentrically arranged about said inner electrode, at least one permselective membrane being concentrically arranged between said electrodes and at least one of the chambers thereby formed being filled with divided solid ion-exchange material. If two or more membranes are present, adjacent membranes are made cation-permeable and anionpermeable respectively, the chamber therebetween forming the treatment chamber for liquid to be demineralized or concentrated. As shown liquid to be treated is supplied to the chamber 37 via pipe 46, and also to the outer anode chamber 38 to form an anolyte, which is withdrawn from the anolyte chamber 38 via pipe 52 and passed into the inner catholyte chamber 32. During passage from anolyte to catholyte some of said fluid may be withdrawn through outlet 55b and replenished through inlet 55a. The anion and cation exchange membranes, 28 and 32 may be arranged either such that the liquid becomes demineralized, or becomes more concentrated. The cell may contain a greater number of membranes, arranged alternatively Fig. 3 (not shown), such that a plurality of deminerization and concentration chambers are formed, and the liquid to be treated may be passed through similar chambers either in series or in parallel. The cell may be used for demineralizing water for domestic or industrial use. In a household water softening system including such electrodialysis cell, Fig. 4 (not shown), hard, raw water is passed to the cell via a sand and gravel filter (82) and demineralized water is passed from the electrodialysis cell via a storage tank (83) and pressure tank (92) to service. In a system for demineralizing boiler feed water, Fig. 5 (not shown), raw water is passed to a degassifier (98) in which carbon dioxide is removed by passage through the water of a stream of air, the degassed water is then chlorinated and passed to a coagulator (100) in which it is coagulated chemically with lime and alum which partially softens the water. The resultant water is then passed via sand and gravel filters (106) to a bank of electrodialyis deionizing cells according to the present invention, which cells operate in parallel.