Method for recycling phosphorus and fluorine in phosphoric acid concentrated sludge acid and producing low-fluorine water-soluble fertilizer through cogeneration

Abstract

The invention discloses a method for recycling phosphorus and fluorine in phosphoric acid concentrated sludge acid and producing a low-fluorine water-soluble fertilizer through cogeneration. The method comprises the following steps: putting process water, potassium sulfate / potassium carbonate, active kieselguhr and concentrated sulfuric acid into phosphoric acid concentrated sludge acid, removing free fluorine in the sludge acid, converting semi-hydrated gypsum in the sludge acid into dihydrate gypsum to release inter-crystal phosphorus, and performing filtering separation so as to obtain a water phase, namely low-fluorine phosphoric acid; and enabling solid phase filter cakes to react with the concentrated sulfuric acid to decompose fluosilicate, performing water washing on a gas phase so as to obtain fluosilicic acid, pulping a reaction material with water, performing filtering separation, and neutralizing the liquid phase with liquid ammonia / ammonium hydroxide, thereby obtaining a mixed water-soluble fertilizer of oligomerization APP (Ammonium Polyphosphate), ammonium sulfate and potassium sulfate, and a solid phase, namely anhydrite. By adopting the method, recycling and reuse of phosphoric acid and fluosilicic acid in phosphoric acid concentrated sludge acid are achieved, the low-fluorine water-soluble fertilizer is produced through cogeneration, efficient utilization of phosphorus and potassium is achieved, and the difficulties that phosphoric acid is hard to recycle and fluorine impurities are hard to separate from phosphoric acid concentrated sludge acid, a sludge acid byproduct fertilizer is high in fluorine content, and the potassium element cannot be efficiently utilized, are solved.

Description

technical field [0001] The invention relates to the technical field of phosphorus chemical industry, in particular to a method for recovering phosphorus and fluorine in concentrated phosphoric acid slag acid and co-producing low-fluorine water-soluble fertilizer. Background technique [0002] my country is a country with a large amount of phosphorus resources, as well as a major producer and consumer of phosphorus chemical products. After more than 40 years of development, my country has established a modern phosphorus chemical technology and industry based on phosphorus compound fertilizers and fine phosphate as the main body. Phosphorus chemical industry has become an important basic industry of the national economy. [0003] Most of my country's phosphorus chemical industry is produced by wet process, that is, sulfuric acid is used to extract phosphate rock to produce dilute phosphoric acid with a mass fraction of 20-25%. The content of impurities in phosphoric acid prod...

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Problems solved by technology

[0009] The purpose of the present invention is to provide a method for recovering phosphorus and fluorine in concentrated phosphoric acid slag acid to co-produce low-fluorine water-soluble fertilizer, which solves the difficulties in the recovery of phosphoric acid in concentrated acid slag acid, the difficulty in separating fluorine impurities, and the by-product fertilizer product fluorine in slag acid. The problem of high content and poor utilization of potassium

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