Patent ID: 7393378

Claim:
A method for recovering purified sodium bicarbonate and ammonium sulfate from an inlet solution, containing sodium sulfate, comprising the steps of: A) providing an inlet solution containing sodium sulfate; B) converting in a conversion step, the inlet solution to form a sodium bicarbonate precipitate said conversion step including i) adding combined salt containing ammonium bicarbonate and Glauber's salt to the inlet solution; ii) adding at least one of (a) carbon dioxide and ammonia gas or (b) ammonium bicarbonate to the said inlet solution; iii) maintaining an ammonium to sodium ratio of not less than 1; iv) removing said sodium bicarbonate precipitate out of solution from step (iii); C) mixing said solution from step B) (iv) with an ammonium sulfate/sodium sulfate double salt; D) cooling said mixture from step C) to form a combined salt; E) precipitating said combined salt and removing said combined salt out of solution from step D); F) removing residual bicarbonate from said solution from step E); G) mixing said solution from step F with a mother liquor prepared from steps A) to G) and further cooled to precipitate out and remove therefrom a double salt and from which ammonium sulfate has been concentrated and removed; H) cooling the mixture from step G) to precipitate double salt; I) separating precipitated double salt from the said solution from step H) and recycling to step C; and J) recovering ammonium sulfate by concentrating the solution of step I).