Process for recovering chemicals from the waste liquors of sulfate cellulose digestion and the waste waters of bleaching

摘要

A process for the recovery of chemicals from the waste liquors of sulfate cellulose digestion and from the waste waters of bleaching, wherein a melt from a soda-ash roaster, mainly containing sodium sulfide and sodium carbonate, but also sodium chloride, is dissolved and clarified to produce green liquor containing carbonate, sulfide and chlorides is dissolved. The carbonate is separated from the sulfide and the chlorides, at least part of the sodium chloride is separated from the sulfide in solution, at least part of the carbonate is causticized into hydroxide, and the hydroxide and sulfide in solutions is mixed together in a ratio suitable to form a digestion solution with a desired sulfide content.