Method for preparing ammonium chloride through co-production of baking soda

Abstract

The invention discloses a method for preparing ammonium chloride by co-production of baking soda, which comprises the following steps: 1) performing primary precipitation of baking soda to obtain crude baking soda and crude mother liquor M1; 2) sodium precipitation: adding sodium chloride into the crude mother liquor M1 to enable residual ammonium bicarbonate and sodium chloride in the crude mother liquor M1 to be subjected to double decomposition reaction again, filtering to obtain fine mother liquor M1 and baking soda, and returning the baking soda to the step 1); (3) cold separation crystallization; 4) salting-out crystallization; 5) secondary separation of baking soda; and 6) mother liquor circulation. According to the sodium precipitation step, residual ammonium bicarbonate in the crude mother liquor M1 further reacts with sodium chloride, and ammonium bicarbonate is decomposed before subsequent cold separation crystallization; the method avoids the phenomenon that sodium bicarbonate generated by reacting ammonium bicarbonate with sodium chloride in the subsequent cold separation process is difficult to separate from ammonium chloride at low temperature due to high content of ammonium bicarbonate in the crude mother liquor, further reduces the content of sodium salt in ammonium chloride, improves the content of ammonia, and also effectively improves the yield of sodium bicarbonate.

Description

technical field [0001] The invention relates to the technical field of chemical production, in particular to a method for preparing ammonium chloride through combined production of 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 number is CN201910000924.4, a circ...

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Problems solved by technology

[0006] In addition, due to the addition of a large amount of sodium chloride solid salt in the salting-out kettle during the salting-out process, when the ammonium chloride crystal slurry crystallized out of the salting-out kettle is directly input into the crystallization kettle through the crystal slurry outlet, the sodium chloride will Ammonium chloride directly enters the crystallization tank, causing the sodium ion in the ammonium chloride product crystallized from the crystallization tank to exceed the standard, making it difficult for the ammonium chloride to reach the agricultural standard and reducing the product quality of the ammonium chloride;

[0007] 2) The content of ammonium salt in the baking soda product prepared by this method is high. The reason is that in the late stage of the metathesis reaction, the concentration of sodium ions becomes thinner, and the metathesis reaction tends to ease from intense, forming an unsuitable sodium chloride and ammonium bicarbonate. The atmosphere of the metathesis reaction makes some of the ammonium bicarbonate lack reaction power and coexist with baking soda in the form of solid crystals, and enter the drying process together with baking soda after filtration and centrifugation. The temperature when drying the baking soda is 50 -60°C, ammonium bicarbonate crystals are difficult to decompose into free ammonia and volatilize at this drying temperature, so that ammonium bicarbonate remains in the baking soda product. However, this method does not include the step of reducing the ammonium salt content in baking soda , and then cause the ammonium salt content in the baking soda product to exceed the standard; another part of ammonium bicarbonate is directly dissolved and cannot collide with the metathesis ions under low sodium conditions to form crystal nuclei, resulting in slow formation of crystal nuclei and slower growth of crystal nuclei, resulting in more crystallization. Fine phenomenon, and then will reduce the follow-up filtration effect and affect the yield of baking soda;

[0008] 3) After the external cooler in this method has been running for a long time, scars formed by a large number of ammonium chloride crystals are attached to the inner wall and the outer tube wall of the exchange tube inside the outer cooler, resulting in the loss of this part of ammonium chloride , it also increases the difficulty of cleaning the external cooler and the exchange tube, thereby reducing the production efficiency of baking soda and ammonium chloride and the yield of ammonium chloride

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