Patent Application
20240314916
The present disclosure relates to a device and method for generating free radicals between a discharge electrode assembly and a counter electrode, which may be liquid in a liquid bath.
Cold plasma discharge through air or molecular gases and the resulting radicals such as: O*, N*, OH*, H*, CH2*, etc., have many practical applications ranging from sterilization, surface treatment, and pollutant removal from gas streams.
The most widely used method of generating discharge in a gas is by the use of a dielectric barrier between two conductors and then applying a high voltage between the electrodes to cause discharge in the gap, which is commonly known as “DBD discharge” in the art. At a sufficiently high voltage between the electrodes the discharge starts in the gas volume. It spreads out until it reaches the electrodes, but at the dielectric surface it builds up a space charge that cancels the applied electric field. At that moment the discharge stops.
An alternative method utilizes an asymmetric electrode pair without the use of a dielectric barrier between them. Streamer or filament type discharges initiate from regions with strong electric fields that exist at a surface of an electrode with high curvature (needle, wire etc.). After being formed, a streamer is able to propagate for a long distance even in space where the field is relatively weak. However, to prevent complete breakdown (arcing) in the discharge gap, high voltage short pulses are used to stop the discharge before it transitions into an arc. The most common electrodes used in practice for this purpose are point-to-plane and wire-in-cylinder geometries.
Streamer discharge devices utilizing an asymmetric electrode pair are easier to scale up particularly for large gas flows. Typically, the electric field required to ignite streamers in air-like mixtures is about 102-103 kV·cm−1. Such high fields can easily be generated by using sharp electrodes such as wire and pins, with a modest applied voltage that is orders of magnitude lower. The field enhancement in front of the streamer head is high enough to ensure a positive net ionization coefficient. A streamer can be considered as a self-sustained ionization wave propagating in neutral gas that is converted into low-temperature plasma behind the wave front, resulting in a channel-like appearance. The interior of the streamer channel consists of a conducting plasma with roughly the same electron and ion densities. The self-induced electric field of the streamer head allows the streamer to continue propagating even into regions where the applied electric field is insufficient to ensure a positive net ionization, and hence gives the scalability to these devices.
One of the problems of electric discharge systems is the stability and lifetime of the electrodes. Electrodes are exposed to electron and ion bombardment, UV irradiation, deposition of reactive particles and electrolytic corrosion. As a result, the original shape of the electrode changes, the electrode surface becomes dirty, and the surface conductivity changes. Also, contamination reduces the emission of electrons, making the emission of electrons uneven over the surface of the electrode. This increases the concentration of current at some small points on the surface of the electrodes and assists to the formation of a spark.
For some applications, it is desirable to provide free radicals in a liquid, for treatment of the liquid or use of the liquid for other purposes. In one approach, free radicals are generated in a gas, such as air, as discussed above and the gas is then added to the liquid to transfer free radicals. However, many of the free radicals are short lived and free radicals are not efficiently added to the liquid in this way.
Another approach has been to use a liquid as the counter electrode. Use of a liquid as the counter electrode addresses some of the above issues.
In systems using liquid as a counter electrode, as well as in system using a solid counter electrode, it is challenging to maintain the generation of free radicals while avoiding sparks. Sparking is undesirable for a number of reasons, including that it may damage the electrodes.
The main problem is that the amplitude of the breakdown voltage for every pin of multi-pin electrode system is different, and even for the individual pin, it fluctuates too much within a narrow range, and the amplitude of the breakdown voltage tends to drop over time. Because the current-voltage curve is close to flat (low slope) before the transition to the sparking mode, a small drop in the breakdown voltage leads to a big reduction in both the discharge current and discharge power, which leads to a significant drop in the number of ionized particles and radicals.
The common technique to prevent APGD from going into spark mode is the use of high velocity gas blowing. Due to the blowing off of the charge particles from the discharge gap, it makes it possible to control the transition of the APGD to the spark mode. Unfortunately, such a technic is not always acceptable, especially for the producing of the high radical concentration.
There are a number of techniques to attempt to prevent the transition from discharge to spark. One of them is the control of the voltage form applied to the discharge. If the applied voltage changes between Vignition (Vmin) and Vbreakdown (Vmax) and the cycle time is sufficient to remove and/or neutralize the charge particles from the discharge gap, then every new discharge cycle will start under identical conditions for every electrodes of the multi-pin electrode system, which allows for stabilization of the amplitude of the breakdown voltage.
A liquid counter electrode system as in
A second problem associated with a liquid counter electrode is the buildup of moisture due to electrostatic evaporation. The breakdown voltage usually decreases with an increase in humidity levels, and the breakdown voltage can easily fall below the applied voltage, especially considering the high humidity level in the discharge gap due to the electrostatic evaporation.
From the aforementioned it is apparent that there are problems with the generation of radicals with a high density and with high efficiency even when a liquid counter electrode is used. As such, new methods and devices are needed for effective generation of radicals.
The following summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the various aspects of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.
Certain embodiments of the present invention address some of the shortcomings of prior art free radical generators. In one example, a discharge electrode assembly is provided, having a plurality of discharge electrode pins in an array arranged in a radial pattern and electrically configured to receive one or more voltage pulses. A counter electrode may be a solid electrode or may be a liquid electrode. An exemplary liquid electrode includes a liquid bath configured to hold a liquid having an upper surface disposed at a liquid level separated from the discharge electrode pins by a discharge gap. In an example, a motive element is operable to rotate the discharge electrode assembly such that the array of discharge electrode pins rotates about an axis and the plurality of pins move relative to the counter electrode, such as the liquid in the liquid bath.
The rotational movement of the array of discharge electrode pins changes the discharge gap between each pin as the pin moves relative to the counter electrode, such as the liquid surface. This changing of the gap length is a technique for controlling electrical breakdown across the gap. This creates a cyclical variation of the discharge gap and may lengthen the streamers. This means that if the gap is short, the discharge condition approaches the breakdown voltage, and if the length of the discharge gap increases, then the electric field strength will decrease, and the rate of generation of charged particles will also become low, and the discharge will collapse/damp. A rotary electrode system may also have another advantage. Considering that the spark and arc discharge are tied to certain points on the electrodes, in case the discharge transitions into the spark/arc mode, the rotation will lead to the elongation of the spark/arc channel, reducing the voltage across the channel and, as result, the channel breakdown.
In some aspects, the liquid in the liquid bath has a controlled depth and the bath may have a porous bed. Further aspects are discussed below.
In an embodiment, a free radical generator includes a discharge electrode assembly with a plurality of discharge electrode pins in an array arranged in a radial pattern and electrically configured to receive one or more voltage pulses. A counter electrode has a surface separated from the discharge electrode pins by a discharge gap. A motive element is operable to rotate the discharge electrode assembly such that the array of discharge electrode pins rotates about an axis and the plurality of pins move relative to the counter electrode.
In an example, the counter electrode is a solid counter electrode. In a further example, the counter electrode is a liquid bath configured to hold a liquid having an upper surface disposed at a liquid level, the upper surface of the liquid defining the surface of the counter electrode.
In some versions, the plurality of discharge electrode pins each have one or more ignition tips, each ignition tip defined by an angle, each ignition tip positioned at a terminus of the respective discharge electrode pin proximal to the counter electrode.
In some versions, the array of discharge electrode pins includes a plurality of rows of the discharge electrode pins extending substantially perpendicular to a length of the discharge electrode assembly. The discharge electrode assembly may include a plurality of electrode elements, each element defining one of the rows of discharge electrode pins. Each subsequent row of discharge electrode pins proceeding in the length of the discharge electrode assembly may be angularly offset from a preceding one of the rows. Each of the electrode elements is an electrode disc.
In some versions, the discharge electrode assembly may further include a central rod and each row of the plurality of rows of the discharge electrode pins is a disc having a central hole and the discharge electrode pins extending therefrom. Each disc may be placed on the central rod to form the plurality of rows of the discharge electrode pins.
In some versions, the axis is a lengthwise axis and the plurality of discharge electrode pins extend generally perpendicularly to the lengthwise axis.
In some versions, the liquid bath is adjustable to adjust the liquid level, thereby adjusting the discharge gap.
In some versions, the discharge gap between a closest one of the discharge electrode pins
and the counter electrode surface is in the range of 0.5 to 30 mm.
In some versions, the liquid bath further has a porous bed. In further versions, the generator has a pump operable to pump the liquid into or out of the liquid bath to create a liquid flow relative to the discharge electrode assembly. The liquid flow may have a flow direction in the liquid bath, the flow direction being generally parallel to the axis of rotation of the discharge electrode assembly or perpendicular thereto.
In some versions, the generator has a circuit in electrical communication with the discharge electrode assembly and the counter electrode, the circuit operable to generate electrical pulses between the discharge electrode assembly and the counter electrode such that a plasma is created between tips of the discharge electrode pins and the counter electrode as the tips move relative to the counter electrode.
In some versions, the generator further has a reactor housing including a reactor tube, the discharge electrode assembly disposed in the reactor tube. The reactor tube may formed of a non-conductive material. The reactor housing may have gas inlets and gas outlets for a flow of gas through the discharge gap.
In an embodiment, a liquid treatment system includes a free radical generator according to any disclosed embodiment. The system may further have a gas flow generating element operable to flow a gas through the gap of the free radical generator and a gas introduction element operable to introduce the gas into a liquid to be treated. In some versions, the system further includes a liquid flow generating element operable to introduce a liquid into or remove a liquid from the liquid bath such that the liquid is treated.
In an example, the liquid is water.
In an embodiment, a method of cleaning a liquid includes providing any generator disclosed herein or any liquid treatment system disclosed herein, flowing a liquid to be cleaned through the liquid bath, and/or introducing a gas from the discharge gap into the liquid to be cleaned.
In an example, the method of liquid treatment includes a process of removing microplastics from liquid environments, further including agglomerating or precipitating the microplastic particles, and removing the agglomerated or precipitated particles, such as by filtration.
In an example, the method of liquid treatment is operable for disinfection against microbials and/or decontamination from chemicals and/or particulates.
In an embodiment, a gas treatment system includes a free radical generator as described herein, a gas flow generating element operable to flow a gas to be treated, a column in fluid communication with the gas flow generating element such that the flow of gas flows through an interior space of the column, and a liquid introduction element operable to introduce the liquid from the liquid bath into the interior space of the column such that the flow of gas is exposed to the liquid. The system may include a porous exchange bed disposed in the column. The liquid introduction element may include at least one sprayer for spraying the liquid in the interior space of the column. The system may include a reservoir for receiving the liquid introduced into the interior space after the flow of gas is exposed to the liquid and a recirculation element operable to move liquid from reservoir back to the liquid bath. A pump may be included for pumping the liquid from the liquid bath to the liquid introduction element. The system may further include a filter disposed such that the flow of gas passes through the filter after being exposed to the liquid, the filter being a hydrophilic or hydrophobic filter. The system may further include a chilled element disposed such that the flow of gas passes through the filter after being exposed to the liquid, thereby removing humidity from the flow of gas. The system may further include a chilling element operable to reduce a temperature of the liquid before the liquid is introduced into the interior space. The flow of gas may be a flow of air. The system may have an outlet for the flow of gas to exit the system after passing through the column. The outlet may be in fluid communication with the discharge gap such that a flow of free radicals is mixed into the flow of gas exiting the system.
In an embodiment, a system for treatment of an area is provided. The system includes a gas treatment system as described above wherein the outlet is in fluid communication with the discharge gap such that a flow of free radicals is mixed into the flow of gas exiting the system.
In an embodiment, a system is provided for treatment of an area. The system includes a free radical generator according to any embodiment herein and a gas flow generating element operable to flow a gas through the discharge gap, thereby introducing free radicals into the flow of gas.
In an embodiment, a dehumidifier, an air conditioner, or a ventilation system includes a gas treatment system according to any embodiment here.
In an embodiment, a method of fumigating a space or local surface treatment in the space, includes a system for treatment of an area or a gas treatment system as described above wherein the outlet is in fluid communication with the discharge gap such that a flow of free radicals is mixed into the flow of gas exiting the system.
In an embodiment, a method is provided for treatment of an area, including providing a system according to an embodiment herein and introducing the flow of gas with free radicals from the system into the space. The liquid in the liquid bath may contain one or more of: Iodine; Hydrogen Peroxide; Quaternary ammonium; L-Lactic Acid; Peracetic Acid; Citric Acid; Chlorine Dioxide; Isopropanol; Sodium Hypochlorite; or Ethanol.
In an embodiment, a method of treating a gas includes providing a generator or a system according to any embodiment herein and flowing a gas to be treated through the generator or system.
In an embodiment, a process of producing a radical in a fluid includes passing a fluid through the discharge gap of any embodiment of a free radical generator herein, applying a pulse voltage between the one or more discharge electrode pins and the counter electrode, the pulse voltage applied for a pulse time, and generating one or more streamers extending between the one or more discharge electrode pins and the counter electrode, the one or more streamers generating a free radical within the fluid. The fluid may be a gas and the gas may include oxygen and nitrogen. The radical may be a nitrogen radical or a hydroxyl radical.
In examples, the pulse voltage is 5 kV to 20 kV.
In examples, the process may further include applying a bias voltage between the discharge electrode pins and the counter electrode, the applying being successive voltage pulses. The bias voltage may be in the range of 1 to 500 V or 1 to 2000V.
In examples, the gas velocity is 0.1 m/s to 200 m/s, or optionally 5 m/s to 50 m/s.
In examples, the process may further include repeating the step of applying and the step of generating, the repeating defined by a pulse width, the pulse width from 10 nanoseconds to 50 microseconds, or optionally 400 nanoseconds to 1 microsecond.
In examples, the process may further include repeating the step of applying and the step of generating, the repeating defined by a pulse frequency, the pulse frequency from 100 Hz to 100 kHz, or optionally 10 kHz to 30 kHz.
In examples of the free radical generator, the discharge electrode pins each include 3 to 8 ignition tips.
In examples of the free radical generator, the discharge electrode pins each include a tip profile substantially perpendicular to a length of the discharge electrode pin, wherein the tip profile is in the shape of a triangle, a square, a pentagon, a hexagon, a heptagon, or an octagon.
In an embodiment, a system for fumigation of crops in an interior grow enclosure, includes an indoor grow enclosure configured to have crops disposed therein and an air treatment system according to any embodiment herein.
In an embodiment, a method for fumigation of crops in an interior grow enclosure includes providing an indoor grow enclosure with crops disposed therein, providing an air treatment system according to any embodiment herein, passing air through the system so as to introduce free radicals and/or other reactive species into the air passing through the system, and introducing the air with the free radicals and/or other reactive species into the indoor enclosure, thereby exposing the crops to the air with the free radicals and/or other reactive species.
In an embodiment, a system for sterilizing a device such as a medical instrument includes a housing having a receiving area for receiving the medical instrument, the receiving area including a liquid bath disposed therein such that the device received in the receiving area is at least partially positioned in the liquid bath. A discharge electrode assembly includes a plurality of discharge electrode pins in an array arranged in a radial pattern and electrically configured to receive one or more voltage pulses. A portion of the liquid bath defines a counter electrode having a surface separated from the discharge electrode pins by a discharge gap. A motive element is operable to rotate the discharge electrode assembly such that the array of discharge electrode pins rotates about an axis and the plurality of pins move relative to the counter electrode.
In an example, a dividing element separates the portion of the liquid bath defining the counter electrode from a portion of the liquid bath receiving the device for sterilization.
In an example, an impeller is configured for circulating the liquid bath.
In an embodiment, a method of sterilizing a device such as a medical instrument includes providing a system as described above, receiving the device in the receiving area, generating active species in the liquid bath with the discharge electrode assembly, thereby generating a sterilant liquid, and flowing the sterilant liquid over a surface of the device, thereby sterilizing the device.
Detailed aspects are disclosed herein; however, it is to be understood that the disclosed aspects are merely exemplary in nature and may be embodied in various and alternative forms. The figures are not necessarily to scale. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. The term “or a combination thereof” means a combination including at least one of the foregoing elements.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Throughout this specification, where publications are referenced the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains.
The following terms or phrases used herein have the exemplary meanings listed below in connection with at least one aspect:
A “dielectric” material as used herein is a medium or material that transmits electrical force without conduction and as such has low electrical conductivity. An illustrative example of a dielectric material is glass.
“Discharge space” as used herein means the gap between the active electrode and the ground electrode.
“FRG” as used herein means “Free Radical Generator” operating according to the teachings of this disclosure.
“Carbonaceous material” as used herein includes graphite, woven carbon or graphite fiber filled with binders, graphitized carbon materials, and compacted carbon materials, among others.
“Mist” as used herein includes a cloud of tiny droplets of a liquid suspended in a gas wherein droplet weight is lower than the drag force exerted by the gas.
“Fumigation” as used herein includes applying a gaseous fume of certain radicals to disinfect or to rid of biological organisms or toxins.
“Superbugs” as used herein includes a strain of bacteria, virus or fungi that has become resistant to one or more antibiotic drugs and other medications commonly used to treat infections it causes.
“Toxins” as used herein includes an antigenic poison or venom of plant or animal origin, optionally one produced by or derived from microorganisms and causing disease when present at low concentration in the body.
“Streamer” means a self-sustained ionization wave having substantial field enhancement in the range of 100-250 kV·cm−1 and propagating in neutral gas which is converted into low-temperature plasma behind the wave front, resulting in a channel like appearance. The interior of the streamer channel consists of a conducting plasma with roughly the same electron and ion densities.
“Free radical” means an atom or group of atoms that has an unpaired valence electron and is therefore unstable and highly reactive as those terms are recognized in the art. For example, free oxygen radicals are produced by following inelastic electron collisions:
which are expressed in a generic form as: O2+e−→O*+O*. Other radicals may be produced by similar inelastic collisions depending upon the composition of the gas in the discharge space, such as:
“Field” means the electric field, which can be positive or negative in nature. Similar fields repel each other and opposite fields attract each other.
“Motive element” means any structure operable to provide motion. Typical examples include an electric motor operable to provide rotation of another structure.
Certain embodiments of the present invention address some of the shortcomings of
prior art free radical generators. In one example, a discharge electrode assembly is provided, having a plurality of discharge electrode pins in an array arranged in a radial pattern and electrically configured to receive one or more voltage pulses. A counter electrode may be a solid electrode or may be a liquid electrode. An exemplary liquid electrode includes a liquid bath configured to hold a liquid having an upper surface disposed at a liquid level separated from the discharge electrode pins by a discharge gap. In an example, a motive element is operable to rotate the discharge electrode assembly such that the array of discharge electrode pins rotates about an axis and the plurality of pins move relative to the counter electrode, such as the liquid in the liquid bath.
A rotary electrode system may also have another advantage. Considering that the spark and arc discharge are tied to certain points on the electrodes, in case the discharge transitions into the spark/arc mode, the rotation will lead to the elongation of the discharge channel, reducing the voltage across the channel and, as result, the channel breakdown.
As discussed above with reference to
Further steps may be taken to further control wave formation.
Additionally, the liquid 41 may flow relative to the electrode assembly 30, as indicated by arrows B. In this example, the liquid flows in a direction opposed to the direction of movement of the pins 32 as they rotate clockwise. In a further example, the liquid flows in a direction generally parallel to the axis of rotation. Other flow directions are also possible.
The rotating electrode assembly 30 also acts as a fan to push evaporated water out of the discharge gap, further reducing the likelihood of breakdown.
The use of some or all of these steps may provide for improved performance.
Referring now to
In one example, liquid is continuously pumped into the liquid stage such that the liquid level is maintained at the height of the sides 118. A liquid inlet 124 and liquid outlet 126 are provided in the outer portion 112. The liquid stage likewise has a liquid inlet 128, which is fluidly connected to the liquid inlet 124 in the outer portion 112. A pump 130 continuously pumps liquid into the liquid stage 114, through the inlets 124 and 128. In the illustrated embodiment, the liquid inlet 128 of the liquid stage is connected to a receiving chamber 132 below a center region of the bottom 116 of the stage, with a grid or screen 134 between the chamber 132 and the remainder of the stage. Liquid flows into the chamber and then up into the stage 114 where it then flows out and causes continuous overflow of the stage 114 to maintain the liquid level. The overflowing liquid falls into the outer portion 112 and exits via the liquid outlet 126.
A main housing 140 is disposed on top of the liquid bath 110. The liquid bath may be connected to the main housing by height adjusting screws 142. As will be clear to those of skill in the art, by adjusting the screws 142, the position of the liquid bath, and therefore the position of the liquid surface defining the counter electrode, may be adjusted to change the discharge gap. Alternatively, the relative positions may be adjusted in other ways, such as adjusting the position of the liquid stage within the outer portion.
The main housing 140 is elongated with a pair of side walls 144 extending parallel to the sides of the liquid stage 114, with the side walls 144 spaced apart and extending upwardly to define a receiving space 146 therebetween, for receiving the discharge electrode assembly.
In this example, the discharge electrode assembly 150 an elongated central rod 152 with plurality of discs 154 arranged thereon, in a spaced apart mutually parallel arrangement. Each disc 154 has a plurality of discharge electrode pins extending radially outwardly therefrom. The central rod 152 defines an axis of rotation of the electrode assembly. The discs 154 extend along the central rod 152 for a length generally corresponding to the length of the liquid stage 114 such that each disc utilizes the liquid surface as a counter electrode. The liquid stage may have liquid provided near the center of the stage, as described above. As such, the flow of the liquid in the stage will be from the center outward, such that the flow is generally in the longitudinal direction of the elongated central rod and the elongated direction of the liquid stage, generally parallel to the axis of rotation of the discharge electrode assembly. The liquid flow is therefore perpendicular to a tangent to the pin movement. That is, as the pins rotate to a position closest to the liquid surface, they are moving in a direction generally perpendicular to the direction of liquid flow. Alternative approaches to liquid flow may also be used.
In this example, the discharge electrode assembly 150 is disposed in a reactor tube 160 formed of a non-conductive material. In this example, the reactor tube 160 has a generally circular cross-section but is open at the bottom 162 so that the pins of the electrode assembly 150 may discharge to the liquid counter electrode. In further examples, the reactor tube may have other cross-sectional shapes, such as square, rectangular, or polygonal. The discharge electrode assembly 150 is rotationally supported in the reactor tube 160 by a pair of reactor end caps 164 and 166, which are received in opposing ends of the reactor tube 160. The reactor end caps include bearings for rotational support of the central rod 152. The reactor tube 160, the end caps 164 and 166, and the discharge electrode assembly 150 are received between the side walls 144 of the main housing and held in place by retaining members 168 and 170. An electrical contact assembly 172 is provided at one end of the discharge electrode assembly 150, and provides a high voltage supply to the discharge electrode assembly.
Rotation of the discharge electrode assembly 150 may be accomplished in any way known to those of skill in the art. A motive element provides rotation. In the illustrated embodiment, the motive element is an electric motor 176 operable to rotate the central rod 150 through gears 178. Other approaches may also be used. In examples, the motive element or electric motor is electrically isolated from the discharge electrode assembly. This may be accomplished in any way known to those of skill in the art. In one example, the gears are non-conductive, such as made of polymer. A non-conductive belt may be used between the motor and central rod. As a further example, a motive element is coupled to the discharge electrode assembly by a magnetic coupling with an air gap. As yet another example, a mechanical coupling may be used wherein a dielectric material separates two sides of the coupling.
In the illustrated embodiment, the side walls 146 of the main housing have inlet openings 180 in one wall and outlet openings 182 in the other wall, to allow for air or gas to flow into and out of the area between the discharge electrode assembly 150 and the liquid bath. Air or gas may be blown through this area to remove moisture and discourage breakdown of the discharge gap.
The electrode pins are illustrated as generally square in cross section with flat ends, such that the four corners define ignition tips. Other shapes and arrangements are also possible.
As will be clear to those of skill in the art, any of the embodiments of the present invention disclosed herein may also be used to clean polluted liquid, such as water including microbes.
In some examples of a system for liquid treatment, the free radical generator includes a liquid bath as the counter electrode and the free radical generator creates free radicals in the liquid bath. The system for liquid treatment may include an additional pump for adding liquid to and/or removing liquid from the liquid bath such that the liquid is cleaned as it is passed through the liquid bath. As an alternative, the free radical generator generates free radicals in a gas and the gas is added to the liquid to be cleaned. This may utilize a solid counter electrode or a liquid counter electrode. As a further alternative, the above approaches may be combined, with liquid fed through the liquid bath and gas also introduced into the liquid. In examples, the liquid is water. A method of liquid treatment may include using such a system, adding gas to a liquid to be cleaned and/or passing liquid to be cleaned through the liquid bath.
The system as described above, and/or such as shown in
For certain embodiments of the present invention, the liquid of the liquid counter electrode is water, which may be deionized or otherwise treated. According to further embodiments of the present invention, various additives may be present in the liquid, with the liquid typically being water. Non-limiting examples of additives include one or more of the following:
A combination of one or more of the above could also be possible; as a non-limiting example, the combination of Quaternary ammonium and Isopropanol. The use of one or more additives may be useful for surface treatment and for other purposes.
As discussed above, a system such as shown in
The presence of iodine reduces or eliminates ozone in the treatment vapor, making use of the system possible with people present in a treatment area. As shown in
As an alternative, sodium chloride may be added to the water, or a combination of iodine and sodium chloride. As a further alternative, lactic acid or peracetic acid may be added.
As an alternative to the above design, the scrubbing tower may be replaced with a spray tower, without the bed of porous exchange media. Instead, sprayers may be provided in a column to introduce liquid into the moving airstream, thereby exposing the flow of gas to the liquid.
Embodiments of the present invention may be used for air treatment. In an example, air moves through the scrubber portion of the device where a high exchange surface area is provided for water and air to interface. Contaminants (chemical, biological, particulate, etc.) are transferred from the air stream to the water. Treated air then exits the device, while the water is disinfected and decontaminated by the action of the free radical generator. Any of the embodiments described herein may be used for air treatment in this way.
This approach may be used with the packed bed or with the spray tower.
As known to those of skill in the art, the porous exchange bed may be constructed in a variety of ways, as long as it allows interaction between a wetted surface and the airflow.
The ratio of water flow rate to air flow rate through the scrubber, defined as L/Q in units of liters/m3, is an important efficiency parameter. In general, a higher L/Q is preferred to achieve uniform wetting of the media and consequently a larger interface surface area for the water and the air. Values for L/Q may range from 0.5 liters/m3 to 20 liters/m3, preferably between 2 liters/m3 and 10 liters/m3. L/Q values beyond 20 liters/m3 require higher pumping requirements and water retention capacities whilst not offering a significant efficiency boost.
The residence time of air through the packed media bed impacts the capture efficiency of the scrubber, with longer residence time leading to higher efficiency. Residence time can range from 0.05 s to 5 s, with a preferred residence time between 0.1 s and 1 s. A variable in relation to the residence time that also impacts collection efficiency is the linear velocity of air through the packed media bed. The linear velocity range may be between 0.1 m/s and 1 m/s and preferably between 0.2 m/s and 0.6 m/s.
Referring now to
In an example, the sterilizing bath is filled with a liquid, commonly water. The free radical generator processes the liquid, creating active species in situ with sterilant characteristics. The instrument requiring sterilization is then placed in the sterilization bath. The mechanical flow of the sterilant liquid across the instrument surfaces for a prescribed time period achieves sterilization of the instrument.
Those of skill in the art will recognize that the embodiments disclosed herein may be operated using a range of parameters, such as the speed of rotation of the discharge electrode assembly, the pulse frequency and characteristics, the speed and volume of gas flow, the gap size, etc. As non-limiting examples, the speed of rotation of the discharge electrode assembly may be in the range of 100 to 10,000 RPM, such as 200 to 5,000, or such as approximately 1000 RPM. The energy per pulse and the pulse frequency are two important parameters that determine the overall power consumption by the device. The energy dissipated per discharge pin may optionally be between 0.1 μJ to 100 μJ, optionally between 1.0 and 20.0 μJ. The frequency may optionally range between 100 Hz to 100 kHz, optionally between 10 kHz and 30 kHz.
The gas flow rate considerably influences the energy that can be delivered to the device and in turn the radical concentration as well as quantity. While low gas flow increases the radical concentrations, the yield is lowered due to competition between generation and destruction rates as well as space charge build up which leads to unstable ignition voltage and arcing. Higher gas flow reduces the radical concentration but improves the yield. For a given pressure gradient, the gas flow rate depends on the discharge gap, and hence, the gas velocity in the discharge space is a useful parameter for proper device operation. The gas velocity in the discharge space may optionally be in the range of 0.1 m/s to 200 m/s. As such, the gas velocity in the discharge space is optionally 2 m/s, optionally 5 m/s, optionally 10 m/s, optionally 15 m/s, optionally 20 m/s, optionally 30 m/s, optionally 40 m/s, optionally 50 m/s, optionally 60 m/s. The volumetric energy, i.e., energy/liter of gas, is an important characteristic of the device. The volumetric energy may optionally vary from 5 J/L to 5 KJ/L, optionally 200 J/L to 1 KJ/L.
The free radical generator may be operated with a bias voltage. The bias voltage is optionally between 0 and 500V compared to the actual pulse voltage (1 to 100 kV, optionally 5 to 20 kV, optionally 7 kV to 20 kV) and its magnitude depends on several parameters such as the gas flow rate and its composition, electrode design, and the applied voltage. Streamer discharge is also known to produce a gas flow. The ions within the discharge space are accelerated and, through collisions, the momentum of ions is transferred to neutrals, resulting in a gas flow. The effect of the bias voltage becomes less important when the gas velocity in the discharge space is high (>5 m/s), as the conductivity is reduced due to migration of space charge from the discharge space, more particularly from the ignition tips.
While aspects of the invention have been illustrated and described, it is not intended that these aspects illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
Various modifications of the present invention, in addition to those shown and described herein, will be apparent to those skilled in the art of the above description. Such modifications are also intended to fall within the scope of the appended claims.
It is appreciated that all reagents are obtainable by sources known in the art unless otherwise specified.
The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. It is the following claims, including all equivalents, which define the scope of the invention.
This application claims priority to U.S. Provisional App. No. 63/192,275, filed May 24, 2021, all of which is hereby incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/030642 | 5/24/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63192275 | May 2021 | US |
