Systems and methods for water gas shift with reduced steam consumption

Patent metadata

Field	Value
Publication number	US-2018339902-A1
Application number	US-201816003716-A
Country	US
Kind code	A1
Filing date	Jun 8, 2018
Priority date	Oct 24, 2014
Publication date	Nov 29, 2018
Grant date	—

Abstract

A water gas shift reaction is carried out on a feed gas comprising carbon monoxide to produce carbon dioxide and hydrogen gas. The feed gas is split into multiple input streams flowed into respective reactors coupled in series. Steam is supplied to the input stream fed to the first reactor. The shift reaction is carried out in each reactor, with an overall reduced consumption of steam relative to the amount of gas shifted. The water gas shift reaction may be performed in conjunction with removing acid gas compounds from a process gas such as, for example, syngas or natural gas, by flowing a feed gas into a desulfurization unit to remove a substantial fraction of sulfur compounds from the feed gas and flowing the resulting desulfurized gas into a CO 2 removal unit to remove a substantial fraction of CO 2 from the desulfurized gas.

First claim

What is claimed is:

1 . A method for removing acid gases from a gas stream, the method comprising:
flowing a feed gas into a desulfurization unit to remove a substantial fraction of a sulfur compound from the feed gas, wherein the desulfurization unit produces a desulfurized feed gas; flowing the desulfurized feed gas into a CO 2 removal unit to remove a substantial fraction of CO 2 from the desulfurized feed gas; and before or after desulfurizing the feed gas, subjecting the feed gas to a water-gas shift reaction by: splitting a flow of feed gas comprising carbon monoxide (CO) into a plurality of feed gas streams comprising at least a first feed gas stream, a second feed gas stream, and a third feed gas stream; combining the first feed gas stream with a steam stream to produce a first input gas stream; flowing the first input gas stream into a first shift reactor containing a first shift catalyst; reacting the CO with the steam in the presence of the first shift catalyst to produce a first product gas stream comprising carbon dioxide (CO 2 ) and hydrogen (H 2 ); combining the first product gas stream with the second feed gas stream to produce a second input gas stream heated by the first product gas stream; flowing the second input gas stream into a second shift reactor containing a second shift catalyst; reacting the CO of the second input gas stream with the steam in the presence of the second shift catalyst to produce a second product gas stream comprising CO 2 and H 2 ; combining the second product gas stream with the third feed gas stream to produce a third input gas stream heated by the second product gas stream; flowing the third input gas stream into a third shift reactor containing a third shift catalyst; and reacting the CO of the third input gas stream with the steam in the presence of the third shift catalyst to produce a third product gas stream comprising CO 2 and H 2 .

2 . The method of claim 1 , comprising a step selected from the group consisting of:
before combining the first product gas stream with the second feed gas stream, adding water as a spray to the first product gas stream to vaporize the water into steam, wherein the first product gas stream is cooled before being combined with the second feed gas stream; before combining the second product gas stream with the third feed gas stream, adding water as a spray to the second product gas stream to vaporize the water into steam, wherein the second product gas stream is cooled before being combined with the third feed gas stream; and both of the foregoing.

3 . The method of claim 1 , comprising adding water as a spray into the first feed gas stream or the first input gas stream.

4 . The method of claim 1 , wherein flowing the feed gas into the desulfurization unit is done in a temperature range selected from the group consisting of: about 400° F. or greater; and about 400° F. to about 1200° F.

5 . The method of claim 1 , wherein flowing the desulfurized gas into the CO 2 removal unit is done in range selected from the group consisting of: about −80° F. to about 30° F.; about 30° F. to about 130° F.; and about 200° F. to about 900° F.

6 . The method of claim 1 , wherein flowing the feed gas into the desulfurization unit comprises flowing the feed gas into contact with a sorbent.

7 . The method of claim 6 , wherein sorbent is selected from the group consisting of: a metal oxide, zinc oxide, copper oxide, iron oxide, vanadium oxide, manganese oxide, stannous oxide, nickel oxide, a metal titanate, zinc titanate, a metal ferrite, zinc ferrite, copper ferrite, a sorbent comprising an alumina (Al 2 O 3 ) support, a sorbent comprising a silicon dioxide (SiO 2 ) support, a sorbent comprising a titanium dioxide (TiO 2 ) support, a sorbent comprising a zeolite support, a sorbent having an average particle size in a range from about 35 μm to about 175 μm, and a combination of two or more of the foregoing.

8 . The method of claim 6 , wherein flowing the feed gas into contact with a sorbent comprises flowing the feed gas into contact with a sorbent stream comprising the sorbent and a carrier gas.

9 . The method of claim 8 , wherein flowing the feed gas into contact with the sorbent stream is done in an adsorber unit, and further comprising outputting the desulfurized gas and sulfided sorbent from the adsorber unit.

10 . The method of claim 9 , comprising flowing the sulfided sorbent into a regenerating unit to produce a regenerated sorbent and a sulfur compound, and flowing the regenerated sorbent into the adsorber unit.

11 . The method of claim 1 , wherein flowing the desulfurized gas into the CO 2 removal unit comprises flowing the desulfurized gas into contact with a CO 2 removing agent.

12 . The method of claim 11 , wherein flowing the desulfurized gas into contact with the CO 2 removing agent is done in an absorber or adsorber unit, and further comprising outputting from the absorber or adsorber unit a treated gas comprising the substantially reduced fractions of sulfur and CO 2 .

13 . The method of claim 12 , wherein flowing the desulfurized gas into contact with the CO 2 removing agent produces in the absorber or adsorber unit a CO 2 -rich stream comprising the CO 2 removing agent and CO 2 , and further comprising:
flowing the CO 2 -rich stream from the absorber or adsorber unit to a regenerator unit; removing CO 2 from the CO 2 -rich stream in the regenerator unit to produce a CO 2 -lean fluid stream; and flowing the CO 2 -lean stream into the absorber or adsorber unit.

14 . The method of claim 1 , wherein the feed gas comprises syngas.

15 . The method of claim 1 , wherein the first shift catalyst, the second shift catalyst, and the third shift catalyst are sulfur-tolerant.

16 . The method of claim 1 , wherein the plurality of feed gas streams comprises one or more additional feed gas streams, and further comprising reacting the CO of the one or more additional feed gas streams with steam in one or more additional shift reactors, respectively, downstream from the third shift reactor.

17 . The method of claim 1 , comprising producing a local steam supply by flowing liquid water into thermal contact with a heated gas stream selected from the group consisting of: the first feed gas stream; the second feed gas stream; the third feed gas stream; the first input gas stream; the second input gas stream; the third input gas stream; and a combination of two or more of the foregoing.

18 . The method of claim 17 , wherein combining the first feed gas stream with the steam stream comprises flowing steam from the local steam supply into the first feed gas stream.

19 . The method of claim 1 , comprising heating the first feed gas stream or the first input gas stream by flowing the first feed gas stream or the first input gas stream into thermal contact with a heated gas stream selected from the group consisting of: the first product gas stream; the second product gas stream; the third product gas stream; and a combination of two or more of the foregoing.

20 . The method of claim 1 , wherein the plurality of feed gas streams comprises a bypass gas stream, and further comprising combining the bypass gas stream with the third product gas stream to produce an output gas stream having a desired H 2 /CO ratio.

21 . The method of claim 1 , comprising controlling a steam/dry gas ratio in the first input gas stream by a step selected from the group consisting of: controlling a flow rate o

Assignees

• Res Triangle Inst

Inventors

• Turk Brian S
• Gupta Vijay
• Denton David L
• Gupta Raghubir P
• Paliwal Himanshu

Classifications

• C10L2290/541

  Absorption of impurities during preparation or upgrading of a fuel · CPC title

• C10L2290/12

  Regeneration of a solvent, catalyst, adsorbent or any other component used to treat or prepare a fuel · CPC title

• B01D53/62

  Carbon oxides · CPC title

• B01J2219/00594

  Gas-phase processes · CPC title

• C01B2203/042

  Purification by adsorption on solids · CPC title