Process and plant for the production of urea

Process for urea production in a synthesis loop based on CO2 stripping which comprises the following steps of:

• performing a reaction between ammonia (NH3) and carbon dioxide (CO2) in a vertical reaction space (reactor R) to obtain a mixture comprising urea with minimum residual content of unreacted CO2 (maximum CO2 intrinsic conversion yield) in presence of minimum content of water (H2O);
• subjecting said reaction mixture to a stripping treatment with the use of CO2 feed as stripping agent in a counter current apparatus (Stripper) to remove most of the unreacted CO2 and NH3 and to obtain a first flow comprising NH3 and CO2 in vapour phase and a second flow comprising urea and residual carbamate and free NH3 in aqueous solution, such residual carbamate and free NH3 being removed downstream the loop in a urea recovery unit, and recycled to the loop in a third flow aqueous solution (carbamate recycle solution:
• CRS);
• subjecting said first flow comprising NH3 and CO2 in vapour phase to total condensation in a carbamate condenser to obtain a carbamate solution which is sent to the bottom zone of the reactor space R using an ejector E;
• subjecting at least part of said third flow (carbamate recycle solution CRS) to a treatment (carbamate stripper) of carbamate decomposition and removal of free ammonia to obtain a vapour flow containing CO2 and NH3 with minimum content of water, and a weak water carbamate solution sent back to the urea recovery unit URS;
• directly feeding at least part of above vapour flow containing CO2 and NH3 with minimum content of water to the bottom zone of the reaction space.