Abstract:
A plasma generator, reactor and associated systems and methods are provided in accordance with the present invention. A plasma reactor may include multiple sections or modules which are removably coupled together to form a chamber. Associated with each section is an electrode set including three electrodes with each electrode being coupled to a single phase of a three-phase alternating current (AC) power supply. The electrodes are disposed about a longitudinal centerline of the chamber and are arranged to provide and extended arc and generate an extended body of plasma. The electrodes are displaceable relative to the longitudinal centerline of the chamber. A control system may be utilized so as to automatically displace the electrodes and define an electrode gap responsive to measure voltage or current levels of the associated power supply.

Description:
STATEMENT OF GOVERNMENT RIGHTS 
     The United States Government has certain rights in this invention pursuant to Contract No. DE-AC07-99ID13727, and Contract No. DE-AC07-05ID14517 between the United States Department of Energy and Battelle Energy Alliance, LLC. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to plasma arc reactors and systems and, more particularly, to a modular plasma arc reactor and system as well as related methods of creating a plasma arc. 
     2. State of the Art 
     Plasma is generally defined as a collection of charged particles containing about equal numbers of positive ions and electrons and exhibiting some properties of a gas but differing from a gas in being a good conductor of electricity and in being affected by a magnetic field. A plasma may be generated, for example, by passing a gas through an electric arc. The electric arc will rapidly heat the gas by resistive and radiative heating to very high temperatures within microseconds of the gas passing through the arc. Essentially any gas may be used to produce a plasma in such a manner. Thus, inert or neutral gasses (e.g., argon, helium, neon or nitrogen) may be used, reductive gasses (e.g., hydrogen, methane, ammonia or carbon monoxide) may be used, or oxidative gasses (e.g., oxygen or carbon dioxide) may be used depending on the process in which the plasma is to be utilized. 
     Plasma generators, including those used in conjunction with, for example, plasma torches, plasma jets and plasma arc reactors, generally create an electric discharge in a working gas to create the plasma. Plasma generators have been formed as direct current (DC) generators, alternating current (AC) plasma generators, as radio frequency (RF) plasma generators and as microwave (MW) plasma generators. Plasmas generated with RF or MW sources are called inductively coupled plasmas. For example, an RF-type plasma generator includes an RF source and an induction coil surrounding a working gas. The RF signal sent from the source to the induction coil results in the ionization of the working gas by induction coupling to produce a plasma. DC- and AC-type generators may include two or more electrodes (e.g., an anode and cathode) with a voltage differential defined therebetween. An arc may be formed between the electrodes to heat and ionize the surrounding gas such that the gas obtains a plasma state. The resulting plasma may then be used for a specified process application. 
     For example, plasma jets may be used for the precise cutting or shaping of a component; plasma torches may be used in applying a material coating to a substrate or other component; and plasma reactors may be used for the high-temperature heating of material compounds to accommodate the chemical or material processing thereof. Such chemical and material processing may include the reduction and decomposition of hazardous materials. In other applications plasma reactors have been utilized to assist in the extraction of a desired material, such as a metal or metal alloy, from a compound which contains the desired material. 
     Exemplary processes which utilize plasma-type reactors are disclosed in U.S. Pat. Nos. 5,935,293 and RE37,853, both issued to Detering et al. and assigned to the assignee of the present invention, the disclosures of each of these patents are incorporated by reference herein in their entireties. The processes set forth in the Detering patents include the heating of one or more reactants by means of, for example, a plasma torch to form from the reactants a thermodynamically stable high temperature stream containing a desired end product. The gaseous stream is rapidly quenched, such as by expansion of the gas, in order to obtain the desired end products without experiencing back reactions within the gaseous stream. 
     In one embodiment, the desired end product may include acetylene and the reactants may include methane and hydrogen. In another embodiment, the desired end product may include a metal, metal oxide or metal alloy and the reactant may include a specified metallic compound. However, as recognized by the Detering patents, gases and liquids are the preferred forms of reactants since solids tend to vaporize too slowly for chemical reactions to occur in the rapidly flowing plasma gas before the gas cools. If solids are used in plasma chemical processes, such solids ideally have high vapor pressures at relatively low temperatures. However, these type of solids are severely limited. 
     As noted above, process applications utilizing plasma generators are often specialized and, therefore, the associated plasma jets, torches and/or reactors need to be designed and configured according to highly specific criteria. Such specialized designs often result in a device which is limited in its usefulness. In other words, a plasma generator which is configured to process a specific type of material using a specified working gas to form the plasma is not likely to be suitable for use in other processes wherein a different working gas may be required, wherein the plasma is required to exhibit a substantially different temperature or wherein a larger or smaller volume of plasma is desired to be produced. 
     In view of the shortcomings in the art, it would be advantageous to provide a plasma generator and associated system which provides improved flexibility regarding the types of applications in which the plasma generator may be utilized. For example, it would be advantageous to provide a plasma generator and system which enables the direct processing of solid materials without the need to vaporize the solid materials prior to their introduction into the plasma. It would further be advantageous to provide a plasma generator and associated system which produces an improved arc and associated plasma column or volume wherein the arc and plasma volume may be easily adjusted and defined so as to provide a plasma with optimized characteristics and parameters according to an intended process for which the plasma is being generated. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention an apparatus for generating a plasma is provided. The apparatus includes a chamber, a first set of electrodes and at least one other set of electrodes. Each set of electrodes may include three individual electrodes disposed about a longitudinal axis of the chamber and displaced along the longitudinal axis relative to any other set of electrodes. Each set of electrodes may further be configured for coupling with a single phase of a three-phase alternating current (AC) power supply. The electrode sets may be oriented at specified angles relative to the longitudinal axis and also disposed circumferentially about the longitudinal axis in a specified orientation. 
     In accordance with another aspect of the present invention, an arc generating apparatus is provided. The apparatus includes a first set of electrodes and at least one other set of electrodes. Each set of electrodes may include three individual electrodes disposed about a defined axis and displaced along the defined axis relative to any other set of electrodes. Each set of electrodes may further be configured for coupling with a single phase of a three-phase alternating current (AC) power supply. The electrode sets may be oriented at specified angles relative to the defined axis and also disposed circumferentially about the defined axis in a specified orientation. 
     In accordance with yet another embodiment of the present invention, a plasma arc reactor is provided. The reactor may include a first chamber section and at least one other chamber section which is removably coupled to the first chamber section. The chamber sections cooperatively define a chamber body. The reactor may further include a first set of electrodes associated with the first chamber section and at least one other set of electrodes associated with the other chamber section. Each set of electrodes may include three individual electrodes disposed about a longitudinal axis of the chamber body and displaced along the longitudinal axis relative to any other set of electrodes. Each set of electrodes may further be configured for coupling with a single phase of a three-phase alternating current (AC) power supply. 
     In accordance with a further aspect of the present invention, a system for processing materials is provided. The system may include a chamber having an inlet at a first end thereof and an outlet at a second end thereof. The system may further include a first set of electrodes and at least one other set of electrodes. Each set of electrodes may include three individual electrodes disposed about a longitudinal axis of the chamber and displaced along the longitudinal axis relative to any other set of electrodes. A first power supply including three-phase AC electrical service may be coupled with the first set of electrodes and another power supply including three-phase AC electrical service may be coupled to the other set of electrodes. The power supplies may each further include a silicon controlled rectifier (SCR) configured to control the phase angle firing of each electrode in an associated electrode set. 
     In accordance with yet another aspect of the present invention, a method is provided of generating a plasma. The method includes introducing a gas into a chamber and providing a first set of electrodes and at least a second set of electrodes. Each set of electrodes may include three individual electrodes disposed about a longitudinal axis of the chamber and displaced along the longitudinal axis relative to any other set of electrodes. The electrode sets are coupled with associated three-phase AC power supplies. An arc is produced among the electrodes of the first and second set of electrodes within the chamber in the presence of the gas to produce a plasma therein. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic showing a plasma reactor system in accordance with an embodiment of the present invention; 
         FIG. 2  is a perspective view of a portion of the system of  FIG. 1 ; 
         FIGS. 3A–3C  show partial cross-sectional views of an exemplary plasma reactor at various levels of detail; 
         FIG. 4  is a schematic side view of an electrode arrangement which may be utilized in conjunction with the reactor of  FIG. 3 ; 
         FIGS. 5A–5C  are plan views of various electrode sets as indicated in  FIG. 4 ; 
         FIG. 6  is a schematic showing the independent power supply and control of multiple electrode sets in accordance with an embodiment of the present invention; 
         FIG. 7  is a general schematic of a power supply for an individual electrode set; 
         FIG. 8  is a more detailed schematic of a power supply for an individual electrode set in accordance with an embodiment of the present invention; 
         FIG. 9  is a schematic of a transformer connection diagram which may be used in a plasma reactor system in accordance with an embodiment of the present invention; and 
         FIG. 10  is a schematic of a motor control diagram associated with the placement of individual electrodes in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a schematic of a system  100  is shown which includes a plasma reactor  102 . The reactor  102  may include a plurality of electrode assemblies  104  electrically coupled to a power supply  106 . A cooling system  108  may be configured to transfer thermal energy from the reactor  102 , from the electrode assemblies  104  or both. Sensors  110  may be utilized to determine one or more operational characteristics associated with the reactor  102  such as, for example, the temperature of one or more components of the reactor  102  or the flow rate of a material being introduced into and processed by the reactor  102 . Similarly, sensors  112  or other appropriate devices may be utilized to determine various electrical characteristics of the power being supplied to the electrodes  104 . 
     A control system  114  may be in communication with various components of the system  100  for collection of information from, for example, the various sensors  110  and  112  and for control of, for example, the power supply  106 , the cooling system  108  and/or the electrode assemblies  104  as desired. While not specifically shown, the control system  114  may include a processor, such as a central processing unit (CPU), associated memory and storage devices, one or more input devices and one or more output devices. In another embodiment, the control system  114  may include an application specific processor such as a system on a chip (SOC) processor which includes one or more memory devices integrally formed therewith. 
     Referring to  FIG. 2 , a perspective view is shown of a reactor  102  and an associated cooling system  108  in accordance with an embodiment of the present invention. The cooling system  108  may include a plurality of cooling lines  120 , such as tubing or conduits, configured to circulate a cooling fluid through various portions of the reactor  102 . For example, the cooling lines  120  may circulate cooling fluid to individual electrode assemblies  104  or to portions of a chamber  122  which acts as a housing for the reactor  102 . A pump  124  may circulate the fluid through the cooling lines  120 , through the various components of the reactor  102  and then back to a heat exchanger  126 . The cooling fluid circulated through the cooling lines  120  serves to transfer thermal energy away from various components of the reactor  102  such as the electrode assemblies  104  and/or the reactor chamber  122 . The cooling fluid then flows through the heat exchanger  126 , to transfer any thermal energy accumulated by the cooling fluid thereto, and is then recirculated through the cooling lines  120 . 
     The heat exchanger  126  may include, for example, a counterflowing arrangement wherein the cooling fluid circulated through the cooling lines  120  flows in a first direction along a defined path within the heat exchanger  126  and wherein a second fluid is introduced through additional conduits  128  to flow in a second path adjacent to the first flow path but in a substantially opposite direction thereto. The counterflowing arrangement allows heat or thermal energy to be transferred from the cooling fluid of the cooling lines  120  to the second fluid flowing through the additional conduits  128 . The fluid introduced through the additional conduits  128  may include, for example, readily available plant water or an appropriate refrigerant. 
     Of course, other types of heat exchangers may be used including, for example, ambient or forced air type heat exchangers, depending on various heat transfer requirements. Those of ordinary skill in the art will recognize that the heat exchanger, pump and other equipment associated with the cooling system  108  may be sized and configured in accordance with the amount of thermal energy which is to be removed from the reactor  102  and that various types of systems may be utilized to effect such heat transfer. 
     As noted above, the reactor  102  may include a housing or chamber  122  in which chemical processes, material processes or both may be carried out. The reactor chamber  122  may be coupled with additional processing equipment such as, for example, a cyclone  130  and a filter  132 , for separating and collecting the materials processed through the reactor  102 . 
     Referring to  FIG. 3 , an enlarged, partial cross-sectional view of the reactor chamber  122  is shown. The reactor chamber  122  includes various chamber sections  122 A– 122 C. The chamber  122  may further include an outlet section  122 D which may, for example, include a converging nozzle and an outlet conduit for flowing materials out of the chamber  122 . 
     The chamber sections  122 A– 122 C may each include various ports formed through the sidewalls thereof. Such ports may be configured as view ports  140 A, as electrode ports  140 B, or as coolant ports  140 C for coupling with an associated cooling line  120  ( FIG. 2 ). 
     Associated with each chamber section  122 A– 122 C is an electrode set, which may also be referred to herein as a torch. For example, the first chamber section  122 A may have plurality of electrode assemblies  104 A– 104 C associated therewith, the second chamber section may have a plurality of electrode assemblies  104 D– 104 F (electrode assembly  104 F not shown in  FIG. 3A ) associated therewith, and the third chamber section  122 C may have a plurality of electrode assemblies  104 G– 104 I (electrode assembly  104 I not shown in  FIG. 3A ) associated therewith. 
     Referring to  FIG. 3B , a chamber section  122 C and associated electrode assemblies  104 G– 104 I are shown in greater detail. The chamber section  122 C may include, for example, a generally tubular body  142  having a flange  144  coupled therewith at each end of the body  142 . The flanges  144  may be configured for coupling to flanges of adjacent sections (e.g., chamber section  122 B and outlet section  122 D). A pocket or channel  146  may be formed in the body  142 . For example, in one embodiment, the body  142  may be formed from two concentric tubular members which are sized and positioned relative to one another so as to leave a substantially annular gap therebetween, the annular gap defining the pocket or channel  146 . The cooling ports  140 C ( FIG. 3B ) may be in fluid communication with the channel  146  so as to circulate cooling fluid therethrough and maintain the chamber section  122 C at a desired temperature. 
     The electrode assemblies  104 G– 104 I are coupled with the electrode ports  140 B such that electrodes  148 G– 148 I extend through their respective electrode ports  140 B, through the body  142  and into the interior portion of the chamber section  122 C. The electrodes  148 G– 148 I may be formed, for example, as graphite electrodes. In another embodiment, the electrodes may be formed as a substantially hollow metallic members configured to receive a cooling fluid therein. 
     As shall be discussed in greater detail below, the electrodes  148 G– 148 I may be symmetrically arranged circumferentially about a longitudinal axis  150  of the chamber section  122 C (and of the reactor chamber  122 ) and configured to provide an arc and also establish a plasma within any gas which may be present within the reactor chamber  122 . 
     Referring to  FIG. 3C  along with  FIG. 3B ,  FIG. 3C  shows a partial cross-sectional view of the chamber section  122 C and an associated electrode assembly  104 G in further detail. As noted above, the electrode assembly  104 G is coupled with an electrode port  140 B. The electrode assembly  104 G includes an electrode  148 G which extends into an interior region of the chamber section  122 C as defined by the body  142 . The electrode assembly  104 G further includes an actuator  152  which is configured to adjust the position of the electrode  148 G relative to the chamber section  122 C. For example, the actuator  152  may include a threaded drive rod  154  which is linearly displaceable along a defined axis  156 . The actuator may include, for example, a linear positioning servo motor configured to control the position of the drive rod  154  as will be appreciated by those of ordinary skill in the art. 
     A slidable frame member  158  may be coupled to the drive rod  154  and slidably disposed about one or more linear rod bearings  160  which extend between the actuator  152  and a coupling member  162  and substantially parallel to the defined axis  156 . The coupling member  162  is mechanically coupled with the electrode port  140 B thereby fixing the relative position of the actuator  152 , linear rod bearings  160  and coupling member  162  relative to the chamber section  122 C. 
     The slidable frame member  158  is also coupled with the electrode  148 G and, upon displacement of the slidable frame member  158  by way of the actuator  152  and associated drive rod  154 , effects displacement of the electrode  148 G relative to the chamber section  122 C in a direction generally along the defined axis  156 . The electrode assemblies  104 – 104 I are thus adjustable so that an arc gap, or distance between adjacent electrodes  148 G– 148 I, may be set to obtain a desired arc therebetween. Additionally, as the electrodes  148 G– 148 I wear due to repeated arcing, they may be advanced by their associated actuators  152  so as to maintain a desired arc gap. 
     As also shown in  FIG. 3C , the electrode  148 G may include a first tubular member  163  and a second tubular member  164  which may be disposed substantially concentrically within the first tubular member  163 . The first and second tubular members  163  and  164  may be sized, located and configured such that an annular gap  165  is defined therebetween. A fluid inlet  166  may be in fluid communication with an interior portion of the second tubular member  163  and a fluid outlet  167  may be in fluid communication with the annular gap  165 . Thus, in operation, cooling fluid may be introduced through the fluid inlet  166 , flow through the interior of the second tubular member  164 , into the annular gap  165  and out of the fluid outlet  167 . Such a configuration enables efficient cooling of the electrode  148 G and improves the operating life thereof. 
     The tubular members  163  and  164  may be formed of, for example, a metallic material which is both electrically and thermally conductive. Additionally, the electrode  148 G may include a replaceable tip  168  which is removably coupled with, for example, the first tubular member  163  such that worn tips may be replaced when desired. Additionally, the electrode assembly  104 G may include an electrically insulating sleeve  169  disposed, for example, between the first tubular member  163  and the electrode port  140 B to insulate the electrode therefrom. Such a sleeve  169  may be formed of, for example, boron nitride or a composite material of boron nitride and aluminum nitride. 
     The electrode sets, as associated with each chamber section  122 A– 122 C, may be configured geometrically to provide a desired arc and associated plasma column therefrom. For example, referring to  FIGS. 3A and 4 , in one embodiment, each of the electrodes  148 A– 148 C of the first set may be positioned and oriented such that they extend from the reactor chamber  122  (represented in  FIG. 4  as a dashed line for purposes of clarity) to define an acute angle α ( FIG. 3A ) with respect to the longitudinal axis  150 . Another set of electrodes  148 D– 148 F may be displaced from the first set of electrodes  148 A– 148 C a desired distance and oriented such that they extend substantially transverse to the longitudinal axis  150 . A further set of electrodes  148 G– 148 I may be displaced from the first set of electrodes  148 D– 148 F a desired distance and may be oriented such that they also extend substantially transverse to the longitudinal axis  150 . 
     Referring to  FIG. 5A , the first set of electrodes  148 A– 148 C may be circumferentially arranged substantially symmetrically about the longitudinal axis  150 , as represented by the intersection of two other Cartesian axes  170  and  172  which are orthogonal with respect to each other as well as to the longitudinal axis  150  ( FIG. 3A ). For example, the angle of one electrode (e.g.,  148 A) relative to an adjacent electrode (e.g.,  148 B) may be approximately 120°. More particularly, relative to the defined axes  170  and  172 , a first electrode  148 A may be positioned at approximately a 90° orientation, a second electrode  148 B may be positioned at approximately a 210° orientation, and a third electrode  148 C may be positioned at approximately a 330° orientation. 
     Referring to  FIG. 5B , the second set of electrodes  148 D– 148 F may also be circumferentially arranged substantially symmetrically about the longitudinal axis  150  but at a different orientation relative to the defined axes  170  and  172  as compared to the first set of electrodes  148 A– 148 C. For example, relative to the defined axes  170  and  172 , a first electrode  148 D may be positioned at approximately a 30° orientation, a second electrode  148 D may be positioned at approximately a 150° orientation, and a third electrode  148 F may be positioned at approximately a 270° orientation. 
     Referring to  FIG. 5C , the third set of electrodes  148 G– 148 I may also be arranged substantially symmetrically about the longitudinal axis  150  but at a different orientation relative to the defined axes  170  and  172  as compared to the second set of electrodes  148 D– 148 F. For example, relative to the defined axes  170  and  172 , a first electrode  148 G may be positioned at approximately a 90° orientation, a second electrode  148 H may be positioned at approximately a 210° orientation, and a third electrode  148 I may be positioned at approximately a 330° orientation. Thus, the first set of electrodes  148 A– 148 C may be oriented similarly to the third set of electrodes  148 G– 148 I. 
     It is noted that in such an electrode configuration as described with respect to FIGS.  4  and  5 A– 5 C, the first set of electrodes  148 A– 148 C exhibits a first angular orientation or arrangement about the longitudinal axis  150  while the second set of electrodes  148 D– 148  exhibits a second angular orientation about the longitudinal axis  150  such that, when viewed from a plane transverse to the longitudinal axis  150 , the electrodes  148 D– 148 F of the second set appear to be rotationally interspersed among the electrodes  148 A– 148 C of the first set. A similar arrangement is noted with respect to the second set of electrodes  148 D– 148 F and the third set of electrodes  148 G– 148 I. 
     Such a configuration provides the advantage of a uniform distribution of electrodes  148 A– 148 I within the chamber  122  for the production of a long, high temperature arc between the electrodes  148 A– 148 I. The resultant high temperature arc provides substantial thermal energy for heating, melting and evaporating various materials. The arc also produces a substantially uniform column or body of plasma within the reactor chamber  122 . Furthermore, the stacked arrangement of electrode sets (i.e.,  148 A– 148 C,  148 D– 148 F and  148 G– 148 I) and the resulting lengthened arc and plasma column provide a longer residence time for any reactant flowing therethrough. Thus, due to the modular nature of the reactor  102  ( FIG. 2 ), including the separate chamber sections  122 A– 122 C, a column of plasma of variable length may be formed by introducing additional chamber sections or removing existing chamber section to tailor the resultant plasma to a desired process. Additionally, a spacer  179 , such as is shown in  FIG. 3B , may be coupled to each end of a chamber sections  122 A– 122 C ( FIG. 3A ) to alter the distance along the longitudinal axis between adjacent electrode sets (e.g.,  148 A– 148 C and  148 D– 148 F). In other words, while only shown on the lower portion of the chamber section  122 C in  FIG. 3B  for purposes of clarity, a similar spacer  179  may be disposed at each end of the chamber section such that at least one spacer  179  is disposed between each chamber sections  122 A– 122 C. 
     It is further noted that the various sets of electrodes  148 A– 148 C,  148 D– 148 F and  148 G– 148 I may exhibit different angular orientations than that which is described with respect to FIGS.  4  and  5 A– 5 C. For example, with the first set of electrodes  148 A– 148 C configured as shown in  FIGS. 4 and 5A , the second set of electrodes  148 D– 148 F may be oriented, relative to the defined axes  170  and  172 , at 10°, 130° and 250°, respectively, while the third set of electrodes  148 G– 148 I may be oriented, relative to the defined axes  170  and  172 , at 50°, 170° and 290°, respectively. Of course other arrangements may be utilized depending, for example, on the number of electrode sets being utilized and the distance between each electrode set along the longitudinal axis  150 . 
     Referring back to  FIGS. 3A and 4 , an inlet  180  may be formed in the chamber to introduce materials, such as reactants, into the reactor chamber  122 . In one particular embodiment, the inlet  180  may be configured to introduce materials along the longitudinal axis  150  such that materials pass through the center of the arc formed by the plurality of electrodes  148 A– 148 I. The ability to pass materials substantially through the center of the arc enables the melting and/or evaporation of solid materials such that preconditioning of such materials is not required prior to their introduction into the chamber  122 . 
     Referring now to  FIG. 6 , an exemplary schematic is shown of the reactor  102  regarding the power supply and related actuator control. Electrical service  188 A– 188 B provides three phase alternating current (AC) power at 480 volts (V) and 60 amps (A) to individual electrode set power supplies  190 A– 190 C. A power measurement device or system  192 A– 192 C may be associated with each power supply  190 A– 190 C. Each power measurement system  192 A– 192 C may be configured to monitor, for example, the voltage and current of each phase of power for its associated power supply  190 A– 190 C. 
     A transformer  194 A– 194 C may be coupled between the each power supply  190 A– 190 C and the reactor  102 . More specifically, each transformer  194 A– 194 C may be coupled between an associated power supply  190 A– 190 C and a defined set of electrodes (e.g., electrodes  148 A– 148 C,  148 D– 148 F or  148 G– 148 I). A plurality of actuator control devices  196 A– 196 C are also coupled the reactor  102 . More particularly, each actuator control device  196 A– 196 C is coupled to the actuators  152  ( FIGS. 3B ,  3 C) of a defined set of electrodes. 
     Referring to  FIGS. 7 and 8 , exemplary schematics of an electrode set power supply  190 A are shown. It is noted that the power supply  190 A may include a silicon controlled rectifier (SCR)  198 . With a single phase of each three phase power supply being coupled to a single electrode (e.g., electrode  148 A) of an electrode set (e.g.,  148 A– 148 C), the SCR  198  may be used to control the phase angle firing of each electrode. In one particular embodiment the SCR  198  may be rated at 480 V and 75 A. Such a device is commercially available from Phasetronics of Clearwater, Fla. 
     Referring briefly to  FIG. 8 , an exemplary schematic is shown of a transformer  194 A which may be used in accordance with an embodiment of the invention. The transformer  194 A is utilized to limit the high instantaneous currents associated with arc ignition. More particularly, the inductive reactance of the transformer reduces the initial current from the associated power supply  190 A such that circuit protection devices are not activated. 
     Referring to  FIG. 9 , an exemplary schematic is shown for an actuator control system or device  196 A. The control of actuators  152  ( FIGS. 3A and 3B ) may be responsive, for example, to measured current and voltage values of the individual phases of electrical power which are coupled with electrodes. Based on the current and voltage measurements taken from an associated power supply (e.g.,  190 A), individual electrodes of a given set (e.g., electrodes  148 A– 148 C) may be displaced, as discussed above, to change the gap or distance therebetween. Continual monitoring of the voltage and/or current and attendant adjustment of the individual electrodes of an electrode set enables a more efficient arc production by such electrodes. Additionally, during startup, the actuators may be controlled so as to define a smaller gap among the electrodes to provide easier startup of the reactor. Upon establishment of an arc, the electrodes may be repositioned for optimal performance during normal operation. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.