Stripping-type urea plant for def production

Patent metadata

Field	Value
Publication number	US-2024059623-A1
Application number	US-202318256554-A
Country	US
Kind code	A1
Filing date	Feb 14, 2023
Priority date	Feb 15, 2022
Publication date	Feb 22, 2024
Grant date	—

Abstract

A urea plant and urea production process of the stripping type are provided that are adapted for making Diesel Exhaust Fluid (DEF) or precursor thereof in a DEF production unit downstream of a treatment section. The treatment section receives a part of the urea synthesis stream from a reaction zone, in particular bypassing the HP stripper.

First claim

1 . A urea production plant for producing a first urea-containing product and a second urea-containing product, wherein the second urea-containing product is Diesel Exhaust Fluid (DEF) or DEF precursor, the plant comprising a high pressure (HP) synthesis section comprising a reaction zone, a high pressure stripper, a condensation zone, and a flow splitter adapted for dividing a urea synthesis stream from said reaction zone into a first stream and a second stream and a flow line for said first stream to said HP stripper, the plant further comprising:
a urea processing section for processing stripped urea solution from said HP stripper into said first urea-containing product, the urea processing section comprising a recovery section comprising one or more recovery section decomposers for processing said stripped urea solution; an expansion device for expanding said second stream to give an expanded second stream; a treatment section comprising one or more treatment section decomposers for purifying said expanded second stream into a purified urea solution, wherein the one or more treatment section decomposers are arranged in parallel to the one or more recovery section decomposers; and a DEF production unit for producing DEF and/or DEF precursor from said purified urea solution.

2 . The urea production plant according to claim 1 , wherein the treatment section comprises a treatment section low pressure (LP) decomposer and the recovery section comprises a recovery section low pressure decomposer parallel to the treatment section LP decomposer.

3 . The urea production plant according to claim 1 , wherein the treatment section comprises a steam stripper for stripping urea solution by injection of steam.

4 . The urea production plant according to claim 1 , wherein the DEF production unit comprises an inlet for adding clean water to the purified urea solution.

5 . The urea production plant according to claim 1 , wherein the DEF production unit comprises a dry flashing unit.

6 . The urea production plant according to claim 1 , wherein the plant does not include a flow line for stripped urea solution from the HP stripper or for urea solution obtained from the stripped urea solution from the HP stripper to a flow line or unit in the plant which receives the second stream or which receives urea solution originating from said second stream.

7 . The urea production plant according to claim 1 , wherein at least one of the one or more recovery section decomposers is the recovery section LP decomposer, wherein the recovery section optionally comprises a medium pressure decomposer between the outlet for stripped urea solution of the HP stripper and said recovery section LP decomposer; wherein the plant further comprises a low pressure carbamate condenser for condensing gas from said recovery section LP decomposer, wherein said LP carbamate condenser is optionally also used for condensing gas from a treatment section LP decomposer comprised in said treatment section.

8 . The urea production plant according to claim 1 , wherein the HP stripper uses at least a part of the CO 2 feed for stripping, and wherein preferably the stripper is a shell-and-tube heat exchanger comprising stripper tubes made of duplex stainless steel.

9 . A urea production plant according to claim 1 , wherein the urea processing section comprises an evaporation section for converting urea solution into urea melt downstream of the recovery section and a liquid flow connection for urea solution from the treatment section to the evaporation section.

10 . A urea production process wherein a urea synthesis stream is split into a first part and a second part, wherein the first part is stripped in a high pressure stripper, recovered in a recovery section comprising one or more recovery section decomposers, and processed into a first urea-containing product, preferably a urea fertilizer product, and wherein the second stream is sent to a treatment section comprising one or more treatment section decomposers without passing through the HP stripper, wherein the one or more treatment section decomposers operate separately from and in parallel to the one or more recovery section decomposers and wherein the treatment section produces a urea-comprising stream which is suitable for use as Diesel Exhaust Fluid (DEF) or for preparation of DEF by dilution with water;
wherein preferably no urea solution is supplied from the HP stripper to the treatment section, and wherein preferably no urea solution is supplied from the recovery section to the treatment section.

11 . The process according to claim 10 , wherein the urea-comprising stream at 32.5 wt. % urea has an alkalinity as NH 3 of max. 0.2 wt. %; biuret max. 0.3 wt. %; PO 4 , Ca, Fe, Al, Mg, Na and K each max. 0.5 ppm by weight; and Cu, Zn, Cr and Ni each max. 0.2 ppm by weight.

12 . The process according to claim 10 , wherein the recovery section comprises a recovery section low pressure decomposer and the treatment section comprises a treatment section low pressure decomposer arranged parallel to the recovery section low pressure decomposer.

13 . The process according to claim 10 , carried out in a plant according to claim 1 .

14 . A method of modifying an existing urea plant of the stripping type comprising a high pressure (HP) synthesis section comprising a reaction zone, a condensation zone, and a HP stripper, and a recovery section, wherein the recovery section comprises a recovery section low pressure decomposer,
the method comprising adding to the existing plant:
a flow splitter for dividing a urea synthesis stream from the reaction zone into a first part and a second part, the first part being supplied to the HP stripper;
a treatment section for processing said second part,
wherein the treatment section comprises a treatment section low pressure (LP) decomposer in parallel to the recovery section low pressure (LP) decomposer.

15 . The method of claim 14 , wherein the added treatment section comprises a steam stripper.

Assignees

• Stamicarbon

Inventors

• Van Den Tillaart Johan Albert Arno
• Mostert Eelco

Classifications

• C05C9/00 Primary

  Fertilisers containing urea or urea compounds · CPC title

• C05G5/23

  Solutions · CPC title

• C07C273/04

  from carbon dioxide and ammonia · CPC title

• C07C273/16 Primary

  Separation; Purification · CPC title