| 摘要 |
<p>In the prodn. of chlorine and an aq. alkali metal hydroxide soln. by the electrolysis of a conc. aq. soln. of alkali metal chloride in a cell having a selective permeable membrane and removing from the cell a dilute aq. soln. of alkali metal chloride which is divided into 2 distinct fractions comprising a first fraction which is evapd. and a second fraction which is recycled to the cell with a complementary amt. of alkali metal chloride and water, the improvement is as follows:- Evapn. of the first fraction is controlled to crystallise alkali metal chloride and produce a mother liquor contg. a max. of 30 g sulphate ions per kg. The complementary amt. of alkali metal chloride and water consists of (a) the alkali metal chloride crystallised from the first fraction, which is dissolved in the second fraction, and (b) a satd. alkali metal chloride soln. The process obviates drawbacks of similar processes described in JA-A-54/023099 (Asahi Glass KK) and US-A-4169773 (P.Lai et al), namely, the necessity of storing solid alkali metal chloride, limitation of the purificn. step to a low feed rate of alkali metal chloride aq. soln. and requirement of a special acidification step to decompose chlorate ions.</p> |
