INTRODUCTION AND BACKGROUND

This invention relates to an apparatus and method for production of gases, and more particularly, but not exclusively, to an apparatus and method for production of gases from an electrolytic solution and the subsequent separation thereof in the same process, and a system for the production and separation of gases from an electrolytic solution incorporating said apparatus and method.

Various devices and methods for production of gases by way of electrolysis of a solution or water are known in the art. Most electrolysers utilise a diaphragm or separator, with another alternative using a so-called proton or ion exchange membrane (PEM) which is permeable to ions, but impermeable to gases. In use, the membranes separate the electrodes, which in turn causes separation of the gases produced by the electrolyser during the electrolysis process.

The disadvantages and shortcomings of membranes, diaphragms and PEM's have been well documented, with significant associated cost ramifications and limited lifespan being the main concerns. Reasons for the limited lifespan are that these membranes are brittle, cannot handle high pressures and temperatures and are prone to cross gas contamination. A further disadvantage lies in the fact that these membranes have a current density threshold, which means that they cannot perform optimally at high gas production rates.

It has accordingly become an objective in the industry to lower the capital costs involved with known electrolysers and electrolytic processes. Various attempts have been made in the art to develop a so-called membraneless electrolyser with which the various disadvantages experienced with prior art electrolysers could be overcome.

United States patent application number 2002/0074237A1 in the name of Takesako et al is aimed at producing electrolyzed water from a liquid. The method described in the patent teaches of using plate electrodes, albeit porous or solid, and after applying a DC voltage to the electrodes, an electrolyzed water is produced within the electrolyzed cell which is then removed from the cell. In accordance with the Takesako et al document, electrolyzed water contains a large number of fine bubbles, as hydrogen, oxygen and other gases, the electrolyzed water having use in a variety of applications. Although Takesako et al does not specifically refer to a membrane, and can therefore be considered to be membraneless, it does not provide for the separation of gases following the production thereof by electrolysis. This is perceived as a disadvantage in operations requiring the constituent gases of an electrolyte to be separable from each other following the electrolysis process. Takesako et al also relies on opposing electrodes, one being solid and the other perforated, which complicates and extends the flow path of the electrolytic solution, and accordingly increases the pressure drop within the system. The flow passage along the electrodes potentially causes unwanted extended exposure of the electrolytic solution to solid plate electrodes, which increases the formation of bubbles on the electrodes and further increases the bubble fraction within the electrolytic solution, thereby reducing the effective reactive area on the electrode, and ultimately increasing ohmic resistance.

United States patent number 8,357,269 in the name of Smedley teaches of an electrolysis system for generating hydrogen and oxygen gas, and an outlet for gases produced via the electrolysis system to supplement the fuel supply to an internal combustion engine. It does not teach the use of a membrane in the process. However, the gases, being hydrogen and oxygen, produced from the membraneless electrolysis of the electrolyte are not separated, and are contained in a single compartment within the electrolyser and supplied to the engine of a vehicle in a combination with each other. Although this has perceived advantages in its own right, the objective of separation of the gases produced by the electrolysis process is not achieved.

United States patent number 4,620,902 in the name of Tetzlaff et al teaches of an electrolysis process wherein electrolytic cells can be non- partitioned, or partitioned by separators such as ion exchange membranes. The non-partitioned electrolytic cells are membraneless as such, but the operation of the non-partitioned electrolytic cells are dependent on a long path terminating in restriction points within the cell that directs the flow of electrolyte, which significantly increases the pressure drop experienced within the system, potentially allowing for cross gas contamination within the cell, and therefore detrimentally affects the efficiency of the system. In this regard it is important to note that the flow path is very closely linked to the flow velocity of the electrolyte. Subsequently, if the flow path is too long, the occurrence of inactive flow regions are more prominent, which results in inefficient operation.

The direction of flow within the electrolytic cell in relation to the porous electrode is also required to be parallel to the so-called transport of charge and also parallel to the surface of the electrodes, which further limits the efficiency of the electrolytic cell.

OBJECT OF THE INVENTION It is accordingly an object of the invention to provide an apparatus, method and system for the production and separation of gases by way of electrolysis and associated steps, and to overcome the above disadvantages experienced with known electrolysers. SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an apparatus for separation of gases upon production by decomposition of an electrolytic solution, the apparatus comprising:

a sealed chamber for containing an electrolytic solution, the chamber further being provided with at least one inlet;

first and second tubular members projected into the chamber, the tubular members each being connected to a power supply pole located outside of the chamber;

an electrode assembly consisting of a first permeable electrode (anode) fitted to an operative end of the first tubular member causing circumferential positive charge at the first permeable electrode, and a second permeable electrode (cathode) fitted to an operative end of the second tubular member causing circumferential negative charge at the second permeable electrode, the arrangement of the electrode assembly causing the electrodes to be fully submerged in the chamber and spaced apart from and opposing each other resulting in an electrode gap between the first and second permeable electrodes; pressurised electrolytic solution introduced into the chamber via the inlet and passing from the chamber through the permeable electrodes and into the tubular members,

wherein upon supply of power to the tubular members, even current distribution across the electrodes and electrolysis of the electrolytic solution ensues, resulting in a first bi-phase flow consisting of fluid electrolytic solution and a first constituent gas through the first permeable electrode into the first tubular member, and a second bi-phase flow consisting of fluid electrolytic solution and a second constituent gas through the second permeable electrode into the second tubular member.

Further according to the invention, the permeable electrodes may comprise a conductive filtration mesh. Alternatively, the permeable electrodes may comprise a porous metallic foam. The apertures in the filtration mesh or metallic foam may have an absolute aperture micron rating ranging between 50 and 500 microns. The filtration mesh or metallic foam may be manufactured from a material selected from the group consisting of aluminium, nickel, platinum, titanium, stainless steel, palladium, ruthenium, iridium and cobalt.

Further according to the invention, the first bi-phase flow may comprise an oxygenated fluid, and the second bi-phase flow may comprise a hydrogenated fluid. The first constituent gas may be oxygen, and the second constituent gas may be hydrogen.

Further according to the invention, a plurality of electrode assemblies may be provided within the chamber. The plurality of electrode assemblies may be submerged in the pressurised chamber, and may be exposed to equal pressure within the chamber. The plurality of electrode assemblies may further be interconnected outside of the chamber at a second end of each of their respective tubular members.

Even further according to the invention, the power supply may provide a continuous or pulsed DC charge. The electrical potential of the DC charge may be between 1 and 12VDC. The power supply may be a fluctuating power source such as a renewable energy source, including solar power, hydropower or wind power. Alternatively, the power supply may be obtained from an electrical grid.

Even further according to the invention, the apparatus may be capable of immediate production and separation of gases upon supply of power to the tubular members.

The electrode gap may be in the range of 0.1 mm to 1 mm. Alternatively, the electrode gap may be in the range of 0.1 mm to 5mm depending on the application.

Still further according to the invention, the electrolytic solution may be potassium hydroxide (KOH), sodium hydroxide (NaOH), seawater or otherwise impure or contaminated water, including acid contaminated water. Stili further according to the invention, the tubular members may be substantially circular in cross section. Alternatively, the tubular members may be substantially oval, substantially rectangular or substantially square in cross section. An outer surface of the tubular members that is operatively exposed to electrolytic solution may be electrically isolated.

Yet further according to the invention, wherein the flow of electrolytic solution through the permeable electrodes removes gas accumulating on the electrodes, thereby increasing the current density threshold. The current density threshold may be 20 OOOmA/cm ² .

According to a second aspect of the invention there is provided a system for separation of gases upon production by decomposition of an electrolytic solution, the system comprising:

- the sealed container and the arrangement of first and second tubular members and the electrode assembly according to the first aspect of the invention, the sealed container being provided with pressurised electrolytic solution;

- a pump for regulating flow rate of electrolytic solution within the system;

- a heater for heating the electrolytic solution to an optimised temperature range;

- a power supply for facilitating electrolysis of the electrolytic solution; the arrangement being such that the pressurised chamber, pump, power supply, heater and arrangement of tubular members and the electrode assembly being arranged in a closed loop and in fluid flow communication with each other, wherein upon supply of power to the tubular members, even current distribution across the electrodes and electrolysis of the electrolytic solution ensues, resulting in a first bi-phase flow consisting of fluid electrolytic solution and a first constituent gas through the first permeable electrode into the first tubular member, and a second bi-phase flow consisting of fluid electrolytic solution and a second constituent gas through the second permeable electrode into the second tubular member.

Further according to a second aspect of the invention, the system may be provided with at least first and second gas/liquid separators for separating the first and second bi-phase flows into residue electrolyte which is fed back into the chamber via the inlet, and first and second constituent gases.

The system may be pressurised, and pressurised first and second constituent gases may be captured and contained in suitable pressurised containers.

Yet further according to the invention, the flow velocity may range between 0.01 m/s to 0.2m/s. The optimised temperature range for the electrolytic solution may be 20°C to 200°C. According to a third aspect of the invention there is provided a method for separation of gases upon production by decomposition of an electrolytic solution, the method including the steps of:

- introducing pressurised electrolytic solution into a chamber via at least one inlet;

- projecting first and second tubular members into the chamber,

- connecting the first and second tubular members to a power supply pole located outside of the chamber;

- fitting a first permeable electrode (anode) to an operative end of the first tubular member causing circumferential positive charge at the first permeable electrode, and fitting a second permeable electrode (cathode) to an operative end of the second tubular member causing circumferential negative charge at the second permeable electrode;

- submerging the electrodes within the electrolytic solution in the chamber and spacing the electrodes relative to each other to define an electrode gap between the electrodes;

- supplying power to the tubular members, which causes even current distribution across the electrodes and electrolysis of the electrolytic solution, resulting in a first bi-phase flow consisting of fluid electrolytic solution and a first constituent gas through the first permeable electrode into the first tubular member, and a second bi-phase flow consisting of fluid electrolytic solution and a second constituent gas through the second permeable electrode into the second tubular member.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now be described further by way of non-limiting examples with reference to the accompanying drawings wherein: figure : is a plan view of an exposed electrolyte chamber of an apparatus for producing and separating gases according to a first aspect of the invention; figure 2: is a detail view of one of the electrode assemblies contained within the apparatus of figure 1 , and further showing a cross-sectional view of the electrode assembly along line B-B'; figure 3: is a plan view of a lid placed on the electrolyte chamber of figure 1 to allow for the chamber to be pressurised; figure 4: is a cross-sectional side view along line A-A of the electrode assembly of figure 2, indicating the production and separation of gases in accordance with the apparatus, method and system of the invention; figure 5: is a schematic representation indicating the bi-phase flow of hydrogenated and oxygenated fluids pursuant to the production and separation of gases in accordance with the apparatus, method and system of the invention; and figure 6: is a schematic representation indicating a pressurised sealed system for the production and separation of gases, and subsequent capturing and pressurised containment of gases produced and separated by the apparatus, method and system of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

Referring to figures 1 to 6, an apparatus for producing and separating gas according to a preferred embodiment of the invention is generally designated by reference numeral 10.

The apparatus 10 comprises a plurality of electrode pole pairs 12 arranged in a chamber 14 having an inlet (not shown) for introducing electrolytic solution 18 into the chamber 14. In figure 1 , the chamber 14 is exposed to indicate the electrode configuration within the chamber 14. In use, chamber 14 is closed by lid 14.1 , as shown in figure 3, which allows for pressurising of the chamber 14. Conductive tubular members 20 and 22 project into the chamber and directly oppose each other.

A first permeable electrode is located at the operative end of tubular member 20, which is connected to the positive pole of a power supply at its exposed end on the outside of the chamber (not shown). A second permeable electrode is similarly located at the operative end of tubular member 22, which is connected to the negative pole of the power supply at its exposed end outside of the chamber (not shown).

The linear disposition of the permeable electrodes relative to each other causes the electrodes to be submerged in electrolytic solution 18 in chamber 14, and further leads to an electrode gap 28 to be present between the operative ends of the electrodes. The electrode gap 28 is in the form of an annular slit present between the permeable electrodes, the annular slit arrangement ultimately leading to elimination of preferential flow of electrolytic solution. The electrolytic solution is typically an alkaline water solution, and more specifically sodium hydroxide (NaOH), potassium hydroxide (KOH) or sea water.

In a preferred embodiment of the invention illustrated in figures 1 to 4, the chamber 14 is manufactured from polypropylene, stainless steel and nickel. Tubular members 20 and 22 are manufactured from nickel to allow electrical conductivity, whilst an outer surface 20.1 of tubular member 20, and an outer surface 22.1 of tubular member 22 is electrically isolated in order to prevent electrolysis occurring at these points. The exposed ends of tubular members 20 and 22 located outside the chamber 14 are threaded and complimentary threaded adjusting members 20.2 and 22.2 screw onto the tubular members 20 and 22 respectively to hold the tubular members in place, and to allow for adjustment of the permeable electrodes relative to each other, thereby increasing or decreasing the width of the electrode gap 28.

In this particular embodiment, as indicated in figure 4, filtration mesh 30 is fitted onto conductive heads 32 and 34, with conductive head 32 screwing onto tubular member 20, and conductive head 34 screwing onto tubular member 22. Polypropylene tensioning covers 40 screw onto conductive heads 32 and 34 respectively to tension and hold the filtration mesh 30 in place. In this particular embodiment, a circular aperture 24 of diameter 30mm is presented within a frontal aspect of the tensioning cover 40 of both the electrodes, which opening presents a permeable passage for flow of electrolytic solution through the permeable electrodes. A filtration mesh

30 is manufactured from nickel, and is typically of plain dutch weave type, with an absolute aperture micron rating of 120 microns and a warp and weft wire diameter of 0.35 mm and 0.25 mm respectively. When used as an electrode base material, the filtration mesh is preferably manufactured from nickel, stainless steel or titanium, whereas, when used as an electrode catalytic element, the filtration mesh is preferably manufactured from nickel, platinum, ruthenium, iridium, cobalt or aluminium (as standalone and as combinatorial catalysts and combinatorial catalysts of metal oxides and stand alone metal oxides). The filtration mesh is preferably manufactured from nickel, which assists in making the apparatus economically attractive, but other appropriate platinum group materials (PGM's) or metals such as stainless steel will also suffice. The warp to weft ratio is 1 10:24 wires per inch, but alternative warp to weft ratios are also foreseen. The conductive heads are manufactured from stainless steel or nickel. Nickel is utilised in respect of the anode, with a platinum coated base metal utilised in respect of the cathode. As shown in figure 2, a 30mm opening on the frontal aspect of the polypropylene tensioning cover 40 is exposed to enable the flow of electrolytic solution 18 through the electrodes 24 and 26 and into the tubular members 20 and 22. This particular embodiment consists of six electrode assemblies submerged in electrolytic solution 18 contained in a pressurised chamber 14, which allows flow in a non-preferential manner to the electrodes 24 and 26. It also allows for accurate adjustment and alignment of the electrode gap 28. In addition, the arrangement of the electrodes 24 and 26 relative to each other allows for electrolytic solution 18 to flow from the chamber 14 through the permeable electrodes 24 and 26 and into the tubular members 20 and 22 in directly opposing directions, with the peripheral flow of electrolytic solution 18 across electrodes 24 and 26 causing a uniform pressure drop across each electrode. The direct opposing bi-phase flow further prevents cross gas contamination.

When an electrical current is supplied to the conductive heads 32 and 34, the circumferential supply of positive electric charge at the circular anode 24 and concurrent negative electric charge at the circular cathode 26 provides for even current distribution across the electrodes. In the process, as depicted in figures 4 and 5, electrolysis of the electrolytic solution 18 ensues, resulting in a bi-phase flow consisting of oxygenated electrolytic solution 36 through the first permeable electrode 24 into tubular member 20, and a bi-phase flow of hydrogenated electrolytic solution 38 through the second permeable electrode 26 into the second tubular member 22. During electrolysis, formation of gas bubbles occur on both the anode 24 (oxygen), and cathode 26 (hydrogen). In general, gas formation on and between the electrodes of a known electrolyser can typically reduce the efficiency of the electrolytic process. However, according to the invention, no gas accumulation occurs between the electrodes. Therefore, when an optimal flow rate of electrolytic solution 18 is introduced, no gas is allowed to accumulate in the electrode gap, and the gas forming and accumulating on the filtration mesh 30 is instantly removed by the diverging flow of electrolytic solution through the filtration mesh 30, causing a negligible gas meniscus to form on the exposed ends of the filtration mesh 30 (i.e. relative to the electrode gap 28). This eliminates the potential effects of void fracture, allowing the electrodes to be placed as close as 0.1 mm apart, whilst still demonstrating stable performance and high hydrogen purity, for current densities as high as 20 000mA/cm2. Current density is determined as the ratio of the total current passing through a single pole pair of electrodes, to the flat cross sectional area available for charge transfer, which in this case is the 30mm cross sectional area of the mesh electrodes. An optimal flow velocity can range from between 0.01 m/sec to 0.2m/sec.

In a further embodiment of the invention, shown in figure 6, a system 50 for the production and separation of gases by the dissolution of an electrolytic solution and subsequent containment of such gases is shown.

Apparatus 10 according to the preferred embodiment of the invention is connected to a power supply, being a renewable power supply 52 (solar power, hydropower or wind power) or an electrical grid 54, with the positive pole connected to the anode of apparatus 10, and the negative pole connected to the cathode of apparatus 10. Upon electrolysis by apparatus 10, oxygenated electrolytic solution 56 is delivered to a separation system 58, where oxygen is separated from the oxygenated electrolytic solution by way of centrifugal forces, gravitational forces, filtration and surface tension, with electrolytic solution being reintroduced into the system by chemical pump 60. Hydrogenated electrolytic solution 62 is similarly introduced into separation system 64, and hydrogen is separated from the hydrogenated electrolytic solution by solution by way of centrifugal forces, gravitational forces, filtration and surface tension, with electrolytic solution being reintroduced into the system by chemical pump 60, which assists in increasing the temperature within the system. The system is a closed loop, and replenishment of electrolytic solution is accomplished by introducing fresh water into the system at an accessible point (not shown). A heater within the separation system (not shown) also heats the electrolytic solution to an optimal temperature range, which ranges from 20°C to 200°C. An increase in temperature causes a favourable increase in current density and subsequent efficiency of the system, and furthermore benefits the overall process by reducing the pressure drop of the solution by making the solution flowing through the mesh electrodes less viscous and thereby increasing the ease at which bubbles are evolved from the electrode surface, which in turn increases the effective reactive surface area. A nitrogen purge system 66 purifies the oxygen and hydrogen from contaminant atmospheric gases, and essentially pure oxygen gas 68 and hydrogen gas 70 is ultimately released. The oxygen gas 68 and hydrogen gas 70 may be contained in separate containers 72 and 74 and respectively be made available for use in appropriate applications. It is foreseen that the hydrogen gas 70 contained in containers 74 may be used for household applications 76, such as fuelling a vehicle or a fuel cell, or providing an alternative energy source. The system 50 is pressurised, and containers 72 and 74 may be filled utilising the pressure within the system, without having to incorporate alternative means for filling pressurised containers. It is accordingly asserted that the disadvantages associated with known devices for producing and separating gases could be alleviated with the device according to the invention.

In particular, the main disadvantages experienced with known electrolysers are overcome due to the apparatus, method and system not being dependent on a membrane or diaphragm. This causes a significant increase in lifespan and affordability of the apparatus and the method and system utilising the apparatus.

The disadvantage of having restriction points in a cell to guide electrolyte flow within a cell is overcome by the apparatus providing for electrode emersion in a pressurised chamber, and circumferential flow through the electrode gap and into the electrode. The flow of electrolytic solution parallel to the electrode causes an unwanted increase in flow path, with the apparatus according to the invention having a substantially shorter flow path, thereby avoiding dead fluid flow regions. The resistance generally experienced in the cell is therefore significantly reduced, leading to increased efficiency. Furthermore, no directional flow within the apparatus is required. By merely introducing electrolytic solution into the pressurised chamber, electrolytic solution is channelled into the circumferentially accessible electrode gaps and through the electrodes. Essentially pure hydrogen and oxygen gases may be obtained by utilising the invention, which gases may be used in alternative applications, and in particular in alternative energy applications in the case of hydrogen gas. The opposing pressurised flow of hydrogenated and oxygenated electrolytic solution prevents back flow of electrolytic solution and subsequent contamination of gases. The opposite flow of electrolytic solution further overcomes the disadvantages of ohmic drop contribution and performance threshold limitations of conventional electrolyse rs. Although the application of the apparatus, method and system of the invention is predominantly aimed at electrolysis of water for production and separation of oxygen and hydrogen gases from an electrolytic solution, it is further foreseen that the invention may be applied to other spheres, including electrolysis of sea water and for a multitude of purification purposes in acid mine water or otherwise contaminated water.

It is foreseen that industrial size usage of the apparatus, and method and system incorporating the apparatus may be pursued, but the apparatus, method and system according to the invention also lends itself to the commercialisation of a cost effective small scale hydrogen production plant for residential and neighbourhood use that will prove competitive with existing units that deliver similar hydrogen production rates. The absence of a membrane or diaphragm, the use of non-precious metal catalysts and the capability of operating at high current densities above current prior art operating limits, will work towards the development of a compact and cost effective alkaline electroiyser that has the potential of expanding the apparatus, method and system in accordance with the invention to additional markets.

It will be appreciated that in terms of the invention, variations in details are possible without departing from the scope of the appended claims.