Method for processing phosphogypsum

Abstract

The invention discloses a method for treating phosphogypsum, which comprises the following steps: firstly, fully mixing the phosphogypsum and ammonium bicarbonate according to the mass ratio, adding water into the mixture, and performing full reaction on mixture and separating out ammonium sulfate and calcium carbonate; secondly, fully mixing the obtained ammonium sulfate and ferric oxide according to the mass ratio, and performing full reaction to obtain ferric sulfate and ammonia gas; and thirdly, fully decomposing the ferric sulfate to obtain the ferric oxide and sulfur trioxide. The method utilizes a conversion concept to fully convert the state of sulfur element and calcium element in the phosphogypsum through chemical reaction for a plurality of times, and prepares products with high added value such as purified calcium chloride, purified solidifed carbon dioxide, purified ammonia water, purified concentrated sulfuric acid, and the like. The ferric oxide is adopted as a catalyst, so that the decomposition efficiency of intermediate products is improved; the ferric oxide can be recycled, so that the resource utilization rate is improved; the purified ammonia gas and the sulfur trioxide are synchronously obtained, so that the technological steps are reduced; the utilization rate of the phosphogypsum is improved to be 99.5 percent; and the obtained products are directly used for reproduction, so that the resource utilization channel is shortened and the application path of the phosphogypsum is widened.

Description

technical field [0001] The invention relates to the treatment of phosphogypsum produced in industries such as wet-process phosphoric acid, phosphate fertilizer production, calcium dihydrogen phosphate and calcium hydrogen phosphate production, and desulfurized gypsum in coal-fired power plants, in particular to a method for treating phosphogypsum. Background technique [0002] Industrial phosphogypsum refers to the industrial waste residue mainly composed of calcium sulfate dihydrate produced in the production process of wet-process phosphoric acid. The wet-process phosphoric acid process uses sulfuric acid and phosphate rock as raw materials to produce phosphoric acid and phosphate fertilizer, and a large amount of phosphogypsum waste residue will be produced as a by-product; Desulfurization gypsum in coal-fired power plants refers to the waste residue produced by the removal of sulfur trioxide in flue gas by lime / limestone absorption method in coal-fired power plants. At p...

AI Technical Summary

Problems solved by technology

But the disadvantage is that when phosphogypsum is used as sulfur fertilizer, calcium fertilizer and soil improver, the radionuclides and leachate components in phosphogypsum will cause secondary pollution to the environment.

[0006] Phosphogypsum is used as a gypsum building material to remove various phosphates, fluorides, organic matter and soluble salts in phosphogypsum to meet the requirements of building products. The purified phosphogypsum is calcined and dried to remove physical water and semi-crystalline water. After aging, it becomes hemihydrate gypsum, that is, building gypsum, and then adding auxiliary materials such as face-protecting paper to the building gypsum can produce paper-faced gypsum boards, fiber gypsum boards, gypsum bricks or hollow strips, plastering gypsum, etc., but The disadvantage of this processing method is that it is easy to use, and its added value is low

[0007] Phosphogypsum is converted into potassium sulfate, and the filtered potassium sulfate is washed and dried to make potassium sulfate products. The filtrate is used to make nitrogen, phosphorus and potassium compound fertilizers. The conversion rate of phosphogypsum can generally reach 90%-93%, and the conversion rate of potassium can reach Up to about 73%; but there are shortcomings such as incomplete conversion and low resource utilization

Of course, there are different treatment methods such as high-temperature reduction of phosphogypsum to produce industrial sulfuric acid, production of industrial sulfuric acid from phosphogypsum by phosphoric acid method, and low-temperature decomposition of phosphogypsum to produce industrial sulfuric acid. However, the above-mentioned treatment methods are too simple and incomplete, and can only produce A single product is obtained, and it is easy to cause secondary pollution by residual by-products, and the economic added value is low

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