| 摘要 |
PURPOSE:To recover the titled chemicals from a mixture of sodium chloride and sodium sulphate by subjecting a sodium chloride-sodium sulphate eutectic composition liquid obtained by concentrating a sodium chloride-sodium sulphate mixed solution and separating sodium sulphate by precipitation or the composition liquid in the vicinity thereof to electrolysis. CONSTITUTION:For example, a dust of an electric dust collector (EP ash) of a pulp mill is dissolved in water in a dissolving tank (a) and, after NaOH, Na2CO3 etc. is added, the obtained solution is introduced in a stationary tank (b) and Mg compound, Ca compound or the like precipitated therein are withdrawn from a pipe 2. The overflow solution of the tank (b) is introduced into an evaporation boiler (c) and concentrated by steam from a pipe 19. The precipitated sodium sulphate is withdrawn from a pipe 5 and the sodium chloride-sodium sulphate eutectic composition liquid is further concentrated in an evaporation boiler (d) to precipitate the sodium chloride-sodium sulphate mixture. This precipitate is dissolved again in water from a pipe 9 in a dissolving tank (e). A part of the residual liquid after precipitation in the boiler (d) is purged by a pipe 7. The dissolving solution is electrolyzed in an electrolytic tank (f) and a Cl2 gas and a NaOH solution preduced therein are introduced into a sodium hypochlorite reaction tower (g) and reacted therein. |
