SU109938A1 - Method of cleaning technical phosphoric acid - Google Patents

Description

Methods are known for purifying TexHii phosphoric acid from magnesium, calcium, iron and other salts by neutralizing with soda, followed by the decomposition of the sodium phosphate thus obtained with sulfuric acid. Processes are also known using phosphoric acid distillation or by extraction with organic solvents.

The present invention provides a method for the purification of phosphoric acid from magnesium salts with the help of hydrofluorosilicic acid HQSiFg.

The method is based on the low solubility of magnesium silicofluoride in phosphoric acid and in magnesium phosphate solutions. The method provides a more complete purification of the kianoty from magnesium salts and makes it possible to obtain coarse-grained magnesium silicofluoride.

Suidness of the method is as follows.

Extraction phosphoric acid from the collector / (see drawing) through the pressure tank 2 enters the Chemiko type evaporator 5, where 10% hydrochlorofluoric acid solution from the collector 4 is added to the evaporator 4 through the pressure tank 5 for binding. magnesium in the form of magnesium silicate MgSiFe-GHsO. The residue is produced under vacuum at a temperature not higher than 70 °, since at 80 mg silica fumes decompose to form fine MgFa and SiOs.

The precipitate of MgSiFe bNaO in the crystallizer 6 and in the centrifuge 7, which is separated during the acid attack, undergoes thermal dissociation in a countercurrent drum 8 at a temperature higher than 80 ° C, and 2-3% of sand is added to the precipitate for better release.

In the drawing, the mixer is designated 9.

In the heat treatment process, the magnesium silicate fluoride is almost completely decomposed and the escaping fluorine in the form of SiF.i is captured by water to form hydrofluoric acid, which is returned to the process.

The residue after decomposition of MgSiFa, consisting of magnesium fluoride and silicic acid in a mixture with phosphoric acid, remains; it is in the sediment after filtration of AlgSiFe bNzO,

This is subjected to calcination at 800-1000. In this case, fluorine 3 is stripped off the gas phase and magnesium fluoride B is converted to magnesium metaphosphate, which is used as a high-percentage ballast-free fertilizer.

Distilled fluorine is partially used for the precipitation of magnesium silicon fluoride in the first stage of the process, and can be partially issued as a stand-alone product.

Subject invention

The method of purification of technical phosphoric acid from magnesium salts by converting magnesium salts into insoluble compounds is different, and so that, in order to purify phosphoric acid from magnesium more thoroughly and to simplify the process, the precipitation of magnesium salts from solutions is carried out with using cream-hydrofluoric acid to produce magnesium silicate fluoride precipitate.