Preparation method of modified phosphogypsum

Abstract

The invention discloses a preparation method of modified phosphogypsum. The method includes the operation steps of: 1) mixing phosphogypsum with water, and performing slurrying to obtain a phosphogypsum slurry; subjecting the phosphogypsum slurry to aging treatment to obtain pretreated phosphogypsum; 2) adding CaCO3 into the pretreated phosphogypsum, and keeping the mass percentage content of CaCO3 at one third of the final mass percentage content of CaCO3; and performing stirring to mix the phosphogypsum and CaCO3 uniformly; 3) dehydrating the phosphogypsum at 210DEG C-250DEG C; 4) stirring and crushing the phosphogypsum into powder; 5) then adding CaCO3 into the mixed phosphogypsum and CaCO3, and controlling the mass percentage content of CaCO3 at 20%-30%; and stirring the substances uniformly; and (6) adding a gelling agent into the mixed phosphogypsum obtained in step (5), and controlling the mass ratio of the mixed phosphogypsum to the gelling agent at 3-3.5:1. The method providedby the invention reduces the release of harmful substances, greatly improves the resource utilization of phosphogypsum, and reduces the phosphogypsum filling cost and environmental protection burdenof enterprises.

Description

technical field [0001] The invention relates to phosphogypsum, in particular to a preparation method of modified phosphogypsum. Background technique [0002] Phosphogypsum is a by-product of sulfuric acid decomposition of phosphate rock to produce phosphoric acid. Unlike ordinary tailings filling technology that uses inert tailings (mainly composed of silica) as aggregate, phosphogypsum aggregate used in phosphogypsum filling technology is mainly The ingredient is calcium sulfate dihydrate, which contains a large amount of residual acid and harmful impurities such as phosphorus and fluorine. Studies have shown that the gelling hydration reaction system of conventional gelling materials such as cement and alkali-activated gelling agents requires pH ≥ 11.5, while the pH of phosphogypsum is only 1-5, which contains a large amount of residual acid, which will reduce the hydration system. In addition, the soluble fluorine compounds and soluble phosphorus compounds in phosphogyps...

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Problems solved by technology

[0003] Among the above methods, the water washing method and the natural aging method are simple to operate, but no matter whether water is used in the water washing method or rainwater is used in the natural aging method to treat phosphogypsum, it is easy to cause secondary pollution, and the water consumption of the water washing method is too large, which is not economical. ; Lime neutralization method is not easy to cause secondary pollution, but the cost is high, it is difficult to meet the economic and technical requirements of phosphogypsum filling, and too much lime addition will reduce the mechanical properties of phosphogypsum-based filling body; screening method, ball milling method, The calcination method is complex in operation and high in cost, and it is difficult to be popularized and applied in the filling process of phosphate rock production enterprises, and the ball milling method cannot fundamentally pretreat phosphogypsum