US 6,284,922 B1Granted

Method for modernizing a urea production plant

AssigneeUreacasale S.A.

InventorsGiorgio Pagani, Federico Zardi

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Abstract

A method for the modernization of a plant for urea production of the type comprising a reactor (2) for urea synthesis, a stripping unit (3) with carbon dioxide and at least one vertical condensation unit (4) of the film type, foresees the provision of means (36) for feeding a major portion of a flow comprising ammonia and carbon dioxide in vapor phase leaving the stripping unit (3) to the condensation unit (4) and the provision in said condensation unit (4) of means (37) for subjecting to substantially total condensation such major portion of the flow comprising ammonia and carbon dioxide in vapor phase, obtaining a flow comprising urea and carbamate in aqueous solution, then fed to the reactor (2) for urea synthesis. Thanks to the present method of modernization, the efficiency of the condensation unit (4) is remarkably improved, thus permitting an increase of its capacity.

Claims5

Dependent claims

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).

4 more elements

Dependencies are inferred from the claim text.