Stacked-block system and method for plasma discharge in liquid

Abstract

A stacked-block system for generating a plasma discharge in liquid includes a liquid inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked-block reactor, a top block disposed over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor, at least one spacer block disposed under the liquid inlet block, and a ground electrode in fluid communication with the interior space of the reactor, the ground electrode being in direct contact with the at least one spacer block. A high-voltage electrode block disposed coaxially with a central axis of the reactor at a bottom side of the reactor is included.

Description

STACKED-BLOCK SYSTEM AND METHOD FOR PLASMADISCHARGE IN LIQUIDCROSS-REFERENCE

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 561 ,418, filed on March 5, 2024, and entitled “STACKED-BLOCK SYSTEM AND METHOD FOR PLASMA DISCHARGE IN LIQUID” which is hereby incorporated by reference in its entirety.BACKGROUND

[0002] Per- and poly-fluoroalkyl substances (PFAS) are a class of manmade amphophilic compounds ( / .e., surfactants with a chemical structure that includes a hydrophilic “head” group and a fluorinated “tail”) that have been used to manufacture consumer products and industrial chemicals, including, inter alia, aqueous film forming foams (AFFFs). AFFFs have been the product of choice for firefighting at military and municipal fire training sites around the world. AFFFs have also been used extensively at oil and gas refineries for both fire training and firefighting exercises. AFFFs work by blanketing spilled oil / fuel, cooling the surface, and preventing re-ignition. PFAS in AFFFs have contaminated the groundwater at many of these sites and refineries, including more than 100 U.S. Air Force sites.

[0003] PFAS are very difficult to treat largely because they are extremely stable compounds which include carbon-fluorine bonds. Carbon-fluorine (C-F) bonds are among the strongest known bonds in nature and are highly resistant to breakdown.

[0004] Due to PFAS contamination in groundwater, surface water, agriculture, and drinking water and their associated health risks, there has been a great focus on developing practical and effective water treatment technologies.Treatment technologies developed so far have included adsorptive and destructive methods. Some PFAS can associate strongly to proteins through either electrostatic or non-electrostatic (hydrophobic / hydrophilic) physisorption as well as site specific chemisorption. Based off these properties, adsorptive methods have been developed to remove these specific compounds from water, but are not effective for all PFAS compounds. Adsorptive methods to date include granular activated carbon (GAC), ion exchange (IX), polymers, and protein addition. These methods show promise in effectively removing some of the compounds from contaminated water, but do not destroy the PFAS compound, leading to the generation of PFAS contaminated residues and concentrates.

[0005] Due to the recalcitrant nature of PFAS and the C-F bond, destructive methods development has come with difficulties. Destructive methods of PFAS in contaminated water that have been studied for their treatment ability include sonolysis, thermal degradation, photocatalytic ozonation, electrochemical oxidation, persulfate, alkaline hydrothermal treatment, microwave / persulfate, UV, ionizing radiation electron beam, gamma-irradiation, boron-doped diamond film electrode oxidation, electrical discharge plasma, and biodegradation. Novel reductive processes such as photogenerated hydrated electrons (e’aq) are also being developed as a treatment technology. The methods described above have been demonstrated to be effective in degradation and lead to varying degrees of destruction involving reduction in chain length, cleaving of the C-F bond, and removal of the head group. When any PFAS destruction method is applied to a large volume (e. g., 1 gallon or more) of water, such as municipal drinking water, the treatment method must be robust enough to break down the carbon-fluorine bond,and achieve a low target contaminant concentration, on the order of nanograms per liter in the resulting treated water.

[0006] A promising treatment technology, non-equilibrium plasma discharge, is not in thermodynamic equilibrium and only the electron temperature is much hotter than the rest of the gas. Non-equilibrium plasma can generate a reactive environment of heat, ultraviolet (UV) radiation, and highly reactive chemical species such as electrons, ions, and reactive neutral species. At the gas-liquid interface, nonequilibrium plasma generates diverse reactive environments containing a variety of reactive chemical species like reactive oxygen species (ROS, such as1O2, H2O2, O3, etc.), reactive nitrogen species (RNS, such as peroxynitrite, ONOO', and peroxynitrate, ONOOO'), radicals (H', O*, OH', NO', NO2 , as well as hydrated electrons (e'aq). These reactive species are responsible for targeting anything dissolved or suspended, including contaminants in the water and potentially degrading them in the plasma water treatment system. Plasma water treatment applications include a multitude of different discharge types, such as pulsed corona / streamer / spark discharge, DC pulseless corona discharge, dielectric barrier discharge, gliding arc discharge, DC glow discharge, DC arc discharge and AC arc discharge, all leading to different reactive environments with different treatment potentials.

[0007] Generation of plasma discharge requires the use of two or more electrodes, for example, at least one cathode and one anode, positioned relatively close together (e.g., 1 -8 mm for discharge in gas). When the voltage between the two electrodes increases to a certain value, such as 2 kV, breakdown of gas between the two electrodes takes place, generating a discharge of plasma. Depending on the magnitude of the voltage across the two electrodes and otherfactors such as the geometry of the electrodes, a variety of different types of plasma discharges can be produced and controlled, including corona, spark, and arc.

[0008] When one attempts to produce plasma discharges in liquid such as water, it is more complicated. As soon as two electrodes with high voltage are immersed in water, electrolysis occurs, generating gas bubbles at both electrodes. When there are sufficient amounts of gas at the two electrodes, the “breakdown” of water can occur, and subsequently plasma discharge takes place in water. The use of gas bubbles generated from electrolysis can result in breakdown in a small volume of water, for example, as in a beaker. However, in order to treat several gallons of water per minute or more, plasma generation using gas bubbles generated from electrolysis is a method that is neither sufficient nor practical.

[0009] Another technical challenge in generating plasma discharge in water treatment applications such as seawater is their high electric conductivity. The conductivity of some water to be treated can be in the range of 100-200 mS / cm due to a large amount of dissolved ions such as sodium, calcium, chloride, magnesium, and others, whereas that of seawater is about 50 mS / cm. In liquids with such high conductivity, electrons instantly and continually flow from cathode to anode as high electric conductivity water provides an effective path for electrons to flow, a phenomenon that can be referred as electron leakage in liquid. Accordingly, compressed gas is injected at or between the two electrodes to provide a gap to assist breakdown such that plasma is able to be discharged in high conductivity liquid using only a moderately high voltage of ~1 kV. When gas injection is utilized to assist the generation of plasma discharges in high electric-conductivity liquids, it is essential to have gas bubbles remain in the gap between the two electrodes suchthat the breakdown of water takes place, leading to the generation of plasma discharge.

[0010] At the moment when gas bubbles occupy the space between the two electrodes by displacing liquid, breakdown occurs, generating plasma discharge. However, since gas density is approximately 1 ,000 times smaller than that of liquid ( / .e., water), gas bubbles tend to rise in a liquid-filled plasma reactor due to the buoyancy force created by the density difference between gas and liquid.

[0011] For the treatment of liquid with a very high electric conductivity, increasing the distance between the two electrodes increases the impedance, which is helpful in igniting and stabilizing the plasma discharge.

[0012] Therefore, there is a need in the art for a plasma reactor that can generate a plasma discharge in liquid with a variable distance between the two electrodes.SUMMARY

[0013] Various embodiments disclosed herein relate to methods and apparatus for fluid treatment with plasma discharges. In accordance with one or more embodiments, a stacked-block system for generating a plasma discharge in liquid includes a liquid inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked-block reactor, a top block disposed over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor, at least one spacer block disposed under the liquid inlet block, and a ground electrode in fluid communication with the interior space of the reactor, the ground electrode being in direct contact with the at least one spacer block. Thestacked-block system further includes a high-voltage electrode block disposed coaxially with a central axis of the reactor at a bottom side of the reactor, and including a central solid cylindrical rod high-voltage electrode inserted at least partially into and coaxial with a cylindrically-symmetric electrode housing for generating a plasma discharge between the high-voltage electrode and the ground electrode, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod. In certain embodiments, the high-voltage electrode block can include an outlet for removing solids from the interior electrode housing space. In some embodiments, the ground electrode can be a ground electrode block disposed between the at least one spacer block and the high-voltage electrode block. In some other embodiments, the ground electrode can be a flange disposed between the at least one spacer block and the high voltage electrode block. In certain embodiments, the electrode housing can be formed of an electrical insulator material. In some embodiments, the electrode housing can be a cylindrical electrode housing. In certain embodiments, the electrode housing can be a divergent-cone- shaped electrode housing. In some embodiments, the electrode housing can be a convergent-cone-shaped electrode housing. In certain embodiments, the electrode housing can be an hourglass-shaped electrode housing. In some embodiments, the electrode housing can be a bell-shaped electrode housing. In certain embodiments, the stacked-block system can further include a liquid reservoir in fluid communication with the liquid outlet of the reactor, the liquid reservoir including a head space. In some of these embodiments, the stacked-block system can further include a vacuumpump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet of the reactor. In certain embodiments, the vacuum pump can be a scroll pump. In some embodiments, the vacuum pump can be a diaphragm pump. In certain embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction. In certain other embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions. In some embodiments, the central solid cylindrical rod can be formed of one of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, and carbon. In certain embodiments, an end of the central solid cylindrical rod proximal to the ground electrode can be disposed above a top side of the electrode housing. In some of these embodiments, the stacked-block system can further include a means for slidably adjusting a distance between the end of the central solid cylindrical rod and the ground electrode.

[0014] In accordance with one or more embodiments, a method of generating a plasma discharge in liquid includes flowing a liquid through an inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked- block reactor, disposing a top block over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor, disposing at least one spacer block under the liquid inlet block, and providing a ground electrode in fluid communication with the interior space of the reactor, theground electrode being in direct contact with the at least one spacer block. The method further includes disposing a high-voltage electrode block coaxially with a central axis of the reactor at a bottom side of the reactor, and inserting a central solid cylindrical rod high-voltage electrode at least partially into and coaxial with a cylindrically-sym metric electrode housing for generating a plasma discharge between the high-voltage electrode and the ground electrode, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod.

[0015] In accordance with one or more embodiments, a system for generating a plasma discharge in liquid includes a liquid inlet and a liquid outlet in fluid communication with an interior space of a cylindrical liquid vessel having a central axis, the inlet and outlet both disposed near a top side of the liquid vessel, the liquid outlet disposed at a center of the cylindrical liquid vessel, and both configured to generate a vortex liquid flow in the interior space of the liquid vessel, a high voltage electrode and a ground electrode spaced apart, the high voltage electrode disposed coaxially with the central axis of the cylindrical liquid vessel at a bottom side of the liquid vessel, and including a central solid cylindrical rod inserted at least partially into and coaxial with a cylindrically-symmetric electrode housing, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around thecentral solid cylindrical rod, and a liquid reservoir in fluid communication with the liquid outlet, the liquid reservoir including a head space. The system further includes a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet. In certain embodiments, the vacuum pump can be a scroll pump. In some embodiments, the vacuum pump can be a diaphragm pump. In certain embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction. In certain other embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions. In some embodiments, the central solid cylindrical rod can be formed of one of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, and carbon. In certain embodiments, an end of the central solid cylindrical rod proximal to the ground electrode can be disposed above a top side of the electrode housing. In some of these embodiments, the system can further include a means for slidably adjusting a distance between the end of the central solid cylindrical rod and the ground electrode.

[0016] In accordance with one or more embodiments, a method of generating a plasma discharge in liquid includes providing a liquid inlet and a liquid outlet in fluid communication with an interior space of a cylindrical liquid vessel having a central axis, the inlet and outlet both disposed near a top side of the liquid vessel, the liquid outlet disposed at a center of the cylindrical liquid vessel, and both configured to generate a vortex liquid flow in the interior space of the liquid vessel, providing a high voltage electrode and a ground electrode spaced apart, the high voltage electrode disposed coaxially with the central axis of the cylindrical liquidvessel at a bottom side of the liquid vessel, and including a central solid cylindrical rod inserted at least partially into and coaxial with a cylindrically-symmetric electrode housing, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod, and providing a liquid reservoir in fluid communication with the liquid outlet, the liquid reservoir including a head space. The method further includes providing a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet.

[0017] The water treatment systems and methods described herein have many advantages, including enabling a variable distance between the two electrodes, such that the impedance between the two electrodes can be varied, enabling the treatment of PFAS-concentrated water with a wide range of electrical conductivity (e.g., in a range of between about 1 mS / cm and about 200 mS / cm).BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The foregoing purposes and features, as well as other purposes and features, will become apparent with reference to the description and accompanying figures below, which are included to provide an understanding of the invention and constitute a part of the specification, in which like numerals represent like elements, and in which:

[0019] FIG. 1 A is a simplified side view of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0020] FIG. 1 B is a simplified perspective view of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0021] FIG. 1 C is a simplified cross-section view of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0022] FIG. 1 D is another simplified side view of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0023] FIG. 1 E is a simplified top-down view of a liquid inlet block of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0024] FIG. 2 is another simplified cross-section view of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0025] FIG. 3 is a simplified perspective cross-section view of a ground electrode block of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0026] FIGS. 4-8 are simplified cross-sectional views of electrode housings of stacked-block fluid treatment systems in accordance with one or more embodiments.

[0027] FIG. 9 is a schematic diagram of a stacked-block fluid treatment system in accordance with one or more embodiments.

[0028] FIG. 10 is a simplified cross-section view of a high-voltage electrode in accordance with one or more embodiments.

[0029] FIG. 11 is a flow chart of a method of generating a plasma discharge in liquid in accordance with one or more embodiments.

[0030] FIG. 12A is a schematic diagram of a fluid treatment system in accordance with one or more embodiments.

[0031] FIG. 12B is a simplified top-down view of an electrode housing of a fluid treatment system in accordance with one or more embodiments.

[0032] FIG. 13 is another simplified cross-section view of a high-voltage electrode in accordance with one or more embodiments.

[0033] FIG. 14 is another flow chart of a method of generating a plasma discharge in liquid in accordance with one or more embodiments.DETAILED DESCRIPTION OF THE INVENTION

[0034] It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clearer comprehension of the present invention, while eliminating, for the purpose of clarity, many other elements found in systems and methods of plasma discharge in liquid. Those of ordinary skill in the art may recognize that other elements and / or steps are desirable and / or required in implementing the present invention. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements and steps is not provided herein. The disclosure herein is directed to all such variations and modifications to such elements and methods known to those skilled in the art.

[0035] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.

[0036] As used herein, each of the following terms has the meaning associated with it in this section.

[0037] The articles “a” and “an” are used herein to refer to one or to more than one ( / .e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.

[0038] “About” as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20%, ±10%, ±5%, ±1 %, and ±0.1 % from the specified value, as such variations are appropriate.

[0039] “HV” as used herein means high-voltage, such as a voltage in excess of 1 ,000 V (1 kV).

[0040] Ranges: throughout this disclosure, various aspects of the invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Where appropriate, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1 , 2, 2.7, 3, 4, 5, 5.3, and 6. This applies regardless of the breadth of the range.

[0041] In accordance with one or more embodiments, a stacked-block reactor system 100 for generating a plasma discharge in liquid, shown in FIGS. 1A- 1 D, includes a liquid inlet block 110 including a liquid inlet 120, and a top block 130disposed over the liquid inlet block 110. As shown in FIG. 1 B, the top block 130 includes a liquid outlet 140 disposed at a center of the top block 130. As shown in FIG. 10, the liquid outlet 140 includes a center tube extension 150 of the liquid outlet 140 into the interior space 160 of the reactor 100, at least one spacer block 165 disposed under the liquid inlet block 110 (two spacer blocks 165 shown in FIGS. 1A- 1 D), and a ground electrode 170 in fluid communication with the interior space 160 of the reactor 100, the ground electrode 170 being in direct contact with the at least one spacer block 165. The stacked-block reactor system 100 further includes a high-voltage electrode block 175 disposed coaxially with a central axis 176 (shown in FIG. 1 D) of the reactor 100 at a bottom side of the reactor 100, and including a central solid cylindrical rod high-voltage electrode 180 inserted at least partially into and coaxial with a cylindrically-symmetric electrode housing 185 (shown in FIGS. 1A-1 D) for generating a plasma discharge between the high-voltage electrode 180 and the ground electrode 170, the electrode housing 185 including a gas inlet 190 (shown in FIGS. 1A-1 B) disposed tangentially to the central solid rod 180 along an interior wall 186 (shown in FIG. 1C) of the electrode housing 185 for gas injection into an interior electrode housing space 187 (shown in FIG. 1 C) of the electrode housing 185, the gas inlet 190 configured to generate a vortex gas flow within the interior electrode housing space 187 around the central solid cylindrical rod 180. The central solid cylindrical rod 180 can be formed of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, carbon, such as high-density carbon graphite, or any other conductive material. The ground electrode 170 can also be formed of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, carbon, such as high-density carbon graphite, or any other conductive material. The reactor blocks can beconstructed from any electrically insulating material. Resistance to high temperatures is also a desirable property, as is chemical stability and compatibility with water. Materials that meet these criteria include polymers, such as polycarbonate, nylon, acetal, polyetherimide (PEI), polyether ether ketone (PEEK), polybenzimidazole (PBI), polyamide-imide (PAI), and polysulfone. Other high- temperature electrical insulators that are suitable as materials for the reactor blocks include ceramics, such as alumina, Macor, titania, zirconia, Cordierite, and Steatite. As shown in FIGS. 1A-1 D, threaded rods 105, that are threaded into the electrode housing 185, hold the several blocks together, with gaskets (not shown) between each block.

[0042] As shown in FIG. 1 E, the liquid inlet 120 is disposed tangentially relative to a sidewall 125 of the liquid inlet block 1 10, in order to generate a vortex liquid flow in an interior space 126 of the liquid inlet block 110 and around the center tube extension 150 into the interior space 160 of the stacked-block reactor system 100 shown in FIG. 1 C. In some embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction. In some other embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions.

[0043] As shown in FIG. 2, the high-voltage electrode block 275 can include an outlet 277 for removing solids from the interior electrode block space 274. In some embodiments, as shown in FIG. 3, the ground electrode 370 can be a ground electrode block 371 disposed between the at least one spacer block 165 and the high-voltage electrode block 175 shown in FIGS. 1A-1 D. In some other embodiments, as shown in FIGS. 1A-1 D, the ground electrode 170 can be a flange170 disposed between the at least one spacer block 165 and the high voltage electrode block 175. The number of spacer blocks 165 and the location of the ground electrode 170 can be based on the conductivity of the liquid to be treated by the plasma discharge.

[0044] The electrode housing is formed of an electrical insulator material, such as Teflon, glass-filled Teflon, sapphire, or ceramic into a variety of shapes, as shown in FIGS. 4-8. As shown in FIG. 4, the electrode housing can be a cylindrical electrode housing 485. The gas inlet 490 is also shown in FIG. 4. As shown in FIG. 5, the electrode housing can be a divergent-cone-shaped electrode housing 585. The gas inlet 590 is also shown in FIG. 5. As shown in FIG. 6, the electrode housing can be a convergent-cone-shaped electrode housing 685. The gas inlet 690 is also shown in FIG. 6. As shown in FIG. 7, the electrode housing can be an hourglassshaped electrode housing 785. The gas inlet 790 is also shown in FIG. 7. As shown in FIG. 8, the electrode housing can be a bell-shaped electrode housing 885. The gas inlet 890 is also shown in FIG. 8.

[0045] As shown in FIG. 9, the stacked-block system 900 optionally further includes a liquid reservoir 910 in fluid communication with the liquid outlet 940 of the reactor 905, the liquid reservoir 910 including a head space. The stacked-block system 900 further includes a vacuum pump 930 having a vacuum inlet 950 and a vacuum outlet 960, the vacuum inlet 950 being in fluid communication with the head space 920 of the liquid reservoir 910, and the vacuum outlet 960 being in fluid communication with the gas inlet 990 of the reactor 905. A variety of vacuum pumps, such as a scroll pump or a diaphragm pump, are suitable for drawing a vacuum in a range of between about -7 psig and about -12 psig, such as -10 psig, on the head space 920 of the liquid reservoir 910, and therefore drawing a vacuum atthe liquid outlet 940 of the reactor 905. At this vacuum pressure, according to thePaschen curve, the breakdown voltage significantly decreases, thereby improving the energy efficiency of PFAS destruction, in addition to improving the ignition and stability of the plasma discharge. Furthermore, the vacuum pump 930 draws foam from the head space 920 in liquid reservoir 910 back into the reactor 905 through the gas inlet 990. The foam enters the electrode housing 985 tangentially, thus creating a foam-vortex flow and moving through the annular gap formed by the cylindrical ceramic insulator 975 and the high-voltage rod electrode 980. Thus, the foam vortex flow cools the high-voltage rod electrode 980, and, at the same time, foam recirculation in a closed flow system enables PFAS adsorbed on the foam surface to make close contact with the plasma discharge, enhancing the destruction of PFAS molecules. The closed flow gas recirculation system shown in FIG. 9 produces no gas emissions to the external environment, with both water and gas / foam being continuously treated by the plasma discharge, thereby destroying any harmful substances therein.

[0046] Turning back to FIG. 1 C, an end 181 of the central solid cylindrical rod 180 proximal to the ground electrode 170 can be disposed above a top side 182 of the electrode housing 185. In some embodiments, as shown in FIG. 10, a high voltage electrode 1000 includes a motor or gearing 1005 for slidably adjusting the position of the central solid cylindrical rod 1080 within the electrode housing 1085, and thereby adjusting the distance between the end 181 of the central solid cylindrical rod 180 and the ground electrode 170 shown in FIG. 1 C. The dynamical adjustment of the distance between the end 181 of the central solid cylindrical rod 180 and the ground electrode 170 can be based on a feedback measurement of the impedance and distance between the two electrodes, the conductivity of the liquid toY1be treated by the plasma discharge, and / or erosion of the central solid cylindrical rod180 over time.

[0047] In accordance with one or more embodiments, as shown in FIG. 11 , a method 1100 of generating a plasma discharge in liquid includes flowing 1110 a liquid through an inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked-block reactor, disposing 1120 a top block over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor, disposing 1130 at least one spacer block under the liquid inlet block, and providing 1140 a ground electrode in fluid communication with the interior space of the reactor, the ground electrode being in direct contact with the at least one spacer block. The method further includes disposing 1150 a high-voltage electrode block coaxially with a central axis of the reactor at a bottom side of the reactor, and inserting 1160 a central solid cylindrical rod high-voltage electrode at least partially into and coaxial with a cylindrically-sym metric electrode housing for generating a plasma discharge between the high-voltage electrode and the ground electrode, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod.

[0048] In accordance with one or more embodiments, as shown in FIG. 12A, a system 1200 for generating a plasma discharge in liquid includes a liquid inlet 1205 and a liquid outlet 1210 in fluid communication with an interior space1215 of acylindrical liquid vessel 1220 having a central axis 1235, the inlet 1205 and outlet1210 both disposed near a top side 1225 of the liquid vessel 1220 and configured to generate a vortex liquid flow in the interior space 1215 of the liquid vessel 1220, a high voltage electrode 1250 and a ground electrode 1240 spaced apart, the high voltage electrode 1250 disposed coaxially with the central axis 1235 of the cylindrical liquid vessel 1220 at a bottom side 1226 of the liquid vessel 1220, and including a central solid cylindrical rod 1250 inserted at least partially into and coaxial with a cylindrically-sym metric electrode housing 1255, the electrode housing 1255 including a gas inlet 1260 for gas injection into an interior electrode housing space 1265 of the electrode housing 1255, the gas inlet 1260 configured to generate a vortex gas flow within the interior electrode housing space 1265 around the central solid cylindrical rod 1250. In some embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction. In some other embodiments, the liquid inlet and outlet, and gas inlet can be configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions. The central solid cylindrical rod 1250 can be formed of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, carbon, such as high-density carbon graphite, or any other conductive material. The system 1200 further includes a liquid reservoir 1270 in fluid communication with the liquid outlet 1210, the liquid reservoir 1270 including a head space 1275.

[0049] As shown in FIG. 12A, the system 1200 further includes a vacuum pump 1280 having a vacuum inlet 1281 and a vacuum outlet 1282, the vacuum inlet 1281 being in fluid communication with the head space 1275 of the liquid reservoir 1270, and the vacuum outlet 1282 being in fluid communication with the gas inlet 1260. A variety of vacuum pumps, such as a scroll pump or a diaphragm pump, aresuitable for drawing a vacuum in a range of between about -7 psig and about -12 psig, such as -10 psig, on the head space 1275 of the liquid reservoir 1270, and therefore drawing a vacuum at the liquid outlet 1210 of the liquid vessel 1220. The advantages of drawing a vacuum at the liquid outlet 1210 are described above.

[0050] The electrode housing 1255 includes a gas inlet 1260 that, as shown in FIG. 12B, is disposed tangentially to the central solid cylindrical rod 1250 along an interior wall 1256 of the electrode housing 1255 for gas injection into an interior electrode housing space 1265 of the electrode housing 1255, the gas inlet 1260 configured to generate a vortex gas flow 1266, shown in FIG. 12A, within the interior electrode housing space 1265 around the central solid cylindrical rod 1250. The advantages of drawing foam from the head space 1275 into the gas inlet 1260 are described above.

[0051] Turning back to FIG. 12A, an end 1251 of the central solid cylindrical rod 1250 proximal to the ground electrode 1240 can be disposed above a top side 1256 of the electrode housing 1255. In some embodiments, as shown in FIG. 13, a high voltage electrode 1300 includes a motor or gearing 1305 for slidably adjusting the position of the central solid cylindrical rod 1380 within the electrode housing 1385, and thereby adjusting the distance between the end 1251 of the central solid cylindrical rod 1250 and the ground electrode 1240 shown in FIG. 12A. The dynamical adjustment of the distance between the end 1251 of the central solid cylindrical rod 1250 and the ground electrode 1240 can be based on a feedback measurement of the impedance and distance between the two electrodes, the conductivity of the liquid to be treated by the plasma discharge, and / or erosion of the central solid cylindrical rod 1250 over time.

[0052] In accordance with one or more embodiments, as shown in FIG. 14, a method 1400 of generating a plasma discharge in liquid includes providing 1410 a liquid inlet and a liquid outlet in fluid communication with an interior space of a cylindrical liquid vessel having a central axis, the inlet and outlet both disposed near a top side of the liquid vessel and configured to generate a vortex liquid flow in the interior space of the liquid vessel, providing 1420 a high voltage electrode and a ground electrode spaced apart, the high voltage electrode disposed coaxially with the central axis of the cylindrical liquid vessel at a bottom side of the liquid vessel, and including a central solid cylindrical rod inserted at least partially into and coaxial with a cylindrically-symmetric electrode housing, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod, and providing 1430 a liquid reservoir in fluid communication with the liquid outlet, the liquid reservoir including a head space. The method further includes providing 1440 a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet.

[0053] The disclosures of each and every patent, patent application, and publication cited herein are hereby incorporated herein by reference in their entirety. While this invention has been disclosed with reference to specific embodiments, it is apparent that other embodiments and variations of this invention may be devised by others skilled in the art without departing from the true spirit and scope of the invention.

Claims

CLAIMSWhat is claimed is:

1. A stacked-block system for generating a plasma discharge in liquid, the system comprising: a liquid inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked-block reactor; a top block disposed over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor; at least one spacer block disposed under the liquid inlet block; a ground electrode in fluid communication with the interior space of the reactor, the ground electrode being in direct contact with the at least one spacer block; and a high-voltage electrode block disposed coaxially with a central axis of the reactor at a bottom side of the reactor, and including a central solid cylindrical rod high-voltage electrode inserted at least partially into and coaxial with a cylindrically-sym metric electrode housing for generating a plasma discharge between the high-voltage electrode and the ground electrode, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod.

2. The system of claim 1 , wherein the high-voltage electrode block includes an outlet for removing solids from the interior electrode housing space.

3. The system of claim 1 , wherein the ground electrode is a ground electrode block disposed between the at least one spacer block and the high-voltage electrode block.

4. The system of claim 1 , wherein the ground electrode is a flange disposed between the at least one spacer block and the high voltage electrode block.

5. The system of claim 1 , wherein the electrode housing is formed of an insulator material.

6. The system of claim 1 , wherein the electrode housing is a cylindrical electrode housing.

7. The system of claim 1 , wherein the electrode housing is a divergent-cone- shaped electrode housing.

8. The system of claim 1 , wherein the electrode housing is a convergent-cone- shaped electrode housing.

9. The system of claim 1 , wherein the electrode housing is an hourglass-shaped electrode housing.

10. The system of claim 1 , wherein the electrode housing is a bell-shaped electrode housing.11 . The system of claim 1 , further including a liquid reservoir in fluid communication with the liquid outlet of the reactor, the liquid reservoir including a head space.

12. The system of claim 11 , further including a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet of the reactor.

13. The system of claim 12, wherein the vacuum pump is a scroll pump.

14. The system of claim 12, wherein the vacuum pump is a diaphragm pump.

15. The system of claim 1 , wherein the liquid inlet and outlet, and gas inlet are configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction.

16. The system of claim 1 , wherein the liquid inlet and outlet, and gas inlet are configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions.

17. The system of claim 1 , wherein the central solid cylindrical rod is formed of one of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, and carbon.

18. The system of claim 1 , wherein an end of the central solid cylindrical rod proximal to the ground electrode is disposed above a top side of the electrode housing.

19. The system of claim 18, further including a means for slidably adjusting a distance between the end of the central solid cylindrical rod and the ground electrode.

20. A method of generating a plasma discharge in liquid, the method comprising: flowing a liquid through an inlet block including a liquid inlet disposed tangentially relative to a sidewall of the liquid inlet block in order to generate a vortex liquid flow in an interior space of a stacked-block reactor; disposing a top block over the liquid inlet block, the top block including a liquid outlet disposed at a center of the top block, the liquid outlet including a center tube extension of the liquid outlet into the interior space of the reactor; disposing at least one spacer block under the liquid inlet block; providing a ground electrode in fluid communication with the interior space of the reactor, the ground electrode being in direct contact with the at least one spacer block; and disposing a high-voltage electrode block coaxially with a central axis of the reactor at a bottom side of the reactor, and inserting a central solid cylindrical rod high-voltage electrode at least partially into and coaxial with a cylindrically-sym metric electrode housing for generating a plasma discharge between the high-voltage electrode and the ground electrode, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod.21 . A system for generating a plasma discharge in liquid, the system comprising: a liquid inlet and a liquid outlet in fluid communication with an interior space of a cylindrical liquid vessel having a central axis, the inlet and outlet both disposed near a top side of the liquid vessel, the liquid outlet disposed at a center of the cylindrical liquid vessel, and both configured to generate a vortex liquid flow in the interior space of the liquid vessel; a high voltage electrode and a ground electrode spaced apart, the high voltage electrode disposed coaxially with the central axis of the cylindrical liquid vessel at a bottom side of the liquid vessel, and including a central solid cylindrical rod inserted at least partially into and coaxial with a cylindrically- symmetric electrode housing, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod; a liquid reservoir in fluid communication with the liquid outlet, the liquid reservoir including a head space; and a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet.

22. The system of claim 21 , wherein the vacuum pump is a scroll pump.

23. The system of claim 21 , wherein the vacuum pump is a diaphragm pump.

24. The system of claim 21 , wherein the liquid inlet and outlet, and gas inlet are configured such that the vortex liquid flow and the vortex gas flow rotate in the same direction.

25. The system of claim 21 , wherein the liquid inlet and outlet, and gas inlet are configured such that the vortex liquid flow and the vortex gas flow rotate in opposite directions.

26. The system of claim 21 , wherein the electrode housing is formed of an insulator material.

27. The system of claim 21 , wherein the electrode housing is a cylindrical electrode housing.

28. The system of claim 21 , wherein the electrode housing is a divergent-cone- shaped electrode housing.

29. The system of claim 21 , wherein the electrode housing is a convergent-cone- shaped electrode housing.

30. The system of claim 21 , wherein the electrode housing is an hourglassshaped electrode housing.31 . The system of claim 21 , wherein the electrode housing is a bell-shaped electrode housing.T132. The system of claim 21 , wherein the central solid cylindrical rod is formed of one of stainless steel, titanium, tungsten, copper, copper tungsten, silver, titanium oxide (TiOx), iron, and carbon.

33. The system of claim 21 , wherein an end of the central solid cylindrical rod proximal to the ground electrode is disposed above a top side of the electrode housing.

34. The system of claim 33, further including a means for slidably adjusting a distance between the end of the central solid cylindrical rod and the ground electrode.

35. A method of generating a plasma discharge in liquid, the method comprising: providing a liquid inlet and a liquid outlet in fluid communication with an interior space of a cylindrical liquid vessel having a central axis, the inlet and outlet both disposed near a top side of the liquid vessel, the liquid outlet disposed at a center of the cylindrical liquid vessel, and both configured to generate a vortex liquid flow in the interior space of the liquid vessel; providing a high voltage electrode and a ground electrode spaced apart, the high voltage electrode disposed coaxially with the central axis of the cylindrical liquid vessel at a bottom side of the liquid vessel, and including a central solid cylindrical rod inserted at least partially into and coaxial with a cylindrically-sym metric electrode housing, the electrode housing including a gas inlet disposed tangentially to the central solid rod along an interior wall of the electrode housing for gas injection into an interior electrode housing space of the electrode housing, the gas inlet configured to generate a vortex gas flow within the interior electrode housing space around the central solid cylindrical rod;providing a liquid reservoir in fluid communication with the liquid outlet, the liquid reservoir including a head space; and providing a vacuum pump having a vacuum inlet and a vacuum outlet, the vacuum inlet being in fluid communication with the head space of the liquid reservoir, and the vacuum outlet being in fluid communication with the gas inlet.

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