Controlling biuret in urea production

Patent metadata

Field	Value
Publication number	US-10766856-B2
Application number	US-201916698734-A
Country	US
Kind code	B2
Filing date	Nov 27, 2019
Priority date	May 3, 2016
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

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.

First claim

The invention claimed is:

1. A method of modernizing a pre-existing plant for the production of urea, said plant comprising a urea synthesis section having a first 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 a second 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 a third inlet of the synthesis section, said outlet for a purified urea aqueous stream being in fluid communication with a fourth 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 downstream of the recovery section, through a fifth inlet connected to said supply member.

2. The method of claim 1 , wherein the fifth inlet is added in a position upstream of the concentration section.

3. The method of claim 1 , wherein the fifth inlet is added in a position in the concentration section.

4. The method of claim 1 , wherein the fifth inlet is added in a position downstream of the concentration section.

5. The method of claim 1 , wherein the fifth inlet is added in a position in the finishing section.

6. The method of claim 4 , wherein the fifth inlet is added in a position that is both downstream of the concentration section and upstream of the finishing section.

7. The method of claim 1 , wherein the ammonia-abatement section is an ammonia-neutralizing section.

8. The method of claim 7 , wherein the ammonia-neutralizing section comprises one or more acidic scrubbers.

9. The method of claim 1 , wherein the ammonia comprising liquid is liquid ammonia.

10. The method of claim 6 , wherein said fifth inlet is added to a supply line for a urea melt having a urea concentration greater than 90 wt % between said concentration section and said finishing section and wherein said supply line is configured for maintaining said urea melt at 130 to 140° C. after the addition of the liquid ammonia.

11. The method of claim 10 , wherein ammonia comprising liquid is liquid ammonia.

Assignees

• Stamicarbon

Inventors

• Mostert Eelco

Classifications

• B01J4/008

  Feed or outlet control devices · CPC title

• C07C273/04 Primary

  from carbon dioxide and ammonia · CPC title

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• C07C275/62

  Y being a nitrogen atom, e.g. biuret · CPC title

• C07C275/02

  Salts; Complexes; Addition compounds · CPC title