GB732131A - Improvements in or relating to the production of alkali metal hydroxides - Google Patents

Abstract

732,131. Heating and cooling liquids by direct contact with liquids. IMPERIAL CHEMICAL INDUSTRIES, Ltd. July 29, 1953 [July 30, 1952], No. 19265/52. Class 64 (1). [Also in Group XXXVI] In the manufacture of alkali metal hydroxide by electrolysis of an alkali metal chloride solution using a flowing mercury cathode and thereafter reacting the alkali metal amalgam so formed with water in a separate denuder, heat is transferred from the hot mercury leaving the denuder to the cold amalgam entering the denuder through the medium of an aqueous liquid which is brought into direct heat transfer relationship with both the hot mercury and the cold amalgam. The aqueous liquid may be a solution of the alkali metal hydroxide. In a particular embodiment of the invention, sodium chloride solution is electrolysed in a cell, from which amalgam flows to a counter-current heat interchanger 2 and thence to a denuder 3 where it reacts with water entering at 4. Mercury and dilute sodium hydroxide solution from the lower end of denuder 3 are raised by a pump 5 and delivered into a mercury shoot 7, the mercury flowing into cell 1. A water feed entering at 8 washes the mercury and then flows over a weir 9 to join the hot solution; the hot solution then flows down a pipe 10 to enter the heat interchanger 2, where it flows counter-current to the amalgam from the cell, and then flows along a pipe 11 to the pump end 4 of the denuder 3. Specification 19842/48, as open to inspection under Sect. 91, is referred to.