Patent ID: 6284922
Filing Date: 2001-09-04
Classification: B01D,B01J,C07C,Y02P

Abstract:
A process for producing urea comprising the steps of:reacting ammonia and carbon dioxide in a reaction space (2), obtaining a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution;feeding said reaction mixture to a stripping unit (3) with carbon dioxide and subjecting said mixture to a treatment of partial decomposition of carbamate and partial separation of free ammonia, obtaining a flow comprising ammonia and carbon dioxide in vapour phase and a flow comprising urea and residual carbamate in aqueous solution;feeding said flow comprising urea and residual carbamate in aqueous solution to an urea recovery section;characterised in that it further comprises the steps of:feeding a minor portion of said flow comprising ammonia and carbon dioxide in vapour phase directly to said reaction space (2);feeding a major portion of said flow comprising ammonia and carbon dioxide in vapour phase to at least one condensation unit (4) and subjecting such major portion to a substantially total condensation, obtaining a flow comprising urea and carbamate in aqueous solution;feeding said flow comprising urea and carbamate in aqueous solution to said reaction space (2).