AU2022380594A1 - Advanced commercial electrolysis of seawater to produce hydrogen - Google Patents

Abstract

An apparatus for electrolysing seawater is disclosed. In one embodiment, the apparatus comprises diaphragm-less electrolytic cells comprising an anode and a cathode. The anode comprises a plurality of anode cells in series and the cathode comprises a plurality of cathode cells in series to control the cell voltage and substantially prevent the production of oxygen and chlorine in the cells while hydrogen is being produced. Also disclosed is a membrane type Unipolar electrolytic cell when used to process alkaline seawater to produce twice the hydrogen and oxygen compared to a conventional electrolysis of seawater.

Description

ADVANCED COMMERCIAL ELECTROLYSIS OF SEAWATER TO PRODUCE HYDROGEN

PRIORITY DOCUMENT

[0001] The present application claims priority from Australian Provisional Patent Application No. 2021903553 titled “ADVANCED COMMERCIAL ELECTROYSIS OF SEAWATER TO PRODUCE HYDROGEN” and filed on 7 November 2021, the content of which is hereby incorporated by reference in its entirety.

INCORPORATION BY REFERENCE

[0002] The following publications are referred to in the present application and their contents are hereby incorporated by reference in their entirety:

Australian Patent 2008209322;

United Kingdom Patent GB2460000 B;

China Patent 101663236 B;

Patent HK1137408.

TECHNICAL FIELD

[0003] The present disclosure relates generally to electrolytic cells. In a particular form the present disclosure relates to electrolytic cells for the production of hydrogen from seawater.

BACKGROUND

[0004] Hydrogen production for industrial or commercial use is becoming more commonplace throughout the world. To date, hydrogen for these uses has been largely supplied from fossil fuels. However, demand for hydrogen continues to rise and there is a pressing need for systems and technology to produce hydrogen in commercial quantities from non-fossil fuel sources.

[0005] The present applicant has been granted Australian Patent 2008209322, United Kingdom Patent GB2460000, China Patent 101663236 and Hong Kong Patent HK1137408 concerning the unipolar electrolysis of seawater to produce hydrogen using a diaphragm-less electrolytic cell. An example of the apparatus is shown in Figure 1.

[0006] With this prior art cell, if the cathode cell voltage exceeds 0.828 volts, oxygen and chlorine along with hydrogen, may be produced and at the anode cell and if the voltage exceeds 0.401 volts, oxygen and chlorine along with hydrogen may be produced. This limitation in voltage reduces the capacity to produce pure hydrogen as shown by the following table:

[0007] There is thus a need to provide apparatus and/or processes that provide increased production of hydrogen from seawater compared to prior art apparatus and/or processes.

SUMMARY

[0008] A first aspect of the present disclosure provides an apparatus for electrolysing seawater, the apparatus comprising diaphragm-less electrolytic cells comprising an anode and a cathode, wherein the anode comprises a plurality of anode cells in series and the cathode comprises a plurality of cathode cells in series to control the cell voltage and substantially prevent the production of oxygen and chlorine in the cells while hydrogen is being produced.

[0009] In certain embodiments of the first aspect, there are more anode cells in series than there are cathode cells in series.

[0010] In certain embodiments of the first aspect, a gap between the anode and the solution electrode is greater than a gap between the cathode electrode and the solution electrode. [0011] A second aspect of the present disclosure provides a membrane type Unipolar electrolytic cell when used to process alkaline seawater to produce twice the hydrogen and oxygen compared to a conventional electrolysis of seawater.

[0012] In certain embodiments of the second aspect, the membrane in the Unipolar electrolytic cell allows only electrons to pass between the anode and the cathode allowing OH ions to build up at the cathode cell and H ions to build up at the anode cell and when electrolytes are passed through another set of cells, current flows and another lot of hydrogen and oxygen is produced.

[0013] A third aspect of the present disclosure provides a process for electrolysing seawater using diaphragm-less electrolytic cells with the anode comprising a plurality of anode cells in series and the cathode comprising a plurality of cathode cells in series to control the cell voltage and substantially prevent production of oxygen and chlorine in the cells while hydrogen is being produced.

[0014] In certain embodiments of the third aspect, there are more anode cells in series than there are cathode cells in series.

[0015] In certain embodiments of the third aspect, a gap between the anode and the solution electrode is greater than a gap between the cathode electrode and the solution electrode.

[0016] In certain embodiments of the third aspect, alkaline seawater produced is used to sequester carbon dioxide into stable metal carbonates.

[0017] A fourth aspect of the present disclosure provides a process for electrolysing seawater using a membrane type Unipolar electrolytic cell, the process comprising passing alkaline seawater through the anode and cathode cell under conditions to produce twice the hydrogen and oxygen compared to a conventional electrolysis of seawater.

[0018] In certain embodiments of the fourth aspect, the membrane in the Unipolar electrolytic cell allows only electrons to pass between the anode and the cathode allowing OH ions to build up at the cathode cell and H ions to build up at the anode cell; when electrolytes are passed through another set of cells, current flows and according to Faraday, another lot of hydrogen and oxygen is produced.

[0019] In certain embodiments of the first, second, third or fourth aspects, the electrodes are made of mesh or plate copper sparged with fine particles of Hastelloy c-276. In certain other embodiments of the first, second, third or fourth aspects, the electrodes are made of mesh or plate graphene sparged with fine particles of Hastelloy c-276. BRIEF DESCRIPTION OF DRAWINGS

[0020] Embodiments of the present disclosure will be discussed with reference to the accompanying drawings wherein:

[0021] Figure 1 is a schematic diagram of a prior art seawater electrolyser as described, for example, in Australian Patent 2008209322;

[0022] Figure 2 is a schematic diagram of a seawater electrolyser with a resistor before the anode cell and cathode cell in accordance with an embodiment of the present disclosure;

[0023] Figure 3 is a schematic diagram of a seawater electrolyser with no resistors but five anode cells and three cathode cells in accordance with a further embodiment of the present disclosure;

[0024] Figure 4 is a schematic diagram of a seawater electrolyser showing the orientation of H276c mesh electrodes and sheet electrodes with two DC supplies in accordance with an embodiment of the present disclosure;

[0025] Figure 5 is a schematic diagram of a system for the sequestration of CO2 in accordance with an embodiment of the present disclosure; and

[0026] Figure 6 is a schematic diagram showing the principle of membrane type unipolar seawater electrolysis to produce hydrogen in accordance with an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0027] The present disclosure arises from the inventor’s further developments in relation to the seawater electrolysis apparatus described in Australian Patent 2008209322. In particular, the apparatus and processes of the present disclosure allow higher cell voltages without producing chlorine and hydrogen in the same cell which, in turn, allows higher rates of production of pure hydrogen. A Unipolar membrane type electrolysis of seawater to produce hydrogen is also disclosed.

[0028] In a first embodiment of the present disclosure, a resistor is installed at the cathode or anode circuit to reduce the voltage at the cathode or anode cell and prevent chlorine or oxygen being produced as shown in Figure 2. Figure 2 shows the cell voltage can be reduced so that chlorine or oxygen are not produced in the anode or cathode cell where hydrogen is being produced; however, the resistor consumes energy without producing any useful product. [0029] In a second embodiment of the present disclosure, the apparatus for electrolysing seawater comprises diaphragm-less electrolytic cells comprising an anode and a cathode. The anode comprises a plurality of anode cells in series and the cathode comprises a plurality of cathode cells in series to control the cell voltage and substantially prevent the production of oxygen and chlorine in the cells while hydrogen is being produced. Thus, the cathode and anode cells are installed in series and this achieves a reduction in individual cell voltage of the anode and the cathode. This allows a higher total cell voltage without increasing the cathode or anode cell voltage that may result in producing unwanted chlorine or oxygen. The second embodiment is shown in Figure 3. In Figure 3, there are five anode cells with gaps of 4 mm and three cathode cells with gaps of 6 mm.

[0030] Table 2 shows the total cell voltages with the resulting anode and cathode voltages based on five anode cells with 3 mm gap between electrodes and three cathode cells with 6 mm gap between electrodes. Other combinations are possible to achieve individual anode voltage of less than 0.401 and individual cathode voltage of less than 0.848 volts.

[0031] In Table 2, this combination allows the total cell voltage to go as high as 8.2 volts where the voltage at the anode cells is 0.394 volts and the cathode cell volts is 0.656 volts.

[0032] More combinations are possible. For example, making the gap of electrodes at the cathode greater than 6 mm may result in higher voltage at the cathode cell closer to 0.848 volts.

[0033] Also disclosed herein is a process for electrolysing seawater using diaphragm-less electrolytic cells with the anode comprising a plurality of anode cells in series and the cathode comprising a plurality of cathode cells in series to control the cell voltage and substantially prevent production of oxygen and chlorine in the cells while hydrogen is being produced. [0034] An arrangement of cells in a commercial plant electrolysing seawater and producing only pure hydrogen is shown in Figure 4. In this illustrated embodiment, the cathode and anode electrodes are mesh copper electrodes coated with a material similar to Hastelloy c-276. The solution electrodes are plate copper electrodes coated with Ruthenium/Iridium material. In a preferred embodiment, the electrodes are made of mesh graphene electrodes and the cathode electrodes producing the hydrogen are sparged with tiny globules of Hastelloy c-276.

[0035] Commercial Importance of this Diaphragm-less Electrolysis of Seawater

[0036] Worldwide there is great concern about global warming and disastrous climate change; however, many industrialised countries have their economy dependent on coal and natural gas power plants, producing large amounts of carbon dioxide. The solution being trialled is carbon capture and geosequestration where the carbon dioxide is purified and then liquefied before storing in underground structures. Underground structures with temperatures above 31 °C are not suitable because carbon dioxide will not liquefy at temperatures above 31 °C. This technology is not only expensive but it is limited and not sustainable.

[0037] The present disclosure provides a more sustainable option as many coal and gas power plant are located at seaside and, if a reasonable distance from oceans, the flue gas can be piped to seaside. The US DOE and EIA have published a study that the oceans of the world can accommodate 10,000 years of the world’s carbon emissions, however, this will make the oceans acidic and affect the marine environment. The apparatus and processes of the present disclosure allow alkaline seawater to sequester the carbon dioxide and convert it to stable metal carbonate as shown by the following:

1. Seawater naturally contains ions including

4 CO h t t d ith t f

Permanent disposal of safe carbonates

[0038] The coal and natural gas power plants are allowed to operate and supply electricity while maintaining jobs in the coal and gas industries until new clean energy can replace these polluting power plants.

[0039] The apparatus and processes of the present disclosure can also be used to sequester carbon emissions from polluters such as cement plants, steel plants, and aluminium refineries.

[0040] The International Maritime Organisation is looking for means to reduce the carbon emission from ships and bulk carriers. The apparatus and processes of the present disclosure will allow ships to produce alkaline seawater to sequester their carbon dioxide emissions.

[0041] Membrane Type Cells

[0042] To achieve higher capacity, the current needs to be increased and this requires an increase in the cell voltage. With the diaphragm-less cells described above, increasing the cell voltage above a certain point may result in the production of oxygen and chlorine in the same cell where the hydrogen is produced. This is dangerous.

[0043] The answer is to use the membrane type cells as described in United States Patent 10,316,416. Briefly, a membrane type cell according to United States Patent 10,316,416 comprises at least a first electrolytic cell having at least one anode compartment housing an anode electrode and alkaline electrolyte producing oxygen and at least one cathode compartment housing a cathode electrode and acidic electrolyte producing hydrogen with a partition member separating the anode compartment from the cathode compartment and a DC supply applied to the anode and cathode electrodes. It also comprises at least a second electrolytic cell having at least one cathode compartment housing a cathode electrode receiving the positively charged alkaline electrolyte from the first anode cell and producing hydrogen, and having at least one anode compartment housing an anode electrode and receiving the negatively charged acidic electrolyte from the first cathode cell and producing oxygen with a partition member separating the anode cell from the cathode cell, when the anode electrodes and the cathode electrodes are connected in short circuit. There is at least one partition member separating the anode and cathode compartments in each of the first and second electrolytic cells; and the partition member is a porous diaphragm or an electronic membrane.

[0044] For the present disclosure, instead of an alkaline electrolyte at the anode cell and an acidic electrolyte at the cathode cell, only alkaline seawater is passed through the anode and cathode cell. The electrodes and membrane are made of copper and coated with a protective layer and catalyst. A conductive membrane that allows only electrons to pass is in place. The positive and negatively charged seawater are then de-gassed before passing to another set of cells that neutralise the seawater resulting in the production of more hydrogen and oxygen.

[0045] These membrane type cells may also use graphene electrodes sparged with fine particles of Hastelloy c-276.

[0046] The apparatus and processes of the present disclosure will allow the commercial production of pure hydrogen from seawater that will be a major boost in the use of hydrogen to replace all carbon fuels. Hydrogen can be produced in many parts of the world so long as there is seawater available.

[0047] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

[0048] It will be understood that the terms “comprise” and “include” and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

[0049] In some cases, a single embodiment may, for succinctness and/or to assist in understanding the scope of the disclosure, combine multiple features. It is to be understood that in such a case, these multiple features may be provided separately (in separate embodiments), or in any other suitable combination. Alternatively, where separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

[0050] It will be appreciated by those skilled in the art that the disclosure is not restricted in its use to the particular application or applications described. Neither is the present disclosure restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the disclosure is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims (21)

1. An apparatus for electrolysing seawater, the apparatus comprising diaphragm-less electrolytic cells comprising an anode and a cathode, wherein the anode comprises a plurality of anode cells in series and the cathode comprises a plurality of cathode cells in series to control the cell voltage and substantially prevent the production of oxygen and chlorine in the cells while hydrogen is being produced.

2. The apparatus according to claim 1, wherein there are more anode cells in series than there are cathode cells in series.

3. The apparatus according to either claim 1 or claim 2, wherein a gap between the cathode and the solution electrode is greater than a gap between the anode electrode and the solution electrode.

4. The apparatus according to any one of claims 1 to 3, wherein the electrodes are made of mesh or plate copper sparged with fine particles of Hastelloy c-276.

5. The apparatus according to claims 1 to 3 wherein the anode electrode is made of coppere coated with ruthenium-iridium.

6. The apparatus according to any one of claims 1 to 3, wherein the electrodes are made of mesh or plate graphene sparged with fine particles of Hastelloy c-276.

7. A membrane type Unipolar electrolytic cell when used to process alkaline seawater to produce twice the hydrogen and oxygen compared to a conventional electrolysis of seawater.

8. The membrane type Unipolar electrolytic cell according to claim 7, wherein the membrane in the Unipolar electrolytic cell allows only electrons to pass between the anode and the cathode allowing OH ions to build up at the cathode cell and H ions to build up at the anode cell and when electrolytes are passed through another set of cells, current flows and another lot of hydrogen and oxygen is produced.

9. The membrane type Unipolar electrolytic cell according to any one of claims7 to 8, wherein the electrodes are made of mesh or plate copper sparged with fine particles of Hastelloy c-276.

10. The membrane type Unipolar electrolytic cell according to any one of claims 7 to 8, wherein the electrodes are made of mesh or plate grapheme sparged withy fine particles of Hastelloy c-276.

11. A process for electrolysing seawater using diaphragm-less electrolytic cells with the anode comprising a plurality of anode cells in series and the cathode comprising a plurality of cathode cells in series to control the cell voltage and substantially prevent production of oxygen and chlorine in the cells while hydrogen is being produced.

12. The process according to claim 11, wherein there are more anode cells in series than there are cathode cells in series.

13. The process according to either claim 11 or claim 12, wherein a gap between the cathode and the solution electrode is greater than a gap between the anode electrode and the solution electrode.

14. The process according to any one of claims 11 to 13, wherein alkaline seawater produced is used to sequester carbon dioxide into stable metal carbonates.

15. The process according to any one of claims 11 to 14, wherein the electrodes are made of mesh or plate copper sparged with fine particles of Hastelloy c-276.

16. The process according to any one of claims 11 to 14, wherein the electrodes are made of mesh or plate graphene sparged with fine particles of Hastelloy c-276.

17. A process for electrolysing seawater using a membrane type Unipolar electrolytic cell, the process comprising passing alkaline seawater through the anode and cathode cell under conditions to produce twice the hydrogen and oxygen compared to a conventional electrolysis of seawater.

18. The process according to claim 17, wherein the membrane in the Unipolar electrolytic cell allows only electrons to pass between the anode and the cathode allowing OH ions to build up at the cathode cell and H ions to build up at the anode cell; when electrolytes are passed through another set of cells, current flows and according to Faraday, another lot of hydrogen and oxygen is produced.

19. The process according to any one of claims 17 to 18, wherein the electrodes are made of mesh or plate copper sparged with fine particles of Hastelloy c-276.

20. A process according to claims 17 to 18 wherein the anode electrode3 is copper coated with ruthenium-iridium.

21. The process according to any one of claims 17 to 18, wherein the electrodes are made of mesh or plate grapheme sparged with fine particles of Hastelloy c-276.