WO2000068146A1

WO2000068146A1 - On site carbon monoxide generator

Info

Publication number: WO2000068146A1
Application number: PCT/IB2000/000545
Authority: WO
Inventors: Jean-Renaud Brugerolle; Norbert Rieth
Original assignee: L'air Liquide Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 1999-05-06
Filing date: 2000-04-28
Publication date: 2000-11-16

Abstract

In a process for the production of a carbon monoxide enriched gas (5) by reverse shift of gases rich in carbon dioxide and hydrogen, at least the gas rich in hydrogen is supplied to the unit from a remote source (1) by pipe-line (2) or tanker truck and carbon monoxide enriched gas is produced by purifying a gaseous mixture produced by the production unit.

Description

ON SITE CARBON MONOXIDE GENERATOR.

Chemical and petrochemical industries have increasing pure carbon monoxide (CO) requirements. For large quantities, the answer is a local production through a methane steam reformer followed by purification units such as cryogenic distillation units or PSAs or polymeric membranes. A system of this type is described in US-A-4265868.

For smaller quantities, this arrangement is not competitive.

On the other hand, large carbon monoxide plants can be operated in other locations, and the carbon monoxide transported by pipe-line. Such pipe-lines are feasible, but for obvious safety reasons not very well accepted.

According to an object of the invention, there is provided a process for the production of a carbon monoxide enriched gas in a production unit by reverse shift of carbon dioxide rich gas and hydrogen rich gas wherein at least part of at least the hydrogen rich gas is supplied to the unit from a remote source by pipe- line and/or tanker truck and carbon monoxide enriched gas is produced by purifying a gaseous mixture produced by the production unit.

Optionally :

- the carbon dioxide rich gas is available in the vicinity of the production unit; - the carbon dioxide rich gas is supplied to the unit from a remote source;

- the carbon dioxide rich gas is supplied to the unit by a single pipe-line which also serves to transport the hydrogen rich gas;

- oxygen is used in the converter of the production unit;

- oxygen is supplied to the production unit via a pipe-line. The carbon monoxide enriched gas preferably contains between 95 mol.% and 100 mol.% carbon monoxide. The carbon dioxide rich gas preferably contains between 80 and 100 mol.% carbon dioxide, the balance being preferably composed of inert gases, such as argon or nitrogen. The carbon dioxide rich gas is preferably devoid of catalyst poisons. The hydrogen rich gas preferably contains between 80 and 100 mol.% hydrogen, the balance being preferably composed of inert gases, such as argon or nitrogen. The hydrogen rich gas is preferably devoid of catalyst poisons.

According to a further object of the invention, there is provided an installation for the production of carbon monoxide enriched gas in a production unit by reverse shift of carbon dioxide rich gas and hydrogen rich gas comprising means for transporting at least part of at least the hydrogen rich gas to the unit from a remote source and means for purifying a gaseous mixture from the production unit to produce carbon monoxide enriched gas. Optionally : - the means for transporting at least the hydrogen rich gas is a pipe-line and/or a tanker truck;

- the carbon dioxide rich gas is produced in the vicinity of the production unit;

- there are means for transporting the carbon dioxide rich gas to the unit from a remote source;

- there is a single pipe-line for transporting the carbon dioxide rich gas and the hydrogen rich gas to the production unit.

The idea is to produce hydrogen rich gas and possibly by-product carbon dioxide rich gas in a remote plant and to transport at least one of those two products through one or two pipe-lines to the user's site. There, a simpler carbon monoxide generator fed with hydrogen and carbon dioxide will produce the required carbon monoxide enriched gas (Figure 1).

SUBSTITUTE SHEET (RULE ?6) Carbon monoxide can be obtained by C02 " reverse shift " in presence of hydrogen with the reaction

C0₂+H₂ → CO+ H₂0

This reaction is favored by very high temperatures. The following table shows conversion efficiency depending on temperature (isothermal or adiabatic). The reaction is slightly endothermic. In figure 1 , a plant producing hydrogen and carbon dioxide I sends the two gases in separate respective pipe-lines 2,3 to an on-site carbon monoxide generator 4 which produces carbon monoxide 5. The hydrogen may be derived from any suitable source, such as a steam reformer followed by a shift reaction. Of course, the hydrogen and carbon dioxide may be derived from independent sources.

Pressure : 40 bar abs for all cases

SUBSTITUTE SHEET (RULE 2fS) For conversion factors above 50%, temperatures as high as 1000°C are necessary in adiabatic mode (Figure 2).The hydrogen and carbon dioxide are mixed at a pressure between 15 and 40 bar and heated to over 900°C in 9.The reverse shift takes place in converter 7 and the gases produced are cooled in 11. As the converted gas contains a large amount of CO, metals are to be avoided in heat exchangers 9,11 because of metal dusting around 600°C.

As the number of moles is equal before and after reverse shift, heat exchange is possible in a parallel diagram exchange.

This temperature exchange can be carried out in a ceramic heat exchanger. Ceramics are not sensitive to metal dusting but do not allow large pressure differences between circuits due to low mechanical resistance. In this case the fluids are at almost the same pressure. Such ceramic exchangers can be placed in a pressure vessel 13 pressurized at the process working pressure (figure 3). Another possible arrangement is to use " pebble heaters " 15,17. Those are radial bed regenerators. Used by pairs in switching mode, they allow both very high temperatures (up to 1500°C) and high efficiency in heat recovery at low pressure drop. Since the pebbles, grids and insulation being made of ceramics, alumina and other refractory materials, they are not sensitive to metal dusting (Figure 4). Because the cooling time in the pebble heater is very short, the formation of gases other than carbon monoxide, steam, carbon dioxide and hydrogen is inhibited.

In this case the twin pebble heaters 15,17 and the converter 7 can be put in the same high pressure vessel 18 (Figure 5). Because the reaction is endothermic and the heat recovery system not perfect, some heat 19 has to be brought into the hot part of the system. As impurities must not be introduced in the system, energy can be added either by pure oxygen injection 2 1 , or with a electric heater 23 (Figure 6).

^"SUBSTrTUTE SHEET (RULE 26) Typical compositions of the gas mixture would be 40-70 mol.% hydrogen, 20-30 mol.% carbon monoxide, possibly 1-7 mol.% methane, 5 -20 mol.% carbon monoxide and steam, depending on the types of catalyst used and the composition of the feed gases. At least 98% of the gas after reverse shift is composed of CO, H20, C02 and H2. The last three gases are fast passing gases in polymeric hydrogen membranes. Purification is therefore simple as shown in figure 7 in which carbon monoxide, hydrogen, carbon dioxide and steam from the converter 7 at 20 bars are sent to polymeric membrane 27 to produce carbon monoxide and a mixture of the other three gases at 3 bars. These three gases are compressed in 25 and recycled to the converter 7 following removal of the water. Improvement to figure 7 is made by compressing the gas upstream of the membrane in compressor 31 to a pressure of 60 bars (Figure 8). The permeate gases are then at 21 bars and compressor 25 can be omitted. Higher carbon monoxide purity will be obtained by using two membranes

35,37 in series. Impure CO from membrane 35 is sent to membrane 37.The permeate gases from membrane 35 are recycled to the converter at 21 bars and the permeate gases from membrane 37 are recycled to the inlet of the compressor 3 1 (Figure 9). By coupling the reverse shift converter 27 and the purification using membrane 35, we get the global arrangement as described in figure 10 Figure 11 shows three ways of feeding the CO generator 4.

C02 is generally produced in a hydrogen plant 1 as a by-product, and then can be piped to the CO generator along with the hydrogen. This has the drawback of requiring two pipe-lines 2,3 (figure 11 A).

If no other customer is to be provided with pure hydrogen along the pipeline, the C02 might be piped within the hydrogen pipe itself (figure 11 B).

SUBSTITUTE SHEET (RUI IT. 26) Another answer is to find some by-product C02 locally as exists in many chemical or petrochemical sites (figure 11C).

The preceding invention will allow supply of carbon monoxide to certain customers without having the inconvenience of transporting CO by pipe-line or building a complicated CO reforming plant on-site.

SUBSTITUTE SHEET (RULE 2β)

Claims

1. Process for the production of a carbon monoxide enriched gas (5) in a production unit (4) by reverse shift of gases rich in carbon dioxide and hydrogen wherein at least part of at least the gas rich in hydrogen is supplied to the unit from a remote source (1) by pipe-line (2) or tanker truck and carbon monoxide enriched gas is produced by purifying a gaseous mixture produced by the production unit.

2. The process of Claim 1 wherein the carbon dioxide rich gas is available within the production unit (4).

3. The process of Claim 1or 2 wherein the carbon dioxide rich gas is supplied to the unit from a remote source (1).

4. The process of Claim 3 wherein the carbon dioxide rich gas is supplied to the unit by a single pipe-line (2) which also serves to transport the hydrogen rich gas.

5. The process of any preceding claim comprising adding an oxygen enriched fluid to the production unit.

6. The process of Claim 5 wherein oxygen enriched fluid is supplied to the production unit via a pipe-line.

7. The process of any preceding claim comprising sending a gaseous mixture of which at least 98mol.% is comprised by carbon monoxide, carbon dioxide, steam and hydrogen from the production unit to a membrane purifier and withdrawing carbon monoxide enriched gas from the membrane purifier.

8. Installation for the production of carbon monoxide enriched gas (5) in a production unit (4) by reverse shift of carbon dioxide and hydrogen rich gases comprising means (2) for transporting at least part of at least the hydrogen rich gas to the unit from a remote source (1) and means (27,35,37) for purifying a gaseous mixture from the production unit (7) to produce carbon monoxide enriched gas.

9. The installation of Claim 8 wherein the means for transporting is a pipeline (2).

10. The installation of Claim 8 wherein the carbon dioxide rich gas is produced in the vicinity of the production unit.

11. The installation of Claim 8 comprising means (2,3) for transporting the carbon dioxide rich gas to the unit from a remote source (1).

12. The installation of Claim 11 comprising a single pipe-line (2) for transporting the carbon dioxide rich gas and the hydrogen rich gas to the production unit (4).

SUBSnπJTE SHEET (RULE 2 Mi