MELAMINE PURIFICATION METHOD Russian patent published in 2021 - IPC C07D251/60 C07D251/62 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for the purification of melamine melt (5) containing melamine and side products and obtained using non-catalytic synthesis method carried out at high pressure. The method includes stages of (a1) processing specified melamine melt (5); (a2) decomposing using alkali at least part of the specified side products to obtain alkaline aqueous melamine solution (26); (b) steaming specified alkaline aqueous melamine solution (26) to obtain steamed melamine solution (28); (c) crystallizing melamine from specified steamed melamine solution (28) using first alkali-containing aqueous solution (6b) and separating melamine (7) from mother liquor (8); (d) processing at least part (8b) of specified mother liquor to obtain aqueous solution (11) containing carbonates; (e) decomposing at least part of carbonates contained in specified aqueous solution (11) to obtain carbon dioxide and alkali and to obtain second alkali-containing aqueous solution (30) and water flow (13); (f) recirculating at least part of specified second alkali-containing aqueous solution (30) to at least one of specified stages (a1), (a2) and (c). In the method implementation, alkali-containing aqueous solutions are sodium or potassium hydroxide solutions. The invention also relates to a section of melamine purification contained in a technological plant for melamine production at high pressure and to a method for re-equipment of the section of melamine purification.

EFFECT: reducing salt content in released sewage water, reducing the amount of alkali and fresh water consumption.

17 cl, 6 dwg