US 11,840,520 B2
Process for melamine purification
Andrea Scotto, Breganzona (CH); and Simone Gamba, Pagazzano (IT)
Assigned to CASALE SA, Lugano (CH)
Filed by Casale SA, Lugano (CH)
Filed on Jul. 6, 2021, as Appl. No. 17/368,430.
Application 17/368,430 is a division of application No. 16/318,736, granted, now 11,059,793, previously published as PCT/EP2017/065187, filed on Jun. 21, 2017.
Claims priority of application No. 16180820 (EP), filed on Jul. 22, 2016.
Prior Publication US 2021/0332017 A1, Oct. 28, 2021
Int. Cl. C07D 251/60 (2006.01); C07D 251/62 (2006.01)
CPC C07D 251/62 (2013.01) [C07D 251/60 (2013.01)] 4 Claims
 
1. A melamine purification section of a high-pressure melamine plant comprising:
a quencher, receiving a melamine melt containing melamine and by-products;
a decomposer, wherein at least part of said by-products are decomposed by means of alkali, providing an alkaline aqueous solution of melamine;
a stripper fed with said alkaline aqueous solution of melamine and with a stripping medium, providing a stripped melamine solution;
a crystallizer fed with said stripped melamine solution and a first alkali-containing aqueous solution, wherein melamine is separated from a melamine mother liquor;
a treatment unit for at least part of said mother liquor, providing an aqueous solution containing carbonates;
a decomposition unit of at least part of the carbonates contained in said aqueous solution into carbon dioxide and alkali, providing a second alkali-containing aqueous solution and a water stream;
at least one line for recycling at least a portion of said second alkali-containing aqueous solution provided by the decomposition unit to at least one of the quencher, the decomposer and the crystallizer.