Patent ID: 7074958

Claim:
Integrated process for urea/melamine production comprising the operating steps of: (a)â€”urea synthesis from ammonia and carbon dioxide, obtaining molten urea and a gaseous mixture comprising steam and ammonia; (b)â€”condensation of said gaseous mixture comprising steam and ammonia, obtaining a cold aqueous ammoniacal solution; (c)â€”melamine synthesis from urea with formation of off-gases, comprising ammonia and carbon dioxide; said process being characterized in that it comprises the further steps of: (d)â€”absorption of said off-gases in at least one fraction of the cold aqueous ammoniacal solution obtained in said step (b), with formation of a carbamate aqueous solution; (e)â€”decomposition of said carbamate aqueous solution, obtaining ammonia, carbon dioxide and steam, and a residual aqueous ammoniacal solution; (f)â€”recycling of the ammonia and of the carbon dioxide obtained in said step (e) for the urea synthesis; (g)â€”treatment of the residual aqueous ammoniacal solution obtained in said step (e) for the recovery from it of ammonia and carbon dioxide for the urea synthesis.