Wet-process defluorination method for phosphoric acid

Abstract

The invention discloses a wet-process defluorination method for phosphoric acid. The method comprises the following steps: adding fluorine-containing phosphoric acid into a defluorination tower from the top of the defluorination tower, adding steam into the defluorination tower from the bottom of the defluorination tower, subjecting the fluorine-containing phosphoric acid and the steam to countercurrent contact, and allowing fluoride in the fluorine-containing phosphoric acid to enter a gas phase and to be discharged out of the defluorination tower along with the steam so as to obtain defluorinated phosphoric acid, wherein the defluorination tower is divided into an upper tower and a lower tower, the absolute pressure of the upper tower is 15-20 KPa, the absolute pressure of the lower tower is 20-30 KPa, and a pressure difference of the upper tower and the lower tower is smaller than or equal to 10 KPa. The defluorination method of the invention is good in defluorination effect, low inphosphoric acid consumption, low in phosphorus loss and small in phosphoric acid concentration change before and after defluorination.

Description

technical field [0001] The invention relates to the technical field of chemical industry, in particular to a wet-process phosphoric acid defluorination method. Background technique [0002] Phosphoric acid is an intermediate product in the production of ammonium phosphate, heavy superphosphate and various phosphate products, and is an indispensable raw material for metallurgy, petroleum, chemical, electronics, medicine, food and other industries. The purity of raw phosphoric acid determines the purity and use of each phosphate in the subsequent product chain. [0003] At present, phosphoric acid can be prepared by wet method. The fluorine content in wet phosphoric acid is relatively high, which is difficult to meet the needs of use. It is necessary to remove the fluorine in phosphoric acid by defluorination process. However, the existing defluorination process has the following problems: (1) defluorination The efficiency is not high; (2) Phosphoric acid consumption is large...

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Problems solved by technology

[0003] At present, phosphoric acid can be prepared by wet method. The fluorine content in wet phosphoric acid is relatively high, which is difficult to meet the needs of use. It is necessary to remove the fluorine in phosphoric acid by defluorination process. However, the existing defluorination process has the following problems: (1) defluorination The efficiency is not high; (2) Phosphoric acid consumption is large: At present, the defluorination and purification of domestic wet-process concentrated phosphoric acid is mostly carried out by chemical precipitation, which uses sodium hydroxide and fluorosilicic acid to generate sodium fluorosilicate It is realized by the low solubility of sodium fluorosilicate in phosphoric acid, resulting in a large consumption of phosphoric acid