Production of urea for diesel exhaust fluid

Patent metadata

Field	Value
Publication number	US-12565622-B2
Application number	US-202419105163-A
Country	US
Kind code	B2
Filing date	Sep 6, 2024
Priority date	Sep 8, 2023
Publication date	Mar 3, 2026
Grant date	Mar 3, 2026

Abstract

Disclosed is a process for the production of an aqueous urea solution suitable for use as a Diesel Exhaust Fluid (DEF), wherein a condensate of off-gas obtained from further purifying an aqueous urea stream in a treatment section adapted to produce DEF, is sent to an LP dissociation section, thereby the removal of ammonia therefrom. This enables water obtained from such condensate to be recirculated to the DEF purification section, and prevents an unwanted build-up of water in recirculation to urea synthesis.

First claim

The invention claimed is:

1 . A process for the production of an aqueous urea solution suitable for use as a Diesel Exhaust Fluid (DEF), the process comprising reacting ammonia and carbon dioxide in a high pressure (HP) synthesis section under urea-forming conditions, thereby obtaining a urea synthesis solution; subjecting the urea synthesis solution to a recovery treatment so as to remove remaining ammonia and carbon dioxide therefrom, said treatment comprising dissociation in a low pressure (LP) dissociation section, resulting in an aqueous urea product stream and an LP dissociation off-gas; subjecting said LP dissociation off-gas to condensation, thereby obtaining an LP condensate; recirculating said LP condensate as a feed to urea synthesis; subjecting the aqueous urea product stream to removal of further ammonia in a DEF purification section, thereby obtaining a purified urea solution and a DEF purification off-gas; subjecting the DEF purification off-gas to condensation thereby obtaining a DEF purification condensate; adjusting the water content of the purified urea solution, thereby obtaining a DEF product solution; wherein the process comprises subjecting at least part of the DEF purification condensate to removal of ammonia in the LP dissociation section.

2 . The process according to claim 1 , wherein the DEF purification section is operated under a pressure of from 0.1 barA to 2 barA.

3 . The process according to claim 1 , wherein the DEF purification section is operated at a sub-atmospheric pressure.

4 . The process according to claim 3 , wherein the pressure is in a range of from 0.3 barA to 0.6 barA.

5 . The process according to claim 1 , wherein adjusting the water content of the purified urea solution comprises dilution with water selected from the group consisting of demineralized water, distilled water, and mixtures thereof.

6 . The process according to claim 1 , wherein adjusting the water content of the purified urea solution comprises dilution with a purified process condensate.

7 . The process according to claim 1 , wherein the aqueous urea product stream has a urea concentration of 60 to 85 wt. %.

8 . The process according to claim 1 , wherein subjecting the aqueous urea product stream to removal of further ammonia in a DEF purification section comprises heating to a temperature below 135° C.

9 . The process according to claim 8 , wherein said heating comprises injecting steam into the aqueous urea product stream.

10 . The process according to claim 1 , wherein
The DEF purification condensate is divided into a portion that is sent to the LP dissociation section, and a portion that is sent to an LP condensation section.

11 . The process according to claim 1 , wherein at least 20 wt. % of the DEF purification condensate, is sent to the LP dissociation section.

12 . A plant for the production of an aqueous urea solution suitable for use as a Diesel Exhaust Fluid (DEF), said plant comprising a high pressure (HP) synthesis section configured to subject ammonia and carbon dioxide to reaction under urea-forming conditions, thereby obtaining a urea synthesis solution; downstream thereof and in fluid communication therewith, a low pressure (LP) recovery section configured to subject a passing urea solution to recovery of remaining ammonia and carbon dioxide contained therein, said LP recovery section comprising an LP dissociation section and an LP condensation section, said LP dissociation section comprising an inlet for a urea solution, said inlet being in fluid communication, optionally via an MP section, with an outlet for a urea synthesis solution from the HP synthesis section, an outlet for an aqueous urea product stream, and an outlet for dissociation off-gas, said outlet for dissociation off-gas being in fluid communication with a gas inlet of the LP condensation section, said LP condensation section having an outlet for LP condensate which outlet is in fluid communication with an inlet of the HP synthesis section; the plant further comprising a DEF purification section configured to subject the aqueous urea product stream to removal of further ammonia, said DEF purification section having an inlet for a liquid urea stream, which inlet is in fluid communication with the outlet for an aqueous urea product stream of the LP dissociation section, an outlet for a purified urea solution, and an outlet for DEF purification off-gas, said outlet for DEF purification off-gas being in fluid communication with an inlet of a DEF purification condensation section configured to subject the DEF purification off-gas to condensation, thereby obtaining a DEF purification condensate, said DEF purification condensation section having an outlet for said DEF purification condensate, which outlet is in fluid communication with an inlet of the LP dissociation section.

13 . A method of modifying a pre-existing plant for the production of an aqueous urea solution suitable for use as a Diesel Exhaust Fluid (DEF), said pre-existing plant comprising a high pressure (HP) synthesis section configured to subject ammonia and carbon dioxide to reaction under urea-forming conditions, thereby obtaining a urea synthesis solution; downstream thereof and in fluid communication therewith, a low pressure (LP) recovery section configured to subject a passing urea solution to recovery of remaining ammonia and carbon dioxide contained therein, said LP recovery section comprising an LP dissociation section and an LP condensation section, said LP dissociation section comprising an inlet for a urea solution, said inlet being in fluid communication with an outlet for a urea synthesis solution from the HP synthesis section, an outlet for an aqueous urea product stream, and an outlet for dissociation off-gas, said outlet for dissociation off-gas being in fluid communication with a gas inlet of the LP condensation section, said LP condensation section having an outlet for LP condensate which outlet is in fluid communication with an inlet of the HP synthesis section; the plant further comprising a DEF purification section configured to subject the aqueous urea product stream to removal of further ammonia, said DEF purification section having an inlet for a liquid urea stream, which inlet is in fluid communication with the outlet for an aqueous urea product stream of the LP dissociation section, an outlet for a purified urea solution, and an outlet for DEF purification off-gas, said outlet for DEF purification off-gas being in fluid communication with an inlet of a DEF purification condensation section configured to subject the DEF purification off-gas to condensation, thereby obtaining a DEF purification condensate, said DEF purification condensation section having an outlet for said DEF purification condensate, which outlet is in fluid communication with the LP recovery section, the method comprising providing a fluid connection between an outlet for the DEF purification condensate of the DEF purification condensation section, with an inlet for a urea solution of the LP dissociation section.

14 . A method of modifying a pre-existing urea production plant comprising a high pressure (HP) synthesis section configured to subject ammonia and carbon dioxide to reaction under urea-forming conditions, thereby obtaining a urea synthesis solution; downstream thereof and in fluid communication therewith, a low pressure (LP) recovery section configured to subject a passing urea solution to recovery of remaining ammonia and carbon dioxide contained therein, said LP recovery section comprising an LP dissociation section and an LP condensation section, said LP dissociation section comp

Assignees

• Stamicarbon

Inventors

• Gao Chuanbo
• Elbassyouni Khaled
• Gevers Lambertus Wilhelmus

Classifications

• C10L2290/56

  Specific details of the apparatus for preparation or upgrading of a fuel · CPC title

• C10L2200/0446

  Diesel · CPC title

• C07C273/04

  from carbon dioxide and ammonia · CPC title

• B01J3/04

  Pressure vessels, e.g. autoclaves · CPC title

• C10L1/22 Primary

  containing nitrogen · CPC title