GB2233329A

GB2233329A - Methanol production

Info

Publication number: GB2233329A
Application number: GB9013002A
Authority: GB
Inventors: Anthony Horton; Frank Clifford Brown
Original assignee: Enserch International Investments Ltd
Current assignee: Enserch International Investments Ltd
Priority date: 1989-06-22
Filing date: 1990-06-11
Publication date: 1991-01-09
Anticipated expiration: 2010-06-11
Also published as: GB2233329B; GB9013002D0; GB8914387D0

Abstract

A process for the production of methanol wherein synthesis gas is produced by reaction between natural gas and/or wherein the synthesis gas is compressed into a conventional methanol loop in which nitrogen is allowed to build up to over 50% and from which a large purge system is taken and passed into a second reaction system containing a mixture of methanol, synthesis catalyst and methanol adsorbent wherein further methanol is produced: this second system operating cyclically - its methanol being recovered by either sweeping the methanol off with desulphurised natural gas and/or depressurising, causing the adsorbed methanol to be dissolved and recovered by condensing the methanol produced in said cyclic system.

Description

METHANOL PRODUCTION This invention relates to a process for making methanol from a synthesis gas containing a very large quantity of nitrogen which would prevent economic synthesis using a conventional methanol synthesis loop alone.

The synthesis gas is made using air as the oxidant in any one of three schemes. These are: (a) Partial oxidation of natural gas with or without steam, by air at between 800-1500"C in a refractory lined vessel operating in the pressure range 10-150bar. The resulting gas is very high in nitrogen and is carbon rich for methanol synthesis.

(b) Catalytic Partial Oxidation This process combusts a natural gas/steam mixture with air, in the top of a catalyst filled vessel.

The temperature in the combustion zone is 1000 1500 C and some reforming takes place autothermally over a catalyst. The reformed synthesis gas leaves the reactor at 800-1400t and at a pressure of 10-150 bar. The gas is high in nitrogen and also carbon rich but not so high as case (a).

(c) Combined (Combi) Reformer In this process there is a catalytic partial oxidation process but the hot product gases at 800-1100 C are used to heat and partially reform the feed gases (natural gas and steam) in a tubular reformer. Since the heat input is controlled by the heat available in the hot gas the extent of the first stage reforming is limited and over half of the natural gas is reformed in the second stage of the process in the catalytic autothermal reactor. In one manifestation of this process the two stages are in separate vessels. In another the oxidant is added in a section of the tubular reactor, thus enabling one vessel to be used.

The combi reformer yields a synthesis gas with the lowest quantity of nitrogen and with an almost stoichiometric synthesis gas for methanol production. Consequently, it is the preferred method for producing the synthesis gas for this invention.

The synthesis gas produced by one the above means is compressed into a conventional methanol loop operating at 40-200 bar, preferably 50-100 bar. In this loop the nitrogen is allowed to build up to over 50% and 50-80t of the synthesis gas is converted into methanol.

From the loop a very large purge gas stream is sent to a SYNBAD unit.

In a SYNBAD unit is a mixture of methanol synthesis catalyst and methanol adsorbent. As the methanol is synthesised it is adsorbed, thus removing it from the reacting gases, thereby promoting more methanol to be formed.

Using the loop and SYNBAD units it is possible to convert over 90% of the carbon oxides to methanol provided sufficient hydrogen is present.

The SYNBAD unit is operated cyclically in large cooled vessels working from 10-200 bar. Each vessel is zone in the temperature range 180-400"C. When the adsorbent is saturated with methanol it is taken offline and may be depressurised to release adsorbed methanol; and/or the methanol can be discharged by sweeping the vessel with desulphurised natural gas.

The methanol from the SYNBAD system is condensed and mixed with the product from the conventional loop.

The crude methanol can be distilled quite conventionally or, by the following improvement to the flowsheet, can be de-watered using another adsorbent which will adsorb the water in a cyclic manner. When the adsorbent is fully loaded, it is regenerated by hot de-sulphurised natural gas, thus returning the produced water to the reforming section. The methanol so de-watered may be sold as fuel.

Fig.I is a diagram showing an embodiment of the invention.

Claims

1) A process for the production of methanol wherein synthesis gas is produced by reaction between natural gas and/or wherein the synthesis gas is compressed into a conventional methanol loop in which nitrogen is allowed to build up to over 50% and from which a large purge system is taken and passed into a second reaction system containing a mixture of methanol, synthesis catalyst and methanol adsorbent wherein further methanol is produced: this second system operating cyclically - its methanol being recovered by either sweeping the methanol off with desulphurised natural gas and/or depressurising, causing the adsorbed methanol to be dissolved and recovered by condensing the methanol produced in said cyclic system.

2) A claim as claimed in Claim 1) substantially as herein described.

3) Methanol when produced by the process of this invention.