Process and apparatus for urea production

A process for urea production, comprising:

• a synthesis step of synthesizing urea from ammonia and carbon dioxide to generate a urea synthesis solution;
• a high-pressure decomposition step of, by heating the urea synthesis solution generated in the synthesis step with use of medium-pressure steam as a heat source, decomposing ammonium carbamate, separating a gaseous mixture containing ammonia and carbon dioxide from the urea synthesis solution and obtaining medium-pressure steam condensate;
• a condensation step of absorbing and condensing at least a part of the gaseous mixture obtained in the high-pressure decomposition step in an absorption medium, and generating low-pressure steam with use of heat generated during the condensation;
• a first medium-low-pressure steam generation step of, by reducing a pressure of the medium-pressure steam condensate obtained in the high-pressure decomposition step to a medium-low pressure lower than a pressure of the medium-pressure steam and higher than a pressure of the low-pressure steam, generating medium-low-pressure steam and medium-low-pressure steam condensate;
• and
• one or both of a medium-pressure decomposition step and an ammonia preheating step, wherein
• in the medium-pressure decomposition step, by heating the urea synthesis solution, said urea synthesis solution having been processed in the high-pressure decomposition step, at a pressure lower than a pressure in the high-pressure decomposition step with use of at least a part of the medium-low-pressure steam generated in the first medium-low-pressure steam generation step as a heat source, ammonium carbamate is decomposed, and a gaseous mixture containing ammonia and carbon dioxide is separated from the urea synthesis solution;
• and
• in the ammonia preheating step, the ammonia to be supplied to the synthesis step is heated with use of at least a part of the medium-low-pressure steam generated in the first medium-low-pressure steam generation step as a heat source.