Method for producing fully water-soluble monoammonium phosphate and co-producing ammonium magnesium phosphate by wet process phosphoric acid

Abstract

The invention provides a method for producing fully water-soluble monoammonium phosphate and co-producing ammonium magnesium phosphate by a wet process phosphoric acid. The method comprises the following steps: deflurinating the wet process phosphoric acid and taking deflurinating filtrate; carrying out first ammoniated treatment on the deflurinating filtrate until the pH value is 2.0-3.0, and then first ageing to obtain a first ageing solution; carrying out second ammoniated treatment on the first ageing solution until the pH value is 4.0-5.0, and carrying out solid-liquid separation to obtain supernatant liquid and bottom slag liquid; carrying out concentration, crystallization and crystal-liquid separation on the supernatant liquid to obtain a crystal substance which is a monoammonium phosphate product; and carrying out third ammoniated treatment on the bottom slag liquid until the pH value is 5.6-6.0, carrying out second ageing and drying to obtain an ammonium magnesium phosphate product. According to the method provided by the invention, products of the fully water-soluble monoammonium phosphate and the ammonium magnesium phosphate are produced by three ammoniated treatments and one separation, iron and aluminum crystals gradually grow by ageing for a period of time after the first ammoniated treatment, precipitate particle size is increased, filtering performance is improved, impurity ions can be totally precipitated by the second ammoniated treatment, and water solubility of the monoammonium phosphate product is improved remarkably.

Description

technical field [0001] The invention belongs to the technical field of phosphoric acid agricultural fertilizer production, and in particular relates to a method for producing fully water-soluble monoammonium phosphate and co-producing magnesium ammonium phosphate with wet-process phosphoric acid. Background technique [0002] With the development of modern agriculture, the original artificial irrigation method is gradually replaced by large-scale sprinkler irrigation facilities. Originally suitable for artificial irrigation, the fertilizer monoammonium phosphate produced by the traditional "concentration method" and "dilute acid slurry method" has poor water solubility and contains more insoluble metal salt impurities, which may easily cause blockage of drip irrigation heads in drip irrigation facilities. [0003] In order to solve the above problems, Ma Jian et al. used wet-process phosphoric acid as raw material in CN102020256A patent to produce industrial monoammonium pho...

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Problems solved by technology

[0004] However, the above method has defects in the purification of wet-process phosphoric acid. After the first neutralization, the first neutralization is directly ammoniated to pH=4.5-5.0, and the crystals formed by metal ions such as iron and aluminum have not had time to grow into large crystals, making It is very difficult to remove impurities by filtration; when the pH is controlled at 5.8-6.2 during the production of ammonium magnesium phosphate, the by-product diammonium phosphate will be formed and the product will be impure, and the pH needs to be adjusted again accurately to ensure the concentration of monoammonium phosphate Purity, which increases the difficulty and cost of production

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