WO2023107080A2

WO2023107080A2 - Integrated gas distribution plate for high-temperature electrochemical hydrogen compressors

Info

Publication number: WO2023107080A2
Application number: PCT/TR2022/051454
Authority: WO
Inventors: Yilser Devri̇m; Can Özgür ÇOLPAN; Gizem Nur BULANIK DURMUŞ
Original assignee: Atilim Üni̇versi̇tesi̇; Dokuz Eylul Universitesi Rektorlugu
Priority date: 2021-12-10
Filing date: 2022-12-08
Publication date: 2023-06-15
Also published as: WO2023107080A3

Abstract

The invention relates to an assembled gas distribution plate developed to provide a homogeneous gas distribution and less pressure drop in cells, which, after the gas enters the cell, distributes it into the cell through a titanium plate in the sieve structure and provides a more homogeneous gas transfer to the gas diffusion layer due to the porous structure of the plate.

Description

INTEGRATED GAS DISTRIBUTION PLATE FOR HIGH-TEMPERATURE

ELECTROCHEMICAL HYDROGEN COMPRESSORS

Technical Field:

State of the art:

Fuel cell systems, one of the most important application areas of hydrogen (H2) energy, are technologies that have started to be used commercially in many applications. However, there are some factors such as economics and logistics in front of the commercialization of these systems. Especially difficulties related to pressurization, storage, and shipment of H2, leading to a considerable increase in the cost of H2 supply. Existing compressor technologies for pressurization H2 in on-site systems are expensive and low-efficient in terms of both investment cost, and maintenance and repair costs.

Electrochemical Hydrogen Compressors (ECHC) with high efficiency and capacity have been used for H2 pressurization and purification in recent years as an alternative to high-cost conventional H2 compressors. ECHC systems have many advantages over conventional methods. The fact that ECHC systems are smaller than conventional systems enables them to compress the same amount of gas at the same pressure more efficiently in a smaller volume and weight. Since these systems do not comprise any moving parts, the risk of failure during the compression process, maintenance and repair costs, and noise levels are low. The oil and metal used in conventional compressor systems cause wear on the compressor parts due to H2 embrittlement, resulting in H2 contamination during pressurization. Since there is no oil requirement in Electrochemical Hydrogen Compressors, high-purity H2 is obtained by compression. ECHC is more easily scalable than conventional systems depending on the type of application.

The H2 purification rate in electrochemical hydrogen compressor systems depends on the gas content fed into the system, the components used in the cell, and the cell design. In cell design, one of the most important parameters affecting the performance of Electrochemical Hydrogen Compressor (ECHC) systems is the design of the gas distribution channels through which the hydrogen and/or reformated gas mixture is distributed to the cells. The gas flow channels of Electrochemical Hydrogen Compressors have a significant impact on the water discharge, flow rate, pressure drop, mechanical strength, and temperature distribution. The geometry of the gas distribution channel in the system should be designed for homogeneous gas distribution, as well as purification in the electrochemical hydrogen compressor. In addition, since H2 pressurization as well as purification will be performed in the electrochemical hydrogen compressor, a flow geometry that minimizes the pressure drop should be used. Due to the high pressure, the gas distribution plates used in the cell should both provide efficient gas distribution and be resistant to high pressures.

The document numbered “AU3054092A”, which is in the state of the art, relates to a membrane electrode assembly with gas flow channels for fuel cells. The incorporation of gas flow passages into the electrode material allows the use of thin, lightweight separator layers. This enables higher power-to-volume and power-to-weight ratios than conventional fuel cells with etched, milled, or molded gas flow passages. In the study of the invention, new gas distribution plates have been developed to improve the performance of already -known ECHCs. In this study, the MEA structure includes a membrane, a catalyst, and a gas diffusion layer.

The document numbered “US20070231619A1”, which is in the state of the art discloses a system for securely sealing openings in a cell stack at low costs in an electrochemical system, such as a fuel cell system or an electrochemical compressor system. Elastomer materials such as silicone, Viton, or EPDM (ethylene/propylene-diene terpolymer) are used in the coating. The sealing ensures that hydrogen diffusion is reduced to an extremely low degree by the gasket. The document numbered “US20150037703A1” discloses a trapezoidal-shaped electrochemical cell stack design connected in series in the state of the art, in particular, a different cell design with a trapezoidal geometry that differs from the standard rectangularshaped systems developed to improve cell performance in electrochemical systems, such as fuel cells, where two reactant gases based on hydrogen and air are used together. Due to the trapezoidal shape proposed in the electrochemical cell stack, the gas inlet side length differs from the gas outlet side length. In the mentioned system, a lower gas stoichiometry is achieved compared to standard rectangular electrochemical cells. This simplifies the design of hydrogen recirculation devices, reduces the amount of power required for the air compressor that needs to be used since the air stoichiometry is reduced, and thus increases the efficiency of the electrochemical cell.

The design of the gas distribution plates that direct the flow of H2 and/or H2 containing gas mixtures entering the electrochemical hydrogen compressor stack is an important parameter that affects the pressure drop on both the anode and cathode side and therefore the electrochemical hydrogen compressor performance. When the gas distribution channel geometries used in existing applications are examined, it is seen that gas distribution plates similar to proton exchange membrane fuel cells are frequently used in electrochemical hydrogen compressor studies. However, the operating principles of electrochemical hydrogen compressors and PEM fuel cells are different and due to the high-pressure operating conditions in electrochemical hydrogen compressors, components with high mechanical strength and efficient gas distribution should be used. In particular, gas distribution plates with gas flow channels made of graphite and similar materials, which are frequently used in PEM fuel cells, are not suitable for the operating conditions of the electrochemical hydrogen compressor. In existing systems, bipolar plates with a flow channel across the entire plate are usually used to disperse H2 and/or ^-containing gas mixtures into the cell, and the gases move to the membrane through the cell gas diffusion layer in contact with the bipolar plate. In this case, there is a decrease in cell performance because the cell contacts the gas diffusion layer while moving through the flow channel and there is a pressure drop along the flow channel.

Classic PEM fuel cells and Electrochemical Hydrogen Compressor systems use bipolar plates for gas distribution. In these classical bipolar plates, flow channels for the flow of gases are located along the entire plate and provide access for the gases to the membrane electrode unit (MEA) located just in front of the bipolar plate. The membrane electrode unit (MEA) in the cell consists of a proton-permeable membrane and a gas diffusion layer coated with catalyst on both surfaces. This diffusion layer is a completely different component from the gas distribution plates. In systems using a bipolar plate with a flow channel along the plate, a pressure drop occurs along the flow of gases through the flow channel. This causes a problem in ECHC systems under high-pressure conditions.

Apart from PEM fuel cells, titanium porous plates can also be used as bipolar plates in some electrolyzer and electrochemical hydrogen compressor systems. However, in this case, due to the lack of a flow channel, the gases entering the cell enter the cell quickly through the porous structure and some of the fed gas leaves the cell without reacting. The gas entering the cell cannot be distributed homogeneously on the MEA. This situation leads to undesired efficiency loss in the systems.

As a result, due to the above-mentioned problems and the inadequacy of the existing solutions on the subject, it has become necessary to make a development in the related technical field.

Brief Description and Objects of the Invention

The main object of the invention is to provide both resistance to high pressures and homogeneous gas distribution in the cells, especially by supporting the MEA structure in the cell. With the assembled gas distribution plate developed, the gas is distributed into the cell through the titanium plate in the sieve structure after entering the cell. Due to the porous structure of the plate, the gas is distributed more homogeneously in the diffusion layer. Thus, a homogeneous gas distribution and less pressure drop in the cells are ensured.

Another object of the invention is to provide a membrane between the anode and cathode with high tolerance to defects, high-temperature resistance, low gas permeability, and high mechanical strength for hydrogen pressurization. For this purpose, the membrane is made of a material that can withstand operating conditions.

Another object of the invention is to ensure homogeneous distribution of the gases fed into the cell without pressure drop on the catalyst layer. FIGURE 1 is a drawing showing the anode and cathode side gas distribution channel design in the system of the invention.

FIGURE 2 is a drawing showing the design of the anode side gas distribution channel integrated with the titanium sieve gas distribution media in the system of the invention.

FIGURE 3 is a drawing showing the appearance of the gas distribution plate in the disassembled electrochemical hydrogen compressor in the system of the invention.

FIGURE 4 is a view of the assembled gas distribution channel developed in the system of the invention being placed in the electrochemical hydrogen compressor cell.

FIGURE 5 is a drawing showing the technical drawing of the assembled gas distribution channel of the invention.

FIGURE 6 is a drawing showing an example of a bipolar plate in electrochemical hydrogen compressors in the present system.

Definitions of the Elements/Parts of the Invention

In order to better explain the double-layer gas distribution plate developed by the present invention, the parts and elements in the figures are numbered and the corresponding numbers are given below:

1. Compression plate

2. Gasket

3. Gas distribution plate

4. Titanium sieve plate

5. Gas diffusion electrode

6. Membrane electrode layer

7. Channel

8. Assembled gas distribution plate A. Anode

A.1 Anode gas inlet

A.2 Anode gas outlet

K. Cathode

K.1 Cathode gas output

Detailed Description of the Invention

The invention relates to an assembled gas distribution plate (8) developed for a homogeneous gas distribution and for ensuring less pressure drop in cells, which enables the gas, after entering the cell, to be distributed into the cell through a titanium plate in the form of a sieve and provides a more homogeneous gas transfer to the gas diffusion layer due to the porous structure of the plate.

The cell components are compression plate (1), gasket (2), gas distribution plate (3), titanium sieve plate (4), gas diffusion electrode (5), membrane electrode layer (6), and channel (7). The assembled gas distribution plate (8) consists of a gas distribution plate (3), and a titanium sieve plate (4) and there are channels (7) in the gas distribution plate (3).

The compression plate (1) is a component that assembles the Electrochemical Hydrogen compressor. The compression plates (1) located on the anode (A) and cathode (K) side of the compressor are compressed with screws in such a way that there is no gas leakage in the cell due to use at high pressures.

One of the most important components affecting the performance of the system is the membrane electrode layer (6). The membrane electrode layer (6) is located between the anode (A) and cathode (K). It forms the membrane electrode unit together with the anode (A), cathode (K), and other elements. The membrane electrode layer (6) has a high tolerance to impurities, high-temperature resistance, low gas permeability, and high mechanical strength for hydrogen pressurization. The membrane electrode layer (6) is made of material with high mechanical strength and high thermal conductivity and can withstand operating conditions.

The gasket (2) is used to prevent leakage and to hold the elements together. For example, the gasket (2) is used to hold the gas distribution plate (3) and titanium sieve plate (4) together. The invention provides a structure comprising gas distribution channels (7) in the system used for gas distribution to the cells in electrochemical hydrogen compressor (ECHC) systems. The system consists of a two-layer gas distribution plate. The first layer of the two-layer gas distribution plate is used for the homogeneous distribution of gases entering the cells. In the first layer, the gases fed into the cell have main inlets on the anode (A) and cathode (K) side and these inlets enter the first layer of the channel in the geometry shown in Figure 1.

The gas distribution channels (3) in the gas distribution plate (7) were determined by the analysis. The gas entering the system from the first layer contacts the titanium sieve plate (4) in the second layer integrated into the first layer. In the second layer, the gases are homogeneously delivered to the gas diffusion layer. Homogeneous gas distribution is provided by the integrated use of titanium plates in the structure of the titanium sieve plate (4) together with gas distribution channels (7). The design of gas distribution channel (7) is designed to provide efficient gas distribution to the titanium sieve plate (4). Titanium-doped steel, and austenite nickel-chromium alloy can also be used instead of titanium in the second layer titanium sieve plate (4) shown in Figure 2. The diameter of the titanium sieve plate (4) is 100.00 mm.

In order to determine the channel design, gas distribution and pressure drop analyses were performed on the gas distribution plates with Solidworks solid modeling and the geometry was determined according to these analyses. The diameters of the gas inlets were determined according to the MEA active area used in the cell and the gas flow rates fed to the cell.

The diameter of the titanium sieve plate should be the same as the MEA used in the ECHC cell. In addition, the active area of the cell may increase or decrease according to the capacity of the ECHC to be produced. Therefore, the diameter of the titanium sieve plate can vary according to the active area of the ECHC MEA.

The two-layer structure ensures homogeneous gas distribution across the entire plate and low- pressure loss. The gases entering the cell from the first layer enter the cell through the appropriate flow channel and are distributed and reach the membrane electrode layer (6) of the cell through the porous layer just above it. In this way, the gases are delivered to the porous layer without pressure drop. Since there is a gas supply from different parts of the porous layer, the gases entering the cell are distributed more homogeneously on the membrane electrode layer (6).

The gas distribution plate (3) shown in Figure- 1 has one anode gas inlet (A.l) and one anode gas outlet (A.2) for the anode (A) side and two cathode gas outlets (K.l) for the cathode (K) side. H2 or the Fh-containing gas mixture fed to the anode (A) side enters the cell through the distribution channel (7) and is distributed and reacted in the cell by means of the titanium sieve plate (4) integrated on top of it and moves towards the cathode (K) side. Unreacted H2 or other mixture gases, if any, exit from the anode gas outlet (A.2).

Considering the mechanical strength of the cell under high-pressure conditions in electrochemical hydrogen compressors, the use of titanium materials gives more efficient results. The titanium sieve plate (4) used in the integrated gas distribution plates provides mechanical support to the membrane electrode attachment (MEA) layer used in the cell and protects the high-pressure difference between the anode (A) and cathode (K). With the gas distribution channel (7) structure designed within the scope of the invention, the gases come quickly from the gas distribution channels (7) to the titanium sieve plate (4) and are homogeneously distributed to different regions of the gas diffusion electrodes through the titanium sieve plate (4).

Through the flow channels on the cathode (K) side shown on the right side in Figure-6, the H2 or the FF-containing mixture advancing by reacting with the anode (A) side exits the cell.

Claims

CLAIMS gas distribution plate used in the ECHC cell, developed to provide a homogeneous gas distribution and less pressure drop in the cells, comprising a gas diffusion electrode (5), a membrane electrode layer (6) with high mechanical strength for hydrogen pressurization, a gasket (2) that prevents leakage and holds the system elements together, a compression plate (1) that enables the cell to be assembled from the anode (A) and cathode (K) sections and compressed in such a way that there is no gas leakage, characterized in that it comprises;

• titanium sieve plate (4), positioned in the middle part of the gas distribution plate (3), enabling H2 or an FL-containing mixture entering the cell to be distributed and reacted, thereby transmitted to the cathode (K) side and maintaining the high-pressure difference that will occur between the anode (A) and cathode (K), ensuring homogeneous distribution of the gases fed into the cell to the catalyst layer and adjacent to the gas distribution channels (7),

• gas distribution plate (3) comprising anode gas inlet (A.l) and anode gas outlet (A.2) belonging to the anode (A) side as well as cathode gas outlet (K.l) belonging to the cathode (K) side, fixed to the anode (A) side and cathode (K) side by the gasket (2), in which the titanium sieve plate (4) located in the center and gas distribution channels on opposite sides of the titanium sieve plate (4),

• gas distribution channels (7) on the gas distribution plate (3) on the two opposite sides of the titanium sieve plate (4) that allow the FL.containing mixture and H2 fed to the anode (A) side to enter the cell and ensure homogeneous gas distribution. gas distribution plate according to claim 1, characterized in that it comprises a titanium sieve plate (4) having a diameter of 100.00 mm.

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