Low-cost electrochemical cell stack for carbon dioxide gas separation equipment

Abstract

In an electrochemical-based carbon dioxide gas separation system, a stack of membrane electrode assemblies (MEAs) is provided, each MEAs having a membrane separator between the anode and the cathode. The cathode contains a charge storage compound that reacts to produce hydroxide, and the anode contains a charge storage compound that reacts to consume hydroxide or produce protons. A double-sided flow field plate is placed between adjacent MEAs in the stack of electrochemical cells. The first and last MEAs in the stack of MEAs are connected to end flow field plates connected to end plates. Each of the cathode and anode has an electrical contact connected to a current supply.

Description

Technical Field

[0001] The present invention relates to the electrochemical separation of carbon dioxide gas from a gas mixture, and particularly to a low-cost electrochemical cell for a carbon dioxide gas separation device.

Background Art

[0002] U.S. Patent Application Publication No. 2021 / 0036350 (Yushan Yan et al.) describes an electrochemical pump (ECP) for separating carbon dioxide from a carbon dioxide-containing gas such as air. The ECP includes a cell having a membrane and two electrodes that can function as an anode or a cathode. Each electrode includes an energy storage compound that reacts to form a hydroxide when functioning as a cathode and reacts to consume the hydroxide or generate protons when functioning as an anode. The membrane is adjacent to the two electrodes and separates them. A gas containing carbon dioxide contacts the electrode functioning as a cathode, and carbon dioxide reacts with hydroxide ions to form bicarbonate ions, carbonate ions, or bicarbonate ions and carbonate ions. The bicarbonate ions, carbonate ions, or bicarbonate ions and carbonate ions are transferred through the membrane to the electrode functioning as an anode, and the bicarbonate ions, carbonate ions, or bicarbonate ions and carbonate ions react at the electrode functioning as an anode to produce carbon dioxide and water. The ECP has means for reversing the flow of current and simultaneously switching the electrode with which the carbon dioxide-containing gas contacts, whereby each electrode can function alternately as an anode and a cathode.

[0003] The electrochemical cell (ECP) described in U.S. Patent Application Publication 2021 / 0036350 allows cells to be electrically connected in series by a conductive bipolar plate. Thus, the ECP has a flow field in which one or more flow channels and conductive material are alternately arranged to electrically connect to anodes, cathodes, or anodes and cathodes to a bipolar plate. One terminal is electrically connected to the anode, and the other terminal is electrically connected to the cathode of an adjacent cell. Electrochemical cells can be stacked to increase process capacity with minimal footprint.

[0004] Referring to Figure 1, a prior art electrochemical stack 10 described in U.S. Patent Application Publication No. 2021 / 0036350 is shown. The main components of the electrochemical stack 10 are a series of membrane electrode assemblies (MEAs) 24, each of which is a membrane electrode assembly containing a membrane separator 20 (not limited to a solid polymer electrolyte or an ion exchange membrane) positioned between two electrodes, a cathode 18 and an anode 22. The series of membrane electrode assemblies (MEAs) 24 are flanked at both ends by end flow field plates 16. Each end flow field plate 16 is adjacent to the inside of a current collector 14, and the current connector 14 is adjacent to the inside of an end plate 12. Thus, at one end of the stack (the left end in the figure), the end flow field plate 16 is positioned adjacent to the cathode 18 of the leftmost MEA 24, and at the other end of the stack (the right end), the rightmost anode 22 is adjacent to the end flow field plate 16. The MEAs 24 can be isolated by a conductive bipolar plate 26 having a flow channel or flow path. Thus, the MEAs 24 are electrically connected in series with the bipolar plate 26. An inlet tube connector 28 and an outlet tube connector 29 can be provided for the airflow through the stack.

[0005] Aside from the inlet and outlet tube connectors, all other components of the stack are made of processed structural materials, typically metallic or graphite-based materials. These materials are used because they conduct electrons well and possess mechanical properties suitable for cell and stack assemblies. During the assembly process, the MEAs24 is compressed between two end plates 12, usually secured by screws or other types of connectors or fasteners. The fasteners require a material strength of at least several MPa (1-10) to withstand the compressive stress, and materials with higher strength (20-100 MPa) offer superior performance. While metallic and graphite-based materials remain stable and do not deform significantly under such stresses, they are expensive to manufacture, whether small or large-scale. [Overview of the Initiative]

[0006] The present invention aims to provide a low-cost electrochemical cell stack for carbon dioxide gas separation, and the details are described below.

[0007] According to a non-limiting embodiment of the present invention, an electrochemical-based carbon dioxide gas separation system is provided, which comprises a stack of membrane electrode assemblies (MEAs). Each MEA comprises a membrane separator between a cathode and an anode, the cathode comprising a charge storage compound that carries out a reaction producing hydroxide, and the anode comprising a charge storage compound that carries out a reaction that consumes hydroxide or produces protons. Double-sided flow field plates are positioned between adjacent MEAs in the stack of MEAs, the first and last MEAs in the stack of MEAs are connected to end flow field plates connected to end plates, and the respective cathode and anode have electrical contacts connected to a current supply.

[0008] According to non-limiting embodiments of the present invention, the end plate, end flow field plate, and double-sided flow field plate are formed from a polymer. [Brief explanation of the drawing]

[0009] The present invention can be more fully understood and recognized by referring to the following detailed description and drawings.

[0010] [Figure 1] Figure 1 is a schematic diagram of a prior art electrochemical-based carbon dioxide gas separation system, which includes a stack consisting of four electrochemical cells, where EP is the end plate, CC is the electrochemical collector, ENDFF is the end flow field plate, and BPP is the bipolar plate. [Figure 2] Figure 2 is a schematic diagram of an electrochemical-based carbon dioxide gas separation system according to an indefinite embodiment of the present invention, which includes a low-cost stack consisting of four electrochemical cells (the number of cells is not limited), where the DSFF is a double-sided flow field, and the minus and plus signs represent direct electrical contacts between the electrodes and the power supply. [Figure 3] Figures 3A, 3B, 3C, and 3D are a simplified perspective view, perspective section view, plan view, and cross-sectional view of an electrochemical cell (MEA) for low-cost manufacturing according to a non-limiting embodiment of the present invention, respectively. [Modes for carrying out the invention]

[0011] Referring to Figure 2, an electrochemical-based carbon dioxide gas separation system 30 according to a non-limiting embodiment of the present invention is shown.

[0012] The electrochemical system 30 is a stack comprising a series of membrane electrode assemblies (MEAs) 32, each MEA comprising a membrane separator 34 (not limited to a solid polymer electrolyte or ion exchange membrane) positioned between two electrodes, a cathode 33 and an anode 35. The series of membrane electrode assemblies (MEAs) 32 are sandwiched at both ends by end flow field plates 36. Each end flow field plate 36 is adjacent to the inside of the adjacent end plate 38. Thus, at one end of the stack (the left end in the figure), the end flow field plate 36 is positioned adjacent to the cathode 33 of the leftmost MEA 32, and at the other end of the stack (the right end), the rightmost anode 35 is positioned adjacent to the end flow field plate 36.

[0013] Each end flow field plate 36 includes a fluid supply opening (typically air in this example) and a fluid exhaust opening formed on the surface of the plate.

[0014] Unlike conventional technology, system 30 does not have a current collector or bipolar plate. Instead, adjacent MEAs 32 are separated from each other by a double-sided flow field plate 40. Each side of the double-sided flow field plate 40 has a fluid supply opening and a fluid exhaust opening formed on the surface of the plate. An inlet tube connector 42 and an outlet tube connector 43 are provided to provide airflow through the stack.

[0015] To reduce the cost of the cell and stack hardware components, the end plates 38, end flow field plates 36, and double-sided flow field plates 40 are manufactured from low-cost polymers such as polypropylene, polyethylene, and other polymers (e.g., polystyrene). Since most polymers do not conduct electrons well, each cathode 33 and anode 35 has electrical contacts 53 and 55 to receive current from the power supply 70. The electrical contacts 53 and 55 thus replace the current collectors of conventional technology. The use of dedicated electrical contacts for each cathode and anode provides the advantage of allowing each cell in the stack to be electrically controlled individually.

[0016] By using polymers, costs can be reduced by one to two orders of magnitude compared to metals or graphite.

[0017] Referring to Figures 3A to 3D, one structure of the MEA32 according to a non-limiting embodiment of the present invention is shown. The electrical contacts 53 and 55 of the MEA32 can be in the form of tabs or other types of contacts. The MEA32 can be mounted on a substrate 50 and surrounded by an elastic seal 52.

[0018] Direct electrical contact between the power supply and each electrochemical cell in a multi-cell stack offers several advantages over conventional technologies. For example, direct electrical contact allows for individual monitoring and control of each cell, improving the modularity and flexibility of the electrochemical cell stack. Other advantages include reduced operating costs and more efficient maintenance. Furthermore, direct electrical contact avoids electrical problems such as short circuits that can occur during stack assembly, thus achieving increased efficiency and cost reduction in the assembly process.

Claims

1. In an electrochemical-based carbon dioxide gas separation system, Equipped with a stack of membrane electrode assemblies (MEAs), Each MEA has a membrane separator between the anode and the cathode. The cathode comprises a charge storage compound that reacts to produce hydroxide, and the anode comprises a charge storage compound that reacts to consume hydroxide or produce protons. A double-sided flow field plate is placed between adjacent MEAs in a stack of MEAs. The first and last MEAs of the electrochemical cell stack are connected to end flow field plates which are connected to end plates. A system characterized in that each of the cathode and anode has an electrical contact connected to a current power source.

2. In the electrochemical-based carbon dioxide gas separation system according to claim 1, A system characterized in that the end plate, the end flow field plate, and the double-sided flow field plate are formed from a polymer.

3. The electrochemical-based carbon dioxide gas separation system according to claim 1 further, A system characterized by comprising an inlet tube connector and an outlet tube connector for the airflow through the system.

4. In the electrochemical-based carbon dioxide gas separation system according to claim 1, A system characterized in that each of the MEAs is mounted on a substrate and surrounded by an elastic seal.

5. In electrochemical-based carbon dioxide gas separation methods, A step of providing a stack of membrane electrode assemblies (MEAs), wherein each MEA has a membrane separator between an anode and a cathode, the cathode contains a charge storage compound that reacts to produce hydroxide, and the anode contains a charge storage compound that reacts to consume hydroxide or produce protons; The step includes providing a double-sided flow field plate between adjacent MEAs in a stack of MEAs, The first and last MEAs of the electrochemical cell stack are connected to end flow field plates which are connected to end plates. A method characterized in that each of the cathode and anode has an electrical contact connected to a current power source.

6. The method according to claim 5, A method characterized by including the step of individually monitoring and controlling the electrical contacts of the cathode and anode, respectively.

7. In the method according to claim 5, A method characterized in that the electrical contacts of the cathode and anode, respectively, improve the modularity and flexibility of the stack.

8. In the method according to claim 5, A method characterized in that the electrical contacts of the cathode and anode, respectively, reduce operating costs and provide efficient maintenance.

9. In the method according to claim 5, A method characterized in that the electrical contacts of the cathode and anode prevent an electrical short circuit when the stack is in use.

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