Urea production with controlled biuret

Patent metadata

Field	Value
Publication number	US-10457633-B2
Application number	US-201715735153-A
Country	US
Kind code	B2
Filing date	Apr 28, 2017
Priority date	May 3, 2016
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

Disclosed is a novel method of controlling the formation of biuret in urea production. This is accomplished by reducing or preventing the formation of biuret in a concentration section, particularly in one or more concentrators or evaporators. The method comprises controlling the residence time of a urea aqueous stream treated in such concentration section in a manner independently of the volume flow per time interval of said stream into said concentration section. The residence time can be controlled, e.g., by providing the concentration section with an adjustable volume or by adding a gas to the urea stream to be treated. A combination of such measures can also be applied.

First claim

The invention claimed is:

1. 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 residence time of the purified urea aqueous stream in the concentration section is controlled independently of the volume flow per time interval of the purified urea aqueous stream into the concentration section.

2. The process of claim 1 , wherein the purified urea aqueous stream is combined with a gas at or before entry into the concentration section.

3. The process of claim 2 , wherein the amount of the gas added is greater than any amount of the gas that is soluble in the purified urea aqueous stream.

4. The process of claim 3 , wherein the gas is selected from the group consisting of air, nitrogen, and mixtures thereof.

5. The process of claim 2 , wherein the gas comprises ammonia.

6. The process of claim 5 , wherein the gas consists essentially of ammonia.

7. The process of claim 1 , wherein the concentrated urea stream has a concentration of more than 90 wt.

8. The process of claim 3 , wherein the gas is substantially insoluble in the purified urea aqueous stream.

9. The process of claim 7 , wherein the concentrated urea stream has a concentration of more than 95 wt. %.

Assignees

• Stamicarbon

Inventors

• Mostert Eelco

Classifications

• B01J19/2415

  Tubular reactors · CPC title

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• C07C273/16

  Separation; Purification · CPC title

• C07C273/04 Primary

  from carbon dioxide and ammonia · CPC title

• B01B1/005 Primary

  Evaporation for physical or chemical purposes; Evaporation apparatus therefor, e.g. evaporation of liquids for gas phase reactions · CPC title