A kind of method for preparing sodium dihydrogen phosphate from wet-process phosphoric acid

Abstract

The invention relates to the technical field of preparing sodium phosphate salt by wet-process phosphoric acid, in particular to a method for preparing sodium dihydrogen phosphate by wet-process phosphoric acid. The wet-process phosphoric acid is mixed with ammonia water or ammonia gas, and the pH value of the solution is controlled between 3.0-7.0. After the reaction is completed, it is filtered to remove impurities in wet-process phosphoric acid to obtain a relatively pure ammonium phosphate slurry, and then sodium is added to the slurry to generate sodium dihydrogen phosphate, and then combined with the The degree of vacuum is controlled at 0-0.01MPa, so that the crystallization speed is effectively controlled, thereby avoiding the defect of poor purity of the product caused by excessive crystallization, and the degree of crystallization in the entire production process is easy to control after being controlled by the degree of vacuum. The difficulty of the production process is reduced.

Description

technical field [0001] The invention relates to the technical field of preparing sodium phosphate salt by wet-process phosphoric acid, in particular to a method for preparing sodium dihydrogen phosphate by wet-process phosphoric acid. Background technique [0002] Sodium Dihydrogen Phosphate (Sodium Dihydrogen Phosphate), colorless orthorhombic crystal, slightly hygroscopic, soluble in water; used for boiler water treatment, electroplating, tanning, baking powder, fuel additives, detergents, mica thorough It is also a raw material for preparing sodium hexametaphosphate and polycondensation salt. In the prior art, the production method of sodium dihydrogen phosphate is mainly produced by reacting thermal phosphoric acid and wet phosphoric acid with sodium components. However, due to the high cost of thermal phosphoric acid production, it has been replaced by wet phosphoric acid in recent years. replaced by a large number. However, since wet-process phosphoric acid is obtain...

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Problems solved by technology

However, since wet-process phosphoric acid is obtained by the action of phosphate rock and inorganic acid, its quality varies with the quality of phosphate rock, and in China, there are many low-grade phosphoric rocks, which leads to the quality of wet-process phosphoric acid. Generally low, the impurity content is more, and the impurity composition is abundant; Therefore, in the process of using wet-process phosphoric acid to prepare sodium dihydrogen phosphate product, wet-process phosphoric acid needs to be purified to ensure the purity of sodium dihydrogen phosphate product. Although a large amount of impurities in wet-process phosphoric acid can be removed, there are still a small amount of impurities, and the composition is relatively complex. In the process of preparing sodium dihydrogen phosphate by wet-process phosphoric acid, due to improper treatment of wet-process phosphoric acid, It will lead to the interaction between the impurities in the wet-process phosphoric acid and the sodium component, and then increase the consumption of sodium component resources; at the same time, in the crystallization process of sodium dihydrogen phosphate, because the traditional crystallization production process is difficult to grasp the degree of crystallization, and then Cause excessive crystallization, so that the purity of sodium dihydrogen phosphate product is still low