Water gas shift process for purifying hydrogen for use with fuel cells

• US 6,375,924 B1
• Filed: 06/30/2000
• Issued: 04/23/2002
• Est. Priority Date: 12/11/1998
• Status: Expired due to Fees

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Towler, Gavin P., Vanden Bussche, Kurt M.
• Primary Examiner(s): Griffin, Steven P.
• Assistant Examiner(s): MEDINA SANABRIA, MARIBEL
• Application Number:
  US09/608,118
• Time in Patent Office: 662 Days
• Field of Search: 423/652, 423/655, 423/656, 252/373, 481/99.FM
• US Class Current: 423/656
• CPC Class Codes: B01J 23/78 with alkali- or alkaline earth metals
• CPC Class Codes: B01J 23/80 with zinc, cadmium or mercury
• CPC Class Codes: B01J 23/862 Iron and chromium
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/0244 the reforming step being an autothermal reforming step, e.g. secondary reforming processes
• CPC Class Codes: C01B 2203/0288 containing two CO-shift steps
• CPC Class Codes: C01B 2203/066 with fuel cells
• CPC Class Codes: C01B 2203/0822 the fuel containing hydrogen
• CPC Class Codes: C01B 2203/0827 at least part of the fuel being a recycle stream
• CPC Class Codes: C01B 2203/0877 by direct injection of fluid
• CPC Class Codes: C01B 2203/1017 characterised by the form of the structure
• CPC Class Codes: C01B 2203/1052 Nickel or cobalt catalysts
• CPC Class Codes: C01B 2203/1058 Nickel catalysts
• CPC Class Codes: C01B 2203/1064 Platinum group metal catalysts
• CPC Class Codes: C01B 2203/107 Platinum catalysts
• CPC Class Codes: C01B 3/16 using catalysts
• CPC Class Codes: C01B 3/384 the catalyst being continuously externally heated
• CPC Class Codes: C01B 3/48 followed by reaction of water vapour with carbon monoxide
• CPC Class Codes: Y02P 20/10 Process efficiency
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

A process and apparatus are disclosed for the operation of a compact water gas shift reactor for use in conjunction with fuel cell to generate electric power from a feedstream comprising a hydrocarbon or an alcohol. The fuel cell comprises a proton exchange membrane which produces electric power from a hydrogen product stream which comprises essentially no carbon monoxide. The hydrogen product stream may be produced from the feedstream in a steam reforming of autothermal reforming zone. The compact water gas shift reactor comprises a vertically aligned vessel having a top end, a bottom end opposite, which defines an interior space. The interior space contains a first water spray zone for contacting a reforming effluent stream comprising hydrogen with a first water stream. A first dispersion zone is disposed below the first water spray zone and above a high temperature shift zone. The high temperature shift zone contains a high temperature shift catalyst to produce a high temperature shift effluent stream. A second water spray zone is disposed below the high temperature shift zone and above a second dispersion zone. A low temperature shift zone is disposed below the second dispersion zone. The low temperature shift zone contains a low temperature shift catalyst to produce a water-saturated hydrogen product stream which comprises less than 50 ppm-mol carbon monoxide. The water dispersion zones simplify the overall shift reaction zone and provide protection for the shift catalysts from temperature shock.

Claims

1. A compact water gas shift process for removing carbon monoxide from a hydrogen stream in the production of electric power from a fuel cell, said water gas shift process comprising:

a) passing a feedstream comprising hydrogen and carbon monoxide to a first water spray zone and therein directly contacting the feedstream with a first water spray to cool a reactor effluent stream to effective high temperature shift conditions and provide a high temperature shift reactor feed admixture;

b) passing the high temperature shift reactor feed admixture through a first dispersion zone to uniformly disperse the first water spray in the high temperature shift reactor feed admixture to provide a dispersed high temperature shift reactor feedstream;

c) passing the dispersed high temperature shift reactor feedstream to a high temperature shift reaction zone, containing a high temperature shift catalyst, to provide a high temperature shift effluent stream;

d) passiffg the high temperature'"'"'shift effluent stream to a second water spray zone wherein the high temperature shift effluent stream is directly contacted with a second water spray stream to cool the high temperature shift effluent to effective low temperature shift conditions and to provide a low temperature shift feed admixture;

e) passing the low temperature shift feed admixture through a second dispersion zone to uniformly disperse the second water spray in the low temperature shift feed admixture and provide a dispersed low temperature shift admixture; and

f) passing the dispersed low temperature shift admixture to a low temperature shift reaction zone, containing a low temperature shift catalyst, wherein the low temperature shift admixture is reacted to produce a low temperature shift effluent stream at a low temperature shift effluent temperature at saturation conditions and having a carbon monoxide concentration less than about 3000 ppm-mol.

2. The process of claim 1 wherein the effective high temperature shift conditions include a high temperature shift temperature of between about 400°

and about 450°

C.

3. The process of claim 1 wherein the high temperature shift catalyst is selected from the group consisting of iron oxide, chromic oxide, and mixtures thereof.

4. The process of claim 1 wherein the effective low temperature shift conditions include a low temperature shift reaction temperature of between about 180°

and about 220°

C.

5. The process of claim 1 wherein the low temperature shift catalyst comprises cupric oxide and zinc oxide.

6. The process of claim 1 wherein a temperature difference between an inlet and an outlet of the low temperature shift reaction zone ranges from about 40°

to about 70°

C.

7. The process of claim 1 further comprising passing the low temperature shift effluent stream to a shift effluent cooler and therein cross exchanging the low temperature shift effluent stream with a third water stream, comprising deionized water, to provide a cooled low temperature shift effluent stream and a partially vaporized preheated water stream and combining the partially vaporized preheated water stream with a desulfurized fuel stream to provide a feedstream to a hydrogen generation zone.

8. The process of claim 7 wherein the hydrogen generation zone comprises a reaction selected from the group consisting of steam reforming, autothermal reforming, and combinations thereof.