METHOD OF PRODUCING UREA AND APPARATUS FOR REALISING SAID METHOD Russian patent published in 2012 - IPC C07C273/04 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing urea from ammonia and carbon dioxide. The method comprises the following steps: feeding ammonia and carbon dioxide into a urea synthesis section operating at given high pressure; reaction of ammonia and carbon dioxide in the synthesis section to obtain an aqueous solution containing urea, ammonium carbamate and ammonia; feeding a first portion of said aqueous solution containing urea, ammonium carbamate and ammonia into a processing section operating at given medium pressure to extract ammonium carbamate and ammonia contained in that solution; dissociation of the first portion of said aqueous solution containing urea, ammonium carbamate and ammonia in the processing section to obtain an aqueous solution of urea and a vapour phase containing ammonia, carbon dioxide and water; condensation of said vapour phase containing ammonia, carbon dioxide and water in the processing section to obtain aqueous ammonium carbamate solution; directing the aqueous ammonium carbamate solution to the repeated cycle in the urea synthesis section. The method also involves feeding aqueous solution of urea obtained at the dissociation step in the processing section into a decomposition apparatus located in the urea extraction section and operating at given low pressure; decomposition of aqueous solution of urea in the decomposition apparatus in the urea extraction section to obtain concentrated urea solution and a second vapour phase containing ammonia, carbon dioxide and water; condensation of the second vapour phase in a condenser located in the urea extraction section and linked to said decomposition apparatus to obtain a first recycle aqueous solution of ammonium carbamate; steam stilling the second portion of aqueous solution containing urea, ammonium carbamate and ammonia while heating in a steam stilling unit essentially at the given high pressure to obtain a second aqueous solution of urea and a third vapour phase containing ammonia, carbon dioxide and water, where said heating is carried out via indirect heat exchange with a vapour stream which forms condensed vapour upon condensation; using at least a portion of the condensed vapour as heat carrier for dissociation of the first portion of the aqueous solution containing urea, ammonium carbonate and ammonia in the dissociation unit located in the processing section at medium pressure. The invention also discloses apparatus for producing urea and a method for upgrading existing apparatus for producing urea.

EFFECT: invention increases production capacity of apparatus for producing urea while simultaneously ensuring high degree of conversion of carbon dioxide to urea.

21 cl, 2 dwg