Integrated production of urea for diesel exhaust fluid and urea ammonium nitrate

Patent metadata

Field	Value
Publication number	US-11083976-B2
Application number	US-201615560460-A
Country	US
Kind code	B2
Filing date	Mar 29, 2016
Priority date	Mar 25, 2015
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

Disclosed is a method for the integrated production of two different urea products. One is an aqueous urea solution suitable for use in NOx abatement (generally indicated as Diesel Exhaust Fluid—DEF). The other is a solution used as a fertilizer, viz. Urea Ammonium Nitrate (UAN). The production of DEF and UAN are integrated as follows: ammonia recovered from the production of urea is used as a feed to the production of ammonium nitrate. At least part of an aqueous urea stream from urea prodution, is mixed with ammonium nitrate so as to obtain UAN.

First claim

The invention claimed is:

1. An integrated system for the production of urea and urea ammonium nitrate, said system comprising
(i) a unit for the production of urea, said unit comprising a urea synthesis section comprising a reactor, a stripper and a condenser in fluid communication with each other so as to form a urea synthesis loop and a urea purification section for separating off CO 2 and NH 3 from an aqueous urea solution comprising said CO 2 and NH 3 , thereby giving purified aqueous urea solution, wherein said urea purification section is downstream of said synthesis section and is in fluid communication with said synthesis section, wherein said purification section has an outlet for NH 3 and a first outlet for said purified aqueous urea solution,
wherein the condenser is a high pressure condenser for condensing gaseous components from the stripper into ammonium carbamate, and
(ii) a unit for the production of aqueous ammonium nitrate solution from ammonia and nitric acid, having an inlet for NH 3 and an outlet for said aqueous ammonium nitrate solution; and
(iii) a unit for mixing said purified aqueous urea solution and said aqueous ammonium nitrate solution,
wherein said system is configured to have no NH 3 recycled to the synthesis section, and
wherein said system further comprises:
(a) a first connection from said outlet for NH 3 of the purification section to said inlet for NH 3 of the unit for the production of ammonium nitrate, and
(b) a second connection from said first outlet for said purified aqueous urea solution of said purification section to said unit for mixing, and
(c) a third connection from said outlet for said aqueous ammonium nitrate solution of said unit for the production of aqueous ammonium nitrate solution connected to said unit for mixing said aqueous urea solution and said aqueous ammonium nitrate solution.

2. The system of claim 1 , further comprising a unit for the production of nitric acid, said unit comprising an outlet for produced nitric acid in fluid communication with an inlet for nitric acid to the unit for the production of aqueous ammonium nitrate.

3. The system of claim 1 , wherein said urea purification section has a second outlet for said purified aqueous urea solution, and the system further comprises a Diesel Exhaust Fluid (DEF) production unit, said DEF production unit comprising a diluting section having an inlet for said purified aqueous urea solution or part thereof connected with said second outlet of said urea purification section, and an inlet for demineralized water, wherein said diluting section is configured for diluting said purified aqueous urea solution or part thereof with said demineralized water.

4. The system of claim 3 , wherein said DEF production unit further comprises a DEF production stripper, said DEF production stripper having an inlet for pressurized steam and an inlet for said purified aqueous urea solution, wherein said DEF production stripper is configured for stripping of said purified aqueous urea solution from said second outlet with direct injection of pressurized steam.

5. The system of claim 3 , wherein said DEF production unit further comprises a heat exchanger for subjecting said purified aqueous urea solution or part thereof to evaporation, wherein said heat exchanger has an outlet connected to said inlet for said purified aqueous urea solution of said diluting section.

6. The system of claim 3 , wherein said urea purification section comprises a urea solution storage tank,
wherein said urea solution storage tank is provided upstream of the first and second outlets for said purified aqueous urea solution or a part thereof,
wherein said urea solution storage tank has an outlet connected to said DEF production unit and an outlet connected to said unit for mixing
such that said purified urea solution from said tank can be supplied to said DEF production unit, to said unit for mixing, or to both said DEF production unit and said unit for mixing.

7. The system of claim 3 , wherein said DEF production unit comprises a DEF production stripper, wherein said DEF production stripper has an inlet for said purified aqueous urea solution from said second outlet, and said DEF production stripper is configured for stripping of said purified aqueous urea solution to remove ammonia from said purified aqueous urea solution into an off-gas,
wherein said DEF production stripper has an outlet for said off-gas, and
wherein the system comprises a connection from said outlet for off-gas of said DEF production stripper to said unit for the production of aqueous ammonium nitrate solution.

8. The system of claim 1 , wherein said urea purification section has a second outlet for said purified aqueous urea solution or a part thereof, and wherein the system further comprises a DEF production unit having an inlet connected with said second outlet of said urea purification section, wherein said DEF production unit comprises a flash crystallization unit configured for flash crystallization of said purified aqueous urea solution or part thereof to form a solid urea powder.

9. The system of claim 8 , wherein said flash crystallization unit is configured for flash crystallization of said purified aqueous urea solution or part thereof at a pressure below 15 kPa to produce said solid urea powder as a free flowing urea powder, and wherein said DEF production unit further comprises a packaging unit for packaging the solid urea powder from said flash crystallization unit to give a packaged product under conditions such that the packaged product has a water content that is maintained below 0.2 wt. %.

10. The system of claim 1 , wherein said urea purification section comprises a rectification column which comprises a shell-and-tube heat exchanger and a gas/liquid separator, and wherein the shell-and-tube heat exchanger is configured for flow of the aqueous urea solution through the tubes and for flow of steam on the shell side, and wherein said gas/liquid separator of said rectification column is provided with said outlet for NH 3 connected to the inlet for NH 3 of the unit for the production of ammonium nitrate.

11. The system of claim 1 , wherein the condenser and reactor are in the form of a submerged condenser/reactor.

Assignees

• Stamicarbon

Inventors

• Dobree Joey
• Mennen Johannes Henricus

Classifications

• B01D3/009 Primary

  in combination with chemical reactions · CPC title

• B01J2219/00024

  Revamping, retrofitting or modernisation of existing plants · CPC title

• C07C273/04 Primary

  from carbon dioxide and ammonia · CPC title

• Y02P20/10

  Process efficiency · CPC title

• Y02P20/50

  Improvements relating to the production of bulk chemicals · CPC title