Process for purifying aqueous buffer solutions
OwnerOlav Ergainventor
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Abstract
The present invention describes a procedure for the removal of sodium sulphate from a phosphate solution that has been used for absorption of SO2 from flue gases, in which a precipitate forms when the absorption solution is regenerated by evaporation. In this procedure a part of the precipitate is separated from its solution and treated with water and SO2 for transformation of disodium-hydrogen phosphate into monosodium dihydrogen phosphate in the aqueous solution. The sodium sulphate remains undissolved and is removed by filtration. The filtrate is then added back to the main process.
Claims6
A process for removal of sodium sulphate from a phosphate solution which has been used for absorption of SO2 from flue gases, comprising:
- subjecting the phosphate solution to evaporation to form a precipitate containing di-sodium-hydrogen-phosphate,
- separating a part of the precipitate from the phosphate solution,
- treating the separated precipitate with water and SO2 to transform the di-sodium-hydrogen-phosphate into mono-sodium-di-hydrogen-phosphate in aqueous solution, wherein the aqueous solution contains undissolved sodium sulphate and optionally undissolved sodium pyrosulphite/sodium hydrogen sulphite,
- removing the undissolved sodium sulphate by filtration to form a filtrate, and
- adding the filtrate back into the phosphate solution for absorption of SO2 from flue gases.
Dependencies are inferred from the claim text.