WO 2017/045519 A1

Method for producing wet-process phosphoric acid and ­byproducing alpha-hemihydrate gypsum and high-purity and high-whiteness alpha-hemihydrate gypsum

(22) 26.08.2016

(43) 23.03.2017

(57) Provided is a method for producing wet-process phosphoric acid and by-producing alpha-hemihydrate gypsum and high-purity and high-whiteness alpha-hemihydrate gypsum. The method comprises: adding phosphoric acid and a phosphate rock powder into an extraction tank and conducting an extraction reaction on same, then adding sulfuric acid to continue the reaction so as to make 30 %-50 % of calcium ions form dihydrate gypsum, the dihydrate gypsum part being sent to a crystal transformation tank, a crystal transformation agent being added, and crystal transformation conditions being controlled so as to obtain 30 %-50 % of an ordinary alpha-hemihydrate gypsum; and make the other 50 %-70 % of calcium ions be present in the form of calcium dihydrogen phosphate in a phosphoric acid extractive solution, separating same and then introducing the phosphoric acid extractive solution into a decalcification reaction tank, adding a sulfuric acid solution diluted by a washing solution, and then firstly performing decalcification, and then controlling the crystal transformation conditions and subjecting a solid to a crystal transformation reaction, so as to generate a highpurity and high-whiteness alpha-hemihydrate gypsum. The method not only reduces the content of phosphorus in the by-product alpha-hemihydrate gypsum, but also realizes the industrial production of phosphoric acid and by-products ordinary alphahemihydrate gypsum and high-purity and high-whiteness alpha-hemihydrate gypsum by a wet-process.

(71) Kingenta Norsterra Chemical Co., Ltd (CN)

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