Nanobubble generation system

Abstract

A nanobubble generation system in which a nanobubble generator receives liquid and gas at inlet ports and outputs liquid containing gas nanobubbles and large bubbles. A separator separates large gas bubbles from the liquid and returns the excess gas via a gas recycling path to the nanobubble generator. The system may have one, two or more nanobubble generators and one, two or more separators which return excess gas to selected nanobubble generators. The system produces high dissolved gas concentrations with high gas use efficiency. There is also disclosed a method of recovering excess oxygen gas from an irrigation system.

Description

[0001] Nanobubble Generation System

[0002] FIELD

[0003] This invention relates to a nanobubble generation system.

[0004] BACKGROUND

[0005] Nanobubbles are nano scale bubbles in a liquid, commonly used to refer to bubbles of a size up to 200nm, but sometimes also including bubbles up to 999nm. Nanobubbles are an effective mechanism for mass transfer of gas to liquid to obtain high dissolved gas concentrations up to six times the concentration of dissolved gas that water can hold under normal circumstances (i.e. from lOmg / litre O2 to 20-60mg / litre O2). Furthermore, nanobubbles have a strong bubble surface charge to repel each other, consequently reducing coalescence and staying in suspension for weeks or months as not exposed to the atmosphere.

[0006] Oxygen nanobubbles may be employed in water delivered by horticultural and agricultural irrigation systems. Nanobubbles in water have a mild oxidative effect that provides a long lasting chemical free treatment against a wide range of pathogens that negatively impact both plant and animal health. In agricultural applications this can reduce methanogens in animal rumens. In horticultural applications oxygen nanobubbles can improve plant growth rate and yield due to the provision of high levels of oxygen and oxygen nanobubbles to the root zone, delivered by water.

[0007] Current nanobubble generation systems used in irrigation systems simply inject gas (typically oxygen for irrigation) into liquid (water for irrigation) and any excess gas that is not dissolved or suspended in the liquid (especially as nanobubbles) is lost and considered wasted. A nanobubble generator has a "gas use efficiency" being the percentage of gas injected into a constant liquid stream through a nanobubble generator which is dissolved into the liquid or suspended as nanobubbles. For a constant water flow rate, a lower gas injection rate will produce a greater gas use efficiency (less gas as percentage wasted) but the liquid will have a low dissolved gas and nanobubble concentration. A greater gas injection rate will produce a lower gas use efficiency (more gas as percentage wasted) but the liquid will have a higher dissolved gas and nanobubble concentration. An operator must therefore make a trade-off as to whether they want a higher gas injection rate with greater biological and nanobubble advantages but lower gas use efficiency or a lower gas injection rate with lower biological and nanobubble advantages but a higher gas use efficiency.

[0008] For the purpose of this specification, and unless otherwise noted, "large bubbles" refers to any bubble size greater than a nanobubble, this includes micro bubbles as defined lpm-lOOpm diameter, fine bubbles defined as 100 pm -3 mm and course bubbles defined as >3mm.

[0009] It is an object of the invention to provide an improved nanobubble generation system or to at least provide the public with a useful alternative.

[0010] SUMMARY

[0011] According to one example embodiment there is provided a nanobubble generation system comprising: a. a nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a separator receiving liquid containing gas bubbles and dissolved gas configured to separate excess gas from the liquid containing gas bubbles and dissolved gas, and c. a gas recycling path from the separator to the nanobubble generator supplying excess gas from the separator to the gas inlet port of the nanobubble generator.

[0012] According to another example embodiment there is provided a nanobubble generation system comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a second nanobubble generator having a liquid inlet port receiving liquid containing gas bubbles and dissolved gas from the first nanobubble generator, a gas inlet port for receiving gas, and an outlet port for supplying liquid containing gas bubbles and dissolved gas, c. a first separator receiving liquid containing gas bubbles and dissolved gas from the second nanobubble generator configured to remove excess gas from the liquid containing gas bubbles and dissolved gas and having a main outlet supplying liquid containing gas nanobubbles from the nanobubble generation system, and d. a gas recycling system recycling excess gas from the separator to the inlet port of the first nanobubble generator and / or the inlet port of the second nanobubble generator.

[0013] According to another example embodiment there is provided a nanobubble generator comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a first separator receiving liquid containing gas bubbles and dissolved gas from the first nanobubble generator configured to separate excess gas from the liquid containing gas bubbles and dissolved gas, c. a second nanobubble generator having a liquid inlet port receiving liquid containing gas bubbles and dissolved gas from the first separator, a gas inlet port receiving gas from the first separator, and an outlet port supplying liquid containing gas bubbles and dissolved gas, d. a second separator receiving liquid containing gas bubbles and dissolved gas from the second nanobubble generator configured to separate excess gas from the liquid containing gas bubbles and dissolved gas having a main outlet supplying liquid containing gas bubbles and dissolved gas from the nanobubble generation system, and e. a gas recycling path from the second separator to the gas inlet port of the first nanobubble generator.

[0014] According to another example embodiment there is provided a nanobubble generation system comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing dissolved gas and gas bubbles, b. a second nanobubble generator having a liquid inlet port receiving liquid containing dissolved gas and gas bubbles from the first nanobubble generator, gas inlet ports for receiving gas, and an outlet port for supplying liquid containing dissolved gas and gas bubbles, c. a separator receiving liquid containing dissolved gas and gas bubbles from the second nanobubble generator configured to separate excess gas from the liquid containing dissolved gas and gas bubbles and having a main outlet supplying liquid containing gas nanobubbles from the nanobubble generation system, and d. a gas recycling system recycling excess gas from the separator to a venturi injector at the liquid inlet port of the first nanobubble generator and / or a venturi injector at the liquid inlet port of the second nanobubble generator.

[0015] According to another example embodiment there is provided a method of providing oxygenated water via an irrigation system comprising: a. generating an oxygenated water supply using a nanobubble generator; b. supplying the oxygenated water through the irrigation system; c. recovering excess oxygen gas in the irrigation system; and d. supplying the excess oxygen back to the nanobubble generator.

[0016] Examples may be implemented according to any one of the dependent claims at the end of this specification.

[0017] It is acknowledged that the terms "comprise", "comprises" and "comprising" may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, these terms are intended to have an inclusive meaning - i.e., they will be taken to mean an inclusion of the listed components which the use directly references, and possibly also of other non-specified components or elements.

[0018] Reference to any document in this specification does not constitute an admission that it is prior art, validly combinable with other documents or that it forms part of the common general knowledge. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention, in which:

[0020] Figure 1 is a schematic diagram of a nanobubble generation system according to a first example;

[0021] Figure 2 is a schematic diagram of a nanobubble generation system according to a second example;

[0022] Figure 3 is a schematic diagram of a nanobubble generation system according to a third example;

[0023] Figure 4 is a schematic diagram of a nanobubble generation system according to a fourth example; and

[0024] Figure 5 illustrates a method of recovering excess gas from an irrigation system.

[0025] DETAILED DESCRIPTION

[0026] Figure 1 shows a nanobubble generation system according to a first example in which a fluid, in this case water, is supplied to a liquid inlet port of nanobubble generator 1 via line 2 and gas, in this case oxygen, is supplied to a gas inlet port of nanobubble generator 1 via gas line 3. Nanobubble generator 1 and those shown subsequently may be of the type described in PCT / NZ2024 / 050007 or otherwise. Whilst the gas provided to form nanobubbles in this and the following examples will typically be oxygen other gasses such as air, ozone, carbon dioxide, methane etc. may be used. The outlet port of nanobubble generator 1 supplies water containing oxygen nanobubbles and larger bubbles to a separator 4 which separates larger gas bubbles from the liquid containing gas nanobubbles (i.e. predominantly large gas bubbles are removed). The separator thus contains water predominantly containing oxygen nanobubbles 5 and excess gas 6. A water level sensor 7 monitors the level of water in the separator and provides this information to a controller 8. Controller 8 controls valve 9 to open when the water level is below a prescribed level to allow gas to flow to bulk moisture removal and demister 10, which can be a packed column and demister. Valve 9 may be a solenoid valve or valve operated by another suitable actuator.

[0027] Gas from moisture removal column 10 is supplied to dryer 11 which may be a refrigerant dryer or any other suitable type of dryer. Dry gas from dryer 11 is supplied to compressor 12 which pressurises the gas and supplies it to gas storage vessel 13. Gas is also supplied to pressure vessel 13 by a gas source 14 when controller 8 turns on controllable valve 15. The gas source 14 can be an oxygen concentrator. Gas from the pressurised gas supply 14 can be mixed with gas from the compressor 12 in a gas storage vessel before being supplied to the gas inlet port of the nanobubble generator 1 when controller 8 opens controllable valve 16.

[0028] Alternatively, recovered gas from downstream separators can be supplied to upstream nanobubble generators with the use of venturi injectors to drop the water pressure at the nanobubble generator liquid inlets below that of the downstream pressure at the separator, and allow the recycled gas to flow upstream to the nanobubble generators.

[0029] This method is possible where existing irrigation infrastructure has spare pressure to be used through the venturi without affecting downstream irrigation. This method is attractive as it requires less equipment to condition the recovered gas and no need to recompress the gas to get it back to an acceptable pressure for reinjection.

[0030] To recycle higher gas flow rates necessary to achieve high dissolved gas and nanobubble concentrations, tighter venturi restriction resulting in greater head loss is required, so a trade-off must be made between simplicity and cost of gas recovery system versus higher energy requirements associated with higher water pressure losses, and the benefit provided to the end user from achieving higher nanobubble and dissolved gas concentrations.

[0031] Figure 2 shows a schematic diagram of a two stage nanobubble generator system of a first configuration. This view has been simplified to explain only the key elements but it will be apparent to the skilled person how the additional elements in Figure 1 may be employed in this and the following examples.

[0032] In this example a liquid, in this case water, is supplied to a liquid inlet port of nanobubble generator 17 via line 18 and gas, in this case oxygen, is supplied to a gas inlet port of nanobubble generator 17 via gas line 19. The outlet port of nanobubble generator 17 supplies water containing dissolved oxygen gas, oxygen nanobubbles and large bubbles to a settling vessel 20 which in turn supplies water containing oxygen nanobubbles and large bubbles to the fluid inlet port of a second nanobubble generator 21. Gas is supplied to nanobubble generator 21 via line 22. This gas recycling path recycles excess gas from the separator 23 to the gas inlet port of the first and second nanobubble generators.

[0033] To efficiently utilise two nanobubble generators in series, a large volume settling vessel 20 can be provided between the two nanobubble generators. The geometry of the settling vessel can be selected to achieve a lower bulk fluid flow velocity through the settling vessel than the nanobubble generator, typically less than 0.75m / s. This can allow the high velocity turbulent flow to settle and disperse nanobubbles evenly throughout the water before it passes through the second nanobubble generator. Without this, the nanobubble and dissolved oxygen concentration may not increase as significantly when using two nanobubble generators in series as compared to using only one.

[0034] Water having an elevated dissolved oxygen and nanobubble concentration after passing through two nanobubble generators is supplied to separator 23 which separates large gas bubbles from the liquid containing gas nanobubbles (i.e. predominantly large gas bubbles are removed). Excess gas from separator 23 is supplied to gas storage vessel 24 and water with a high dissolved oxygen and nanobubble concentration is output from the second nanobubble generator to output line 25. As in the previous example gas from a pressurised gas source 26 is also supplied to gas storage vessel 24. Gas storage vessel 24 supplies gas to the first and second nanobubble generators via lines 19 and 22.

[0035] Figure 3 shows a modified form of the nanobubble generation system shown in Figure 2 and like components have been given like numerals with their operation as described above. In this example rather than excess gas from the separator 23 being supplied to gas storage vessel 24 it is supplied via line 42 to venturi injectors 41 and 42 at the liquid inlets to nanobubble generators 17 and 21 to overcome the pressure differential. The same considerations apply to the use of venturi injectors as discussed above.

[0036] Figure 4 shows a simplified schematic diagram of another two stage nanobubble generator system. In this example a fluid, in this case water, is supplied to a liquid inlet port of nanobubble generator 27 via line 28 and gas, in this case oxygen, is supplied to a gas inlet port of nanobubble generator 27 via gas line 29. The outlet port of nanobubble generator 27 supplies water containing dissolved oxygen gas and oxygen nanobubbles and large bubbles to separator 30. In this case separator 30 supplies water containing dissolved oxygen and oxygen nanobubbles and large bubbles to liquid inlet port of a second nanobubble generator 31 and excess gas to a gas inlet port of second nanobubble generator 31.

[0037] The outlet port of nanobubble generator 31 supplies water containing dissolved oxygen gas and oxygen nanobubbles and large bubbles to separator 32. Nanobubble generator 31 supplies water containing dissolved gas and oxygen nanobubbles to output line 33 with excess gas from large bubbles being supplied to gas storage vessel 34. As in previous examples a gas source 35 also provides gas to gas storage vessel 34 to be supplied to the gas inlet port of first nanobubble generator 27. The gas source 35 may be an oxygen concentrator.

[0038] By removing and consistently injecting the gas from the first separator 30 and injecting it into the second nanobubble generator 31, instead of allowing the same gas to pass through the second nanobubble generator via the incoming water stream, constant and consistent gas injection flow rate can be maintained instead of large slugs of gas unevenly passing through nanobubble generators. This results in improved and more efficient gas to liquid transfer and nanobubble generation.

[0039] The above systems provide high gas injection rates with the use of low volume oxygen concentrators, resulting in lower power consumption, lower equipment cost, high nanobubble and dissolved gas concentration and improved overall efficiency / gas use. The systems avoid large gas volumes / slugs / pockets that can be detrimental in water piping infrastructure as the above systems remove a large portion of gas that would otherwise flow down the line.

[0040] The systems described above can produce a dissolved gas concentration of greater than 25 mg / litre, and commonly greater than 35 mg / litre. The systems can be employed to supply liquid (water with high dissolved gas and nanobubble concentration) to an irrigation system. The dissolved gas will typically be oxygen. Referring to Figure 5 a method for recycling gas from an irrigation system is shown schematically. Water is supplied to a nanobubble generation system 48 via a water supply line 49 and oxygenated water containing gas nanobubbles is provided to an irrigation system via line 50. At some point in the downstream irrigation system is a region of increased volume / pipe diameter, or a high point etc. where gas may separate from the fluid flow and collect 51. From this point a line 52 may recycle excess gas back to nanobubble generation system 48 for the excess gas to be reinjected back into the system. The excess gas can be collected from a high point in the fluid flow path of the irrigation system. The high point of the fluid flow path can be a raised section of a pivot irrigator e.g. the middle of the first span on a lateral or pivot irrigator. This method may be employed using any of the systems described above or any other suitable system.

[0041] Typically in irrigation, gravity separation is used as it is a simple and reliable. Depending on pipework infrastructure, the existing irrigation pipework, that is of larger diameter than the nanobubble generators, can be used as settling area after which the undissolved gas can be separated at a distance downstream of nanobubble generator where a high point exists or is added.

[0042] It will be appreciated that the inclusion and selection of components such as the demister and dryer and the gas recycling path from the separator to the nanobubble generator will vary depending upon the application. The separator may employ gravity separation, centrifugal separation, gas compression separation, membrane separation, vane or packed column separation, pad separation for mist elimination or simply using an existing downstream pipe with an enlarged diameter or high capacity region to capture waste gas as separator.

[0043] The above systems inject increased volumes of gas (typically oxygen), resulting in higher nanobubble and dissolved gas concentration (typically oxygen). They also inject more gas while producing less gas - i.e. a higher gas to water transfer efficiency. They enable use of smaller oxygen concentrators and are less expensive to manufacture. The higher dissolved gas concentration results in lower power consumption, less undissolved gas down the line and higher overall efficiency.

[0044] While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the applicant's general inventive concept.

Claims

CLAIMS:

1. A nanobubble generation system comprising: a. a nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a separator receiving liquid containing gas bubbles and dissolved gas configured to separate excess gas from the liquid containing gas bubbles and dissolved gas, and c. a gas recycling path from the separator to the nanobubble generator supplying excess gas from the separator to the gas inlet port of the nanobubble generator.

2. A nanobubble generation system as claimed in claim 1 wherein gas from a pressurised gas supply is mixed with gas from the gas recycling path and supplied to the gas inlet port of the nanobubble generator.

3. A nanobubble generation system as claimed in claim 2 wherein the gas from the pressurised gas supply is mixed with gas from the gas recycling path in a gas storage vessel before being supplied to the gas inlet port of the nanobubble generator.

4. A nanobubble generation system as claimed in claim 3 wherein a compressor in the gas recycling path compresses and supplies compressed gas to the gas storage vessel.

5. A nanobubble generation system as claimed in claim 3 or claim 4 including a de-mister in the gas recycling path.

6. A nanobubble generation system as claimed in any one of claims 3 to 5 including a dryer in the gas recycling path.

7. A nanobubble generation system as claimed in any one of the preceding claims including a solenoid valve in the gas recycling path.

8. A nanobubble generation system as claimed in claim 7 wherein the solenoid valve is controlled by a level sensor in the separator.

9. A nanobubble generation system as claimed in any one of claims 3 to 6 wherein the pressurised gas supply is an oxygen concentrator.

10. A nanobubble generation system as claimed in any one of claims 3 to 6 and 9 including a solenoid valve between the pressurised gas supply and the gas storage vessel which is controlled to maintain the pressure in the storage vessel at a desired pressure.

11. A nanobubble generation system as claimed in any one of the preceding claims wherein the gas is oxygen.

12. A nanobubble generation system as claimed in any one of the preceding claims configured to produce a dissolved gas concentration of greater than 25 mg / litre.

13. A nanobubble generation system as claimed in any one of the preceding claims configured to produce a dissolved gas concentration of greater than 35 mg / litre.

14. A nanobubble generation system as claimed in any one of the preceding claims configured to supply liquid to an irrigation system.

15. A nanobubble generation system as claimed in claim 14 wherein the system is configured to supply water with dissolved oxygen nanobubbles to an irrigation system.

16. A nanobubble generation system comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a second nanobubble generator having a liquid inlet port receiving liquid containing gas bubbles and dissolved gas from the first nanobubble generator, a gas inlet port for receiving gas, and an outlet port for supplying liquid containing gas bubbles and dissolved gas, c. a first separator receiving liquid containing gas bubbles and dissolved gas from the second nanobubble generator configured to excess gas from the liquid containing gas bubbles and dissolved gas and having a main outlet supplying liquid containing gas nanobubbles from the nanobubble generation system, and d. a gas recycling system recycling excess gas from the separator to the inlet port of the first nanobubble generator and / or the inlet port of the second nanobubble generator.

17. A nanobubble generation system as claimed in claim 16 wherein the gas recycling system recycles excess gas from the first separator to the gas inlet port of the first nanobubble generator and the gas inlet port of the second nanobubble generator.

18. A nanobubble generation system as claimed in claim 16 or claim 17 wherein a settling vessel is provided between the outlet port of the first nanobubble generator and the liquid inlet port of the second nanobubble generator.

19. A nanobubble generation system as claimed in claim 16 wherein the gas recycling system recycles excess gas from the first separator to the gas inlet port of the first nanobubble generator.

20. A nanobubble generation system as claimed in claim 19 including a second separator between the outlet port of the first nanobubble generator and the liquid inlet port of the second nanobubble generator which supplies excess gas from the second separator to the gas inlet port of the second nanobubble generator.

21. A nanobubble generation system as claimed in any one of claims 16 to 20 wherein excess gas from the first separator is supplied to a gas storage vessel from which it is supplied to the gas inlet port of the first nanobubble generator and / or the gas inlet port of the second nanobubble generator.

22. A nanobubble generation system as claimed in claim 21 wherein pressurised gas is supplied to the gas storage vessel.

23. A nanobubble generation system as claimed in claim 22 wherein pressurised gas is supplied from an oxygen concentrator to the gas storage vessel.

24. A nanobubble generation system as claimed in any one of claims 16 to 23 wherein the gas is oxygen.

25. A nanobubble generation system as claimed in any one of claims 16 to 24 configured to produce a dissolved gas concentration of greater than 25 mg / litre.

26. A nanobubble generation system as claimed in any one of claims 16 to 24 configured to produce a dissolved gas concentration of greater than 35 mg / litre.

27. A nanobubble generation system as claimed in any one of claims 16 to 26 configured to supply liquid to an irrigation system.

28. A nanobubble generation system as claimed in claim 27 wherein the system is configured to supply water with dissolved oxygen nanobubbles to an irrigation system.

29. A method of providing oxygenated water via an irrigation system comprising: a. generating an oxygenated water supply using a nanobubble generator; b. supplying the oxygenated water through the irrigation system; c. recovering excess oxygen gas in the irrigation system; and d. supplying the excess oxygen back to the nanobubble generator.

30. A method as claimed in claim 29 wherein excess gas is collected from a high point in the fluid flow path of the irrigation system that collects excess gas.

31. A method as claimed in claim 30 wherein the high point of the fluid flow path is a section of irrigation conduit.

32. A method as claimed in claim 30 wherein the high point of the fluid flow path is a raised section of a pivot irrigator.

33. A method as claimed in claim 32 wherein the high point of the fluid flow path is the middle of the first span of a pivot irrigator.

34. A nanobubble generation system comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing gas bubbles and dissolved gas, b. a first separator receiving liquid containing gas bubbles and dissolved gas from the first nanobubble generator configured to separate excess gas from the liquid containing gas bubbles and dissolved gas, c. a second nanobubble generator having a liquid inlet port receiving liquid containing gas bubbles and dissolved gas from the first separator, a gas inlet port receiving gas from the first separator, and an outlet port supplying liquid containing gas bubbles and dissolved gas, d. a second separator receiving liquid containing gas bubbles and dissolved gas from the second nanobubble generator configured to separate excess gas from the liquid containing gas bubbles and dissolved gas having a main outlet supplying liquid containing gas bubbles and dissolved gas from the nanobubble generation system, and e. a gas recycling path from the second separator to the gas inlet port of the first nanobubble generator.

35. A nanobubble generation system comprising: a. a first nanobubble generator having liquid and gas inlet ports and an outlet port for supplying liquid containing dissolved gas and gas bubbles, b. a second nanobubble generator having a liquid inlet port receiving liquid containing dissolved gas and gas bubbles from the first nanobubble generator, gas inlet ports for receiving gas, and an outlet port for supplying liquid containing dissolved gas and gas bubbles, c. a first separator receiving liquid containing dissolved gas and gas bubbles from the second nanobubble generator configured to separate excess gas from the liquid containing dissolved gas and gas bubbles and having a main outlet supplying liquid containing gas nanobubbles from the nanobubble generation system, and d. a gas recycling system recycling excess gas from the separator to a venturi connector at the liquid inlet port of the first nanobubble generator and / or a venturi connector at the liquid inlet port of the second nanobubble generator.

36. A nanobubble generation system as claimed in claim 35 wherein the gas recycling system recycles excess gas from the separator to a venturi connector at the liquid inlet port of the first nanobubble generator and a venturi connector at the liquid inlet port of the second nanobubble generator.

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