Patent Application
20240368002
The present invention generally relates to water purification methods and devices, and more specifically relates to water purification devices that use plasma to break up PFAS contamination in water.
Water purity is an important issue for maintaining human health and the environment. Unfortunately, much of the drinking water in the United States and elsewhere is severely contaminated with heavy metals, organic pollutants, and other substances that are harmful to human health. One of the categories of pollutants that is ubiquitous, harmful to human health, and difficult to remove from drinking water, is a group of per- and polyfluoroalkyl substances (PFAS). These are manufactured chemicals that have been used in industry and consumer products since the 1940's; there are thousands of different PFAS. These chemicals break down very slowly and therefore build up in people, animals, and the environment over time. Exposure to certain levels of PFAS may lead to decreased fertility, high blood pressure in pregnant women, developmental effects in children, increased risk of some cancers, decreased immune system function, interference with the body's natural hormones, increased cholesterol levels, and increased risk of obesity.
It is therefore very important to remove PFAS from drinking water; however, PFAS compounds do not break down very easily. Conventionally available activated-carbon filters, widely used in many pitcher, refrigerator, and faucet-mounted water purification systems, do not always provide consistent removal of PFAS compounds; in some cases, they actually increase PFAS amounts in the water.
Plasma processes are known as a method of purifying water. To perform water purification using plasma, an electrical current is applied to steam to generate plasma. The plasma then generates various reactive oxygen species, such as OH radicals, H2O2, and O3. These reactive species can sterilize the water by killing microorganisms, and break up PFAS compounds, pharmaceutical residue, and other organic pollutants within the water.
However, the devices used to purify water by plasma generation are frequently cumbersome and complex and not suitable for consumer use. Many of these devices use a lot of energy in order to create plasma throughout the water container. Furthermore, the process of plasma creation overheats the water, which means it needs to be cooled down to be made usable. All of this renders these devices unsuitable for being used in a consumer context.
Also, because the electrodes used in conventional plasma-based water purification systems are at such a high voltage, they wear out and release metal ions into the water. This results in less acceptable water and the recurring costs of replacing the electrodes.
A need exists for a simple and effective way to remove PFAS contamination and other contaminants from water in a way that can be done at a consumer's home.
An object of the present invention is to provide a water purification device that uses plasma to purify water and that is simple and compact.
Another object of the present invention is to provide a water purification device that uses plasma to purify water while the majority of the water remains cool.
Another object of the present invention is to provide a water purification device that uses plasma to purify water without using excessive energy to do so.
In an aspect of the present invention, a water purification device is provided. The water purification device comprises a container of water and a partition placed in the water in such a way as to separate it into a first and second volume of water. The partition is nonconductive, waterproof, and capable of withstanding temperatures up to about 300° C. The partition also comprises a small hole through which water can flow, and a flow control module that causes water to flow through the hole. A power supply delivers alternating current at a specified current and voltage in such a way as to create alternating current between the first and second volume of water. The current and voltage is such that the current density in the first and second volumes of water is not enough to boil the water, while the current density in the hole is such that the water boils and then transitions into a plasma state. This results in a bubble of plasma forming around the hole, which purifies the water as it flows through the hole.
In an aspect of the invention, the partition is an integral part of the container and the entire container is made of a nonconductive material. The power supply is connected to the water via a first and second electrode immersed in the water, one in the first volume and one in the second volume; each of the electrodes has a surface area that is larger than the cross-sectional area of the hole.
In an embodiment, the power supply provides between 1200 and 2000 watts, and the voltage between the electrodes is between 4 kV and 10 kV.
In an embodiment, the partition comprises more than one hole, with the total cross-sectional area of the holes being such that the water passing through the holes transitions into a plasma state while the water in the first and second volume of water does not boil.
In an embodiment, the flow control module causes water to flow through the hole at approximately 0.2 L/min.
In an embodiment, the partition is made of quartz glass, silicon glass, or ceramic.
In an embodiment, the device further comprises a sensor that is configured to determine the strength of the plasma state of the water passing through the hole, and wherein either the flow control module is configured to change the flow rate based on the strength of the plasma state, or the power supply is configured to change the voltage level based on the strength of the plasma state.
In an embodiment, the device comprises a second partition comprising a second hole, wherein the two partitions separate the water in the container into three volumes of water and the water flows from the first to the second volume and then from the second to the third. The power supply is connected to all three volumes of water and delivers a high voltage to the second volume of water while keeping the first and third volumes of water at ground electric potential. The three volumes of water can be located vertically above each other so that water flows upward from the first volume to the second and from the second to the third due to thermal expansion; in this embodiment, the device also comprises a recirculating channel to return the water from the third to the first volume of water, and the device may also comprise a cooling feature to cool the water in the recirculating channel.
The diameter and length of the hole may be optimized to maximize the strength of the plasma within the hole. In another embodiment, the voltage or the flow rate or both may be optimized to maximize the strength of the plasma within the hole.
In an embodiment, the second volume of water is enclosed in a container that is entirely submerged within the first volume of water, with two partitions located in such a way that water flows into the container through the hole in the first partition and flows out of the container through the hole in the second partition. The power supply is connected to the first and second volumes of water in such a way that the first volume of water is at ground electrical potential and there is an alternating current delivered from the second to the first volume of water, wherein the voltage and current levels are such that the water passing through the holes transitions into a plasma state, while the water in the second volume of water does not boil.
In an embodiment, the container is a pipe through which water passes and the partition is a cylindrical disc separating the input pipe from the output pipe. In an embodiment, a middle pipe made of a nonconductive material may be located between the input pipe and the output pipe and a partition is placed at each end of the middle pipe. The water in the input pipe and the output pipe is then kept at ground electric potential while the water in the middle pipe is kept at a high voltage level.
The power supply may connect to the middle pipe via an opening in the pipe through which an electrode is inserted, or via a conductive washer located next to the partition in the water.
In an embodiment, the middle pipe is conductive and electrically separated from the input and output pipes by non-conductive spacers. This enables the power supply to connect to the water in the middle pipe via the conductive wall of the middle pipe.
While several embodiments are described below, it is to be understood that reasonable equivalents to the elements described in the present disclosure are also incorporated into the present invention, as apparent to a person of reasonable skill in the art.
The present invention is a system intended to purify water using plasma without using a lot of energy. In its most basic form, water is passed through a small hole at a slow flow rate, and alternating current is applied to it—the alternating current is such that the current density outside the small hole is not enough to boil or ionize the water, while the current density inside the hole can boil it and create plasma. Thus, a small bubble of plasma is formed around the hole, and the water that passes through the hole is purified. This means that a relatively low amount of power is sufficient to generate the plasma, and that the water outside the hole is not overheated and does not require as much cooling to be usable. At the same time, the plasma is sufficient to kill microorganisms and degrade PFAS compounds and other pollutants.
A flow control module directs water through the inlet pipe 120 into the first compartment, after which it passes through the hole 150 into the second compartment 110 and through the outlet pipe 130. Electrodes 170 and 180 are located in each one of the compartments 100 and 110, respectively. For each electrode, the surface area of the electrode is greater than the cross-sectional area of the hole, as will be discussed below. Power supply 160 is connected to electrodes 170 and 180 and delivers alternating current to them.
In brief, the operation of an embodiment of the present invention is as follows. The flow control module provides a constant water flow through the hole from the first compartment to the second compartment. The power supply provides an electric field gradient between the two electrodes through the water. Due to the difference in cross-sectional area between the compartments and the hole, the current density within each compartment is low and the current density inside the hole is very high-especially since the electrode surface area in the water is much larger than the cross-sectional area of the hole. Because of this, the water in the hole starts boiling and bubbles of steam are created.
Due to the ability of the power source to provide a rapid increase in electric field gradient within the bubbles, as soon as steam bubbles appear, they are ionized and a corona discharge is formed in each bubble. At the same time, the bubbles increase in volume and merge, forming a larger bubble inside and immediately around the hole. The power supply provides the conditions for the formation and maintenance of plasma in this bubble. As the water flows through the hole, it condenses in the second compartment, but the plasma bubble stays around the hole.
Since plasma breaks down organic compounds such as PFAS or pharmaceutical residues and kills microorganisms, the water that passes into the second compartment is purified and suitable for consumption. Also, since only the water passing through the hole is heated, energy consumption is low.
In an embodiment, a flow control module is used to control the flow rate of the water through the hole. The flow control module can be any type of pump that ensures the correct flow rate. As described below, the flow rate may be controlled in order to optimize the level of plasma forming at the hole. In an embodiment, the flow rate is set at approximately 0.2 L/min.
In an embodiment (as shown and discussed below), gravity is used instead of a flow control module.
In an embodiment, the outlet pipe is connected to the inlet pipe so that water circulates through the system more than once. This ensures better water purification.
Each compartment has a metal electrode located internally in such a way that they are in contact with the water. The surface area of each electrode has to be larger than the cross-sectional area of the hole; the surface area has to be large enough to ensure that the water contacting the electrode does not boil, while the hole has to be small enough to ensure a current density inside the hole that will boil the water. The two electrodes are connected to an alternating-current power supply with ballast, built as described in U.S. Pat. No. 9,343,996, which is herein incorporated by reference. In an embodiment, the power levels are adjusted based on the strength of the plasma within the hole.
The hole is preferably between 2 mm and 8 mm diameter, and has a length (i.e. wall thickness) between 0.5 and 15.0 mm. The exact dimensions of the hole may be optimized so that at a given flow rate, electrode diameter and length, ambient temperature, water temperature, and power level, the optimal amount of plasma forms in the hole. Alternately, for any given hole dimensions (length and diameter), the flow rate and power level may be optimized.
In an embodiment, multiple holes are used. In this embodiment, the total cross-sectional area of all the holes has to be less than the total surface area of each electrode. The holes may be placed anywhere on the wall as long as water can flow through them.
Appendix 1 provides a sample Octave script for calculating system parameters to maximize the power in the hole and thus optimize plasma generation. It is to be understood that other programming languages may be used to execute similar scripts, and the sample script and values provided in it are not meant to be limiting.
The sample script provides four different values that may be maximized. The hole dimensions may be optimized to maximize the power levels in the hole, to maximize the energy levels in the hole, to maximize the diameter, or to minimize the length of the hole. Choosing to maximize the power results in the most power going into the plasma in the hole; choosing to maximize the energy results in the most energy going into the plasma over a period of time (which would result in different hole dimensions from the option to maximize power); choosing to maximize the diameter of the hole ensures that there is a good flow; and choosing to minimize the length ensures that the wall is not too thick.
The operation of the sample script is briefly summarized below. The input parameters used are the ambient water temperature (the colder the water, the more energy it takes to generate a corona discharge at the hole), the required water flow rate, the maximum power supply power rating, the electrode diameter and length, and the input (mains) voltage. The script also uses the specific heat capacity of water, the electrical resistivity of the water (which is different depending on whether it is deionized water, drinking water, or sea water), and the minimal and maximal dimensions for the hole diameter and length.
The script initially prompts a user to select which criterion should be optimized. In this embodiment, one of the following four criteria may be selected-power, energy, hole diameter, or hole length (i.e. wall thickness).
The script then normalizes the input parameters and calculates the required temperature rise for the water in the hole to initiate a plasma corona discharge. Then, the script assigns initial values for hole dimensions and power.
Next, the script calculates the energy and power going into the water in the hole based on the initial values for the optimization criteria, and determines the “voltage budget” necessary to produce plasma in the hole given the current constraints. If the voltage budget is zero or less, it is impossible to produce plasma in the hole given the constraints, and the device will not work. If the voltage budget is greater than zero, the program script finds optimal values to maximize either the energy or the power going into the hole, to maximize the diameter of the hole, or to minimize its length, depending on user needs.
It must be noted that the plasma purification method and system here does not depend on the volume of the water container. The only relevant parameter here is the volume of the water within the hole and the flow rate. As long as the current density within the container (but outside the hole) is not enough the boil the water outside the hole, the container can be any size.
The voltage provided by the electrodes is preferably 4-10 kV, and is alternating current. Providing direct current would electrolyze the water, which is not desirable for the present invention. The power supply provides about 1200-2000 watts, and provides a ballast for stabilization. Since plasma varies in impedance from a short-circuit to infinite resistance, the power supply needs to adjust accordingly and not limit the process of ionization, so that the plasma can be sustained. The process for regulating the power supply to sustain the plasma is described in U.S. Pat. No. 9,343,996, and is not a novel part of the present disclosure.
In an embodiment, a third electrode can be added next to the plasma to incorporate an infusion of metal into the water. The third electrode may be made of a metal that is important for human health, such as silver or copper.
In an embodiment, a sensor can be used to determine the strength of the plasma and adjust the voltage and flow rate accordingly. Any sensor may be used to measure plasma intensity for the present invention, as long as it is useful for measuring the properties of a very small volume of plasma and can be done non-invasively. For example, passive spectroscopic methods such as Doppler shift, Doppler broadening, Stark effect, Stark broadening, spectral line ratios, or the Zeeman effect may be used; or active spectroscopic methods such as absorption spectroscopy, beam emission spectroscopy, charge exchange recombination spectroscopy, laser-induced fluorescence, or any other method that can be used for measuring plasma intensity. In an embodiment, a photo-sensor is used.
It is to be understood that the present invention may be practiced in any water container setup in which it is possible for water to pass through a nonconductive partition via a hole and an alternating current to be applied to the water in the abovedescribed way. While the below embodiments are some of the ways the present invention may be practiced, they are not meant to be limiting.
The present invention works well to destroy PFAS and microplastics present in water, kill bacteria and viruses, and produce PW (purified water). It may be used as an entire purification system in itself, a part of one, or simply as a water treatment method for physically modifying the composition of water.
In any of the abovedescribed embodiments that comprise inlet and outlet pipes, the compartments directly connected to those pipes can be kept at ground electrical potential to ensure safety from electrocution.
While the abovedescribed embodiments show the water container as a single entity separated by a wall, it is also possible to practice this invention by simply adapting a pipe through which water can flow. In this embodiment, as shown in
In an embodiment shown in
Sanitary pipe fittings, for example food-grade pipe fittings, may be used for these embodiments of the present invention. All the fittings and gaskets have to be able to withstand a temperature of up to 300° C. The non-conductive disc can be a fused quartz ground and polished disc, with a 2″ diameter and a 1/16″ thickness, with one or more holes drilled into it at any position on its surface. The gasket may be a standard 0.064″ thickness 2″ diameter O-ring for a tri-clamp fitting. The non-conductive pipe section can be a 2″ tri clamp Hop Bong Sight Glass; such devices are used in fermentation. An electrically conductive pipe section can be a Sanitary Spool Tube with a 2″ tri clamp round ferrule. A sanitary tri-clamp can be used to connect the different sections of the device together.
Exemplary embodiments are described above. It will be understood that other embodiments of the present invention also exist and that reasonable equivalents to the embodiments described above are also incorporated into the present disclosure.
The present application takes priority from Provisional App. No. 63/464,314, filed May 5, 2023, which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63464314 | May 2023 | US |
