Controlling biuret in urea production
AssigneeStamicarbon B.V.
InventorEelco MOSTERT
Life of this patent
Estimating the term…
Abstract
Disclosed is a novel method of controlling the formation of biuret in urea production, and particularly reducing, preventing or reversing such formation. This is accomplished by adding liquid ammonia to a urea aqueous stream. This addition is done at one or more positions downstream of a recovery section in a urea plant. The addition of liquid ammonia serves to shift the equilibrium of biuret formation from urea, to the side of the formation of urea from biuret and ammonia. The invention can be accomplished also in pre-existing urea plant, by the simple measure of providing an appropriate inlet for liquid ammonia, in fluid communication with a source of such liquid ammonia.
Claims13
A process for producing urea, the process comprising
- a. subjecting ammonia and carbon dioxide to urea forming conditions in a urea synthesis section, thereby producing a urea aqueous stream;
- b. sending the urea aqueous stream to a recovery section;
- c. subjecting, in the recovery section, the urea aqueous stream to recovery of unreacted ammonia and carbon dioxide from said urea aqueous stream, thereby producing recovered ammonia and carbon dioxide, and a purified urea aqueous stream;
- d. recycling said recovered ammonia and carbon dioxide to the synthesis section;
- e. sending the purified urea aqueous stream to a concentration section;
- f. subjecting, in the concentration section, the purified urea aqueous stream to removal of water, thereby producing a concentrated urea stream;
- wherein the process further comprises
- g. adding, downstream of the concentration section, ammonia to the concentrated urea stream, to give a concentration of ammonia after addition in the range of from 500 to 5000 ppm by weight,
- wherein the process is conducted in a urea plant provided with an abatement section for ammonia-containing gas emissions.
A plant for the production of urea, said plant comprising a urea synthesis section having an inlet for ammonia and carbon dioxide and an outlet for a urea aqueous solution, said outlet being in fluid communication with a recovery section having an inlet for the urea aqueous solution, an outlet for ammonia and carbon dioxide recycle, and an outlet for a purified urea aqueous stream, said outlet for ammonia and carbon dioxide recycle being in fluid communication with an inlet of the synthesis section, said outlet for a purified urea aqueous stream being in fluid communication with an inlet of a concentration section;
- said concentration section having an outlet for steam or steam condensate, and an outlet for a concentrated urea stream which is in fluid communication with a finishing section for the concentrated urea stream, said finishing section comprising a gas outlet in gas flow connection with an abatement section for ammonia-containing gas emissions, wherein the plant comprises a supply member for supplying an ammonia-comprising liquid to the concentrated urea stream downstream of the concentration section.
A method of modernizing a pre-existing plant for the production of urea, said plant comprising a urea synthesis section having an inlet for ammonia and carbon dioxide and an outlet for a urea aqueous solution, said outlet being in fluid communication with a recovery section having an inlet for the urea aqueous solution, an outlet for ammonia and carbon dioxide recycle, and an outlet for a purified urea aqueous stream, said outlet for ammonia and carbon dioxide recycle being in fluid communication with an inlet of the synthesis section, said outlet for a purified urea aqueous stream being in fluid communication with an inlet of a concentration section;
- said concentration section having an outlet for steam or steam condensate, and an outlet for a concentrated urea stream, which is in fluid communication with a finishing section for the concentrated urea stream, said finishing section comprising a gas outlet in gas flow connection with an abatement section for ammonia-containing gas emissions, the modernizing method comprising connecting the plant to a supply member for supplying an ammonia-comprising liquid to the concentrated urea stream downstream of the concentration section.
13-15. (canceled)
Dependencies are inferred from the claim text.