# US 2019/0240621 A1 · Energy efficient removal of co2 from air by integrating with h2 generation

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- Number: US 2019/0240621 A1
- Document ID: US20190240621A1
- Status: Published application
- Kind: A1
- Application number: 15/941,442
- Filed: 2018-03-30
- Published: 2019-08-08
- Earliest claimed: 2018-02-08
- Assignees: Palo Alto Research Center Incorporated
- Applicants: Palo Alto Research Center Incorporated
- Inventors: FRANCISCO E. TORRES; EUGENE SHIN MING BEH; JESSICA LOUIS BAKER RIVEST
- Web page: https://patentgrep.com/patent/US20190240621A1

## CPC

- B01D 53/965: {including an electrochemical process step}
- B01D 53/1425: {Regeneration of liquid absorbents}
- B01D 53/1475: {Removing carbon dioxide}
- B01D 53/1493: {Selection of liquid materials for use as absorbents}
- B01D 53/62: Carbon oxides
- B01D 53/78: with gas-liquid contact
- C01B 3/00: Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen (production of water-gas or synthesis gas from solid carbonaceous material C10J)
- C25B 1/04: by electrolysis of water
- C25B 9/05: Pressure cells
- C25B 9/23: comprising ion-exchange membranes in or on which electrode material is embedded
- C25B 9/73: of the filter-press type
- B01D 2251/304: of sodium
- B01D 2251/306: of potassium
- B01D 2251/604: Hydroxides
- B01D 2251/606: Carbonates
- B01D 2256/16: Hydrogen
- B01D 2257/504: Carbon dioxide
- B01D 2258/0283: Flue gases
- B01D 2258/06: Polluted air
- Y02C 20/40: of CO2
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- Y02P 20/151: Reduction of greenhouse gas [GHG] emissions, e.g. CO2
- Y02P 20/50: Improvements relating to the production of bulk chemicals
- Y02P 30/00: Technologies relating to oil refining and petrochemical industry
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B)
- Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A system has an alkaline capture stream as an input, an alkaline depleted stream as an output, a carbon dioxide removal unit operation having a return stream as an output, and a series of electrolyzers, each electrolyzer to receive a CO2-rich input stream and produce an acidified output stream that is more acidic than the CO2-rich input stream, and to receive a return stream and produce a basified output stream that is more alkaline than the input return stream. A method of removing carbon dioxide from an atmosphere and generating hydrogen includes capturing carbon dioxide from an atmosphere in an alkaline capture solution, sending the alkaline solution as a CO2-rich input solution to a series of electrolyzers in a CO2-rich path, removing carbon dioxide from the acidified CO2-rich solution at a removal unit to produce a CO2-poor solution, sending the CO2-poor solution to the series of electrolyzers in a return path, and returning the return solution to the alkaline capture stream. An electrolyzer is also discussed.

## Claims

### Claim 1

A system, comprising:
an alkaline capture stream as an input;
an alkaline depleted stream as an output;
a carbon dioxide removal unit operation having a depleted stream as an output; and
a series of electrolyzers, each electrolyzer to receive a CO2-rich input stream and produce a CO2-rich output stream that is more acidic than the CO2-rich input stream, and to receive a CO2-poor input stream and produce a CO2-poor output stream that is more alkaline than the CO2-poor input stream, the electrolyzers also to produce hydrogen and oxygen, wherein
at least one initial electrolyzer receives the alkaline capture stream as its CO2-rich input stream,
at least one final electrolyzer sends its acidified CO2-rich output stream to the carbon dioxide removal unit operation,
at least one return electrolyzer receives the depleted stream from the carbon dioxide removal unit operation as its CO2-poor input stream, and
the alkaline depleted stream output from the system comprises basified CO2-poor output streams from one or more electrolyzers.

### Claim 2 (depends on 1)

The system of claim 1, wherein the initial electrolyzer, the final electrolyzer, and the return electrolyzer are the same electrolyzer.

### Claim 3 (depends on 1)

The system of claim 1, wherein the initial electrolyzer and the final electrolyzer are different electrolyzers.

### Claim 4 (depends on 1)

The system of claim 1, further comprising at least one pump to provide pressure to the system, the pump comprising at least one of a system pump or an individual pump for each electrolyzer.

### Claim 5 (depends on 4)

The system of claim 4, wherein the at least one pump maintains a pressure in each electrolyzer greater than a desired partial pressure of carbon dioxide in each cell.

### Claim 6 (depends on 1)

The system of claim 1, wherein the electrolyzers contains at least one of either a cation exchange membrane or an anionic exchange membrane.

### Claim 7 (depends on 1)

The system of claim 1, wherein the dissolved carbon in the alkaline capture stream is captured from one of ambient atmosphere, a mixture of gases, or an exhaust from a combustion process.

### Claim 8 (depends on 1)

The system of claim 1, further comprising at least one regenerator connected to at least one of the carbon dioxide removal unit operation input stream and the depleted stream.

### Claim 9 (depends on 1)

The system of claim 1, further comprising an oxygen-removal conduit connected to the electrolyzers in the initial flow.

### Claim 10 (depends on 1)

The system of claim 1, further comprising a carbon capture tower through which the alkaline capture stream contacts open air as the atmosphere.

### Claim 11 (depends on 1)

The system of claim 1, further comprising an electricity source for the electrolyzers comprising a renewable source of electricity.

### Claim 12

A method of removing carbon dioxide from an atmosphere and generating hydrogen, comprising:
capturing carbon dioxide from an atmosphere in an alkaline capture solution;
sending the alkaline capture solution to a series of electrolyzers in a CO2-rich path, wherein each electrolyzer cell raises the acidity of the input CO2-rich solution;
removing carbon dioxide from the acidified CO2-rich solution at a removal unit operation to produce a CO2-poor solution;
sending the CO2-poor solution to the series of electrolyzers in a return path, wherein each electrolyzer raises the alkalinity of the return CO2-poor solution; and
returning the basified CO2-poor solution to the carbon dioxide capture unit operation.

### Claim 13 (depends on 12)

The method of claim 12, wherein the base solution comprises at least one of the group consisting of: KOH; KHCO3; K2CO3; NaOH; Na2CO3; and NaHCO3.

### Claim 14 (depends on 12)

The method of claim 12, further comprising capturing oxygen from the electrolyzers in the CO2-rich path combined with at least one of minimizing or reabsorbing entrained CO2.

### Claim 15 (depends on 12)

The method of claim 12, further comprising mixing outputs of each electrolyzer in mixing vessels.

### Claim 16 (depends on 12)

The method of claim 12, wherein a pH of the system is in a range between and including pHs of 4 and 14.

### Claim 17 (depends on 12)

The method of claim 12, wherein the electrolyzers use catalysts comprising earth-abundant materials.

### Claim 18 (depends on 12)

The method of claim 12, further comprising controlling the pressures in the electrolyzers to be higher than a partial pressure of carbon dioxide in the CO2-rich output solution.

### Claim 19 (depends on 12)

The method of claim 12, further comprising lowering pressure in the carbon dioxide removal unit operation to drive carbon dioxide out of the CO2-rich solution.

### Claim 20 (depends on 12)

The method of claim 12, further comprising adding a salt that is not redox active to the alkaline capture stream.

### Claim 21

An electrolyzer, comprising:
a first chamber to receive a first input stream, the first chamber to produce a first output stream that is more acidic than the first input stream;
a first electrode in the first chamber;
a second chamber to receive a second input stream, the second chamber to produce a second output stream that is more alkaline than the second input stream;
a second electrode in the second chamber;
a voltage source connected to the electrodes; and
an ion-selective membrane separating the first chamber from the second chamber,
wherein the electrolyzer is configured to control flows of the first input stream and the second input stream to reduce a local pH drop across the ion-selective membrane.

### Claim 22 (depends on 21)

The electrolyzer of claim 21, further comprising at least one spacer positioned in at least one of the first and second chambers.