What are the methods for preparing ammonium chloride?

Ammonium chloride, abbreviated as ammonium chloride. It refers to the ammonium salt of hydrochloric acid, which is mostly a by-product of the alkali industry. Containing 24%~26% of nitrogen, it is white or slightly yellow square or octahedral small crystal. It has two dosage forms of powder and granular. Granular ammonium chloride is not easy to absorb moisture and easy to store, while powdered ammonium chloride is used more. Production of basic fertilizer for compound fertilizer.

Method for preparing ammonium chloride:

1. Recrystallization method: the crude ammonium chloride is added to a dissolver, dissolved by steam, filtered, and the filtrate is cooled and crystallized, centrifuged, and dried to obtain an industrial ammonium chloride product. The centrifuged mother liquor is returned to the dissolver for use;

2. Metathesis method: firstly, the ammonium chloride mother liquor is added to the reactor and heated to 105 ° C, ammonium sulfate and salt are added, and the metathesis reaction is carried out at 117 ° C to form an ammonium chloride solution and sodium sulfate crystals, and the sodium sulfate is removed by filtration. The ammonium chloride saturated solution is sent to a cooling crystallizer, cooled to 32-35 ° C to precipitate crystals, filtered, and the crystals are respectively rinsed with four different concentrations of ammonium chloride solution to control Fe <0.008%, SO42-< 0.001%, after rinsing to pass, the crystals are re-pulped into a slurry with ammonium chloride solution, sent to a centrifuge for separation and dehydration, and then dried by hot air to obtain an industrial ammonium chloride product. The mother liquor is sent to the metathesis reactor for recycling. The separated sodium sulfate is used for the production of Yuan Ming powder;

3. Gas-liquid phase synthesis method: hydrogen chloride gas is introduced from the bottom of the turbulent absorption tower, and is contacted with the circulating mother liquor sprayed at the top of the tower to form a saturated hydrogen chloride ammonium chloride mother liquor flowing into the reactor, and neutralizing with ammonia gas. , a saturated solution of ammonium chloride is formed. It is sent to a cooling crystallizer and cooled to 30 to 45 ° C to precipitate supersaturated ammonium chloride crystals. The upper ammonium chloride solution of the crystallizer is sent to an air cooler for cooling and recycled to the crystallizer; the lower crystal slurry is thickened by a thickener and then centrifuged to obtain a food grade ammonium chloride product. The mother liquor separated by centrifugation is sent to a turbulent absorption tower for recycling;