Method for wet production of phosphoric acid and byproduct, namely white gypsum

Abstract

The invention discloses a method for wet production of phosphoric acid and a byproduct, namely white gypsum, relating to the technical field of phosphorus chemical industry. The method is mainly used for solving the problems in the traditional wet production of phosphoric acid that the byproduct, namely phosphogypsum is high in impurity content, poor in quality and yellow grey, dark grey and black in appearance, can be stacked only as waste and pollutes the environment. The method comprises the steps of firstly, reacting phosphorite powder (slurry) (the content of phosphorus pentoxide in phosphorite is 18-35%) and phosphoric acid of a volume, which is 16-32w% of the weight of phosphorus pentoxide, for 15-60 minutes at the temperature of 45-70 DEG C while stirring, so as to produce mixed slurry containing phosphoric acid, a calcium phosphate solution, phosphorite carrying acid insoluble matters and a small amount of produced calcium fluoride, ferric phosphate and aluminum phosphate solid impurities; continuously or intermittently precipitating the mixed slurry for 1.0-3.5 hours, and carrying out layered separation, so as to obtain a phosphoric acid and calcium phosphate mixed solution and thick slurry containing solid impurities; adding 40-98w% sulfuric acid while stirring, reacting sulfuric acid and the phosphoric acid and calcium phosphate mixed solution for 10-40 minutes, precipitating for layering, and separating, thereby obtaining phosphoric acid and white gypsum. The method has the advantage that the pollution to atmosphere, soil and groundwater due to phosphogypsum stacking is reduced.

Description

technical field [0001] The invention relates to the technical field of phosphorus chemical industry, in particular to a method for producing wet-process phosphoric acid by-product white gypsum. Background technique [0002] The process flow of traditional wet-process phosphoric acid production is as follows: figure 1 As shown, the main production technology of wet-process phosphoric acid is the dihydrate method (named after the by-product dihydrate gypsum, CaSO 4 2H 2 O, to distinguish it from other chemical gypsum, called phosphogypsum), its global production capacity accounts for more than 95% of the total wet-process phosphoric acid. The production method is: phosphate rock powder (slurry), phosphoric acid (solution) and sulfuric acid are mixed and reacted in a reaction tank to produce phosphoric acid, and phosphogypsum is produced as a by-product. Because the main component in phosphate rock powder is calcium fluorophosphate [Ca 5 F(PO 4 ) 3 ], the secondary compon...

AI Technical Summary

Problems solved by technology

At present, more than 90% to 95% of phosphogypsum is discarded or stored uselessly

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