Fine purification and energy-saving dewatering process for phosphogypsum

Abstract

The present invention discloses a method for the purification and the energy-saving dehydration of phosphorous gypsum, and comprises the steps: the insolubale phosphate and other solid foreign matters are separated with gravity from the phosphorous gypsum; the soluble phosphate and other soluble foreign matters are separated in pressurizing and filtering way; after being pressed and compressed, the phosphorous gypsum is dried in air and is dehydrated with machine, and the semi-hydrate gypsum powder product is obtained after being dried. The purity of the product is high, the foreign matter is less and the usage is wide; since the non-thermolics mechanical dehydration is adopted, the free water in the phosphorous gypsum is decreased from 25 to 30 percent to 10 percent, thus saving the drying energy consumption, and greatly reducing the production cost.

Description

Technical field: [0001] The invention belongs to a production method of gypsum, in particular to a purification and energy-saving dehydration method of phosphogypsum. Background technique: [0002] At present, the production of phosphogypsum is mainly produced by the precipitation and crystallization of phosphate rock and sulfuric acid during the production of phosphoric acid by wet process phosphorus chemical industry; one ton of phosphoric acid (P 2 o 5 %) to produce 5-6 tons of solid phosphogypsum. In 2006, my country's wet-process phosphoric acid production was about 8 million tons (P 2 o 5 %), more than 44 million tons of solid phosphogypsum were produced. In the production of wet-process phosphoric acid, the process determines that the decomposition rate of phosphate rock is only 95%, that is, 5% of the phosphate rock remains in the discharged gypsum, which is one of them; Due to the crystallization of the generated gypsum, when the phosphogypsum is separated by f...

AI Technical Summary

Problems solved by technology

Because it is directly used for processing, first, impurities such as phosphorus and fluorine contained in phosphogypsum enter the next step of processing, which not only affects the quality of the processed product, but also often makes the production process difficult, and it is often necessary to mix natural gypsum or salt gypsum, or even add lime to neutralize, so as to reduce the relative content of impurities such as phosphorus and fluorine; the second is a simple repulping method, which cannot remove solid impurities such as non-water-soluble phosphorus in gypsum, and also adds natural gypsum or salt Gypsum to reduce the relative content of solid impurities; third, the free water contained in phosphogypsum is too high, and the heating and drying method of thermodynamic dehydration not only consumes a lot of energy, but also affects the scale of the device, increasing investment and management costs

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