Modular plasma reformer treatment system

A modular plasma treatment system has interchangeable and easily accessible inner and outer electrodes that concentrically nest within an outer housing of one or more plasma reformers. The inner and outer electrodes have self-centering features that allow for blind-fitting of the interchangeable inner and outer electrodes during electrode replacement and maintenance. A plurality of reformers that generate different types of plasmas are preferably arranged serially to allow for a mixture of separate plasmas within the same reaction area and to increase utilization of short-lived radicals.

FIELD OF THE INVENTION

The field of the invention is plasma reformers.

BACKGROUND

Internal combustion engine exhaust streams contain substances that may be harmful to both humans and machinery if left untreated. However, known reformers to treat exhaust streams are difficult to maintain and don't allow easy access to the fundamental components of the reformers. For example, U.S. Pat. No. 6,994,830 to Raybone and U.S. Pat. No. 7,025,939 to Hall both teach reformers for plasma treatment of gases with electrodes supported within a dielectric tube enclosed in a single enclosure without any easily de-coupleable fasteners that allow service members to maintain the fundamental components. Maintenance of such reformers is time-consuming, expensive, and is sometimes impossible without seriously damaging the reformer walls itself—particularly when electrodes need to be maintained or replaced.

Thus, there remains a need for a system and method for improved reformers that are easy to construct, maintain, and assemble/disassemble.

SUMMARY OF THE INVENTION

The inventive subject matter provides apparatus, systems, and methods in which a modular plasma treatment system is built with interchangeable and easily accessible inner and outer electrodes that nest within an outer housing of one or more plasma reformers.

As used herein, a “reformer” comprises a reactor having a reaction zone that reforms substances within an input stream from one substance to another substance—preferably another substance that is less harmful to humans and/or machinery. Exemplary substances to be reformed include, for example, particulate matter (PM), carbon monoxide (CO), nitrogen monoxide (NO), nitrogen dioxide, (NO2) and hydrocarbons (HC) which can be altered to a different substance when introduced to a reactive molecular species, or Radical, created by the reformer such as hydrogen, ozone or oxygen. Such substances, if not passed through a reformer, could react with OH−radicals created when water vapor inside of an exhaust stream is passed through plasma of sufficient energy, which can create harmful substances such as nitrous acid (HNO2) or nitric acid (HNO3).

As used herein, an “input stream” comprises any stream of flowable substances capable of being directed through a conduit, such as a gas, a liquid, a gas having smaller liquid or solid particulate matter (e.g. less than 3 mm, 2 mm, 1 mm, 500 um, 50 um, 10 um, or even 1 um in length), or a liquid having a smaller solid particulate matter.

As used herein, the term Hybrid Plasma Reformer (HPR), which is a reformer having 2 or more different types of plasmas in the same reaction zone. Typically such reformers are built serially downstream another reformer, for example a dielectric Barrier Discharge (DBD) reformer that generates DBD plasma placed downstream of a rotating glide-arc reformer that generates glide-arc plasma.

Exemplary reformers comprise concentric inner electrodes within outer electrodes within an outer housing, which all nest within one another within the outer housing. The dimensions of the outer housing, inner electrodes, and outer electrodes are preferably configured such that, when each is set in place within one another, the inner module does not “substantially move” when set in place. As used herein, “substantially move” comprises moving within 1 mm relative to one another in any direction when dropped on concrete from 5, 10, 20, or 30 cm. in the air. Coupling the inner electrodes and outer electrodes to a voltage transformer, for example a high voltage transformer that provides a voltage difference of at least 1,000, 10,000, 20,000, or even 30,000 volts between the inner electrodes and outer electrodes, the reformer generates plasma between the electrodes to form a reaction zone for streams sent through the reformer. Such voltage power transformers are preferably integrated with a feedthrough of the reformer to deliver power from the voltage power transformer directly to an inner electrode via the feedthrough.

By providing interchangeable inner electrodes and outer electrodes capable of fungibly nesting within the outer housing of a reformer, the system allows for electrodes to be changed to accommodate different voltage differences for different types of plasmas, for example DBD plasma, glide-arc plasma, corona, inductively coupled, and microwave plasma. In some embodiments, the inner electrodes have dimensions that are substantially identical to one another and outer electrodes have dimensions that are substantially identical to one another such that any inner electrode could be fungible with any other inner electrode and any outer electrode can be fungible with any other outer electrode. In other embodiments, only the outer dimensions of the outer electrodes are substantially identical to one another such that the inner dimensions of the outer electrodes and the outer dimensions of the inner electrodes could be shaped differently to accommodate different reformer needs. As used herein, electrodes that are shaped “substantially identical” to one another could replace one another within a nested reformer embodiment without substantially moving relative to one another when set in place.

In some embodiments, the inner dimensions of the outer housing and the outer dimensions of the outer electrodes, and/or the inner dimensions of the outer electrodes and outer dimensions of the inner electrodes, are shaped to have self-centering geometric features that center the inner portion with respect to the outer portion as they are set in place. Such self-centering geometric features could be, for example, a tapered inner wall that hugs the inner portion tighter as the inner portion is slid in place, or a tapered exterior cross-section of the inner portion that expands into a tighter fit as the inner portion is slid in place. Such sliding self-centering features allow for the nested electrodes to have a blind-mate connection (a connection that allows a person to center an electrode in place without need for precise orientation of threads, notches, or other pluralities of protrusions/recesses before sliding an electrode in place). Preferably, the inner apexes of the feedthrough and outlet flanges of the reformer fundamental components comprises self-centering features that allow for such a sliding blind mate between the concentric system components. As used herein, a “fundamental component” of a reformer comprises the outer housing, the inner electrode, and the outer electrode.

Electrodes sized and shaped to generate different types of plasmas could have distinct internal or external geometric features from one another. For example, an outer electrode of a DBD reformer could comprise interior conductive projections that generate electric field gradients between points of the conductive projections. While such conductive projections could be within the interior of the electrode in any manner (e.g. 3-D printed, welded), in preferred embodiments the conductive projections could comprise conductive ferrous screws screwed into holes of the outer electrode. Preferably, the conductive projections comprise different dimensions (lengths, widths, heights, geometric patterns), to provide differing electric field gradients to precipitate particulate matter having different properties.

In some embodiments, inner and/or outer surface features of the inner and outer electrode, and/or inner surface features of the outer housing, could be configured to alter the air pressure in various zones of the reformer to direct input streams in a cyclone motion to points of highest energy density within the excitation chamber. For example, perforations in the wall of the outer electrode could get wider at near the reaction zone where the inner electrodes and outer electrodes are closest to one another, decreasing the air pressure within that zone to help direct the input stream towards the points with the highest energy density. Altering surface features of the fundamental components could be done in any manner known in the art to help direct input streams towards areas where they are the most effective.

As previously stated, reformers are preferably disposed serially to one another such that a plurality of plasmas are present within the same reaction zone. This increases utilization of short-lived singlet oxygen radicals, and increases the control of the amount and type of reactive nitrogen and reactive oxygen radicals that are created. For example, when a stream is below the PM oxidation temperature of NO2(200-500c), ozone can be selectively produced and utilized for PM oxidation, or when the stream is above the temperature where ozone is incapable of being transported relatively long distances to the PM inside a Diesel Particulate Filter (DPF), NO2can be selectively produced. Exemplary serialized reformers include, for example, a DBD reformer placed downstream to a glide-arc reformer. The glide-arc reformer preferably has a rotating glide-arc that directs the output stream to rotate in a vortex such that heavier, particulate matter is directed towards the walls of the reaction zone, further ensuring that the heavier particulate matter is directed towards points of highest energy density inside the excitation chamber.

Magnetic fields and/or microwaves could be directed towards the reaction chamber using magnets, electromagnetic resonators and/or microwave generators, respectively. In some embodiments, a magnetic field generator could target its magnetic field to be centrally targeted around co-axial electrodes that discharge into a plasma of any resonator of the system. In some embodiments, a particulate filter that expels the output stream of any reformer could be placed above the output stream to transfer waste heat from the output stream to an oxidant conduit.

Preferably, air that is introduced to the reformer is pre-dried using an air driver that receives intake air from an air source, such as a blower or an on-board turbocharger, and outputs dried air that is introduced to an inlet of the initial reformer. Such air drivers could use a desiccant, such as silica gel, to remove water vapor from the intake air.

Contemplated systems could be used to reform any stream comprising gaseous, liquid and particulate matter, for example an output exhaust of an internal combustion engine to generate CO2 and H2O, an oil well flare to generate synthesis gas (H2 and CO), air and water treatment system to creates ozone and NOx, or an atmospheric control system for a spaceship to generate oxygen from CO2.

DETAILED DESCRIPTION

One should appreciate that the disclosed techniques provide many advantageous technical effects including providing a modular system for ease of maintenance, accessibility, and replacement of fundamental components of plasma treatment systems. Blind-mate connections allow for the ease of placement of inner and outer electrodes without necessitating a high degree of accuracy when putting the electrodes in place. The system architecture guides streams towards the highest energy density zones within the plasma reaction zones for optimal paths through the reaction zones. Having a plurality of plasmas within the same reaction zone increases utilization of short-lived singlet oxygen radicals, and increases the control of the amount and type of reactive nitrogen and reactive oxygen radicals that are created. By combining who different plasmas, such as glide-arc plasmas and DBD plasmas for NO2production eliminates the need for extremely high voltages that are required with a DBD plasma reformer—which eliminates the need for more expensive insulators and electronics. Utilizing microwave excitation techniques for the production of radicals increases the precision below the threshold of unwanted chemical production. Utilizing ambient air as a feedstock to produce the preferred oxidants with an integrated dryer removes hydrogen and sulfur sources from the air stream, which minimizes the creation of unwanted acidic chemicals as a byproduct. By placing filters/catalyst systems above heat-creating reformers and other modules of the system, the system uses heat exchange to increase the production efficiency of the radicals.

The inventive subject matter provides apparatus, systems, and methods in which a modular plasma treatment system is built with interchangeable and easily accessible inner and outer electrodes that nest within an outer housing of one or more plasma reformers.

InFIG. 1, a reformer100has an outer housing110, outer electrode #1120, outer electrode #2122, inner electrode #1150, and inner electrode #2152. Outer housing110is a housing of a plasma reformer with inlet116for an input stream to enter reformer100and outlet118for an output stream to exit from. Outer housing110has a downstream inner housing press-fit mate114to an exhaust outlet (not shown) for ease of mating during maintenance. Other suitable coupling systems could be used to couple outlet118to an exhaust outlet (not shown), but preferably the coupling system does not require tools (e.g. press-fit systems, hand latches) or commonly available tools (e.g. a screwdriver, a wrench, a bolt socket) to ensure ease of maintenance. Outer housing flange112couples with upstream inner housing press-fit mate130, and is screwed in place with screws142via feedthrough flange140and feedthrough flange162. Again, other suitable coupling systems could be used such as those already named.

Outer electrode #1120and outer electrode #2122have substantially identical geometric features to allow for either electrode to be interchanged within outer housing110. Similarly, inner electrode #1and inner electrode #2152also have substantially identical geometric features, making them geometrically fungible. Preferably, outer electrode #2122comprises a different conductive material from outer electrode #2122, and inner electrode #1150comprises a different conductive material from inner electrode #1152, giving them different conductive properties from one another, and making outer electrode #1120and inner electrode #1150more appropriate for generating a first plasma and outer electrode #2122and inner electrode #2152more appropriate for generating a second plasma different from the first plasma. In other embodiments, the inner geometric features of outer electrode #2122may be different from the inner geometric features of outer electrode #1120, such that the outer geometric features of inner electrode #2152are made to mate with the inner geometric features of outer electrode #2122and the outer geometric features of inner electrode #1150are made to mate with the inner geometric features of outer electrode #1120.

InFIG. 2, a cross-sectional view of a reformer200is shown, having inlet210, outlet220, inner electrode230, outer electrode240, and outer housing250. Here, each of the fundamental components have self-centering geometric features that centers the nested fundamental components relative to one another as they are set in place. The inner chamber of outer housing250is shaped to taper inwards towards the outer walls of outer electrode240such that as outer electrode240advances within the inner chamber of outer housing250, outer electrode240self-centers in place and does not substantially move after being fully advanced within outer housing250. Similarly, the outer walls of inner electrode230are tapered near the base to self-center inner electrode240within outer electrode240as inner electrode230advances in place. This improves the ability for the electrodes to be set in place without need for a high degree of accuracy or even for the installer to be looking inside reformer200during installation.

Inner electrode230comprises a conductor core231coupled to a voltage transformer (not shown) and has a stand off232, spark arrestor233, outer layer234, sleeve235, and insulating material236. In a preferred embodiment, stand off232comprises a quartz stand off, outer layer234comprises a quartz outer layer, and insulating material236comprises a thin layer of quartz wool surrounding the conductor core231, however, any insulating material, or materials, could be used depending on the needs of the reformer. Reaction zone252in between inner electrode2130and outer electrode240has a plurality of conductive projections242that each provide electric field gradients in between one another to precipitate particulate matter. Here, the conductive projections242are steel screw heads screwed into holes of outer electrode240, however conductive projections242could be implemented in a plurality of ways, such as 3-D printed or welded in place. Preferably, conductive projections242have different dimensions from one another. Here, conductive projections242only have a difference in height, such that screws of the same width but different length can provide different electric field gradients to precipitate particulate matter having different properties from one another.

While reformer200shows electrodes with geometries most appropriate for a DBD plasma reformer, outer housing250could be utilized to generate other types of plasma by replacing the inner and outer electrodes set in place.

InFIG. 3, reformer300has an inlet310, outlet320, inner electrode330, outer electrode340, and outer housing350. Here, inner electrode330has a slightly different geometry to inner electrode220, providing a self-centering outer wall that slowly tapers from the tip to the base of inner electrode330. Here, also, outer electrode340has a different geometry to outer electrode240, without the conductive projections of outer electrode240. While inner electrode330has a different geometry to inner electrode230, and outer electrode340has a different geometry to inner electrode240, both sets of electrodes could be installed interchangeably in outer housing250or outer housing350, allowing for functionally fungible electrode pairs if need be.

Inner electrode330has a conductive core331that mates with sleeve335, and is coated with insulator332and334at its base, insulating spark arrestor333from external electromagnetic waves. Spark arrestor333allows for an overvoltage spark within a cavity, which is inside the feedthrough and not in the atmosphere or outside the reformer. Feedthrough flange336allows for a transformer (not shown) to provide voltage to core331, while housing flange337allows for the transformer to provide voltage to outer electrode340.

While reformer300shows electrodes with geometries most appropriate for a rotating glide-arc plasma reformer, outer housing350could be utilized to generate other types of plasma by replacing the inner and outer electrodes set in place.

InFIG. 4, reformer400shows a reformer400having an inlet410, outlet420, inner electrode430, outer electrode440, and outer housing450. Here, outer housing450has a waveguide462that guides microwaves from microwave generator460towards the area where inlet410and outlet420are, exposing the stream to microwave transmissions as the stream enters and exits reformer400. Waveguide462is held in place by choke flange464.

Inlet410guides the input stream in a circular vortex pattern about the outer reaction stream path into reaction zone452between outer electrode440and inner electrode430. As the vortex pattern approaches the best of inner electrode430, the densest portions of the stream flow along the inner wall of outer housing250and converge where the walls of outer electrode440and inner electrode430are the closest, and disperse in a vortex pattern within reaction zone452towards outlet420. Inner electrode430has a core431surrounded by insulator432, and feedthrough flange is conductively coupled to core431of inner electrode430while housing flange434is conductively coupled to outer electrode440.

FIGS. 5-7illustrate external views of exemplary reformer configurations.FIG. 5shows an exploded view of reformer500having inner electrode530, outer electrode540, and outer housing550, where the inlet and outlet are disposed close to one another, providing an optimal geometry for a single microwave generator to be pointed at a section where both the inlet and outlet streams pass.FIG. 6shows a reformer600having an inlet610and an outlet620disposed on opposing sides of the reformer, illustrating a path along the longest length of reformer600.FIG. 7shows a reformer700having an inlet710and an outlet720on opposing sides of the reformer providing a more linear path optimal for chaining several reformers with one another.

FIGS. 8-9show cross-sectional views of exemplary chained reformers that each produce different plasmas.FIG. 8shows a plasma treatment system800having an inlet812into a glide-arc plasma reformer810that feeds into a DBD plasma reformer820to an outlet822.FIG. 9shows a plasma treatment system900having an inlet912into a glide-arc plasma reformer910with a microwave generator that feeds into a DBD plasma reformer920to an outlet922. Many alternative geometries and serial paths could be adapted from the designs presented.

For example,FIGS. 10-12show alternative plan views of chained reformers.FIG. 10shows a plan view of a chained plasma treatment system1000having inlet1010and outlet1020which is a representation of the cross-sectional view of plasma treatment system800.FIG. 11shows a plan view of a plasma treatment system1110with reformers coupled in parallel to one another, having a single inlet1110leading to four separate reformers, whose output streams are joined at outlet1120.FIG. 12shows a plan view of a plasma treatment system1200with three reformers joined in serial having inlet1210and outlet1220. Plasma treatment system1200could be utilized with three different sets of electrodes to provide three different plasmas, or could have the same electrodes to utilize the same plasma in an extended reformation cycle.

FIG. 13shows a reformer1300having a golden ratio designed into the exterior walls of the outer housing, with dimension a for the first length of the first tapered section from the inlet to a second tapered section, dimension b for the second length of the second tapered section from the first tapered section to the base, and dimension c for the total length of both the first and second tapered sections. Experimental data has revealed that utilizing this golden ratio of a to b and b to c provides for an advantageous stream path along the interior wall of reformer1300.

FIGS. 14-16illustrate a reformer1400having an input gas stream path whose velocity enters the point of the highest energy density inside the reaction zone at its highest velocity.FIG. 14illustrates the input gas stream path as having a high density at the top as it enters the reformer, decreasing in density as it travels down to the base of the inner electrode.FIG. 15shows how reformer1400has been divided into three pressure zones—low pressure zone1510, medium pressure zone1520, and high pressure zone1530, which forces the stream path to naturally flow and operate in the low pressure zone1510. Low pressure zone1510is generated by altering the surface features of either the outside electrode or the inner surface wall of the outer housing, or both. Here, the outside electrode in zone1510has perforations spaced a distance of 0.15″ from one another, zone1520has perforations spaced a distance of 0.25″ from one another, and zone1530has perforations spaced a distance of 0.4″ from one another. Differing the spacing of the perforations varies the air pressure zones along the path of the input stream, focusing the input stream towards areas of highest energy density at its highest velocity.FIG. 16shows how the highest density particulate matters hug the inner wall of the outer housing as the vortex travels down towards the base of the inner electrode. Both centrifugal motion and centripetal motion help to direct the stream accordingly.

FIGS. 17-18illustrate alternative embodiments where a filter substrate and/or catalyst, such as particulate filters (PF), diesel oxidation catalysts (DOC) or selective catalytic reduction (SCR) can be placed above either the reactor, an engine, or both to use heat exchange to increase the production efficiency of the radicals.

FIGS. 19-20illustrate a plasma treatment system1900having a transformer core1910that is directly coupled to the reformer to deliver high voltage power directly to the inner and outer electrode. Here, the transformer core1910is coupled directly to the inner and outer electrodes of the reformer with primary coil1920and secondary coil1930transforming the low voltage power input2010to high voltage power out. Ground from the high voltage power out2020is coupled directly to inner electrode2030while the positive VDD from high voltage power out2020is coupled directly to outer electrode2030to provide a voltage potential directly to the electrodes.

FIGS. 21-23illustrate additional configurations of plasma treatment systems. InFIG. 21, plasma treatment system2100treats exhaust from an internal combustion engine2110. Air from an air source, such as from a blower or a turbocharger, is received by dryer2120, which minimizes the formation of unwanted acidic chemicals by removing hydrogen and sulfur sources from ambient air and sends a stream of dried air to reformers2130. Preferably, dryer2120uses a dessicant or some other dryer to remove hydrogen and sulfur sources from the air. Reformers2130generates plasma to form radicals, such as NO2radicals, O1, and O3, which combine with the exhaust stream from internal combustion engine2110to reform substances within the exhaust stream as well as to oxidize soot captured in Diesel Particulate Filter (DPF)2140. By placing DPF2140above heat-producing reformer2130, plasma treatment system2100uses heat exchange properties to increase the production efficiency of the radicals.

InFIG. 22, plasma treatment system2200receives an exhaust stream2210from a source (not shown), which is passed immediately through DPF2220. Air from an input air stream2230is passed through air dryer2240to be fed into reformers2250, which transmits radicals to the input stream2210before the input stream is filtered by DPF2220. Here, heat is recaptured in several areas: (1) heat is recaptured by the heat exchanger recapturing heat from the output exhaust stream from DPF2220, (2) heat is recaptured by placing DPF2220above reactors2250, and (3) heat is recaptured by placing the pipe from reactors2250to the input exhaust stream2210above DPF2220.

InFIG. 23, plasma treatment system2300receives an exhaust stream2310from a source (not shown), which is, again, passed through DPF2220. In this embodiment, output radicals from reformers2230are, again, introduced to exhaust stream2310prior to the exhaust stream being filtered through DPF, reforming some of the particles from exhaust stream2310. Here, reformers2330are placed above DPF2320, helping to recapture and utilize some of the heat from DPF2320, as well as from the output exhaust stream from DPF2320via the heat exchanger running from air dryer2340to reformers2330.