Vent line for use in ammonia and hydrogen plants

Patent metadata

Field	Value
Publication number	US-9695058-B2
Application number	US-201414786062-A
Country	US
Kind code	B2
Filing date	Apr 16, 2014
Priority date	May 10, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

In an ammonia or hydrogen plant comprising a desulfurisation section, a reforming section and a shift section, where the shift section comprises a low temperature shift converter and a medium temperature shift converter, a vent line is arranged downstream from the low temperature shift converter and the medium temperature shift converter in order to allow the shift converters to be re-heated with process gas at a low pressure (typically 3-7 bar). This way condensation of water vapour in the process gas is avoided. By applying this vent line it becomes possible to save significant time, more specifically 8-24 hours, for restarting the production after temporary shut-down thereof, because a heat-up of the LTS/MTS converter in circulating nitrogen is avoided.

First claim

The invention claimed is:

1. An ammonia or hydrogen plant including a synthesis gas generation part comprising a reforming section, a shift section, a carbon dioxide removal unit and a methanator, said shift section comprising a low temperature shift (LTS) converter and/or a medium temperature shift (MTS) converter, and further including a vent line arranged downstream from the shift section comprising the LTS converter and/or the MTS converter, said vent line allowing the shift converter(s) to be re-heated with process gas at a pressure of 3 to 7 bar, and an inlet pressure reducing valve placed at the inlet of the shift section and a vent valve placed in the vent line downstream from the shift section, said valves facilitating the pressure control.

2. An ammonia or hydrogen plant according to claim 1 , wherein the reduced pressure is established by means of an inlet pressure reducing valve and a vent valve, said valves normally being closed and the synthesis gas being led to the MTS and/or LTS section through a normally open valve.

3. A process of using the vent line in the plant of claim 1 , comprising opening a normally closed valve of the vent line and conveying process gas at a pressure of between 3-7 bar from said vent line to said shift section, upstream of the low temperature shift (LTS) converter and/or a medium temperature shift (MTS) converter, to restart the plant after temporary shut-down thereof, where the catalyst has only cooled slightly down, to a temperature of 140-250°.

Assignees

• Haldor Topsoe As

Inventors

• Andersen Niels Ulrik
• Speth Christian

Classifications

• C01B3/025 Primary

  Preparation or purification of gas mixtures for ammonia synthesis · CPC title

• C01B2203/1638

  Adjusting the pressure · CPC title

• C01B3/48

  followed by reaction of water vapour with carbon monoxide · CPC title

• C01B2203/0211

  containing a non-catalytic reforming step · CPC title

• C01B2203/147

  Three or more purification steps in series · CPC title