METHOD OF PROCESSING SPENT SULPHURIC ACID ETCHING SOLUTIONS Russian patent published in 2020 - IPC C23G1/36 C23F1/46 C02F1/04 C02F103/16 

FIELD: metallurgy; machine building.

SUBSTANCE: invention relates to recycling waste sulphate etching solutions of metallurgical and machine building. In the method, calcium chloride sludge is added to the reactor with spent sulphuric acid solution, and after achieving pH equal to 5.0–5.5, limestone waste dust is supplied to the reactor to pH equal to 7.0–8.0, after the reactions are completed, the obtained suspension is transferred into a vacuum crystallizer to form crystalline hydrates of calcium sulphate and calcium chloride. After that, obtained mixture is fed into centrifuge for separation of said crystalline hydrates, and then into combined drier of boiling layer, in which crystalline hydrates are milled to size of 10–15 mcM and simultaneously dried for 15–20 minutes at temperature of 110–340 °C to produce a binder containing gypsum with an admixture of crystalline calcium chloride and iron oxide pigment. In the reactor with the spent sulphuric acid solution, calcium chloride slurry and limestone waste dust are fed at the following ratio of components, wt. %: used sulphuric acid solution of metal etching 67–70, slurry of calcium chloride 20–22, limestone waste dust 10–11.

EFFECT: invention provides simplification of technological scheme of processing spent sulphuric acid etching solutions, as well as implementation of said processing without use of scarce products.

1 cl, 1 dwg, 2 tbl, 2 ex