Method for removing impurities and whitening phosphogypsum

Abstract

The invention discloses a method for removing impurities and whitening phosphogypsum. The method comprises the following steps: (1) carrying out fineness rough machining on a phosphogypsum raw material; (2) carrying out acid leaching on the phosphogypsum obtained in the step (1) by using sulfuric acid, performing heating and keeping the temperature constant to obtain a material; (3) adding a flotation agent into the material obtained in the step (2), and carrying out flotation concentration separation; (4) feeding the slurry subjected to flotation separation obtained in the step (3) into gravity separation operation for impurity removal to obtain concentrate; and (5) filtering the concentrate obtained in the step (4), washing a filter cake, and drying and crushing the filter cake to obtainthe finished product purified gypsum. According to the method, high-whiteness and high-purity anhydrous calcium sulfate is prepared from phosphogypsum by utilizing a flotation / extraction / gravity separation process in a weakly acidic environment.

Description

technical field [0001] The invention relates to the technical field of phosphorus chemical industry, in particular to a method for removing impurities and whitening phosphogypsum, which uses flotation / extraction / re-election processes in an acidic environment to prepare high-whiteness, high-purity anhydrous calcium sulfate from phosphogypsum Methods. Background technique [0002] Phosphogypsum is the industrial waste produced during the reaction of phosphorus-containing minerals represented by apatite and sulfuric acid in the process of phosphoric acid production. Data surveys and related reports show that for every 1 ton of phosphoric acid (P 2 o 5 Total) will produce 4 to 5 tons of phosphogypsum. At present, the annual discharge of phosphogypsum in the world is more than 200 million tons, and the annual discharge of phosphogypsum by my country's phosphorus chemical industry is about 70 million tons, and it is increasing at a rate of 15% per year. At present, the cumulati...

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Problems solved by technology

At present, the cumulative production of phosphogypsum in my country has exceeded 300 million tons, and the stock has exceeded 250 million tons, but its utilization rate is less than 10%, and its stacking takes up a lot of land

[0005] The above processes have their own advantages and disadvantages in the application process, but they have their own limitations for different sources of phosphogypsum raw materials. For example, it is often difficult to completely remove some insoluble impurities by simple water washing, and it is difficult to remove heavy impurities with large particle sizes by simple positive flotation. Moreover, hydrophobic impurities are often mixed into the concentrate products and are difficult to remove. In addition, for the raw materials of the multi-layer inclusion mineral phase, it is difficult to further improve the whiteness and purity by a single flotation method

Phosphoric acid and fluoride will volatilize during simple calcination, which will pollute the environment and corrode equipment. High-temperature calcination consumes a lot of energy and costs, and the calcination method is powerless to quartz impurities

The acid leaching process is generally considered to be a relatively effective purification technology for phosphogypsum, but single acid leaching is difficult to deal with organic impurities and quartz impurities, which seriously affects the purity of gypsum.

[0006] So far, there have been no invention patent reports on decarburization and dephosphorization of phosphogypsum, whitening and impurity removal using impurity removal flotation combined with leaching-extraction process

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