Device and method for producing type II anhydrous gypsum from phosphogypsum

Abstract

The invention provides a device and a method for producing type II anhydrous gypsum from phosphogypsum. The device comprises a pretreatment unit, a drying unit, a calcining unit and a product collecting unit which are sequentially connected, wherein the pretreatment unit comprises a spiral stirring device; the drying unit comprises a scattering device and at least one-stage drying device; the calcining unit comprises a calcining device; and a heat source pipeline is arranged in the calcining device. According to the device disclosed by the invention, the phosphogypsum is accurately converted into the II-type anhydrous gypsum through the combination of pretreatment, drying and calcination processes, soluble phosphorus and fluorine in the phosphogypsum are effectively removed, conversion ofinsoluble phosphorus and decomposition of organic matters are realized, the problem of acid corrosion is solved, and the influence of harmful impurities on gypsum products is reduced; the method improves the comprehensive utilization efficiency of the phosphogypsum, the product is not easy to hydrate, the product can be compounded with super sulfate cement, supersulphated cement or gypsum composite cementing materials, the product has stable performance and high strength, and the application way of the phosphogypsum is expanded.

Description

technical field [0001] The invention belongs to the technical field of solid waste utilization, and relates to a device and method for producing Type II anhydrite from phosphogypsum. Background technique [0002] Phosphoric acid is an important industrial product. Its production is mainly based on sulfuric acid wet process. The by-product of this method is mainly phosphogypsum. Every ton of phosphoric acid produced produces about 7 tons of phosphogypsum containing about 20% of free water. The output of the product is huge, which not only takes up a lot of storage space, but also brings serious pollution to the surrounding environment. Therefore, the recovery and resource utilization of phosphogypsum is essential. However, due to the main and side reactions between phosphate rock and sulfuric acid and the additives added in the beneficiation process, the types of impurities in the by-product phosphogypsum are complex and the concentration range is wide, which will seriously a...

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Problems solved by technology

[0004] CN 109553372A discloses a method for preparing and using a recyclable phosphogypsum roadbed material. Phosphogypsum with a free moisture content of 7-20% is added to a saturated calcium hydroxide solution for neutralization reaction to obtain soluble phosphate radical removal Phosphogypsum with fluoride ions, and then calcined at a high temperature of 170-350 ° C to convert the dihydrate gypsum into Type III anhydrous gypsum, and mix the prepared Type III anhydrous gypsum with water, water reducing agent and waterproofing agent mixed to obtain the phosphogypsum roadbed material, but the anhydrous gypsum prepared by this method is easy to hydrate, and water reducer and waterproofing agent still need to be added, the cost of raw materials is relatively high, and insoluble impurities are not removed during the impurity removal process, affect its performance

[0005] CN 105985036A discloses a processing method of phosphogypsum. After mixing phosphogypsum and lime, it is added to a drying and calcining machine. The end is equipped with a flame-injection furnace. The temperature of the flame-injecting port is higher than 800°C. The outlet of the drying and calcining machine adopts a graded outlet , to obtain hemihydrate gypsum and anhydrous gypsum II respectively, send the exported gypsum to the mixing and homogenizing reduction conveying device, fully contact the mixed gypsum with air, distribute the different forms of gypsum, and send the qualified gypsum to the gypsum crystal structure conversion device for processing Crystal transformation to obtain finished gypsum, but in this method, the drying and calcining machine cannot accurately control the calcining process, and it is necessary to set a classification outlet, and then carry out mixed aging, which produces β-type gypsum powder; the drying and calcining machine is equipped with a flame-injected furnace, which is difficult Control the calcination time, resulting in large product fluctuations

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