WO2023039106A1

WO2023039106A1 - Water electrolysis apparatus and method

Info

Publication number: WO2023039106A1
Application number: PCT/US2022/042962
Authority: WO
Inventors: Mark LOMMERS; Ross SCIARRONE
Original assignee: Downunder Geosolutions (America) Llc
Priority date: 2021-09-09
Filing date: 2022-09-08
Publication date: 2023-03-16

Abstract

An electrolysis cell has a first electrode nested within a second electrode, both connected at one longitudinal end to an end cap. An ionic membrane is nested between the at least one first electrode and the corresponding second electrode. The end cap is removably attachable to one longitudinal end of a housing, which has a fluid inlet on an end opposed to the cap end. The cell has either (i) a flow divider at the longitudinal end having the fluid inlet to divide liquid flow entering through the fluid inlet to a first path defined within first electrode and a second path defined within second electrode, or (ii) another fluid inlet in fluid communication with the second path. The fluid inlet is in fluid communication with the first path. The end cap comprises a fluid outlet for the first path and a fluid outlet for the second path.

Description

WATER ELECTROLYSIS APPARATUS AND METHOD

Background

[0001] This disclosure relates to the field of electrolyzers used to generate hydrogen gas and oxygen gas from an aqueous electrolyte solution.

[0002] Production of hydrogen and oxygen gas by means of water electrolysis is a well- established industrial process. An electric current is passed through water, causing the molecular water (H2O) to split into discrete molecules of hydrogen gas (H2) and oxygen gas (O2).

[0003] A conventional electrolysis cell consists of metallic electrodes immersed in an aqueous solution with a voltage applied across the electrodes to induce oxidation and reduction reactions at the electrodes. The applied voltage is above the decomposition voltage for production of hydrogen and oxygen gas from the water.

[0004] The effectiveness of the electrolysis process is greatly increased by the presence of charged ions in the aqueous solution, which increases the conductivity of the solution to electric charge thereby reducing cell internal resistance. Alkaline electrolysis systems known in the art use a hydroxide based salt, such as potassium hydroxide (KOH), to provide these charged ions. The hydroxide ions participate in the electrolysis reactions in accordance with the following equations:

4OH" -> 2H2O + O2 + 4e’ (oxidation)

4H2O + 4e" -> 2H2 + 4OH" (reduction)

[0005] A reaction activation voltage exists, representing the minimum voltage that must be applied to the electrolysis cell equaling the decomposition voltage of the chemical bonds of the water molecules, plus additional voltage to overcome internal resistances of the electrolysis cell.

[0006] The rate of gas production of the electrolysis cell is proportional to the applied electric current and available conductive surface area of the electrodes, such that increased electrode surface area produces greater volumes of product gases by allowing for proportional increase in applied electric current.

[0007] An alternative method for increasing gas production is to use exotic catalysts on the surface of the electrodes to reduce the reaction activation energy, thereby improving electrolysis cell efficiency. Common catalyst materials include nickel, cobalt and platinum. These materials are expensive and significantly increase the construction cost of electrolysis devices. For this reason, catalysts are typically applied in a thin layer to the surface of an inexpensive substrate to minimize the required mass of the catalyst. Additionally, because these catalyst materials degrade during the routine operation of the electrolysis cell, periodic reapplication of this catalytic surface is required, contributing to the maintenance costs of the cell.

[0008] Conventional electrolysis cells are typically densely packed with multiple electrode plates stacked very closely together, and include complex gas collection manifolds. This form of electrolysis cell structure affords conventional electrolysis cells with high power density, but creates a complex assembly which is difficult and costly to fabricate, assemble and maintain.

[0009] Separation of the two gas producing regions about the opposed polarity electrodes in conventional electrolysis cells is usually obtained by implementing a ceramic based ionic membrane in the space between the electrodes to allow diffusion of hydroxide ions throughout the solution, while reducing the potential for mixing between the product gases.

[0010] Migration of gases across the ionic membrane is driven by pressure differences between the anodic and cathodic regions of the electrolysis cell; minimizing the pressure differential by innovative cell arrangement can increase resultant gas purity by minimizing cross-membrane gas migration.

[0011] Thus, there is a need for a readily maintainable apparatus using low cost materials to decrease the construction and maintenance costs of an electrolysis cell for hydrogen gas production. Summary

[0012] One aspect of the present disclosure is an electrolyzer cell. An electrolyzer cell according to this aspect of the disclosure has a first electrode nested within a second electrode, both connected at one longitudinal end to an end cap. An ionic membrane is nested between at least one first electrode and the corresponding second electrode. The end cap is removably attachable to one longitudinal end of a housing, which has a fluid inlet on an end opposed to the cap end. The cell has either (i) a flow divider at the longitudinal end having the fluid inlet to divide liquid flow entering through the fluid inlet to a first path defined within the first electrode and a second path defined within the second electrode, or (ii) another fluid inlet in fluid communication with the second path, wherein the first fluid inlet is in fluid communication with the first path. The end cap comprises a fluid outlet for the first path and a fluid outlet for the second path.

[0013] In some embodiments, the at least one first electrode comprises a closed circumference.

[0014] In some embodiments, the at least one first electrode comprises an annular cylinder.

[0015] In some embodiments, the corresponding second electrode comprises a closed circumference.

[0016] In some embodiments, the corresponding second electrode comprises an annular cylinder.

[0017] In some embodiments, the at least one ionic membrane comprises a closed circumference.

[0018] In some embodiments, the at least one ionic membrane comprises an annular cylinder.

[0019] In some embodiments, removal of the end cap from the housing correspondingly removes the at least one first electrode, the at least one ionic membrane and the corresponding second electrode. [0020] In some embodiments, the housing comprises a fluid inlet at a longitudinal end of the housing opposed to the longitudinal end having the end cap, the housing comprising a metering plate arranged to direct electrolyte entering the housing through the fluid inlet to direct electrolyte flow and regulate pressure differential between an anode electrolyte flow path and a cathode electrolyte flow path.

[0021] A method for generating hydrogen gas and oxygen gas according to another aspect of this disclosure includes moving an electrolyte solution longitudinally through a first electrode nested within a second electrode. The first electrode and the second electrode having nested between them an ionic membrane. The first electrode, the ionic membrane and the second electrode are each coupled to an end cap at a respective longitudinal end. The end cap is removably coupled to one longitudinal end of a housing. The housing has at least one fluid inlet at a longitudinal end opposed to the one longitudinal end. The end cap has a first fluid outlet in communication with an interior of the first electrode and a second fluid outlet in communication with either or both of (i) a space between an interior of the second electrode and an exterior of the ionic membrane, and (ii) a space between the exterior of the second electrode and the housing in the case of a perforated second electrode. A voltage is applied across the first electrode and the second electrode, and entrained gas is extracted from fluid leaving the first fluid outlet and the second fluid outlet.

[0022] Some embodiments further comprise separating electrolyte solution entering the at least one fluid inlet into a first flow stream entering the interior of the first electrode, and a second flow stream entering the space. The first flow stream and the second flow stream enter the housing at the opposed longitudinal end.

[0023] Some embodiments further comprise separating electrolyte solution entering the housing at the opposed longitudinal end by connecting the at least one fluid inlet to the interior of the first electrode, and connecting a second fluid inlet at the opposed longitudinal end to the space, and moving the electrolyte solution into the at least one fluid inlet and the second fluid inlet. [0024] Some embodiments further comprise disconnecting the end cap from the housing and disconnecting the first electrode, the ionic membrane and the second electrode from the end cap by uncoupling a connecting joint on the end cap having coupled thereto one longitudinal end of the first electrode, the ionic membrane and the second electrode. The first electrode and the second electrode are replaced by connecting respective replacements to the end cap at the connecting joint.

[0025] Some embodiments further comprise disconnecting the end cap from the housing and individually disconnecting the first electrode, the ionic membrane and the second electrode from the end cap by uncoupling the first electrode, the ionic membrane and the second electrode from the support structure. The first electrode and the second electrode are replaced by connecting respective replacements to the respective connecting points.

[0026] An electrolyzer according to another aspect of the present disclosure includes a plurality of electrolysis cells disposed within a housing. Each electrolysis cell includes at least one first electrode nested within a corresponding second electrode. The at least one first electrode and the corresponding second electrodes are connected at one longitudinal end to an end cap. At least one ionic membrane is nested between the at least one first electrode and the corresponding second electrode. The end cap is removably attachable to one longitudinal end of the housing. The housing comprises at least one fluid inlet on a longitudinal end opposed to the end cap. The housing has either (i) a flow divider at the longitudinal end having the at least one fluid inlet to divide liquid flow entering through the at least one fluid inlet to a respective first path defined within a circumference of each of the at least one first electrodes and a respective second path defined within a circumference of the corresponding second electrode, or (ii) a respective second fluid inlet in fluid communication with the respective second path wherein the at least one fluid inlet is in fluid communication with each first path, the end cap comprising a fluid outlet for each first path and a fluid outlet for each respective second path.

[0027] In some embodiments, each at least one first electrode comprises a closed circumference. [0028] In some embodiments, each at least one first electrode comprises an annular cylinder.

[0029] In some embodiments, each corresponding second electrode comprises a closed circumference.

[0030] In some embodiments, each corresponding second electrode comprises an annular cylinder.

[0031] In some embodiments, each at least one ionic membrane comprises a closed circumference.

[0032] Other aspects and possible advantages will be apparent from the description and claims that follow.

Brief Description of the Drawings

[0033] FIG. 1 shows a cross section view of an example embodiment of an electrolyzer according to the present disclosure.

[0034] FIG. 2 shows an embodiment of a single cell electrolyzer having a common flow inlet and metering plate to establish separate anode and cathode electrolyte flow paths.

[0035] FIG. 3 shows an embodiment of a single cell electrolyzer having separate anode and cathode electrolyte flow inlets.

[0036] FIG. 4 shows a multiple cell electrolyzer and associated electrolyte flow dividers.

Detailed Description

[0037] In general, an electrolyzer for producing hydrogen gas and oxygen gas from a water based electrolyte according to the present disclosure includes one or more sets of electrodes arranged as axially elongated, concentric or nested cylinders, or other closed circumference shape that defines an internal volume through which fluid may move longitudinally. Electrolyte paths between the one or more sets of nested electrodes are separated by an ionic membrane. The nested electrodes are supported by a common end cap such that the nested electrodes can be withdrawn from a main electrolyzer housing to enable rapid maintenance or replacement of the components. Electrolyte management is carried out by separated electrolyte flow paths and respective flow discharges containing respective generated hydrogen and oxygen gases.

[0038] An example embodiment of an electrolyzer (30) according to the present disclosure is shown in FIG. 1. The example embodiment shown in FIG. 1 comprises a single electrolysis cell disposed in an electrolyzer housing (5). A first electrode (1), which may produce hydrogen, may be nested within a second electrode (2), which in the present example embodiment may produce oxygen. The first electrode (1) in some embodiments may be concentric within the second electrode (2), and in some embodiments, the first electrode (1) and the second electrode (2) may be in the shape of annular cylinders. The first electrode (1) and the second electrode (2), irrespective of their specific shapes, may each have a closed circumference and thereby define a respective internal longitudinal electrolyte flow path (1A, 2A). The first electrode (1) and the second electrode (2) may be coupled at the same respective longitudinal end to a housing end cap (4), wherein respective electrolyzer outlets (10, 11) may be defined for a respective electrolyte flow path (1A, 2A). The first electrode (1) and the second electrode (2) are disposed within the interior of the electrolyzer housing (5) when the housing end cap (4) is attached to one longitudinal end of the electrolyzer housing (5), and may be removed for service and/or replacement as an assembly simply by removing the end cap (4) from the housing (5).

[0039] The electrolysis cell arrangement may be filled with an electrolyte solution (6) composed of water, and, in the present example embodiment, a strong base, such as potassium hydroxide (KOH), that is caused to flow through the electrolyzer housing (5) along the previously described flow paths (1 A, 2A). A DC electrical power supply (7) to induce an electric potential is connected as shown across the first electrode (1) and the second electrode (2) to induce an electrolysis reaction of the electrolyte solution (6) to generate hydrogen gas and oxygen gas.

[0040] The generated gases are entrained in the respective electrolyte flow streams along the respective flow paths (1 A, 2A) for transport to respective electrolyzer outlets (10, 11) for downstream gas-liquid separation. The electrolyte solution (6) is circulated through the electrolysis cell (30) such that the cathode-electrolyte flow path (1A) and anodeelectrolyte flow path (2 A) are fluidly separated by an ionic membrane (12) to prevent exchange of the generated hydrogen-gas in the cathode electrolyte flow stream (8) and the generated oxygen-gas in the anode electrolyte flow stream (9). The ionic membrane (12) also defines a closed circumference and may be nested between the first electrode (1) and the second electrode (2).

[0041] The ionic membrane (12) may be affixed to a fluid (and therefore ionically) permeable support structure (3), for example, a perforated tube made from rigid plastic. Perforations (not shown separately) in the support structure (3) tube may enable movement of ions through the ionic membrane (12). The support structure (3) may be coupled to the end cap (4) using an assembly joint (21) having one or more features, for example, threads, flanges and the like to enable the support structure (3) to be easily disassembled from the end cap (4). The first electrode (1) may be affixed to or otherwise disposed in the interior of the support structure (3), and the second electrode (2) may be affixed to or otherwise disposed outside the support structure (3) such that disconnecting the support structure (3) by uncoupling the assembly joint (21) enables disassembly of all of the first electrode (1), second electrode (2) support structure (3), and the ionic membrane (12) as a unit for further service or replacement.

[0042] Electrolyte flow path separation through the housing (5) may be obtained by one or more of the following example arrangements.

[0043] For a single cell electrolyzer such as the example embodiment shown in FIG. 1, a common electrolyte inlet (13) may be disposed at a longitudinal end of the electrolyzer housing (5) opposed to the longitudinal end on which the end cap (4) is disposed, and such common electrolyte inlet (13) may be in fluid communication with the interior of the electrolyzer housing (5). The common electrolyte inlet (13) may direct incoming electrolyte flow toward a metering plate (14) disposed within the electrolyzer housing (5) proximate the common electrolyte inlet (13). The metering plate (14) divides the electrolyte flow, and balances pressure differentials, between the anodic electrolyte flow stream (9) and the cathodic electrolyte flow stream (8) within the respective flow paths (1A, 2A) in the interior of the electrolyzer housing (5). In some embodiments, single or multiple cells may be disposed within the same electrolyzer housing (5). FIG. 2 shows a single cell electrolyzer having a common electrolyte inlet (13) and a metering plate (14) similar to that shown in FIG. 1. The end cap (4) may have a separate anode electrolyte outlet (10) and cathode electrolyte outlet (11) through which, respectively, generated oxygen and hydrogen are entrained in their respective flow streams (8, 9).

[0044] FIG. 3 shows an example embodiment of an electrolyzer with a separate anode electrolyte inlet (15) and cathode electrolyte inlet (17), and corresponding electrolyte outlets (16) and (18), respectively, whereby a perforated support structure (19) extends along the entire length of the electrolyzer housing (5) to provide separation between the two electrolyte flow paths.

[0045] Some embodiments, such as the one shown in FIG. 4, may comprise multiple electrolysis cells (40) disposed in a common cell electrolyzer housing (5). Each electrolysis cell (40) may comprise a first electrode nested within a second electrode, separated by an ionic membrane nested between the electrodes substantially as explained with reference to FIG. 1. Each electrolysis cell (40) may have an individual, respective cathode-electrolyte outlet (22, 23), a shared anode-electrolyte outlet (24), and a common electrolyte inlet (25) and an associated metering plate (26) to separate the incoming electrolyte flow through the common inlet (25) into the respective flow streams (22, 23, 24).

[0046] The support structure, including a perforated support tube, the electrodes and ionic membrane in any particular embodiment may be attached at one longitudinal end to the end cap (4) and may therefore be removable from the electrolyzer housing (5) in any of the above described embodiments simply by removing the end cap (4).

[0047] In some embodiments, the electrodes and ionic membrane may be attached at one longitudinal end to the support structure and may therefore be removable from the electrolyzer housing (5) in any of the above described embodiments simply by removing the end cap (4) and detaching the required components from the support structure. [0048] Maintenance of the electrolyzer may be performed by removal of the end cap (4) and withdrawal of the electrolysis cell components as described above to enable disconnection of the electrolysis cell components for replacement at the support structure joint (21).

[0049] In light of the principles and example embodiments described and illustrated herein, it will be recognized that the example embodiments can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific embodiments, but other configurations are also contemplated. In particular, even though expressions such as in “an embodiment," or the like are used herein, these phrases are meant to generally reference embodiment possibilities, and are not intended to limit the disclosure to particular embodiment configurations. As used herein, these terms may reference the same or different embodiments that are combinable into other embodiments. As a rule, any embodiment referenced herein is freely combinable with any one or more of the other embodiments referenced herein, and any number of features of different embodiments are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

Claims What is claimed is:

1. An electrolyzer cell, comprising: at least one first electrode nested within a corresponding second electrode, the at least one first electrode and the corresponding second electrodes connected at one longitudinal end to an end cap; at least one ionic membrane nested between the at least one first electrode and the corresponding second electrode; and a housing, the end cap removably attachable to one longitudinal end of the housing, the housing comprising at least one fluid inlet on a longitudinal end opposed to the end cap; and at least one of (i) a flow divider at the longitudinal end having the at least one fluid inlet to divide liquid flow entering through the at least one fluid inlet to a first path defined within a circumference of the at least one first electrode and a second path defined within a circumference of the corresponding second electrode, and (ii) a second fluid inlet in fluid communication with the second path wherein the at least one fluid inlet is in fluid communication with the first path, the end cap comprising a fluid outlet for the first path and a fluid outlet for the second path.

2. The cell of claim 1 wherein the at least one first electrode comprises a closed circumference.

3. The cell of claim 2 wherein the at least one first electrode comprises an annular cylinder.

4. The cell of claim 1 wherein the corresponding second electrode comprises a closed circumference.

5. The cell of claim 4 wherein the corresponding second electrode comprises an annular cylinder. The cell of claim 1 wherein the at least one ionic membrane comprises a closed circumference. The cell of claim 6 wherein the at least one ionic membrane comprises an annular cylinder. The cell of claim 1 wherein removal of the end cap from the housing correspondingly removes the at least one first electrode, the at least one ionic membrane and the corresponding second electrode. The cell of claim 1 wherein the housing comprises a fluid inlet at a longitudinal end of the housing opposed to the longitudinal end having the end cap, the housing comprising a metering plate arranged to direct electrolyte entering the housing through the fluid inlet to direct electrolyte flow and regulate pressure differential between an anode electrolyte flow path and a cathode electrolyte flow path. A method for generating hydrogen gas and oxygen gas, comprising: moving an electrolyte solution longitudinally through a first electrode nested within a second electrode, the first electrode and the second electrode having nested therebetween an ionic membrane, the first electrode, the ionic membrane and the second electrode each coupled to an end cap at a respective longitudinal end, the end cap removably coupled to one longitudinal end of a housing, the housing having at least one fluid inlet at a longitudinal end opposed to the one longitudinal end, the end cap having a first fluid outlet in communication with an interior of the first electrode and a second fluid outlet in fluid communication with at least one of (i) a space between an interior of the second electrode and an exterior of the ionic membrane and (ii) a space between the housing and the second electrode; applying a voltage across the first electrode and the second electrode; and extracting entrained gas from fluid leaving the first fluid outlet and the second fluid outlet. The method of claim 10 further comprising separating electrolyte solution entering the at least one fluid inlet into a first flow stream entering the interior of the first electrode, and a second flow stream entering the space, the first flow stream and the second flow stream entering at the opposed longitudinal end. The method of claim 10 further comprising separating electrolyte solution entering the housing at the opposed longitudinal end by connecting the at least one fluid inlet to the interior of the first electrode and connecting a second fluid inlet at the opposed longitudinal end to the space, and moving the electrolyte solution into the at least one fluid inlet and the second fluid inlet. The method of claim 9 further comprising: disconnecting the end cap from the housing; disconnecting the first electrode, the ionic membrane and the second electrode from the end cap by uncoupling a connecting joint on the end cap having coupled thereto one longitudinal end of the first electrode, the ionic membrane and the second electrode; and replacing the first electrode and the second electrode by connecting respective replacements to the end cap at the connecting joint. The method of claim 9 further comprising: disconnecting the end cap from the housing; individually disconnecting the first electrode, the ionic membrane and the second electrode from the support structure by uncoupling a connecting joint on the support structure having coupled thereto one longitudinal end of the first electrode, the ionic membrane or the second electrode, respectively; and replacing the first electrode and the second electrode by connecting respective replacements to the support structure at the connecting location. An electrolyzer, comprising: a plurality of electrolysis cells disposed within a housing, each electrolysis cell comprising, at least one first electrode nested within a corresponding second electrode, the at least one first electrode and the corresponding second electrodes connected at one longitudinal end to an end cap, at least one ionic membrane nested between the at least one first electrode and the corresponding second electrode, and wherein the end cap is removably attachable to one longitudinal end of the housing, the housing comprising at least one fluid inlet on a longitudinal end opposed to the end cap; and at least one of (i) a flow divider at the longitudinal end having the at least one fluid inlet to divide liquid flow entering through the at least one fluid inlet to a respective first path defined within a circumference of each of the at least one first electrodes and a respective second path defined within a circumference of the corresponding second electrode, and (ii) a respective second fluid inlet in fluid communication with the respective second path wherein the at least one fluid inlet is in fluid communication with each first path, the end cap comprising a fluid outlet for each first path and a fluid outlet for each respective second path. The electrolyzer of claim 15 wherein each at least one first electrode comprises a closed circumference. The electrolyzer of claim 16 wherein each at least one first electrode comprises an annular cylinder. The electrolyzer of claim 17 wherein each corresponding second electrode comprises a closed circumference. The electrolyzer of claim 18 wherein each corresponding second electrode comprises an annular cylinder. The electrolyzer of claim 15 wherein each at least one ionic membrane comprises a closed circumference. The electrolyzer of claim 20 wherein each at least one ionic membrane comprises an annular cylinder. The electrolyzer of claim 15 wherein removal of the end cap from the housing correspondingly removes each at least one first electrode, each at least one ionic membrane and each corresponding second electrode.