Patent ID: 7982068

Claim:
A process for urea production from ammonia and carbon dioxide, comprising the steps of: feeding ammonia and carbon dioxide into a urea synthesis section operating at a predetermined high pressure; reacting said ammonia and said carbon dioxide in said synthesis section obtaining an aqueous solution comprising urea, ammonium carbamate and ammonia; feeding a first part of said aqueous solution comprising urea, ammonium carbamate and ammonia to a treatment section operating at a predetermined medium pressure for the recovery of the ammonium carbamate and of the ammonia contained in it; subjecting said first part of aqueous solution comprising urea, ammonium carbamate and ammonia to dissociation in said treatment section obtaining an urea aqueous solution and a vapour phase comprising ammonia, carbon dioxide and water; subjecting said vapour phase comprising ammonia, carbon dioxide and water to condensation in said treatment section obtaining an ammonium carbamate aqueous solution; recycling said ammonium carbamate aqueous solution to said urea synthesis section; feeding said urea aqueous solution obtained by dissociation in said treatment section to a decomposer of a urea recovery section operating at a predetermined low pressure; subjecting said urea aqueous solution to decomposition in said decomposer of said urea recovery section obtaining a concentrated urea solution and a second vapour phase comprising ammonia, carbon dioxide and water; subjecting said second vapour phase to condensation in a condenser of said urea recovery section in fluid communication with said decomposer obtaining a first recycle ammonium carbamate aqueous solution; subjecting a second part of said aqueous solution comprising urea, ammonium carbamate and ammonia to stripping including heat in a stripping unit operating substantially at said predetermined high pressure, obtaining a second urea aqueous solution and a third vapour phase comprising ammonia, carbon dioxide and water, said heat being provided through indirect thermal exchange with a steam flow which condensates to condensed steam; and using at least a part of said condensed steam as a heating fluid for dissociating said first part of the aqueous solution comprising urea, ammonium carbamate and ammonia in said dissociation unit of said medium pressure treatment section.