Sodium metabisulfite process
AssigneeSolvay Minerals, Inc.
InventorsVladimir M. Zolotoochin, Jim P. Metziner, David M. Hansen
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Abstract
Sulfur dioxide is introduced into a solution of sodium sulfite and sodium bisulfite to form sodium bisulfite in a solution having dissolved sulfur dioxide present with a pH between 3.5 and 4.2. The solution is drawn to a cooling crystallizer where sodium hydroxide is added to produce additional sodium metabisulfite that increases the yield of sodium metabisulfite crystallizing per pass. The mother liquor is recycled.
Claims21
A process for manufacturing sodium metabisulfite comprising:
- introducing soda ash into an aqueous solution of sodium bisulfite to form a feed liquor of sodium bisulfite and sodium sulfite;
- then introducing sulfur dioxide into the feed liquor and converting sodium sulfite to sodium bisulfite to form a reaction liquor having dissolved sulfur dioxide;
- then introducing caustic soda into the reaction liquor to react with dissolved sulfur dioxide to form sodium bisulfite;
- cooling the reaction liquor to precipitate sodium metabisulfite from the reaction liquor and form a mother liquor, and
- separating sodium metabisulfite from the mother liquor and recycling the liquor.
An improved process for the manufacture of sodium metabisulfite comprising:
- in a contacting tower, providing a solution comprising sodium bisulfite at a substantially saturated concentration and dissolved sulfur dioxide, said solution having a pH from about 3.5 to about 4.2 and a temperature between about 100.degree. F. and 160.degree. F.;
- in a separate vessel, introducing the solution and adding at least sufficient amounts of sodium hydroxide to react with substantially all of the sulfur dioxide in the solution, and crystallizing sodium metabisulfite from the solution at a temperature between about 50.degree. F. and about 115.degree. F.
In a process for the manufacture of sodium metabisulfite wherein a solution of sodium bisulfite close to saturation is formed in a first vessel, the solution is cooled in a second vessel to crystallize sodium metabisulfite and the sodium metabisulfite is recovered, the improvement comprising introducing sodium hydroxide into the second vessel to form additional sodium metabisulfite therein.
Dependencies are inferred from the claim text.