AU2021221402A1

AU2021221402A1 - Method and apparatus for the generation of hydroxyl radicals

Info

Publication number: AU2021221402A1
Application number: AU2021221402A
Authority: AU
Inventors: Adrian Philip Lake; Richard Anthony ZESSIN
Original assignee: Hq Air Ltd
Current assignee: Hq Air Ltd
Priority date: 2021-07-06
Filing date: 2021-08-23
Publication date: 2023-02-02
Also published as: WO2023279154A1

Abstract

A hydroxyl generator unit 1 comprising a duct 10 for the transmission of an airstream therethrough between an air inlet 12 and an air outlet 14. A charged electrode 20 and an ultraviolet light source 22 are disposed within a reaction chamber 24 of the duct 10 for exposure to an airstream passing through the duct 10 in the direction indicated by arrow A. A fan unit 26 may be provided to move air through the duct 10 and to create the airstream. The electrode 20 is disposed proximal to and upstream of the ultraviolet light source 22. The hydroxyl generator unit 1 further comprises a housing 28 for housing various electrical components including a control unit 30 and a power unit 32; and connectors operatively connecting the various electrical components to the power unit 30 and / or the control unit 32. Fig 1. 1/4 AH24(276580501):SCP

Description

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AH24(276580501):SCP

METHOD AND APPARATUS FOR THE GENERATION OF HYDROXYL RADICALS

Field

[0001] The present invention relates to the generation of hydroxyl radicals and in particular to an apparatus and method for the production of hydroxyl radicals for treatment of air.

Background

[0002] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

[0003] Hydroxyl radicals, 10H, are the neutral form of the hydroxide ion (OH-). Hydroxyl radicals or "hydroxyls" are highly reactive and attack most of the organic molecules (e.g., acids, alcohols, aldehyde, aromatics, amines, ethers, ketone, etc.) allowing them to be easily be removed or degraded. For this reason, hydroxyls, which are produced naturally in the upper reaches of the troposphere, are often referred to as the "detergent" of the atmosphere.

[0004] The capacity for hydroxyls to break-down organic molecules may be exploited in air cleaning and purification systems to remove odours, including pollution, cigarette smoke, and cooking and toilet smells, destroy volatile organic compounds (VOCs) and toxins including toxins contained in fine particulate matter, kill bacteria, mould and viruses including those that cause influenza, staph, severe acute respiratory syndrome (SARS). Significantly because hydroxyls are naturally occurring in the atmosphere, they do not present health or safety concerns for people or animals. Accordingly, the production of hydroxyls to be used for the treatment and cleaning of air is highly desirable.

[0005] However, as a result of their highly reactive nature, hydroxyls are short-lived requiring artificial production in situ. There are several potential reaction pathways for producing hydroxyl radicals however most methods of artificial production at least to some degree mimic production pathways of the upper atmospheres and rely upon the photolysis of ozone by ultraviolet radiation.

[0006] Photocatalytic oxidation (PCO) relies on the interaction of low energy photons from a long wavelength UV source with a water molecule on the point of a TiO (Titanium Dioxide) catalyst plate. However, the plate needs to be properly structured to be effective, and is easily contaminated from particulates. Furthermore, *OHformed by this method will typically be bound to the catalyst plate rather than freely airborne. This limits the utility of photocatalytic oxidation in air treatment since any contaminate must pass over the plate in order to interact with the hydroxyl molecules. Another potential drawback of PCO is the substantial risk of formation of formaldehydes which detract from air quality.

[0007] Another proposed method of forming hydroxyls is via the application of high intensity ultra-violet (UV) light to air and water vapour. However, controlling OH ion levels using this method is problematic. The most effective way of increasing and reducing hydroxyl production is by controlling the UV light source. However, many UV light sources, such a gas discharge UV light sources are not readily controllable for intensity.

[0008] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Summary of Invention

[0009] In a first aspect the invention provides a hydroxyl generator unit, comprising: a duct extending between an air inlet and an air outlet; a blower to produce an airstream through the duct from the air inlet to the air outlet; a charged electrode and an ultraviolet light source disposed within a reaction chamber of the duct for exposure to the airstream; wherein the electrode is disposed upstream of said ultraviolet light source.

[0010] In a second aspect the invention provides a hydroxyl generator unit for an air circulation system, said unit comprising: a duct for the transmission of an airstream between an air inlet and an air outlet of the duct; a charged electrode and an ultraviolet light source disposed within a reaction chamber of the duct for exposure to the airstream; wherein the electrode is disposed upstream of said ultraviolet light source.

[0011] In a third aspect the invention provides a hydroxyl generator unit for an air circulation or air treatment system, said unit comprising: a housing comprising a charged electrode and an ultraviolet light source for fitment to a duct of the air circulation system; wherein the duct forms a reaction chamber having an air inlet and an air outlet for the transmission of an airstream through the reaction chamber; wherein the electrode is to be disposed upstream of said ultraviolet light source.

[0012] Preferably ozone is produced at the electrode and the ultraviolet light source recombines the ozone which is destroyed, to produce hydroxyl radicals.

[0013] In another aspect the invention provides a method for generating hydroxyls in an air treatment system said method including the steps of: generating an airstream comprising oxygen and water vapour; directing said airstream through a reaction chamber comprising: a charged electrode to produce ozone; and an ultraviolet light source within a reaction chamber, to recombine ozone which is destroyed, to produce hydroxyl radicals; wherein the charged electrode is upstream of said ultraviolet light source.

[0014] Preferably, the electrode is proximal the ultraviolet light source.

[0015] Preferably, the electrode and ultraviolet light source are spaced by a distance of between cm and 0.5 cm, preferably between 5 cm and 1 cm.

[0016] Preferably, the ultraviolet radiation emitted by the ultraviolet light source has a wavelength of between 170 - 400 nm.

[0017] Preferably, the ultraviolet radiation emitted by the ultraviolet light source is broad spectrum ultraviolet radiation substantially without ultraviolet radiation 185nm wavelength.

[0018] Preferably, the ultraviolet radiation emitted by the ultraviolet light source operating at a frequency of between 10 kHz and 100 kHz preferably around 30 kHz.

[0019] Preferably, the ultraviolet radiation emitted by the ultraviolet light source has an intensity of between 2000 mw/cm2 and 5000 mw/cm2 and preferably around 4000 mw/cm2

.

[0020] Preferably, the ultraviolet light source includes a medium-pressure mercury vapor (MPMV) lamp to emit short intense flashes of broad-spectrum ultraviolet light. Alternatively, the ultraviolet light source includes any one or combination of incandescent lamps, gas discharge lamps, low-pressure mercury vapor (LPMV) lamps, medium-pressure mercury vapor (MPMV) lamps, pulsed xenon lamps, excimer lasers, or light emitting diodes (LEDs).

[0021] Preferably, the electrode is alternating current (AC) and operates at a frequency of between 10 kHz and 100 kHz preferably around 30 kHz.

[0022] Preferably, the electrode has a voltage of between 3,000 volts to 15,000 volts, preferably around 6,000 volts.

[0023] Preferably, the hydroxyl generator unit includes a power unit having a transformer for delivery of current to the electrode.

[0024] Preferably, the hydroxyl generator unit includes a control unit operatively connected to the electrode and UV light source. Preferably the control unit is operatively connected to the fan unit and includes a control interface.

[0025] In some embodiments the control unit is configured to control the production of hydroxyls in accordance with instructions from the control interface and sensor data from one or more sensors.

[0026] Preferably, the hydroxyl generator unit includes at least one sensor for detecting environmental and unit parameters from inside and outside the unit.

[0027] Preferably the one or more sensors include sensors monitoring at least one of air temperature, air pressure, humidity, ionization activity within the reaction chamber, detection of various harmful products and/or particulate matter, UV activity and airflow velocity and/or dynamic pressure. The one or more sensors may be mounted within the duct, reaction chamber or external the duct.

[0028] In one embodiment the control unit operatively controls power to the electrode to control production of ozone within the reaction chamber. In one embodiment the control system varies the production of ozone to control the production of hydroxyls.

[0029] Preferably the hydroxyl generator unit includes at negatively charged electrode downstream of the UV light source for ionizing air at the outlet of the unit. Preferably the negatively charged electrode includes fiber bristles and more preferably carbon fiber bristles.

[0030] The negatively charged electrode may be connected to the AC electrode via a diode.

Brief Description of Drawings

[0031] The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:

[0032] Figure 1 is a cross-sectional schematic view of an embodiment of a hydroxyl generator unit in accordance with the invention;

[0033] Figure 2 is a cross-sectional schematic view of another embodiment of a hydroxyl generator unit in accordance with the invention;

[0034] Figure 3 is a cross-sectional schematic view of another embodiment of a hydroxyl generator unit in accordance with the invention; and

[0035] Figure 4 is a schematic perspective view of a hydroxyl generator unit in accordance with another embodiment of the invention.

Description of Embodiments

[0036] Referring to the drawings there is displayed in Figure 1 a hydroxyl generator unit 1 comprising a duct 10 for the transmission of an airstream therethrough between an air inlet 12 and an air outlet 14. A charged electrode 20 and an ultraviolet light source 22 are disposed within a reaction chamber 24 of the duct 10 for exposure to an airstream passing through the duct 10 in the direction indicated by arrow A. In this embodiment a fan unit 26 is provided to move air through the duct 10 and to create the airstream. As can be seen from the figure, the electrode 20 is disposed proximal to and upstream of the ultraviolet light source 22.

[0037] The hydroxyl generator unit 1 further comprises a housing 28 for housing various electrical components including a control unit 30 and a power unit 32; and connectors operatively connecting the various electrical components to the power unit 30 and / or the control unit 32.

[0038] The power unit 32 which is typically connectable to a mains supply by means of a power cord 34, includes a power modulation unit in the form of a voltage transformer 36 for delivering a high frequency alternating current (AC) to the electrode 20. The voltage of the current provided to the electrode 20 by the transformer 36 is controlled by the control unit 30 between KV and 15KV with a typical operating voltage of around 6KV. In this embodiment the alternating current is delivered a frequency of around 30 kHz but frequencies of between 10kHz and 100kHz may be used.

[0039] Power is also delivered from the power unit 32, as controlled by the control unit 30 to the ultraviolet light source 22. In this embodiment the ultraviolet light source 22 is a 35W broad spectrum (UVA; UVB and UVC) high intensity ultraviolet lamp emitting short intense flashes of broad-spectrum ultraviolet light at a frequency of between 10kHz and 100kHz but preferably around 30 kHz. The lamp has a 185nm cut - meaning that the electromagnetic radiation produced by the light source has a wavelength of between 170 nm and 400 nm and is devoid or substantially devoid of electromagnetic radiation having a 185nm wavelength. Preferably the UV light source has an intensity of between 2000 mw/cm2 and 5000 mw/cm 2 and preferably around 4000 mw/cm 2 .

[0040] In this embodiment, the electrode is in the form of an elongate rod extending from one sidewall of the duct preferably adjacent the housing, to terminate just short of the duct on the opposite sidewall. The rod is substantially centrally positioned within the duct to present to the airstream within. The rod may have a circular cross-section as illustrated, however rods of other cross-sections and shapes are possible. Furthermore, the electrode may take other forms such as a coil or coils, grids, arrays, nets, brushes, ladders, surfaces or the like. In addition, while a single electrode is shown, the device may include multiple electrodes of the same or dissimilar types.

[0041] In this embodiment the ultraviolet lamp is a single medium-pressure mercury vapor (MPMV) lamp, however the use of other UV light source technologies may be applied including but not limited to any one or combination of single or multiple incandescent lamps, gas discharge lamps, low-pressure mercury vapor (LPMV) lamps, medium-pressure mercury vapor (MPMV) lamps, pulsed xenon lamps, excimer lasers, or light emitting diodes (LEDs).

[0042] A control interface 38 is operatively connected to the control unit 30 so as to allow control of the generator unit 1. In this embodiment the control interface 38 is shown as a screen having a hard connection to the control unit 30 however it will be appreciated that the control interface 38 may incorporate wireless connection or be integrated into or operatively connected to other HVAC and/or air treatment/circulation systems.

[0043] Various sensors such as sensor 40 are also connected to the control unit for sensing various environmental and hydroxyl generation parameters from inside and outside the unit used in the control of the unit's operation. In this embodiment, sensor 40 monitors parameters within the reaction chamber such as, air temperature, pressure, humidity, ionization activity, detection of various harmful products, UV activity and airflow characteristics such a velocity, dynamic pressure etc however, in other embodiments sensors may be positioned in other locations both within the reaction chamber 24 and duct 10 or external to the device and operatively connected to the control unit.

[0044] In the embodiment of the invention shown in Figure 1, the generator 1 further includes an air filter 42 at the inlet 12 to filer particulates from the air and a negatively charged electrode 44 downstream of the reaction chamber. In this embodiment, the electrode is connected via a diode 46 to the transformer 36 so as to be negatively charged and ionise air passing from the outlet 14. Preferably the electrode is a carbon bristle electrode.

[0045] As shown in Figure 1 the fan unit 26 comprises a barrel fan 48 disposed downstream of the reaction chamber thereby taking advantage of the upstream air filter 40 to prevent or reduce particulate matter accumulating on moving parts of the fan. However, in other embodiments the fan may be an axial fan, tangential fan, blower or any other type of air moving device. In other embodiments as will be seen, the generator unit 1 may not include a dedicated fan or other air moving device instead relying upon airflow generated by a HVAC and/or air treatment/circulation system.

[0046] In use, the hydroxyl generator unit 1 relies upon a method of producing hydroxyl radicals from the reformation of ozone and hydrogen ions with broad spectrum UV light into hydroxyls. This first requires the production of ozone and hydrogen ions from oxygen and water vapour by high voltage electrical energy and corona discharge, enhanced by ionization from UV light. In this regard it is necessary that the production of ozone and hydrogen ions occurs upstream of reformation at the UV light source but it is also preferable that the electrode is in proximity of the UV light source 22 to capitalize on increase energy levels caused by ionization of the air due to the UV radiation.

[0047] Furthermore, in addition to increasing energy in the air passing the electrode thereby increasing the output of ozone from the electrode and upscaling any oxidant/radicals in the airstream from ozone and/or peroxides to hydroxyls the presence of the UV source also provides a level of sterilisation of the air stream.

[0048] In operation the fan unit 26 creates an airstream through the duct 10 and reaction chamber 24. Air is drawn in the inlet 12 and through the air filter 40 which removes particulates from the air stream. Air passes over the energised electrode 20 which produces ozone and ions (some positive, but mostly negative) from oxygen and water vapour due to a combination of high voltage electrical energy and corona discharge, enhanced by ionisation within the reaction chamber caused by the proximity of the electrode to the UV light source. These reactions are:

302 --* 203 and

H20--* 2 H'+ O

[0049] The ozone and ions (hydrogen and oxygen ions) are carried by the airstream from the electrode 20 toward the UV light source 22 which causes the dissociation of electrons and/or provides sufficient energy to undergo reformation into hydroxyls. The jump from one potential to a higher one requires the input of significant energy to break the bonds and ensure the formation of a stable hydroxyl radical.

03+ 2 H'+ O--- 2'OH+02

[0050] Air passing from the outlet 14 is further ionised by the negatively charged electrode 42 passed from the outlet to control particulates and cause the clustering/dropping out of viral particles, bacterium, spores and other organic particulate matter.

[0051] As noted the control unit 30 controls operation of the hydroxyl generator unit 1 in accordance with instructions provided by the control interface 38. This includes activation of the UV light source 22, electrode 20 and fan unit 26. Since the production of hydroxyls radicals is in part determined by the amount of ozone produced at the electrode, regulation of electrode power may readily be used to control the amount of hydroxyl produced. Sensors 40 provide additional information Preferably at start up the control system activates the ultraviolet light source 22 prior to energizing the electrode 20 to prevent unreacted ozone from being emitted by the device.

[0052] Preferably the hydroxyl generator unit 1 is constructed to prevent escape of the high intensity UV radiation from the reaction chamber. In this regard it will be appreciated that the duct 10 includes surrounding sidewalls impervious to the transmission of UV light thereby providing a radiation shield. At the inlet and outlet, which must allow for the movement of air, the filter and barrel fan assist in blockage of UV radiation and may include one or more transverse wall sections and, or corners to prevent line of sight exit of UV radiation.

[0053] It will be appreciated that the device of the invention shown in Figures 1 - 4 requires the transmission of air both to introduce oxygen and water vapour into the reaction chamber for conversion into hydroxyls and to carry hydroxyls from the unit for distributing and disbursal as required. In this regard the fan unit of the device shown in Figure 1 provides a stream of air from the outlet containing hydroxyl radicals and ionized air. However, the embodiments of the device shown in Figures 2 and 3 are intended for fitment to a HVAC and/or air treatment/circulation system and therefor do not require a dedicated fan unit (although one may be used) instead relying of the HVAC and/or air treatment/circulation system to produce airflow through the duct. In this regard the hydroxyl generator unit shown in Figure 2 omits the fan unit of the device shown in Figure 1 but retains a duct 10 andfilter 42, whilst the hydroxyl generator units shown in Figures 3 and 4 are intended for fitment into an aperture in a side wall of a duct 110 of a HVAC and/or air treatment/circulation system.

[0054] As opposed to other methods for producing hydroxyls, such as by UV radiation only, the method of the invention advantageously allows for greater control of the hydroxyl generation process. That is to say, by varying power to the electrode 20, the amount of ozone produced can be controlled which in turn can be used to control hydroxyl production at the UV light source given consistent UV light intensity for maximum hydroxyl output.

Claims

1. A hydroxyl generator unit, comprising: a duct extending between an air inlet and an air outlet; a blower to produce an airstream through the duct from the air inlet to the air outlet; a charged electrode and an ultraviolet light source disposed within a reaction chamber of the duct for exposure to the airstream; wherein the electrode is disposed upstream of said ultraviolet light source.

2. A hydroxyl generator unit for an air circulation system, said unit comprising: a duct for the transmission of an airstream between an air inlet and an air outlet of the duct; a charged electrode and an ultraviolet light source disposed within a reaction chamber of the duct for exposure to the airstream; wherein the electrode is disposed upstream of said ultraviolet light source.

3. A hydroxyl generator unit for an air circulation system, said unit comprising: a housing comprising a charged electrode and an ultraviolet light source for fitment to a duct of the air circulation system; wherein the duct forms a reaction chamber having an air inlet and an air outlet for the transmission of an airstream through the reaction chamber; wherein the electrode is to be disposed upstream of said ultraviolet light source.

4. A hydroxyl generator unit according to any one of the preceding claims wherein ozone is produced at the electrode and the ultraviolet light source recombines the ozone which is destroyed, to produce hydroxyl radicals.

5. A method for generating hydroxyls in an air treatment system said method including the steps of: generating an airstream comprising oxygen and water vapour; directing said airstream through a reaction chamber comprising: a charged electrode to produce ozone; and an ultraviolet light source within a reaction chamber to recombine ozone, which is destroyed to produce hydroxyl radicals; wherein the charged electrode is upstream of said ultraviolet light source.

ClariqAir Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON

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Figure 2

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