PROCESS FOR PRODUCING SODIUM BICARBONATE

Preparing sodium bicarbonate comprises (a) mixing a stream (A) containing sodium carbonate and at least one impurity comprising a water-soluble alkali metal salt to produce a stream (C); (b) bicarbonizing the stream (C) with a gas (D) comprising carbon dioxide to prepare an aqueous suspension (E) comprising crystals (F), preferably sodium bicarbonate crystals; (c) separating (E) to obtain (F) comprising sodium bicarbonate crystals on the one hand, and an aqueous mother liquor (G) on the other; and (d) partially decarbonizing at least one part of (G). Preparing sodium bicarbonate comprises (a) mixing a stream (A) containing sodium carbonate and at least one impurity comprising a water-soluble alkali metal salt in a concentration (Ci(A)) with at least one portion of a stream (B) to produce a stream (C); (b) bicarbonizing the stream (C) with a gas (D) comprising carbon dioxide to prepare an aqueous suspension (E) comprising crystals (F), preferably sodium bicarbonate crystals; (c) separating (E) to obtain (F) comprising sodium bicarbonate crystals on the one hand, and an aqueous mother liquor (G) on the other; (d) partially decarbonizing at least one part of (G) and removing one part of the water from at least one portion of (G) to obtain the stream (B) having at least one impurity of water-soluble salt of alkali metal at a concentration (Cf(B)) and an optional gas (H); (e) recycling at least one portion of (B) into step (a), so that the ratio of the concentrations Cf(B) to Ci(A) is at least 1.4, preferably 7; and (f) removing the residue of the (B) or the residue of (G) for further processing. An independent claim is included for preparing sodium carbonate and sodium bicarbonate crystal comprising introducing a solution containing sodium carbonate and at least one impurity comprising a water-soluble alkali metal salt in a sodium carbonate crystallizer, preparing a first aqueous suspension comprising sodium carbonate crystal, separating the first aqueous suspension to obtain crystals of sodium carbonate on one hand and a mother liquor, on the other hand, where a part of the mother liquor is removed from the sodium carbonate-crystallizer to obtain sodium carbonate containing the stream (A) and further processing the sodium carbonate containing the stream (A) as above per se.