GB2252317A

GB2252317A - Combined ammonia/methanol process

Info

Publication number: GB2252317A
Application number: GB9100083A
Authority: GB
Inventors: Trevor Williams Nurse
Original assignee: Enserch International Investments Ltd
Current assignee: Enserch International Investments Ltd
Priority date: 1991-01-03
Filing date: 1991-01-03
Publication date: 1992-08-05
Anticipated expiration: 2011-01-03
Also published as: GB2252317B; GB9100083D0

Abstract

A process for the integrated production of ammonia and methanol from a gas produced by steam reforming a hydrocarbon characterised by a) cooling at least part of said gas by heating a secondary reformer feed b) synthesising methanol from at least part of the stream from stop a) in a methanol synthesis unit c) purging inert gas from the methanol synthesis unit in step b) d) heating the purge (as per step a)) and feeding the heated purge gas to a secondary reformer together with an oxygen-and-nitrogen-containing gas e) passing the effluent from the secondary reformer through a carbon monoxide shift reactor f) separating carbon dioxide from the shift reactor effluent from step e) g) methanating oxides of carbon in the effluent gas from step f) h) producing ammonia from dried effluent from step g).

Description

COMBINED AMMONIA/METHANOL PROCESS This invention relates to the integrated production of ammonia and methanol from a hydrocarbon feedstock.

As is well known, the production of methanol from natural gas results in an excess of hydrogen which has to be purged from the synthesis loop and is used as fuel in the Primary Reformer.

In this invention ammonia and methanol are produced from a synthesis gas produced in a Primary Reformer. In essence, the synthesis gas produced from the Primary Reformer is used firstly as synthesis gas for methanol production and the purge from the methanol synthesis loop is then further reformed using a gas containing nitrogen and oxygen, and the synthesis gas from this secondary reforming is processed in the normal way and fed to an ammonia synthesis loop. An important feature of this process is the exchange of heat present in the synthesis gas leaving the Primary Reformer into the feed to the secondary reformer.

It is not essential that all of the synthesis gas from the Primary Reformer is fed to the methanol synthesis loop.

When the feed stock is natural gas, in order to balance the stoichiometry for methanol production it is beneficial to recover carbon dioxide from the stream used to produce the ammonia synthesis gas and to mix the recovered carbon dioxide with the hydrogen rich stream from the Primary Reformer either directly, or indirectly by adding the recovered carbon dioxide to the methanol loop.

The recovery of the carbon dioxide maybe effected as follows: The carbon dioxide maybe removed from the ammonia synthesis gas preparation stream by the use of a physical solvent such as Selexol (Trade Mark) or methanol and the carbon dioxide may then be stripped from the rich solution by using the synthesis gas from the Primary Reformer thereby negating the need to use a carbon dioxide compressor.

If insufficient carbon dioxide can be recovered by such stripping because of insufficient partial pressure of carbon dioxide or because the partial pressure of the carbon dioxide in the synthesis gas from the Primary Reformer is too high then additional carbon dioxide maybe recovered by one of two ways. A small amount of natural gas maybe used to strip additional carbon dioxide after the synthesis gas has stripped out as much as practical and this natural gas/carbon dioxide mix is then added to either the methanol synthesis gas feed or to the methanol synthesis loop.

Alternatively, carbon dioxide maybe added to the natural gas fed to the Primary Reformer by means of stripping it from the physical solvent solution. This having the effect of raising the carbon dioxide level in the effluent from the Primary Reformer and thereby raising its partial pressure and allowing the stoichiometry for methanol production to be balanced as above.

Claims

CLAIM 1

A process for the integrated production of ammonia and methanol from a gas produced by steam reforming a hydrocarbon characterised by a) cooling at least a part of said gas by heating a secondary reformer feed b) synthesising methanol from the stream from step a) in a methanol synthesis unit c) purging inert gas from the methanol synthesis unit in step b) d) heating the purge (as per step a)) and feeding the heated purge gas to a secondary reformer together with an oxygen-and-nitrogen-containing gas e) passing the effluent from the secondary reformer through a carbon monoxide shift reactor f) separating carbon dioxide from the shift reactor effluent from step e).
g) methanating oxides of carbon in the effluent gas from step f h) producing ammonia from dried effluent from step g 2) A process as claimed in claim 1 wherein the effluent from step f is divided into two streams and hydrogen is separated from one such stream and added to the other such stream.
3) A process as claimed in any precceding claim wherein carbon dioxide, recovered from the ammonia synthesis gas preparation section, is stripped by the cooled effluent from the primary reformer.
4) Ammonia and methanol when made by the process of this invention.