Method for preparing large-granule industrial-grade urea phosphate product through continuous reaction crystallization of wet-process phosphoric acid

Abstract

The invention discloses a method for preparing a large-granule industrial-grade urea phosphate product and a byproduct thereof through continuous reaction crystallization of wet-process phosphoric acid. The method comprises the steps: adding the wet-process phosphoric acid, urea and circulating mother liquor into a first reaction crystallizer; feeding a reacted solution to a second-stage crystallizer, adding a urea phosphate seed crystal, continuously outputting reaction obtained slurry, carrying out centrifugation and filtering, carrying out drying so as to obtain industrial-grade urea phosphate, and feeding filter liquor to a circulating mother liquor tank for thorough precipitation; cyclically outputting supernatant obtained through precipitation to the first reaction crystallizer for acyclic reaction, and subjecting a suspension of solid impurities to centrifugation and filtering, so as to obtain second filter liquor and a second filtered solid matter; adding potassium sulfate into the second filter liquor, carrying out a reaction, and carrying out filtering, so as to obtain third filter liquor and a byproduct, i.e., potassium fluorosilicate; and mixing the third filter liquorand the second filtered solid matter, carrying out concentrating, then, carrying out spray drying so as to obtain a sulfenyl nitrogen, phosphorus and potassium compounded fertilizer, and carrying outcyclic continuous production, thereby obtaining a urea phosphate crystal. According to the method, the purity is high, the grain size is large, the distribution is uniform, the crystal form is neat;and meanwhile, fluorosilicate and the sulfenyl nitrogen, phosphorus and potassium compounded fertilizer can be obtained, and no waste gases, waste water and waste residues is discharged.

Description

technical field [0001] The invention relates to the field of preparation of fine phosphate and phosphate fertilizer, in particular to a method for preparing large-grain industrial-grade urea phosphate and its by-products through wet-process phosphoric acid continuous reaction crystallization. Background technique [0002] Phosphate rock is an advantageous mineral resource in my country, and it is also a non-renewable strategic resource. At present, more than 90% of the wet-process phosphoric acid produced by the wet process of medium and low-grade phosphate rock is used for the production of phosphate fertilizer after ammonification. , usually discharged as waste, which not only pollutes the environment but also causes a large amount of phosphorus loss. The reaction of urea and phosphoric acid to recover most of the phosphorus in the form of urea phosphate crystals is a new production method with high phosphorus yield. At the same time, due to its high phosphorus and nitrog...

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Problems solved by technology

However, the production of urea phosphate by thermal phosphoric acid requires high phosphoric acid concentration and high production cost, which limits its production and application and cannot meet market needs. Therefore, the prior art usually uses wet-process phosphoric acid to produce urea phosphate, such as the Tennessee Valley Authority of the United States. In the 1990s, a two-stage cooling and crystallization process for the production of urea phosphate was developed, realizing the continuous production of fertilizer-grade urea phosphate using wet-process phosphoric acid as raw material

[0004] However, there are the following problems in the production of urea phosphate by wet-process phosphoric acid in the prior art: (1) The key operations such as reaction, concentration, and crystallization have not been realized continuously, resulting in a long production process and low production capacity; (2) lack of urea phosphate Effective control of the crystallization process, the product particle size is low, generally the average particle size is less than 500 microns, resulting in many impurities wrapped between crystals, and the removal rate of impurities is low, so the purity of urea phosphate products is relatively low, only fertilizer grade

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