HK1200504B - Method and apparatus for producing gas - Google Patents

Description

Method and apparatus for producing gas

Technical Field

The present invention relates to a method and apparatus for producing gas. More particularly, but not exclusively, the invention relates to an electrolytic cell and method in which combustible gases, such as hydrogen and oxygen, are produced by electrolysis of an aqueous electrolyte solution and are kept separate on production.

Background of the invention

The electrolysis cell uses electricity to convert water into hydrogen and oxygen in the gas phase.

Known electrolytic cells are constituted by any one of the following: a liquid alkaline electrolytic cell that utilizes a porous membrane between electrodes to separate hydrogen and oxygen; or polymer electrolyte electrolytic cells, which utilize proton exchange membranes in order to separate hydrogen and oxygen produced by the electrolytic process. The electrolytic cell further includes an anode disposed along a first side of the proton exchange membrane and a cathode disposed along a second, opposite side of the proton exchange membrane.

Known membranes in liquid alkaline electrolyzers are typically made from porous plastics, whereas in polymer electrode electrolyzers known proton exchange membranes are semi-permeable membranes typically made from ionomers and designed to conduct protons while being impermeable to gases such as oxygen and hydrogen. Proton exchange membranes can be made from pure polymer membranes or from composite membranes in which other materials are embedded in a polymer matrix.

A first drawback of all types of membranes is the current limitation they bring.

A further disadvantage with the membrane is the increased distance between the electrodes, which results in an increased resistance.

A further disadvantage of the known liquid alkaline membranes is that the efficiency decreases with increasing current density. The efficiency of known proton exchange membranes decreases with increasing applied voltage across the cell due to poor gas removal from the membrane. Also, the electrodes may not be stacked too close together, as this would inhibit gas removal.

A further disadvantage of the known liquid alkaline membranes is that they are not able to function effectively at high temperatures and pressures.

A further disadvantage of the known proton exchange membranes is the high cost of the membrane, since it requires the use of a noble metal catalyst (usually platinum) for separating the electrons and protons of hydrogen. Platinum catalysts are also extremely sensitive to carbon monoxide poisoning, such that if hydrogen is derived from an alcohol or hydrocarbon fuel, an additional reactor is required to reduce the carbon monoxide in the fuel gas. This again increases the cost of using known proton exchange membranes.

A further disadvantage of the known proton exchange membranes is their poor electrical conductivity at low relative humidity and their poor mechanical properties at temperatures above about 100 ℃. The operating temperatures of these membranes are relatively low and temperatures close to 100 ℃ are not high enough for useful cogeneration (cogeneration).

The prior art document PCT/IB2011/053050 in the name of hydro x HOLDINGS limed, entitled "Method and apparatus for producing gas", describes the use of a liquid alkaline electrolyser, which uses hydrodynamic shields instead of porous or proton exchange membranes to achieve electrolysis. The present invention brings about great improvements in terms of manufacturing and operating costs and dimensions.

In this specification, the term "combustible fluid" includes within its scope combustible gases comprising predominantly hydrogen and/or oxygen in the gaseous phase.

Objects of the invention

It is therefore an object of the present invention to provide a method and apparatus for producing gas with which the above disadvantages can be overcome and which is a useful alternative to known electrolytic cells and methods for producing gas.

Disclosure of Invention

According to a first aspect of the present invention there is provided a method for producing combustible fluid from a liquid alkaline electrolyte solution during an electrolytic process, comprising the steps of:

-providing an electrolyte solution;

-providing an electrolysis apparatus having a first spaced permeable electrode and a second spaced permeable electrode, said electrodes being immersed in a chamber having at least one inlet and two outlets;

-transferring the solution into the chamber via the inlet; and

applying a voltage across the electrodes to the apparatus to electrolyze the solution between the electrodes such that a first combustible fluid is formed on the first electrode and a second combustible fluid is formed on the second electrode, and the first combustible fluid is conveyed from the first electrode and into the first outlet, and the second combustible fluid is conveyed from the second electrode and into the second outlet, and wherein the first and second electrodes are provided in a close proximity (proximity) of 1mm to 6mm relative to each other.

The electrolyte solution may be potassium hydroxide (KOH) or sodium hydroxide (NaOH).

The combustible fluid may be a hydrogenation and oxidation fluid and more specifically the combustible fluid may be hydrogen and oxygen.

Each permeable electrode may be perforated or apertured.

Each permeable electrode may further be made of a mesh or foam material.

Each permeable electrode may be made of a material selected from stainless steel, nickel, palladium, cobalt or platinum materials.

The first electrode and the second electrode may be substantially parallel.

The first and second permeable electrodes may have a suitable (correct) and predetermined open to closed area ratio, also known as PPI (pores per square inch), which may be influenced by the size of the outlet and the pressure at which the solution is provided to the device.

The first and second permeable electrodes may be a set of permeable electrodes and the apparatus may comprise a plurality of sets of permeable electrodes, all of similar construction.

The electrolysis apparatus may define at least one inlet in fluid flow communication with all of the inlets, and the method may include the step of delivering the solution to the chambers of all of the sets of permeable electrodes via the inlet manifold.

The first combustible fluid outlet channel may be in fluid flow communication with all of the first combustible fluid outlets of the group of all of the permeable electrodes and the second combustible fluid outlet channel may be in fluid flow communication with all of the second combustible fluid outlets of the group of all of the permeable electrodes, the arrangement being such that a first combustible fluid formed on the first electrode is conveyed out of the apparatus via the first combustible fluid outlet and a second combustible fluid formed on the second electrode is conveyed out of the apparatus via the second combustible fluid outlet.

According to a second aspect of the present invention, there is provided an electrolysis apparatus in which combustible fluid is produced from an electrolyte solution (i.e. potassium hydroxide (KOH) or sodium hydroxide (NaOH)) in a liquid alkaline electrolysis process, the apparatus comprising:

-a first spaced permeable electrode and a second spaced permeable electrode immersed in the inlet chamber;

-at least one inlet into an inlet chamber for delivering an electrolyte solution into the inlet chamber; and

-a first combustible fluid outlet and a second combustible fluid outlet;

the arrangement being such that the electrolyte solution is conveyed into the inlet chamber via the inlet, wherein electrolysis takes place; and causing a first combustible fluid to form on the first electrode; and causing a second combustible fluid to form on the second electrode; and further causing the first combustible fluid to be delivered from the first electrode into the first combustible fluid outlet; and passing the second combustible fluid from the second electrode into the second combustible fluid outlet, and wherein the first electrode and the second electrode are provided in relatively close proximity to each other by a distance of from 1mm to 6 mm.

The electrolyte may be potassium hydroxide (KOH) or sodium hydroxide (NaOH) at a concentration of 20% to 50%.

The combustible fluid may be a hydrogenation and oxidation fluid and more specifically the combustible fluid may be hydrogen and oxygen.

Each permeable electrode may be perforated or apertured.

Each permeable electrode may further be made of a mesh or foam material.

Each permeable electrode may be made of a material selected from stainless steel, nickel, palladium, cobalt or platinum materials.

The first electrode and the second electrode may be substantially parallel.

The first electrode and the second electrode may each comprise at least one tab for connection to a power source to provide a voltage across the electrolysis apparatus for electrolysis of the electrolyte solution.

The first and second electrodes may be attached to stainless steel connectors secured to the tab sheet for distributing current around the electrodes.

The PVC sleeve keeps the individual electrodes firmly attached to the connector and electrically insulates the connector from the electrolyte.

The first permeable electrode and the second permeable electrode may have an appropriate and predetermined ratio of open to closed area (or PPI), which may be influenced by the size of the outlet and the pressure at which the solution is provided to the device.

The apparatus can include a first outer end member and a second outer end member, each made from polyethylene.

The shape of the device may be cylindrical, square or polygonal (multi-agonal).

The apparatus may comprise circulation means, such as a pump, to circulate the solution through the apparatus and force the solution into the inlet chamber.

The apparatus may comprise a first combustible fluid collection vessel connected to the first combustible fluid outlet and a second combustible fluid collection vessel connected to the second combustible fluid outlet.

Brief description of the drawings

The invention will now be further described, by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of an electrolysis apparatus according to a first preferred embodiment of the present invention;

FIG. 2 is an exploded perspective view of a part of an electrolysis apparatus according to a second preferred embodiment of the present invention; and

fig. 3 is a cross-sectional view of a single electrode of the device of fig. 2.

Description of the preferred embodiments of the invention

Referring to the drawings, an electrolysis apparatus according to a preferred embodiment of the present invention is generally designated by reference numeral 10.

The electrolysis apparatus 10 is adapted to produce oxygenated and hydrogenated fluids formed during electrolysis of the electrolyte solution delivered to the apparatus 10.

The apparatus 10 includes a first outer end member 12, which is made of polyethylene, and a second outer end member 14, which is also made of polyethylene.

Referring to fig. 1, the first and second outer end members 12, 14 are both square and are arranged substantially parallel to and spaced apart from each other. It is envisioned that the shape of the device may be polygonal or circular and need not be square, such as shown in fig. 2.

The apparatus 10 further includes two spaced apart permeable electrodes, a first permeable electrode 16 and a second permeable electrode 18. The permeable electrodes 16 and 18 are each made of a porous or perforated material. Specifically, each permeable electrode is a stainless steel 316 mesh (e.g., dutch braided wire mesh). The two permeable electrodes 16 and 18 are also arranged substantially parallel to each other, spaced relatively close to each other by 1mm-6 mm. The inlet chamber 20 surrounds the first and second permeable electrodes 16, 18.

The closer the permeable electrodes 16 and 18 are spaced from each other, the lower the resistance between them, which means that less voltage needs to be applied to the device 10, which results in the device 10 being more efficient.

Referring to FIG. 1, in a first embodiment of the invention, two permeable membranes are spaced apart by 4mm, and the mesh diameter is 20mm and the mesh area is 314mm²And the thickness of the grid is 0.8 mm. Using 50% KOH as the electrolyte concentration at a temperature of 60 ℃ and applying a voltage of 1.765VDC, the dimensional combination results in a current density of 73mA/cm². Applicants anticipate that this data can be significantly improved by using higher electrolyte temperatures and reducing the spacing between the electrodes to below 4 mm. Electroplating the electrode with platinum will also greatly improve the catalytic effect of the electrode.

The first and second electrodes may be attached to stainless steel connectors 24 secured to the tab sheet for distributing the current around the electrodes. The PVC sleeve 22 keeps the electrodes firmly attached to the connector and electrically insulates the connector from the electrolyte.

The inlet chamber 20 has two inlets 26 to allow the electrolyte solution to pass into the chamber 20. The apparatus 10 also has an oxygen outlet 28 and a hydrogen outlet 30.

The flow of electrolyte solution through the permeable electrodes 16 and 18 will carry with it the oxygen and hydrogen gas generated at the positive and negative (first and second) permeable electrodes, respectively. Thus, there is a natural separation of hydrogen and oxygen. The proximity of the electrodes 16 and 18 also allows for hydrolysis at very low voltages, allowing for high efficiency and high purity of hydrogen and oxygen.

The first and second permeable electrodes 16, 18 form a set of permeable electrodes. The apparatus 10 may include multiple sets of permeable electrodes arranged in a back-to-front (back-to-front) or parallel arrangement and connected to each other.

The first electrode 16 and the second electrode 18 comprise electrically conductive tab sheets or plates (one being a positive terminal and the other being a negative terminal) for connection to a power source (not shown), such as a battery. The power supply thus provides a voltage of 1V to 6V over the electrolysis apparatus 10 to electrolyze the solution. The inventive apparatus 10 produces hydrogen and oxygen by applying a pure DC voltage or a pulsed DC voltage to the apparatus.

The apparatus 10 further comprises circulation means, such as a pump (not shown), to circulate the solution through the apparatus 10. The electrolyte solution flowing into the chamber 20 via the inlet 26 is pressurised by being pumped into the apparatus 10 by a pump so that the solution is forced through the permeable electrodes 16 and 18. This arrangement allows the electrolyte solution to flow into the first chamber 20, through the permeable electrodes 16 and 18, via the inlet 26. Electrolysis occurs between the first and second permeable electrodes 16 and 18, respectively. The oxidizing fluid is delivered out through an oxygen outlet 28 and the hydrogenating fluid is delivered out through a hydrogen outlet 30.

The apparatus 10 may further include a hydrogen collection vessel (not shown) connected to the hydrogen outlet 30 and an oxygen collection vessel (also not shown) connected to the oxygen outlet 28. The oxygen collection container and the hydrogen collection container each have a second electrolyte solution outlet located toward an operative bottom end of the container and an oxygen gas outlet and a hydrogen gas outlet located toward an operative top end of the respective oxygen collection container and hydrogen collection container, respectively. The electrolyte solution is conveyed out of the oxygen outlet 28 and the hydrogen outlet 30, along with the respective gases, into an oxygen collection vessel and a hydrogen collection vessel. The arrangement is such that hydrogen and oxygen within the fluid delivered to the respective containers are released by gravity and surface tension and are delivered out of the containers via the oxygen outlet and the hydrogen outlet and the electrolyte solution is delivered out of the containers via the second electrolyte solution outlet. The second electrolyte solution outlet is connected to the inlet 26 and the solution is circulated back to the apparatus 10 by means of a pump. The gas is thus stored for later use.

A positive flow is foreseen from the first chamber 20 of the device 10 to the oxygen outlet 28 and the hydrogen outlet 30. From the first chamber 20 to the oxygen outlet 28 and the hydrogen outlet 30, the pressurized flow of electrolyte solution through the permeable electrodes restricts oxygen and hydrogen (after formation on the first and second permeable electrodes 16, 18) from entering the first chamber 20. Ion flow in the apparatus is foreseen to oppose and follow the electrolyte flow, which is a unique feature of the present arrangement.

It is further contemplated that the electrolysis apparatus is substantially free of membranes as in the case of prior art apparatus, and that the gas bubbles formed on the electrodes are removed immediately with the flow of electrolyte. This has several advantages, such as the cost of removing both wet or dry films, and the cost of maintaining the film. Furthermore, the current density is typically reduced by the formation of bubbles on the electrode, however, in the present arrangement, the bubbles are immediately removed in order to maintain a constant current density. Quite significantly, with a current density of 11,000mA/cm, the bubbles remained isolated.

The fact that no membrane is present also removes the pressure and temperature limitations that are typically present with the use of membranes. In the present invention, a permeable electrode is used which does not allow a covered conductive area caused by the movement of gas across the electrode surface. This increases the effective conductive area of the electrode, reducing the effective voltage requirements and thereby improving efficiency, resulting in reduced operating costs.

It is further envisioned that higher current densities and increased efficiencies may be achieved as the spacing between the electrodes is decreased.

It will be understood that the method and apparatus for producing hydrogen and oxygen according to the present invention may vary in detail without departing from the scope of the appended claims.

Claims (21)

1. A method for producing oxygen and hydrogen from a liquid alkaline electrolyte solution during an electrolytic process comprising the steps of:

providing an electrolyte solution;

providing an electrolysis apparatus comprising an inlet chamber having an inlet; first and second conduits having diametrically opposed open ends and defining respective first and second combustible fluid outlets, the first and second conduits projecting into the inlet chamber; first and second spaced apart permeable electrodes, the first and second electrodes being parallel to each other and each provided on an open end of said first and second conduits such that the electrodes are immersed in the inlet chamber, the electrodes being provided at a close distance of 1mm-6mm from each other;

delivering the solution into an inlet chamber via an inlet; and

applying a voltage across the electrodes to the device to electrolyze the solution between the electrodes, such that oxygen gas is formed on the first electrode and hydrogen gas is formed on the second electrode,

wherein the electrolyte solution is split into first and second outlet streams, the first outlet stream being conveyed past a first electrode, thereby removing oxygen that has formed on the first electrode into the first combustible fluid outlet; and passing the second outlet stream through a second electrode, thereby removing hydrogen gas that has formed on the second electrode into the second combustible fluid outlet.

2. The method of claim 1, wherein the electrolyte solution is potassium hydroxide (KOH) or sodium hydroxide (NaOH).

3. A method according to claim 1 or 2, wherein each permeable electrode is further a mesh or a foam material.

4. A method according to claim 1 or 2, wherein each permeable electrode is made from a material selected from stainless steel, nickel, palladium, cobalt or platinum material.

5. The method according to claim 1 or 2, wherein the first permeable electrode and the second permeable electrode have an appropriate and predetermined ratio of open to closed area, also known as PPI (pores per square inch), which is influenced by the size of the outlet and the pressure at which the solution is provided to the device.

6. A method according to claim 1 or 2, wherein the first and second permeable electrodes are sets of permeable electrodes and the apparatus comprises a plurality of sets of permeable electrodes, all of similar construction.

7. A method according to claim 6 wherein the electrolysis apparatus defines at least one inlet in fluid flow communication with all of the inlets and the method includes the step of delivering the solution to the chambers of all of the sets of permeable electrodes via an inlet manifold.

8. The method of claim 7, wherein the first combustible fluid outlet channel is in fluid flow communication with all of the first combustible fluid outlets of the group of all of the permeable electrodes and the second combustible fluid outlet channel is in fluid flow communication with all of the second combustible fluid outlets of the group of all of the permeable electrodes, the arrangement being such that the first combustible fluid formed on the first electrode is conveyed out of the apparatus via the first combustible fluid outlets and the second combustible fluid formed on the second electrode is conveyed out of the apparatus via the second combustible fluid outlets.

9. An electrolysis apparatus in which oxygen and hydrogen are produced from an electrolyte solution, i.e., potassium hydroxide (KOH) or sodium hydroxide (NaOH), in a liquid alkaline electrolysis process, the apparatus comprising:

an inlet chamber;

first and second conduits having diametrically opposed open ends and defining respective first and second combustible fluid outlets, the first and second conduits projecting into the inlet chamber,

first and second spaced apart permeable electrodes, the first and second electrodes being parallel to each other and provided on the open ends of the first and second catheters such that the electrodes are immersed in the inlet chamber, the electrodes being provided at a close distance of 1mm-6mm from each other;

at least one inlet into the inlet chamber for conveying an electrolyte solution into the inlet chamber, wherein electrolysis occurs upon application of a voltage across the electrodes such that oxygen is formed on the first electrode and hydrogen is formed on the second electrode, and wherein the electrolyte solution splits into first and second outlet streams, the first outlet stream being conveyed past the first electrode, thereby removing oxygen that has formed on the first electrode into the first combustible fluid outlet; and passing the second outlet stream through a second electrode, thereby removing hydrogen gas that has formed on the second electrode into the second combustible fluid outlet.

10. An electrolysis apparatus according to claim 9, wherein the first and second conduits are adjustable relative to one another so as to provide that the first and second electrodes provided on the open ends can be adjusted within 1mm to 6 mm.

11. An electrolysis apparatus according to any one of claims 9 and 10 wherein the electrolyte is potassium hydroxide (KOH) or sodium hydroxide (NaOH) at a concentration of 20% to 50%.

12. An electrolysis apparatus according to any one of claims 9 and 10 wherein each permeable electrode is made from a mesh or foam material.

13. An electrolysis apparatus according to claim 9 or 10 wherein each permeable electrode is fabricated from a material selected from stainless steel, nickel, palladium, cobalt or platinum.

14. The electrolysis apparatus according to claim 9 or 10 wherein the first and second electrodes each comprise at least one tab for connection to a power supply to provide a voltage across the electrolysis apparatus for electrolysis of the electrolyte solution.

15. The electrolysis apparatus of claim 14, wherein the first and second conduits comprise stainless steel connectors secured to the tab sheet for distributing the electrical current around the electrodes.

16. The electrolysis apparatus of claim 15 wherein the PVC sleeve maintains each electrode securely attached to the connector and electrically insulates the connector from the electrolyte.

17. The electrolysis apparatus according to claim 9 or 10 wherein the first permeable electrode and the second permeable electrode have a suitable and predetermined ratio of open to closed area, referred to as PPI, which is influenced by the size of the outlet and the pressure at which the solution is provided to the apparatus.

18. The electrolysis apparatus according to claim 9 or 10, comprising a first outer end member and a second outer end member, each made from polyethylene.

19. An electrolysis apparatus according to claim 9 or 10 including circulation means to circulate the solution through the apparatus and force the solution into the inlet chamber.

20. The electrolysis apparatus of claim 19, wherein the circulation device comprises a pump.

21. An electrolysis apparatus according to claim 9 or 10 comprising a first combustible fluid collection vessel connected to the first combustible fluid outlet and a second combustible fluid collection vessel connected to the second combustible fluid outlet.