Patent ID: 7091379

Claim:
Process for urea production of the type comprising the steps of: performing a reaction between ammonia and carbon dioxide in a reaction space to obtain a reaction mixture comprising urea, carbamate and free ammonia in aqueous solution, subjecting said mixture to a stripping treatment with carbon dioxide feed as a stripping agent to obtain a first flow comprising ammonia and carbon dioxide in vapor phase and a flow comprising urea and residual carbamate in aqueous solution, feeding said flow comprising urea and residual carbamate in aqueous solution to a urea recovery section, separating in said recovery section said residual carbamate from the urea to obtain a first flow of carbamate in aqueous solution, characterized in that it comprises the additional steps of: subjecting a first portion of said first flow comprising ammonia and carbon dioxide in vapor phase to a substantially total condensation to obtain a second flow of carbamate in aqueous solution, recycling said second flow of carbamate in aqueous solution to said reaction space, recycling a second portion of said first flow comprising ammonia and carbon dioxide in vapor phase to said reaction space, subjecting at least part of said first flow of carbamate in aqueous solution obtained in said urea recovery section to a treatment of partial decomposition to obtain a second flow comprising ammonia and carbon dioxide in vapor phase and a flow comprising residual carbamate in aqueous solution, recycling said second flow comprising ammonia and carbon dioxide in vapor phase to said reaction space, or recycling said second flow comprising ammonia and carbon dioxide in vapor phase to said first portion of said first flow comprising ammonia and carbon dioxide in vapor phase and subjecting them to a substantially total condensation to obtain said second flow of carbamate in aqueous solution, or recycling said second flow comprising ammonia and carbon dioxide in vapor phase to said first flow comprising ammonia and carbon dioxide in vapor phase and subjecting a first portion thereof to a substantially total condensation to obtain said second flow of carbamate in aqueous solution and recycling a second portion thereof to said reaction space.