EP1379761B1

EP1379761B1 - Emission control device and method

Info

Publication number: EP1379761B1
Application number: EP01918755A
Authority: EP
Inventors: Paul D. Keppel; Randolph M. Wilson
Original assignee: Global Environmental Concepts LLC
Current assignee: Global Environmental Concepts LLC
Priority date: 2001-03-16
Filing date: 2001-03-16
Publication date: 2005-06-01
Anticipated expiration: 2021-03-16
Also published as: WO2002075123A1; CA2447641C; ATE296946T1; DE60111274D1; CA2447641A1; EP1379761A4; MXPA03009488A; EP1379761A1

Abstract

An emission control device (10) and method are provided for treating exhaust gases to reduce pollutants contained therein. The device (10) includes a first chamber (16) through which the exhaust gas passes. First and second metal grids (26,30) are disposed within the first chamber (16) at a predetermined distance from each other. Voltage is supplied to the first grid (26) via an inductive coil (14) at a predetermined frequency. Electrical sparks are generated between the first and second grids (26,30) which electrically ionizes the treatment chamber and a second chamber having strata (46). The strata (46) can further includes noble metals for treatment of the exhaust gas.

Description

FIELD OF THE INVENTION

The present invention relates generally to an apparatus and method for treating exhaust gases, and more particularly to a combustion engine treatment device for removing and/or reducing pollutants contained in the combustion engine effluent gases. In particular, the present invention reduces carbon dioxide, substantially reduces hydrocarbons and virtually eliminates the exhaust of carbon monoxide.

BACKGROUND OF THE INVENTION

With the increasing use of automobiles, trucks, aircraft, and other combustion engine vehicles, growing concern over the gaseous pollutants emitted by these sources is justifiably mounting. Carbon monoxide, the toxic by-product of incomplete combustion, is a major contributor to air pollution and poses a very real threat to public health. Carbon dioxide, although non-toxic, is recognized as an air pollutant that directly causes the "greenhouse effect." Modem fuels generate excessive amounts of carbon dioxide, which scientists report are contaminating the atmosphere worldwide. Today's engines also generate an unhealthy amount of toxic hydrocarbons which are generally responsible for eye irritation, nasal congestion and breathing difficulties.

In addition to the problems caused by exhaust emissions from combustion engines, significant exhaust pollution is also created from industrial effluent stacks. Exhaust pollution is also a significant problem with stray booths, styrene manufacturing and burning of hazardous waste among a variety of industrial processes.

Numerous devices and methods are known in the art for the control of exhaust gas contaminants. Electrostatic precipitation is widely used in such applications and involves the application of high voltages to electrodes positioned in the exhaust gas stream. This process induces ionization of gas particles, which in turn cause particulates suspended in the gas to acquire a charge from contact with the ionized gas particles. The charged particles are then collected at oppositely charged diodes, which must be eventually "cleaned" or "scrubbed". A significant drawback of electrostatic precipitation is that only minute particulate matter can be precipitated out of the exhaust stream. The process is ineffective at removing gaseous contaminants such as carbon monoxide and carbon dioxide.

US 5,733,360 discloses a corona discharge reactor and corresponding method for chemically activating the constituents in an exhaust gas stream by use of corona discharge. The reactor includes within a conduit a discharge plate having a plurality of through openings and a plurality of projecting corona discharge electrodes and an electrode plate having a plurality of through openings displaced from and opposing the tips of the corona discharge electrodes. A pulsed energization scheme is employed to intermittently generate a uniformly distributed corona discharge cloud between the plurality of corona discharge electrode tips and the electrode plate during passage of the gas stream through the conduit. The short durations of voltage application are chosen to suppress the formation of sparks across the gap. The gas flowing through each flow passage is proximally and concurrently exposed to a plurality of such corona discharge points, where electron energy levels are high, so as to realise the occurrence of oxidation, reduction or other chemical activation of the constituents in the gas stream.

A similar arrangement, however, for a different purpose is disclosed in US 5,953,909. Here, electrodes in the form of elongate, parallely arranged rods are forming an ignition module for igniting components in an exhaust stream which are not fully combusted, such as in two-cycle internal combustion engines. The electrodes in each grate are oriented such that their central axes are parallel and substantially coplanar to adjacent electrodes within the same grate. The grates are substantially parallel, but the central axes of the electrodes of one grate being perpendicular to the axis of the electrodes of the opposing grate to create a lattice-type electrode configuration. A cascading electrical arcing pattern and distribution among the nodes formed between various electrodes is controlled by a spark generating module which includes a computer module to appropriately modify arcing variables such as voltage and switching frequency between the electrodes in the respective grates. The combustor, however, is not intended for reducing hydrocarbon and volatile organic compound emissions from the exhaust stream.

Burners, activated carbon and water curtains are widely used to reduce hydrocarbon and volatile organic compound emissions. However, these pollution control devices are impractical for use with internal combustion engine vehicles. Additionally, a significant drawback of burners and water curtains is a large operation cost and activated carbon is easily clogged when treating a particulate laden air stream.

In efforts to meet increasingly more stringent vehicle emissions standards, some manufacturers have begun using multiple catalytic converters. However, a conventional catalytic converter is expensive since about 30 g (one troy ounce) of platinum or rhodium is used in its manufacture.

Masters, U.S. Patent 5,419,123, discloses an emission control device and method for treating exhaust gases to reduce pollutants contained therein. The device includes a treatment chamber having a first metal screen, a second metal screen and a perforated chemical substrate disposed between the first and second metal screens. An electrode disposed a distance from the first screen and is applied a voltage so that sparks are generated between the electrode and the first screen.

Although the Masters patent may reduce emissions in the exhaust gas it has several limitations. Since an electrode is used to deliver the spark the electrified area is concentrated to a portion of the first screen and hence is not evenly distributed over the entirety of the screen. Consequently, a portion of the gas stream is not sufficiently treated. This problem become more pronounced if the plug becomes angled towards or away from the first screen.

Additionally, since the voltage is applied to the electrode via standard wiring there are significant losses such that only about 30% of the voltage generated is applied to the electrode. Accordingly, for 15K volts to be delivered to the plug about 50K volt must be supplied. This high voltage is particularly problematic when used with an automobile since it can cause random cycling frequency in the automobile's circuitry sufficient to send false codes to the automobile's computer or even damage the computer.

Furthermore, by placing the first and second screens on opposite sides of the substrate sparks are not generated between the screens.

SUMMARY OF THE INVENTION

The present invention provides an apparatus and method for reducing or eliminating emissions from a gas stream. The gas stream is treated by a treatment chamber in series with a second chamber having perforated strata. The treatment chamber includes a first metal grid supplied with high voltage and a second metal grid grounded to the treatment chamber to generate sparks over the entirety of the first grid to the second grid thereby causing electronic ionization. Since all of the air stream is required to flow through the first and second grids, all of the air stream is fully treated. The second metal grid is conductively connected to the second chamber and, therefore, the entire connection and the second chamber are also electronically ionized. Due to the treatment caused by electronic ionization the strata can fully perform with significantly less use of noble metals than with conventional catalytic converters. Although maximum pollution reduction occurs with the use of about one 3 g (1/10 troy ounce) of platinum, rhodium, or palladium, favorable results are achieved without the use of any noble metal.

A further advance is a high efficiency induction coil. The coil applies voltage from a source to the first screen at an efficiency of at least eighty percent thereby causing very hot sparks between the first grid and the second grid. Additionally, this coil is configured to dampen the magnetic field created by the induction coil. Dampening the magnetic field is particularly important in automotive applications and other applications which are integrated with a computer since the magnetic field can create random cycling current in the electrical system so as to cause false signals to be sent to the computer.

The present invention substantially reduces carbon dioxide and hydrocarbons and virtually eliminates the exhaust of carbon monoxide. The system can be used to treat emissions from industrial effluent stacks, spray booth, styrene manufacturing, burning hazardous waste, purifying air streams among a variety of other industrial processes, and is particularly useful for treating emissions from the combustion of carbon or fossil fuels. The system can be installed as original equipment, an add on device or as an after market device.

OBJECTS OF THE INVENTION

The principal object of the present invention is to provide an improved apparatus and method for reducing pollutants from a gas stream. The apparatus includes a first body form a first chamber. First and second metal girds are fixed within the first chamber so that the gas stream entering the first chamber passes through the grids. An electrical connector is attached to either the first grid of the second grid and connects that grid to a voltage source causing electrical sparks to be generated between the first grid and the second grid. A pulsing mechanism pulses the applied voltage at a predetermined frequency. A second body forming a second chamber has a perforated strata through which the gas stream flows.

Another object of the invention is to provide a voltage difference between the first grid and the second grid of at least 20,000 volts. Additionally, the pulsing mechanism is capable of pulsing the voltage at a frequency of greater than 1,600 pulses/minute.

A further object of the present invention is to fix the nearer of the first or second grid a distance between 2.54 cm (1 inch) and 30.48 cm (12 inches) from the strata. Additionally, another object is to space the first grid from the second grid a distance between 0.635 cm (1/4 inch) to 2.54 cm (1 inch).

Another object of the present invention is to use an electrical connector which is adapted to apply at least 80 percent of the voltage the connector receives.

A further object of the present invention is to for the electrical connector to include a plurality of bare wires juxtaposed in a first curvilinear row and coiled equal-distantly about a curvilinear centerline thereby forming a curvilinear helix shape. A plurality of insulated wires are juxtaposed in a second curvilinear row and coiled around the bare wires. An insulated center-wire is positioned along the curvilinear centerline and disposed within the bare wires and the insulated wires.

A still further object is for the electrical connector to use four or five bare wires, three insulating wires and an insulated center-wire.

Another object of this invention is to provide a method of treating exhaust gasses to reduce pollutants contained therein. The method includes the steps of passing exhaust gasses through a first body forming a chamber. The gasses are passed through a first grid and a second grid fixed within the chamber. The grids are separated a predetermined distance from each other. Voltage is supplied from a voltage source to either the first or the second gird to generate sparks between the first grid and the second grid. The voltage is pulsed at a predetermined frequency. The exhaust gasses also pass through a strata.

A further object of the invention is to provide a voltage difference between the first grid and the second grid of at least 20,000 volts at a frequency of at least 1,600 pulses/minute.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects will become more readily apparent by referring to the following detailed description and the appended drawings in which:

Figure 1 is a diagrammatic view of an embodiment of the present invention shown in use as an emission control device;

Figure 2 is a perspective view shown in partial cut-away of a induction coil;

Figure 2a is a perspective view of a detail showing the induction coil of Figure 2;

Figure 3 is a perspective view shown in partial cut-away of a treatment chamber;

Figure 4 is a perspective fragmentary view taken along line 4-4 of Figure 1 showing a second chamber having a strata; and

Figure 5 is an perspective view shown in partial cut-away showing an alternative embodiment of the second chamber having baffles.

DETAILED DESCRIPTION

Figure 1 generally illustrates a system 10 for treating exhaust gases by reducing pollutants contained therein. The system 10 includes a voltage source 12, an induction coil 14, a first chamber 16 and a second chamber 18. The first chamber 16 includes a continuous outer wall 20 an intake end 22 and an exhaust end 24. A first metal grid 26 is disposed within the treatment chamber and separated from the outer wall 20 by an insulator 28. A second metal grid 30 is disposed within and attached to the treatment chamber 16 a predetermined distance from the first metal grid 26. The voltage source 12 is connected to the first metal grid 26 via the induction coil 14. A frequency mechanism 32 is provided for pulsing the voltage supplied to the first metal grid 26 at a predetermined optimum frequency.

As shown in Figures 2 and 2-A, the induction coil 14 comprises a standard plug wire 34, a plurality of copper wires 36 juxtaposed in a row and a plurality of insulated copper wires 38 juxtaposed in a row. The insulated copper wires 38 are wrapped throughout the length of the copper wire 3 6 cluster, and the combination thereof is wrapped throughout the length the plug wire 34. Although any number of arrangements are possible, preferably the insulated copper wires 38 are a group of three, and four or five wires comprise the cluster of copper wires 36. And eyelet can be provided to ground the induction coil 14. The

wires

34, 36, 38 are standard wires. For example, the plug wire can be 8 mm, the copper wires36 can be 1 mm (18 gauge) and the insulated wires 38 can be 1 mm (18 gauge).

The first chamber 16 a segment of an exhaust gas conduit 40. Although the first chamber 16 is shown in Figure 1 as upstream of the second chamber 18, the first chamber 16 can also be placed generally anywhere in-line in the exhaust system such as, for example, after the second chamber 18. Referring to Figure 3, the first chamber 16 is preferably cylindrical and formed of metal. The first and

second metal grids

26, 30 are perpendicular to a central axis 40 of the first chamber 16. The

grids

26, 30 have a meshed pattern and completely fill the cross-sectional area of the first chamber 16 so that all of the exhaust gases pass therethrough. The first grid 26 is insulated from, and secured to, the continuous wall 20 by any conventional means 28. The second grid 30 is conductively secured to the continuous wall 20 by any conventional means such as welding. It is preferred that the

grids

26, 30 are fabricated from chromium, stainless steel or magnesium alloy. However, other conductive compositions can also be used. The induction coil 14 passes through the continuous wall 20 and attaches to the first grid 26 to directly apply voltage thereto. When voltage is applied to the first grid 26, the entire grid 26 is placed at the supplied voltage potential causing a myriad of electrical sparks to be generated across the gap between the first grid 26 and the second grid 30. Although the first grid is shown upstream of the second grid 30, this positioning can be reversed.

As shown in Figure 4 and 5 the second chamber 18 is preferably cylindrical and has a metal shell 42. The second chamber 18 includes a proximal diffusion end 44, a central portion filled with strata 46 and a distal end 48 for exhausting the treated exhaust gases. The strata 46 can be formed of silica or metal having between 7.9 holes per cm (20 holes per inch) and 157.5 holes per cm (400 holes per inch) to allow the exhaust gas stream to flow therethrough. Larger holes 50 are preferred when treating heavier emissions such as emissions from a diesel engine while smaller holes 50 are used with lighter emissions. Preferably, the holes 50 are generally linear and parallel with a central axis of the second chamber 18. However, a honeycomb strata can be used. Typically the strata 46 will contain about 3 g (1/10 of one troy ounce) or less of noble metals such as palladium, platinum or rhodium. Alternatively, the strata can be formed without containing noble metals. As shown in Figure 5 the distal end 48 can be provided with a series of baffles 52 which muffles sound and can serve to replace a standard muffler.

In operation, pollutant laden exhaust gas stream flows through the exhaust gas conduit 40 into the first chamber 16 through the intake end 22, pass through the first grid 26, then through the second grid 30 before exiting the exhaust end 24. A predetermined distance between the first and

second grids

26, 30 typically ranges from 0.635 cm (1/4 inch) to 2.54 cm (one inch) depending on the voltage of the first grid 26. In general, the

grids

26, 30 are spaced apart 0.318 cm (1/8 inch) for the first 20K volts and then an additional 0.318 cm (1/8 inch) for each 10K volt increment. The first chamber 16 can be located anywhere in-line the exhaust system but generally is placed between 2.54 cm (one inch) and 30.48 cm (12 inches) from the second chamber 18.

Any voltage source and pulsing mechanism sufficient to supply the necessary voltage at the proper frequency can be used. The applicant has determined that a voltage of at least 20K volts at a pulse rate of at least 1600 pulses/minute is preferred for optimizing reduction of carbon monoxide, carbon dioxide and hydrocarbons depending on the exhaust gas stream being treated. Typically the voltage will be in the range of 40K to 100K volts and the pulse rate will be in the range of 1500 to 10,000 pulses/minute. In general, wetter exhaust such as exhaust from a diesel internal combustion engine requires higher voltage and pulse frequency than emissions from lighter fuels such as unleaded gasoline or propane. For example, with a gasoline powered automotive IC engine, an output between 40K - 60K volts at 2000 - 3000 pulses/minute is preferred for optimizing reduction of carbon monoxide, hydrocarbons and carbon dioxide. The voltage and frequency are also set in proportion to the displacement of the engine with the upper values more suitable for larger engines.

A voltage source 12 can be any voltage source which provides the predetermined voltage. A pulsing mechanism can be any device which sets the voltage at the proper frequency. As an example, and not to so limit the present invention, Figure 1 illustrates that the voltage source 12 can comprise a voltage box 54 and an automotive battery 56. The primary windings of the voltage box 54 is supplied with 3 volts from a 12 volt automotive battery 56 and outputs 40K volts to the induction coil 14 at a pulse rate of about 2500 pulses/minute. As a further example, small engines such as two cycle engines which have a magneto, can supply voltage at the proper frequency to the first grid 26 by the magneto without use of a battery or voltage box.

The inventive induction coil 14 is configured to deliver at least 80% of the voltage to the first grid 26 and to dampen the magnetic field created by the induction coil 14 so to not create amperage greater than 0.5 amp, and preferably not greater than 0.4, amp in adjacent wiring. Current supplied through the plug wire 34 creates a magnetic field. This magnetic field is dampened by the combination of copper wires 36 and the insulated copper wires 38. Dampening the magnetic field is particularly important in automotive applications and other applications which are integrated with a computer since the magnetic field can create random cycling current in the electrical system. At a level of about 0.5 amp false signals are sent to the computer.

While not wishing to be bound to any particular theory, it is believed that exhaust gas pollutants are treated by electronic ionization at both the chemical and thermal level. Electronic ionization is caused by supplying voltage at a frequency to the first grid 26. Electronic ionization occurs between the first and

second screens

26, 30. Additionally, the exhaust gas conduit 40 and second chamber 18 including the strata 46 are ionized. Since the first grid 26 receives all the exhaust gas air stream and the voltage is supplied to the entirety of the first gird 26, all of the exhaust gas is fully treated by electronic ionization.

Exhaust gas exiting the first chamber 16 enters the second chamber 18 and passes through the strata 46. The second chamber 18 treats the exhaust gas stream by use of a catalyst in addition to electronic ionization. Presently, the preferred strata 46 contains about 30 g (one troy ounce) of noble metals such as, for example, platinum, or palladium, which serve as a catalyst. The catalyst oxidizes carbon monoxide and hydrocarbon pollutants to form carbon dioxide and water. The strata 46 also has the benefit of producing oxygen (O₂) during operation of the emission control system 10. Ozone (O₃) is created at the first grid 26. The strata 46 oxidizes the ozone and generates oxygen therefrom.

Alternatively, the second chamber 18 can be made of metal without use of a noble metal. The applicant has found that the pollutant removal efficiency of the system 10 free of noble metals is comparable to that of current catalytic converters, but less than the preferred embodiment. Although the present invention can be used with a standard catalytic converter, the reduction or elimination of noble metals from the second chamber 18 provides a significant cost savings.

Another important benefit of the present invention is its extremely short start-up time. The system 10 can be at full operating condition in as little as thirty seconds. For automotive use, voltage is supplied to the first chamber 16 as soon as the ignition is turned to the "key-on" position thereby generating electrical sparks before exhaust gasses are generated. Furthermore, although higher temperatures can be used, the second chamber 18 fully operates at low heat typically in the range of 54°C (130°F) to 93°C (200°F) as measured at the outside shell 42. This shell temperature correlation to an exhaust gas temperature of about 204°C (400°F). Conventional catalytic converters take four or five minutes of engine warm-up time to reach operating temperatures of about 316°C (600°F) at the outside shell and 982°C (1800°F) for the exhaust gas. Since the system 10 operates at low heat, extensive heat shielding is not required for the second chamber 18. Additionally, since the system 10 operates independently of the engine, it does not require expensive interactive controls with the engine, nor is a thermocouple necessary.

Although the present invention has been explained primarily in use with an automobile, the present invention is not limited to such. For example, the system 10 could be mounted to an industrial effluent stack, to an exhaust stack from a spray booth, or to other such effluent stacks. For each the first chamber 16 could be supplied pulsed voltage from any number of independent sources.

SUMMARY OF THE ACHIEVEMENT OF THE OBJECTS OF THE INVENTION

From the foregoing, it is readily apparent that I have invented an improved method and apparatus for reducing or eliminating pollutants, including gaseous pollutants, from an exhaust gas stream.

It is also apparent that the reaction occurs at the grids and the catalytic converter and is operable at a low temperature.

It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the apparatus by those skilled in the art, without departing from the scope of the appended claims.

Claims

A system (10, 12) for treating exhaust gases for reducing pollutants therein, said system comprising:

a first body (40) forming a first chamber (16), said chamber having an intake end (22) and an exhaust end (24);

a first metal grid (26) fixed within said first chamber (16) so that a gas stream entering said first chamber passes through said first grid;

a second metal grid (30) fixed within said first chamber (16) so that the gas stream passes through said second grid after passing through said first grid;

an electrical connector (14) attached to either of said first grid or said second grid;

a voltage source (12) connected to said electrical connector for supplying a voltage to said electrical connector (14); and

a pulsing mechanism (32) operatively configured with said voltage source (12) to cause the voltage supplied to said electrical connector (14) from said voltage source to be pulsed at a predetermined frequency; characterized by

a second body (42) forming a second chamber (18) having a section of perforated strata (46) therein, said second body (42) in communication with said first body (40);

wherein said first and second grids each have a meshed pattern; and
wherein said voltage source (12) supplies a voltage necessary to generate electrical sparks between said first grid (26) and said second grid (30).
The system according to claim 1 wherein said voltage source (12) is adapted to provide a voltage difference between said first grid (26) and said second grid (30) of at least 20,000 volts.
The system according to claim 2 wherein said voltage source (12) is adapted to provide a voltage difference between said first grid (26) and said second grid (30) between 40,000 and 60,000 volts.
The system according to claim 2 wherein said pulsing mechanism (32) is adapted to provide a pulse frequency greater than 1600 pulses/minute.
The system according to claim 3 wherein said pulsing mechanism (32) is adapted to provide a pulse frequency between 2,000 and 3,000 pulses/minute.
The system according to claim 4 wherein the strata (46) is comprised primarily of a rare earth oxide or metal.
The system according to claim 6 wherein the strata (46) further comprises a noble metal.
The system according to claim 7 wherein the noble metal is selected from the group consisting of platinum, palladium, and rhodium.
The system according to claim 6 wherein said perforations are generally linear and parallel with each other.
The system according to claim 9 wherein said strata (46) contains between 7.1 and 31.9 perforations/cm² (20 and 400 of said perforations/inch²).
The system according to claim 4 wherein said first body (40) is disposed either before or after said second body(42).
The system according to claim 11 wherein the nearer of said first grid (26) and said second grid (30) is disposed a distance between a range of about 2.54 cm (1 inch) to 30.48 cm (12 inches) from said strata (46).
The system according to claim 4 wherein said first grid (26) is spaced from said second grid (30) a distance in the range of 0.635 cm (1/4 inch) to 2.54 cm (1 inch).
The system according to claim 13 wherein said first grid (26) is spaced a distance from said second grid (30) according to 0.317 cm (1/8 inch) for 20,000 volts and an additional 0.317 cm (1/8 inch) for each additional 10,000 volts.
The system according to claim 4 wherein said first grid (26) and said second grid (30) are at least partially manufactured from the group consisting of stainless steel, chromium and magnesium alloy.
The system according to claim 4 wherein the system is fully functioning when an outer surface of said second body (42) reaches a temperature of no more than 93.3 °C (200 °F).
The system according to claim 4 wherein said electrical connector (14) is adapted to apply at least 80% of the voltage supplied to said electrical connector to one of said first grid (26) or said second grid (30).
The system according to claim 17 wherein said electrical connector (14) includes:

a plurality of bare wires (36) juxtaposed in a first curvilinear row and coiled equal-distantly about a curvilinear centerline forming a curvilinear helix;

a plurality of insulated wires (38) juxtaposed in a second curvilinear row and

coiled around said bare wires forming a curvilinear generally rectangular chamber around said bare wires; and

an insulated center-wire (34) along the curvilinear centerline and disposed within said bare wires and said insulated wires.
The system according to claim 18 wherein said plurality of bare wires (36) is four or five bare wires.
The system according to claim 19 wherein said plurality of insulating wires (38) is three insulating wires.
The system according to claim 5 wherein said system is mateable to an automobile's exhaust system.
A method for treating exhaust gasses to reduce pollutants contained therein, said method comprising the steps of:

passing exhaust gasses through a first body (40) forming a first chamber (16) wherein said first chamber has a first grid (26) and a second grid (30) fixed therein and separated from each other by a predetermined distance;

supplying voltage from a voltage source (12) to either said first grid (26) or said second grid (30); and

pulsing the voltage at a predetermined frequency;

characterized by the additional step of
passing the exhaust gasses through a strata (46);
wherein said first and second grids (26, 30) each have a meshed pattern and
wherein said voltage is applied in an amount necessary to generate sparks between said first grid and said second grid.
The method of claim 22 further including the steps of creating a voltage difference between said first grid (26) and said second grid (30) of at least 20,000 volts and wherein said frequency is greater than 1,600 pulses/minute.