Cyclic manufacturing method for coproduction of baking soda and ammonium chloride

Abstract

The invention relates to a cyclic manufacturing method for coproduction of baking soda and ammonium chloride. The cyclic manufacturing method comprises the steps of primary precipitating of baking soda, cold precipitation crystallization, salt precipitation crystallization and mother liquor cycling which are conducted sequentially; and the cyclic manufacturing method further comprises the step that the step of secondary precipitating of baking soda is arranged between the salt precipitation crystallization step and the mother liquor cycle step, and the step of secondary precipitating of bakingsoda is used for further precipitating the baking soda from baking soda mother liquor (I-II) generated after salt precipitation crystallization. By adopting the cyclic manufacturing method, energy consumption of ammonium chloride recovering through cold precipitation crystallization can be decreased, the baking soda and the ammonium chloride are efficiently produced, meanwhile, full cycle of motor liquor generated in a reaction in the production process is achieved, the process is easy, and the production cost is low.

Description

technical field [0001] The invention relates to a technical field of chemical production, in particular to the production of baking soda (NaHCO 3 ) method, in particular to a recycling method for preparing baking soda and co-producing ammonium chloride. Background technique [0002] In the production process of preparing baking soda and co-producing ammonium chloride by double decomposition method, the separated baking soda mother liquor contains NaCl, NaHCO 3 , NH 4 Cl, wherein sodium bicarbonate is in a saturated state. In the prior art, the mother liquor is directly frozen and added to NaCl for salting out. Sodium bicarbonate is also precipitated together with ammonium chloride due to supersaturation, so that the quality of the ammonium chloride product cannot reach Requirements of national standards (regulation in the national standard of agricultural ammonium chloride of 92 editions: Na in agricultural ammonium chloride + Content ≤ 1.4%); And the nitrogen content in ...

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Problems solved by technology

[0002] In the production process of preparing baking soda and co-producing ammonium chloride by double decomposition method, the separated baking soda mother liquor contains NaCl, NaHCO 3 , NH 4 Cl, wherein sodium bicarbonate is in a saturated state. In the prior art, the mother liquor is directly frozen and added to NaCl for salting out. Sodium bicarbonate is also precipitated together with ammonium chloride due to supersaturation, so that the quality of the ammonium chloride product cannot reach Requirements of national standards (regulation in the national standard of agricultural ammonium chloride of 92 editions: Na in agricultural ammonium chloride + content ≤ 1.4%); and the nitrogen content in ammonium chloride products does not reach the national standard of 25%

[0003] However, if the mother liquor is discharged directly, the ammonia nitrogen will seriously pollute the river water source. In order not to discharge waste water, it is often used to recover ammonium chloride and salt by evaporation, but this method has many disadvantages. On the one hand, the mother liquor contains ammonium chloride The total amount of sodium chloride and sodium chloride does not exceed 200g / L, and every ton of ammonium chloride needs to evaporate 5-6 tons of water, and consumes 0.8 tons of coal. In addition, the evaporated salt is difficult to reach industrial-grade standards

These factors make it difficult to industrialize the use of metathesis soda, and the economical practicability is poor

[0004] Chinese patent CN102107889B discloses a method for treating ammonium chloride in baking soda mother liquor at normal temperature. It specifically discloses the baking soda mother liquor after filtration and centrifuge dehydration. The content of free ammonia in the mother liquor is less than 1.3%, and the pH value is 6.5-7.1; hydrochloric acid is reacted with free ammonia and a small amount of ammonium bicarbonate to generate ammonium chloride, and hydrochloric acid is reacted with a small amount of sodium bicarbonate to generate sodium chloride; The consumption is large, the process cost is high, and the mother liquor after salting out is not reclaimed baking soda, the yield of baking soda is 60%~80%

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