An improved method for gas collection

Abstract

A gas collection system is disclosed comprising a siphon through which liquid flows. The siphon has an up leg and a down leg and an outlet located along the down leg of the siphon in fluid communication with the flowing liquid. A vacuum can be created at the outlet in the down leg of the siphon, the vacuum being collectable by a pump. A gas scrubber can be provided comprising a medium onto which gas is adsorbed. The vacuum collected by the pump at the outlet in the down leg of the siphon can be used to remove adsorbed gas from the medium.

Description

[0001] An improved method for gas collection

[0002] Technical field

[0003] The present invention relates to a siphon formed by fluid flow. In some aspects, the invention relates to the collection of dissolved gas(es) from a flowing liquid stream. In other aspects the invention relates to a vacuum that can form at the down leg of the siphon.

[0004] Background

[0005] Most water contains dissolved gases, such as oxygen and carbon dioxide, which are absorbed from the atmosphere. These gases dissolve in water due to the natural interactions between water molecules and gas molecules. The amount of dissolved gas depends on factors like temperature, pressure and the presence of other solutes.

[0006] Sometimes dissolved gases in water become problematic and the gases need to be removed or the concentration of the dissolved gas needs to be reduced. For example, high levels of dissolved oxygen can cause corrosion in pipelines and boilers. Excess dissolved carbon dioxide can lead to acidic conditions, which can harm aquatic life and damage infrastructure. Additionally, dissolved gases like hydrogen sulphide can produce foul odours and cause taste issues in drinking water.

[0007] Current methods for removing dissolved gases from water include aeration, vacuum degasification and chemical treatment. Aeration involves adding air to the water to strip out gases. Vacuum degasification uses a vacuum to lower pressure and release dissolved gases. Chemical treatments, such as using sodium sulphite, neutralise unwanted gases. These processes can be energy intensive.

[0008] Once removed, dissolved gases can be captured and repurposed. For example, oxygen can be used in medical applications and or industrial processes. Carbon dioxide can be used in carbonation for beverages or as a refrigerant. Captured gases can also be safely vented or stored to prevent environmental harm.

[0009] In some systems, separation or purification of gas(es) is achieved by scrubbing the gases with water. Water scrubbing techniques exploit differences in solubility among gases, such as the high solubility of carbon dioxide compared to oxygen or nitrogen. Operating the scrubber under elevated pressure can enhance absorption, and depressurisation may be used to release the absorbed gas for recovery or reuse. Alternatively, gas mixtures can be treated using solid-phase materials such as molecular sieves or other adsorbent media. These materials selectively capture gases based on molecular size, polarity, or other properties. Regeneration of the media may involve heating, purging, or applying a vacuum to release the captured gases and restore the material’s capacity for reuse.

[0010] There is a need for an improved method of gas collection that provides a useful commercial alternative to existing systems.

[0011] Summary of invention

[0012] In an aspect there is provided a system for isolating gas from a liquid having the gas dissolved therein, the system comprising: a gas isolation chamber having an inlet and an outlet, wherein the liquid flows past the inlet of the gas isolation chamber under the influence of a siphon and the dissolved gas moves from the liquid into the gas isolation chamber; wherein the gas in the gas isolation chamber is at a pressure below atmospheric pressure; a pump for pumping the gas out from the gas isolation chamber; increasing the pressure of the gas removed from the gas isolation chamber to atmospheric pressure; and optionally further increasing the pressure of the gas to above atmospheric pressure.

[0013] In an embodiment, the invention is characterised in that the gas is selectively pumped out of the gas isolation chamber. Thus, a selected gas can be substantially isolated from the liquid. In an embodiment, the gas isolation chamber is configured to cause the separation of CO2 and N2. The selected gas can therefore be CO2.

[0014] In an embodiment, the pump used to draw the gas from the gas isolation chamber is a vacuum powered gas pump. In an embodiment, the invention is characterised in that a vacuum is created at the down leg of the siphon, wherein said vacuum is used to power the vacuum pump and or any other vacuum pump used to increase the pressure of the gas removed from the gas isolation chamber. This can create a closed cycle system.

[0015] In an embodiment, there is no gas isolation chamber but a vacuum is created at the down leg of the siphon. The vacuum can be used to power a vacuum powered gas pump. The vacuum can be used in a further process. The further process can be a gas isolation process.

[0016] In another aspect there is provided a gas isolation system, the system comprising: a siphon through which liquid flows, the siphon having an up leg and a down leg; an outlet located along the down leg in fluid communication with the flowing liquid; a vacuum created at the outlet in the down leg, the vacuum being collectable by a pump or storable; a gas scrubber comprising a medium to which gas is adsorbed; wherein the vacuum collected by the pump is used to remove the adsorbed gas from the medium; and the gas is collected for further use.

[0017] Where there is a vacuum drawn from the siphon, the vacuum can be used in a gas removal process. The gas removal process can be CO2 scrubbing process where the vacuum is used to draw the CO2 molecules from a sieve bed. Other similar processes are within the spirit and scope.

[0018] The invention may, in embodiments, provide the advantage of the removal of gas from liquid / solid under circumstances where low energy input is required to do same. In some embodiments the process is free from the use of any electricity. While prior systems employ e.g. active sonic agitation and vacuum pumping to force degassing, the present system may advantageously enable passive gas separation sufficient for lower-throughput applications, avoiding the need for complex mechanical components.

[0019] The liquid from which gas is removed can be any medium in or on which there is an adsorbed or a dissolved gas. For example, solvents like water, ethanol, acetone and hexane can comprise dissolve gases such as oxygen, nitrogen and carbon dioxide. The solubility of gases in liquid solvents depends on factors like temperature, pressure and the specific properties of the solvent. Any liquid can be subject to the invention provided it is flowable. In one or all embodiments, the liquid is substantially aqueous. The liquid can be water. The water can be any type including but not limited to drinking water, seawater, river water, grey water, distilled water, spring water and wastewater.

[0020] Depending upon the liquid, the gas can be one or more selected from carbon dioxide (CO2) or oxygen (02). Other possible target gases (for removal from bodies of water) include: nitrous oxide (N20), radon (Rn), xenon (Xe), hydrogen (H2), krypton (Kr), neon (Ne), sulphur dioxide (S02), helium (He), argon (Ar), ammonia (NH3), hydrogen sulphide (H2S), methane (CH4), nitrogen (N2). Other gases are within the spirit and scope provided they are dissolvable in liquid and removable using the method as herein described.

[0021] In some embodiments, the focus is on the isolation of super pollutants such as nitrous oxide and methane. Climate super pollutants are warming agents that are far more potent than carbon dioxide per ton. They include methane, tropospheric ozone and its precursors (such as carbon monoxide and volatile organic compounds), fluorinated gases (F-gases; such as HFCs), nitrous oxide, and black carbon.

[0022] The liquid can be saturated with the dissolved gas(es). The liquid can have some gas dissolved therein. There can be one gas type dissolved in the liquid. The liquid can comprise more than one gas. In the present description, reference to gas may mean one or more gases unless the context makes clear otherwise. The liquid can be from a manmade source. The liquid can be from a natural source.

[0023] In an embodiment, the liquid in the system can be caused to flow past an inlet of a gas isolation chamber. The gas isolation chamber can be any enclosed chamber suitable for holding a gas. The gas isolation chamber if present is substantially airtight. The walls of the gas isolation chamber can be solid. The walls of the chamber can be insulated. The walls of the gas isolation chamber can be flexible. The gas isolation chamber can be inflatable. The gas isolation chamber can have an internal volume in the range of from about 100 to 500 cm3. However, it should be understood that in some embodiments, the chamber will be smaller where the siphon is small, and the gas volume is low. In some embodiments, the chamber can have a larger volume where the amount of gas to be collected is larger. The volume of the gas isolation chamber can be adjustable by a volume reducing means. The volume reducing means can be a diaphragm or other movable wall.

[0024] In an embodiment, the gas isolation chamber has a first section in fluid communication with the liquid, and a second section in fluid communication with the first section. The first section and second section can be joined by a passageway of narrow diameter.

[0025] The chamber can be made from any suitable material including plastic, metal or other. In an embodiment, the gas isolation chamber can be made from a polymer such as polyethylene which is corrosive resistant, low cost and widely used in engineering projects. Steel or other high strength materials will be required for any large diameter components at deep vacuum to prevent implosion.

[0026] For application on the ocean or other large waterway, the system will likely be mounted on a barge, ship or disused oil platform or similar.

[0027] The gas isolation chamber has an inlet. The inlet can allow gas or gases to pass into the gas isolation chamber. The inlet can comprise a valve. The valve can be a one-way valve that allows gas to enter the chamber but not to exit though the same pathway. In one or all embodiments, the inlet is not associated with a valve and instead the gas collects into the chamber and remains in the chamber once collected. The gas isolation chamber has an outlet. The outlet can allow the gas to pass out of the chamber. The outlet can comprise a valve. The valve can be operable to only allow exit of gas when demanded by an operator. The gas can be removed on demand by a pump.

[0028] Initially, the gas isolation chamber with no valve at the inlet will be filled or at least partially filled with the flowing liquid as it moves past the inlet. As the gas passes from the liquid into the gas isolation chamber, the volume of gas above the liquid in the gas isolation chamber will naturally increase. The liquid level will correspondingly drop. A float in the liquid can be used to determine the liquid level and thus the gas volume in the gas isolation chamber. The float can be used to ensure gas is extracted once the level of gas in the chamber reaches a certain level / pressure. The float can ensure that only gas is extracted by a vacuum- powered gas pump, by making sure there is only gas / air at the level of the outlet. The gas can be extracted once the gas has filled about 50% to about 100%, such as 75% to about 90%, of the total available space in the gas isolation chamber. However, this range can be adjusted depending on the system operation and parameters.

[0029] The liquid is caused to flow past the inlet of the gas isolation chamber by any means. In one or all embodiments, the liquid is flowing under natural forces, such as a working head on a weir or in a flowing stream. In one or all embodiments, the liquid is pumped to cause it to flow.

[0030] In an embodiment, the liquid flow adjacent the gas isolation chamber is due to a siphon effect. A siphon is a system that transfers liquid from a higher elevation to a lower elevation using a tube together with the principles of gravity and atmospheric pressure. To operate a siphon, the tube is initially filled with liquid (primed), with one end (upper leg) submerged in a high container or body of liquid and the other end (down leg or lower leg) placed in a lower container or body of liquid. Once primed, gravity causes the liquid to flow continuously from the higher liquid level, over the elevation difference, along the lower leg and into the lower liquid level, as long as the outlet end remains below the liquid level of the higher container. The siphon can be created in a natural waterway by making use of a weir or dam to create water levels at different heights. The siphon can be created using containers of liquid arranged as described in a commercial or industrial set up.

[0031] In an embodiment, the siphon described for use herein can be caused to operate in the absence of a working head provided by the higher water level. The siphon effect can be generated by a pump such as an electrical pump or an air pump. Alternatively, the siphon can be created by providing check valves in the downcomer or lower leg of the siphon to create a chamber where air is cyclically blown in and sucked out. The air can be blown in and sucked out by a pump. The pump can be a wind-powered compressor to drive a pump such as a diaphragm pump. Alternatively, the movement of air can be generated by a natural motion such as a wave in the sea or ocean or other large water body. The rise and fall of the wave can change the air pressure in the head of a vessel. The vessel can be referred to as an Oscillating Water Column wave energy converter. The Oscillating Water Column wave energy converter can be caused to cycle the water through the siphon in the absence of a working head. Essentially, this uses the energy of the wave as the wave passes to move the water in the siphon.

[0032] In the present system, gas separation can be achieved without requiring boiling or a Torricelli vacuum. Instead, a gas isolation chamber is positioned such that liquid naturally enters the chamber as it flows through the system. Dissolved gas is released from the liquid into the chamber under normal flow conditions, accumulating in the space above the liquid. The present configuration can in embodiments enable passive gas separation and controlled extraction without the need for elevated vertical lift or pressure-induced boiling.

[0033] The passageway of the siphon can be formed by a tube. The tube can have any cross section. The tube can have a diameter in the range of from about 200mm to about 3000mm. The diameter of the siphon tube is not limited and can be any that is suitable to cause the siphon effect. The siphon can include one or more constrictions therein which affects fluid flow.

[0034] As described herein the siphon has an upper or up leg and a down leg or down comer. There is also a substantially horizontal section joining the pair of legs. In an embodiment, the substantially horizontal section is curved. In an embodiment, the substantially horizontal section has the same diameter as the pair of siphon legs. In an embodiment, the horizontal section of the siphon has a larger diameter than the pair or legs. In an embodiment, the cross-sectional area of the siphon is increased at the top substantially horizontal section. This can cause the water flow to slow to allow more time for the outgassed gas bubbles to rise. This could include partitioning the pipe so that the bubbles do not have to traverse the whole pipe diameter. In an embodiment, therefore, the horizontal section of the siphon is horizontally segmented. The large diameter and the segments could increase the collection efficiency of the gases coming out of solution.

[0035] Water passes up through the siphon and past the inlet of the gas isolation chamber, if present, experiencing a reduction in pressure due to conservation laws. This reduction in pressure, caused by the siphon, is thought to cause dissolved gases to move to the gas phase and collect in the chamber. If the partial pressure of the dissolved gas in the liquid is higher than in the gas isolation chamber, the gas from the chamber will tend to diffuse into the chamber to reach equilibrium. This is driven by the natural tendency of substances to move from areas of higher concentration to lower concentration. This mixture of gases collects in the gas isolation chamber which can, in some embodiments, be above the siphon.

[0036] The gas isolation chamber can be located at the head of the siphon, along the substantially horizontal section, to collect the rising gases through the inlet. The pressure in the gas isolation chamber can be set at a low pressure relative to ambient pressure to encourage the gas to move into the chamber. Gases tend to move from areas of higher pressure to areas of lower pressure. The low pressure in the gas isolation chamber can be established by a vacuum powered gas pump. However, gas will move from the liquid to the gas isolation chamber even if the pressure therein is not reduced. It may be preferable from an energy input point of view not to lower the pressure in the chamber.

[0037] In an embodiment, the liquid is modified prior to entering the system. In an embodiment, the modification is acidification. The liquid can be acidified on entry to the siphon, and de-acidified on exit to increase the collection efficiency of gas such as CO2.

[0038] In an embodiment, the gas isolation chamber is configured to allow for selective gas isolation. The chamber can comprise a volume reducing means such as a diaphragm that reduces the volume of the chamber so that more soluble gases such as CO2 remain in solution, while other less soluble gases such as N2 fill the chamber. This selective isolation of gases will be effective where there are two or more gasses which have differing solubilities. This approach exploits the higher solubility of gases such as CO2 relative to gases such as N2. This approach can mean that separate scrubbing of a gas is not required. It is postulated that this approach is also more energy efficient than using a separate scrubber because it partially separates N2 and CO2 as the gas is brought up to atmospheric pressure. Therefore, the maximum pressure required to achieve a given separation is reduced.

[0039] The gas or mixture of gases once collected in the gas isolation chamber is typically at a low pressure. Once collected, the pressure of the gas in the gas isolation chamber can be in the range of from about 0.1 to about 0.5 bar, such as 0.2 to 0.3 bar.

[0040] The pressure of the collected gas can be increased. The pressure of the collected gas can be increased to atmospheric pressure (about 1 bar). The pressure of the collected gas can be further increased to above atmospheric pressure to provide a pressurised gas. The pressure of the gas once further pressurised can be at least about 5, 10, 12 or 15 bar.

[0041] Gas can be pressurised by various means. Compression is commonly used, where gas is compressed into a smaller volume using compressors or pumps, increasing its pressure according to Boyle's Law. In the present process, the collected gas can be pressurised by any means. In an embodiment, the collected gas is pressured by a pump. The pump can be a vacuum powered gas pump. These pumps are simple, reliable and do not require electricity, making them suitable for various applications where a vacuum is needed to manipulate gases efficiently. In the present system, as described, after gas is passively collected in the gas isolation chamber under low-pressure conditions, it is pressurised to facilitate downstream use or storage. This approach may provide flexibility in managing the collected gas, allowing it to be delivered at atmospheric or elevated pressures, for example, at least about 5 to 15 bar, depending on application requirements. Unlike prior systems which continuously maintain low pressure within the collection chamber to sustain degassing, the present system may allow for controlled accumulation of gas followed by pressurisation. This contrasts with systems such as siphon degassers relying on continuous vacuum extraction, where gas is immediately and continuously removed to maintain low-pressure degassing conditions, inherently preventing pressurisation of collected gas. By enabling selective pressurisation post-collection, the present system may provide operational advantages, including simplified gas handling, energy-efficient storage and adaptability to end-use applications, without the complexity of maintaining constant low-pressure gas removal.

[0042] In the present system, the flow of the liquid through the siphon system can be used to create a vacuum. The creation of a vacuum is at a location in the siphon along the down leg. The vacuum created can be used to power the vacuum powered gas pump. The vacuum created can be used in another gas removal process.

[0043] The vacuum created at the down leg can be at least about -40, -50, -60, -70 or -80 kPa, depending on the siphon height and flow conditions. For example, assuming a maximum height of 10 metres and accounting for a loss of about 2 metres due to a high-radius curve to maintain laminar flow, the vacuum can reach approximately - 80 kPa. The vacuum can be increased by an intensifier. The intensifier can be a hydraulic pump intensifier. The vacuum can be intensified to about 85, -90 or -95 kPa.

[0044] In certain embodiments, therefore, the system comprises a siphon having a down leg positioned downstream of a gas isolation chamber, wherein the down leg includes at least one vacuum draw-off port or outlet positioned along its length. Due to the elevation of the down leg relative to the outlet, fluid flowing through the down leg is under sub-atmospheric pressure. The vacuum draw-off outlet can be positioned at a location of reduced pressure and the vacuum can be collected.

[0045] In some embodiments, the same or an additional gas port along the down leg can be configured for injection of gas into the flowing liquid stream. The injected gas could be oxygen recycled into the system to facilitate gas reintroduction or oxygenation of the liquid.

[0046] The siphon pipe(s) can include a constriction. Even without a constriction in the pipe, the pressure in the pipe will be below atmospheric pressure due to the fact it is elevated relative to the outlet. When water flows through a constricted pipe or nozzle, according to Bernoulli's principle, its speed increases and its pressure decreases. Accordingly, the down leg of the siphon can include one or more constrictions. The decrease in pressure in a flowing liquid can create a partial vacuum at the narrowest point of the constriction. Making use of the Venturi effect, the constriction can cause a deeper vacuum at the location of draw. Thus, the siphon can be used to create a vacuum which can optionally be used to power the vacuum powered gas pump described above and in embodiments the separation process in the gas isolation chamber; and or the vacuum can be used for some other purpose such as the removal of gas from a gas scrubber apparatus.

[0047] In some embodiments, at the location of the vacuum draw in the down leg of the siphon, there can also be the injection of a gas into the flowing water. The injected gas could be, for example, oxygen to oxygenate the water. The oxygen could be a gas isolated by the present process and recycled into the flowing water.

[0048] The system can include either a single siphon system. The system can include one or more such as multiple siphon systems arranged in parallel. Optimal efficiency for weir height is expected at about 2 meters. Therefore, in locations with a total available fall of about 20 meters, it would be feasible to install up to 10 siphons in series, with the outlet of each upper siphon discharging into a pond that serves as the inlet for the next siphon downstream. This arrangement aims to maximise the volume of air transferred per unit volume of flowing water. In some embodiments, there can be a central elevated water tower and a surrounding array of progressively shorter ground mounted water towers arranged in a configuration such as a helical or spiral configuration. Each water tower can be coupled to a siphon. The down leg of each siphon can generate a vacuum. The vacuum could be used as described herein. Alternatively, or in addition, the vacuums generated from each siphon could be used to drive one or more hydrogenerators. The cumulative energy generated from multiple hydrogenerators could be used to pump the water from the ground mounted water tank, back up to the central tank, for the next cycle. This would provide a self-sustaining closed-loop system for distributed gas separation and capture. The pump powered by the siphons can contribute to one or more other pumps also operating in the system. There could be up to 10 to 20 or 25 to 30 siphons (or more) attached to a number of water tanks operating in series, each with head such as a 2m head.

[0049] In an embodiment, there is transfer of heat to one or more siphons. Heat transfer can be by immersing the siphon into warmer water outside the siphon.

[0050] A mixture of gases withdrawn from the one or more siphon systems can be pressurised and then sent to a scrubber. The scrubber can be to concentrate one or more target gases. In an embodiment the target gas is CO2. Scrubbers are known that are designed to selectively concentrate CO2. These systems typically involve chemical absorption processes where CO2 is captured from a gas stream and then concentrated for further use or sequestration. The scrubber can enrich the CO2 in a gas stream.

[0051] One exemplary scrubber is a water scrubber, so the medium to which the gas is associated is water. The working principle can be the same as the ocean absorption of CO2 in water, where it is noted that CO2 has a much higher Henry solubility than other gases in water. The non-condensable gas mixture from the siphon system can be fed to the intake of a compressor that compresses the mixture to about 10, 15 or 20 bar. The compressed non-condensable gas mixture is introduced into an absorber column, where pressurised sorbent water can be injected at the top in counterflow with the gases. The CO2 is absorbed into the water, while the nitrogen and oxygen for a large part are not absorbed and exit the column at the top. The waste gases are then led over an expander to regain a large part of the compression energy. The CO2 dissolved in the recycle water is depressurised in a flash vessel, where CO2 is flashed out of the recycle water as a result of depressurisation. The recycle water can then be again pumped to the absorber to take up new CO2. The compressor and expander can be thermally coupled to each other; the compression heat of each compression stage can be delivered to the expander stages in order to approach a reversible, isothermal compression for at least the nitrogen part.

[0052] Other scrubbers or gas isolation techniques are within the spirit and scope. For example, to specifically remove oxygen from a gas mixture, there are various methods can be employed. Chemical absorption could be used, making use of sodium sulfite solutions. Alternatively, iron powder or other known oxygen sorbents or scavengers can effectively remove oxygen. The choice of method can depend on the oxygen concentration, the composition of the gas mixture and operational requirements.

[0053] In certain embodiments, the system includes a gas scrubbing unit comprising a sieve bed configured to selectively adsorb a gas such as carbon dioxide from a gas stream. The sieve bed can contain an adsorbent material, such as a silica bead, zeolite or amine-functionalised solid, having a high surface area and chemical affinity for the desired gas e.g. carbon dioxide. During operation, the gas stream is directed through the sieve bed whereby the target gas is retained on the adsorbent surface while other gases pass through. This Direct Air Capture approach will eventually require desorption of water off the silica bead (or similar desiccant) bed when it becomes saturated. This removal of water and gas can be achieved with high heat. However, using the present invention in embodiments the removal can be achieved with a deep vacuum. Accordingly, the system can be configured to regenerate the sieve bed by applying a regeneration cycle in the form of a vacuum swing process, to release the adsorbed gas for collection or disposal. In an embodiment, the vacuum collected from the siphon is used in the vacuum swing process. A hydraulic intensifier can be used to deepen the vacuum to e.g. get a very deep e.g. -95 kPa vacuum. Carbon dioxide (CO2) can outgas from seawater when deep cold water is brought to the surface, as occurs in Ocean Thermal Energy Conversion (OTEC) systems. The reduction in pressure and increase in temperature causes dissolved CO2 to become less soluble and be released from the water. Dissolved carbon dioxide will begin to outgas naturally as deep ocean water rises and experiences a pressure drop. The present siphon system may provide a controlled low-pressure region that can receive the deep cold water and then assist in localising the degassing of the CO2. The vacuum in the down leg of the siphon may facilitate more efficient gas release from the deep cold water. Furthermore, the system may enable a more effective capture of the outgassed CO2 into a gas isolation chamber for recovery or further processing. The present system, in embodiment, may enhance the OTEC efficiency by recovering and reusing the degassing gases that are otherwise lost or vented during the process.

[0054] If the system is used to isolate oxygen, the oxygen could be reintroduced into a waterway. Fish require dissolved oxygen to grow and thrive. Dissolved oxygen improves the feed conversion efficiency, the key metric in a profitable aquaculture venture. The present system can in embodiments reduce two significant input costs: energy consumption and oxygen purchases. In wastewater treatment plants, aeration provides oxygen to bacteria for treating and stabilising wastewater. Oxygen can be provided through aeration via paddle wheels and pumped oxygen.

[0055] If the system is used to isolate CO2, then the gas could be on-sold to industrial gas buyers. CO2 can be produced as a by-product of an ammonia synthesis process in petrochemical plants, then purified and sold to (for example) beverage manufacturers. The present system can provide industrial gases such as CO2 that come from nature positive sources, such as ocean decarbonisation.

[0056] Decarbonisation as a source of CO2 may also be attractive since oceans are getting increasingly acidic, which reduces its ability to absorb CO2 from the atmosphere, while also harming marine life. The present system may provide a low energy method of decarbonising the ocean (or other waterway), allowing dissolved gases such as CO2 to be removed from the ocean in a nature positive way.

[0057] The present system can be used for denitrification. The present system can be used for deacidification. A volume (cubic meters) of excess / harmful gases could be removed from e.g. which may involve the protection, rehabilitation and remediation of natural environment. In another embodiment, the system can be installed into a waste water treatment plant. The system could be used to assist in the reduction in volume of fugitive emissions of super pollutants (i.e. methane) which is produced in huge volumes at such locations sites. The water coming out of the siphon will be lower in N2 content and less acidic than the water entering the siphon which also may be valuable in its own right, irrespective of what happens to the extracted gas.

[0058] In embodiments, the present system requires close to zero energy to generate or extract gases. The present system can, in embodiments, be used to restore and enhance the health of water bodies through innovative biogeochemical interventions. Leveraging advanced scientific principles and cutting-edge technologies, issues such as pollution, molecular imbalances, and habitat degradation can be addressed to improve water quality and ecosystem resilience.

[0059] Brief Description of the Figures

[0060] Embodiments of the invention will now be described with reference to the accompanying drawings which are not drawn to scale and which are exemplary only and in which:

[0061] Figure 1 is a schematic of a system according to an embodiment.

[0062] Figure 2 is a is a schematic of a system according to an alternative embodiment.

[0063] Figure 3 is an embodiment of the present system making use of a CO2 scrubber for the collected gas, and in which there is a vacuum powered gas pump.

[0064] Figure 4 is an embodiment showing selective gas removal.

[0065] Figure 5 is a close up of an embodiment of the gas isolation chamber of Figure 4 over the stages of an embodiment of the process. Figure 6 is a schematic showing vacuum draw.

[0066] Figure 7 is a schematic showing an alternative embodiment of vacuum draw.

[0067] Detailed Description of Embodiments of the Invention

[0068] Figure 1 shows an embodiment of a siphon system 10 according to one embodiment. To operate a siphon, the tube 14, 16, 18 is initially filled with water (primed), with one end (upper leg) 14 submerged in a high container or body of water and the other end (down leg or lower leg) 16 placed in a lower container or body of water. Once primed, gravity causes the liquid to flow continuously from the higher water level 14, around the top of the siphon 18 over the elevation difference, along the lower leg 16 and into the lower water level, as long as the outlet end remains below the water level of the higher water level. The siphon shown can be created in a natural waterway such as a river by making use of a weir 15 to create the water levels at different heights.

[0069] In the embodiment shown in Figure 2, the siphon system 10 can be caused to operate in the absence of a working head provide by the higher water level. In this embodiment, the siphon effect can be created by providing check valves 30 in the downcomer leg 16 of the siphon to create a chamber where air is cyclically blown in and sucked out. The Figure shows that in an embodiment, the rise and fall of a wave can change the air pressure in an Oscillating Water Column wave energy converter 32. The Oscillating Water Column wave energy converter 32 can be caused to cycle the water through the siphon 10 in the absence of a working head.

[0070] As shown, the siphon has an upper leg 14 and a down leg 16. There is also a substantially horizontal section 18 joining the pair of legs. In an embodiment, the substantially horizontal section is more curved than shown in the Figures.

[0071] The water 12 can flow past an inlet 17 of a gas isolation chamber 20. The gas isolation chamber 20 is located at the head of the siphon, along the substantially horizontal section 18, to collect the rising gases through the inlet 17. The inlet 17 allows gas 28 or gases to pass into the gas isolation chamber 20. The inlet is open so that the water can flow into the gas isolation chamber 20 as shown. The gas isolation chamber 20 is suitable for holding a gas 28. In an embodiment, as shown in Figure 4 and Figure 5, the gas isolation chamber 20 has a first section C2 in fluid communication with the water, and a second section C1 in fluid communication with the first section C2. The first section and second section can be joined by a passageway of narrow diameter. The volume of the gas 28 is the second section C2 can be adjustable by a volume reducing means 34.

[0072] The gas isolation chamber 20 has an outlet 26. The outlet 26 can allow the gas 28 to pass out of the chamber 20. The outlet 26 can comprise a valve. The valve can be operable to only allow exit of gas 28 when demanded by an operator. The gas 28 can be removed on demand by a pump.

[0073] As the gas 28 moves from the water to the gas isolation chamber 20, the volume of gas 28 above the water in the gas isolation chamber 20 will naturally increase. A float 22 in the water can be used to allow gas to be extracted once the level of gas 28 in the chamber 20 reaches a certain level / pressure. The float 22 can ensure that only gas 28 is extracted by a pump.

[0074] In the embodiment shown in Figure 5, the gas isolation chamber 20 is configured to allow for selective gas isolation. Initially, chambers C1 and C2 are filled with water. Gases CO2 and N2 move from the water into chamber C1 gradually increasing the gas volume. The pressure in chamber C1 may rise slightly (but still be at deep vacuum) as gas collects in the chamber. This is because the pressure is defined by the height of the isolation chamber above the water level at the outlet and gravity and the density of the fluid. Diaphragm 34 can be used to decrease the volume of chamber C1 which causes the more soluble gas CO2 to redissolve into the water in chamber C2. The remaining N2 can be extracted by opening valve (4). CO2 can then be allowed to re-enter the chamber for removal. This approach exploits the higher solubility of gases such as CO2 relative to Nitrogen. In this approach a separate scrubbing step may not be required since the gas extracted is not a mixture of gases. The gas 28 or mixture of gases 28 once collected in the gas isolation chamber 20 is typically at a low pressure. Once collected, the pressure of the gas 28 in the gas isolation chamber 20 can be in the range of from about 0.1 to about 0.2 bar. The pressure of the collected gas 28 is increased. As shown in kju, this can be undertaken by a vacuum powered gas pump. Alternatively, an air pump or an electrical pump could be used. A first pump can increase the pressure of the collected gas 28 to atmospheric pressure (1 bar). A second pump can increase the pressure of the collected gas 28 to above atmospheric pressure (about 10 bar).

[0075] In an embodiment of the present system, the flow of the water through the siphon system 10 is used to create a vacuum that powers at least one of the vacuum powered gas pumps in the system 10. As shown in Figure 1 and Figure 3, the creation of a vacuum can be undertaken at a location 24 in the siphon along the down leg 16. Due to its height above the outlet, in accordance with conservation laws or Bernoulli's principle a suction or draw in air (vacuum 19) is created at the down leg 16. Thus, the siphon 10 can be used to create a vacuum 19 which can be used to power the vacuum powered gas pump described above.

[0076] The system 10 as described can comprise one siphon or a plurality of siphons. The mixture of gases withdrawn from the one or more siphons can be collected, combined and pressurised and then sent to a scrubber.

[0077] In Figure 3, the gas collection is shown on the left side of the graphic. The scrubber is shown on the right side of the graphic. The lines show the travel of the gas in the overall system. The non-condensable gas 28 mixture from the siphon system 10 can be fed to the intake of a compressor that compresses the mixture to about 10 to 20 bar. The compressed non-condensable gas mixture is introduced into an absorber column 40, where pressurised sorbent water can be injected by a pump at the top in counterflow with the gases. The CO2 is absorbed into the water, while the nitrogen and oxygen for a large part are not absorbed and exit the absorber column 40 at the top. The waste gases are then led over an expander 42 to regain a large part of the compression energy. The CO2 dissolved in the recycle water is depressurised in a flash vessel 44, where CO2 is flashed out of the recycle water as a result of depressurisation. The recycle water can then be again pumped to the absorber 40 to take up new CO2. The depressurisation can be provided by a vacuum pump No3. The vacuum for the pump can be provided by the down leg of the siphon.

[0078] In Figures 5 and 6, the system includes a gas scrubbing unit 60 comprising a sieve bed 64 configured to selectively adsorb a gas such as carbon dioxide from a gas stream. The sieve bed 64 can contain an adsorbent material, such as a zeolite or amine-functionalised solid, having a high surface area and chemical affinity for the desired gas e.g. carbon dioxide. During operation, the gas stream is directed through the sieve bed 64 whereby the target gas is retained on the adsorbent surface while other gases pass through. The system can be configured to allow the vacuum draw 70 at the outlet 72 on the down leg 16 to draw the gas over the sieve bed.

[0079] The gas can pass through a hydraulic intensifier 62. The hydraulic intensifier 62 or which can operate by converting low-pressure hydraulic fluid into high-pressure output on the gas side using differential piston areas. Hydraulic fluid drives a large- diameter piston, which is mechanically linked to a smaller-diameter piston in contact with the gas, thereby generating a strong vacuum through force multiplication. In the depicted system, the intensifier reduces the gas pressure to e.g. about -85, -90, -95 kPa. Following CO2 removal, the gas can flow through water selective silica beads 66 which adsorb moisture (H2O), ensuring the gas stream is at least partially dried before further processing. A final filtration stage 68 removes particulate contaminants from the now-cleaned gas before it is released or used.

[0080] In an embodiment not shown the vacuum draw 70 can also be used to regenerate the sieve bed 64 by applying the vacuum to the sieve bed 64.

[0081] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

[0082] Any promises made in the present description should be understood to relate to some embodiments of the invention, and are not intended to be promises made about the invention as a whole. Where there are promises that are deemed to apply to all embodiments of the invention, the applicant / patentee reserves the right to later delete them from the description and does not rely on these promises for the acceptance or subsequent grant of a patent in any country.

Claims

CLAIMS1. A gas collection system, the system comprising: a siphon through which liquid flows, the siphon having an up leg and a down leg; an outlet located along the down leg of the siphon in fluid communication with the flowing liquid; a vacuum created at the outlet in the down leg of the siphon, the vacuum being collectable by a pump; a gas scrubber comprising a medium onto which gas is adsorbed; wherein the vacuum collected by the pump at the outlet in the down leg of the siphon is used to remove adsorbed gas from the medium; and the gas is collected for further use.

2. The system of claim 1 , wherein the gas scrubber is a CO2 gas scrubber and the medium is a molecular sieve; and the gas collected for further use is CO2.

3. The system of claim 1 , wherein the gas scrubber is a water scrubber and the medium is water; and the gas collected from the water for further use is CO2.

4. The system according to any one of the preceding claims, wherein there is at least one constriction in the siphon.

5. The system according to any one of the preceding claims, wherein the siphon is formed by an Oscillating Water Column wave energy converter.

6. The system according to any one of the preceding claims, wherein the siphon has an up leg and a down leg and a horizontal section joining the up leg and the down leg, wherein the horizontal section of the siphon has a larger diameter than the upper leg or the down leg.

7. The system according to any one of the preceding claims, wherein the siphon has an up leg and a down leg and a horizontal section joining the up leg and the down leg, wherein the horizontal section of the siphon is horizontally segmented.

8. The system according to any one of the preceding claims, wherein the collected vacuum is intensified to about 85, -90 or -95 kPa.

9. The system according to any one of the preceding claims wherein the liquid flow through the siphon is at least partially from deep in the ocean using an Ocean Thermal Energy Conversion technique.

10. The system according to any one of the preceding claims wherein there is more than one siphon each in fluid communication with the other arranged in series.11 . The system of claim 10 wherein the siphons are arranged in a spiral or helical shape in series.

12. The system of claim 10 or 11 , wherein vacuum collected is used to power a hydrogenator, wherein the hydrogenator can be used to pump liquid flow to the first siphon in the series.

13. A siphon comprising a pipe system configured for use in the system of any one of the preceding claims.

14. Gas when produced by the system of any one of claims 1 to 12.

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