Method for preparing baking soda with low ammonium salt content by co-production of baking soda and ammonium chloride

Abstract

The invention discloses a method for preparing baking soda with low ammonium salt content by co-production of baking soda and ammonium chloride, the method comprises the following steps: 1) performing primary precipitation of baking soda to obtain crude baking soda and mother liquor M1; 2) carrying out cold separation crystallization; 3) salting out and crystallizing, and separating and recovering ammonium chloride; 4) secondary separation of baking soda; 5) mother liquor circulation: collecting the brine generated by ammonium chloride separation in the step 3) and the brine generated in the step 4) to obtain a supernatant, and returning the supernatant to the step 1) as mother liquor M2 for recycling; and 6) deamination: mixing the mother liquor M2 and the coarse baking soda, carrying out replacement reaction again to generate fine baking soda, and filtering, washing, dehydrating and drying the obtained fine baking soda to obtain the baking soda with low ammonium salt content. According to the method, the mother liquor M2 and the crude baking soda are further reacted through the deamination step to obtain the baking soda, residual unreacted ammonium bicarbonate is decomposed, the yield of the baking soda is increased, the ammonium salt content in the baking soda product is reduced, and the baking soda product reaches the national food standard.

Description

technical field [0001] The invention relates to the technical field of chemical production, in particular to a method for preparing baking soda with low ammonium salt content by co-producing ammonium chloride with baking soda. Background technique [0002] Baking soda, also known as sodium bicarbonate, is a kind of inorganic salt, white crystalline powder, odorless, alkali taste, soluble in water, widely used in pharmaceutical industry, food processing, fire fighting equipment and other industries, its industrial preparation It is mainly made of brine and ammonium bicarbonate by metathesis reaction. The metathesis reaction is the reaction of ammonium bicarbonate and sodium chloride in brine to generate baking soda and ammonium chloride, thereby realizing the purpose of co-producing ammonium chloride with baking soda . [0003] In the prior art, there are many improvements to the method of co-producing ammonium chloride with baking soda. For example, the patent application n...

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Problems solved by technology

[0004] When adopting the above method to prepare baking soda, due to the later stage of the metathesis reaction, the concentration of sodium ions becomes thinner, and the metathesis reaction tends to ease from the intense, forming an atmosphere that is not suitable for the metathesis reaction of sodium chloride and ammonium bicarbonate, so that a part of the ammonium bicarbonate Lack of reaction kinetics and co-exist with baking soda in the form of solid crystals and enter the drying process together with baking soda after filtration and centrifugation, while the drying temperature of baking soda is 50-60 ° C, it is difficult for ammonium bicarbonate crystals to dry in this It decomposes into free ammonia and volatilizes under the drying temperature, so that ammonium bicarbonate remains in the baking soda product. However, the method does not include the step of reducing the ammonium salt content in the baking soda product, which leads to the excessive ammonium salt content in the baking soda product Another part of ammonium bicarbonate is directly dissolved and cannot collide with metathesis ions under low sodium conditions to form crystal nuclei, resulting in slow formation of crystal nuclei and slower crystal growth, resulting in finer crystallization, which in turn reduces the subsequent filtration effect And affect the yield of baking soda

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