Method for preparing food-grade diammonium hydrogen phosphate from industrial wet-process phosphate

Abstract

The invention discloses a method for preparing food-grade diammonium hydrogen phosphate from industrial wet-process phosphate, which comprises the following steps of: 1, removing arsenic and lead from a raw material phosphate: adding phosphorus pentasulfide into the raw material phosphate, performing hydrolysis reaction at normal temperature, standing, and filtering to obtain wet-process purified acid; 2, performing primary neutralization reaction: introducing ammonia into the wet-process purified acid in a reactor for neutralization reaction to form mixed ammonium salt consisting of ammonium dihydrogen phosphate and diammonium hydrogen phosphate; and 3, performing secondary neutralization reaction: adding water to dissolve an ammonium phosphate salt mixture, introducing ammonia for continuous reaction, concentrating feed liquor, cooling slurry, filtering, and drying to obtain the food-grade diammonium hydrogen phosphate. The method has the advantages that: the technological operation process is concise and easy to control; the yield of the food-grade diammonium hydrogen phosphate is high and the quality is stable; and mother liquid subjected to neutralization reaction twice can be continuously used for producing industrial-grade or feed-grade ammonium phosphate salt.

Description

【Technical field】 [0001] The invention relates to the technical field of chemical engineering, and relates to a crystallization production method of diammonium hydrogen phosphate, in particular to a method for preparing food-grade diammonium hydrogen phosphate with industrial-grade wet-process phosphoric acid. 【Background technique】 [0002] Phosphorus is one of the essential elements for the human body. As an important food ingredient and functional additive, phosphate has been widely used in processed poultry products, fruit products, vegetable products, dairy products, soybean products, baked foods, seafood products and convenience foods. [0003] At present, the production of phosphate above food grade is usually carried out using thermal phosphoric acid as raw material. Among them, thermal phosphoric acid has higher requirements on the grade of raw materials (ore), and its preparation process requires high energy consumption and large pollution. The cost remains high; ...

AI Technical Summary

Problems solved by technology

However, this method does not carry out purification of heavy metal ions such as arsenic and lead to wet-process phosphoric acid, and heavy metal ions such as arsenic and lead are impurities generally contained in phosphate rocks. Therefore, the implementation of this method requires high-quality raw material phosphoric acid, especially for The content of heavy metal impurities has strict requirements

Secondly, the first step of the method removes some impurities in wet-process phosphoric acid by pre-neutralizing wet-process phosphoric acid to pH=1.6~2.0; the second step uses ammonium dihydrogen phosphate crystals as an intermediate product for preparing diammonium hydrogen phosphate, therefore, The yield of preparing food-grade diammonium hydrogen phosphate by this method is low

Thirdly, this method only purifies wet-process phosphoric acid through desulfurization and pre-neutralization to partially remove impurities. The viscosity of the subsequent neutralization reaction system is relatively high, which requires high equipment and operation, and its product quality is easily affected by fluctuations in the quality of raw phosphoric acid.

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