Process for the preparation of urea

Details Process for the preparation of urea Process for the preparation of urea

1983-04-21

1985-09-03

Bashore, S. Leon

Distillation: processes, separatory

Convective distillation with normally gaseous medium, e.g., air

203 87, 203 91, 159 472, 562555, 564 69, 564 70, 564 73, B01D 300, B01D 500

Patent

active

045390770

ABSTRACT:
An improved process for the preparation of urea from carbon dioxide and excess ammonia at elevated temperature and pressure. The urea solution from the urea synthesis zone is heated and stripped at an elevated pressure to decompose a portion of the ammonium carbamate contained therein and the ammonium and carbon dioxide containing off-gas produced is condensed in a first condensation zone. The stripped urea solution is heated at a reduced pressure in a decomposition zone to decompose a further portion of ammonium carbamate, and the ammonia and carbon dioxide containing off-gas thereby produced is condensed in a second condensation zone to form an aqueous ammonium carbamate solution. A portion of this aqueous carbamate solution is introduced into a desorption zone so as to produce an off-gas more concentrated with respect to ammonia and carbon dioxide than the ammonium carbamate solution, and the off-gas from this desorption zone is condensed into a further portion of such aqueous ammonium carbamate solution in a third condensation zone, maintained at a pressure between the pressure in the decomposition zone and about 40 bar, to form a more concentrated ammonium carbamate solution which is recycled to the urea synthesis zone.

REFERENCES:
patent: 2701262 (1955-02-01), Cook
patent: 3146263 (1964-08-01), Otsuka
patent: 3232982 (1966-02-01), Finneran et al.
patent: 3759992 (1973-09-01), Maurovic
patent: 4066693 (1978-01-01), Venderbos
patent: 4115449 (1978-09-01), Biermans et al.
patent: 4231839 (1980-11-01), Barron et al.
patent: 8300862 (1983-03-01), Nassau et al.
Weyermuller et al., Dutch Urea Process, Chemical Processing, 1962, pp. 19-22.

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