WO1992015714A1

WO1992015714A1 - Methods and chemo-thermal reactor apparatus for extracting mineral values from particulate materials

Info

Publication number: WO1992015714A1
Application number: PCT/PL1991/000002
Authority: WO
Inventors: Juliusz Boleslaw Czaja; Jerzy Leslaw Romanowski
Original assignee: Avny Industries Corporation Spólka Z O.O.
Priority date: 1991-02-27
Filing date: 1991-02-27
Publication date: 1992-09-17
Also published as: MX9200855A; IL101089A0

Abstract

A method and apparatus for chemo-thermal separation of mineral values from mineral containing particulate materials in a plasma reactor (100). The plasma reactor (100) includes a reaction chamber (110) wherein the particles are contacted with a plasma arc (105) rotating at a rate of at least 16,000 RPM causing the mineral values in the particles to liquify and to be transported from the reaction chamber (110) through a cooling zone (112) wherein agglomerated mineral value particles are formed for collection after passing through a countercurrent air flow zone (114) in which the mineral values are further separated.

Description

DESCRIPTION

METHODS AND CHEMO-THERMAL REACTOR APPARATUS FOR EXTRACTING MINERAL VALUES FROM PARTICULATE MATERIALS

TECHNICAL FIELD

The present invention relates in general to methods and apparatus for extracting mineral values from mineral containing particulate material. More particularly, it relates to methods and apparatus for extracting essentially pure mineral values from particulate raw materials including such waste materials as fly ash, slag and the like as well as recovering other valuable by-products.

DESCRIPTION OF THE RELATED ART

A wide variety of methods and apparatus have been proposed heretofore for extracting and recovering mineral values from waste materials such as fly ash, slag and the like. For example, U.S. Patent Nos. 3,175,900; 3,574,537;

3,783,167; 3,819,363; 3,843,351; 3,932,171 3,945,575;

4,002,466; 4,082,832; 4,048,285; 4,177,060 4,225,565;

4,252,777; 4,310,350; 4,337,900; 4,361,441 4,394,978;

4,410,358; 4,436,550; 4,454,013, 4,474,735 4,508,040;

4,610,722; 4,617,180; 4,652,433, 4,668,352 4,789,532; Re.

28,750 and British Patents 1,273,523 and 1,317,888 show different processing techniques and apparatus for extracting and recovering various mineral values from a variety of raw material sources. However, the prior methods and apparatus have generally demonstrated inherent problems which have prevented their economic implementation. Some processes have been too heavily dependent on energy, while others have required utilization of uneconomical amounts or types of reactants or other process constituents. Other processes have been overly time consuming and have required commercially unacceptable numbers of processing stages. Still others of these prior processes have either failed to provide for environmentally acceptable and economically feasible disposal of the unutilized constituents accompanying the initial waste material or have created additional environmental waste disposal problems as a result of the practice of the processes. p_or example, some of the prior processes have required excessively costly and elaborate gas handling and other cleaning systems to reduce atmospheric and other environmental pollution concerns.

SUMMARY OF THE INVENTION

The present invention has been developed in response to the above-noted shortcomings of the prior art. The invention provides economically advantageous methods having exceptional environmental and commercial attributes for treating mineral containing particulate material to extract essentially pure mineral values therefrom and apparatus for use in such methods. In addition to the recovery of the valuable mineral content from the particulate raw material, the methods of this invention also provide for the extraction and recovery of valuable by-products from the raw material which have commercially advantageous utility as, for example, building materials, fillers, binders and the like. Accordingly, the methods

SUBSTITUTE SHEET of the present invention provide for the utilization of essentially all of the raw material particulates providin substantial environmental benefits.

Depending on the particular raw material to be processed and the composition thereof as well as the desired degree of purification intended to be achieved by virtue of the processing of the raw material and other like considerations within the discretion of the operator, the methods of the present invention may comprise either single stage or multiple stage processes. More specifically, a method of the present invention may include a two-stage recovery system for treating a raw material stock which incorporates both physical and chemical separation techniques or the method may comprise only one or the other of these two stages in order to accomplish the desired extraction and recovery of mineral content from the raw material stock as well as to provide other valuable by-products from the process residuals. In this regard, the raw material stock for use herein may be derived from fly ash, flue dust, industrial slag, foundry or metallurgical processing residues such as those from the ferro-chrome or the galvanization process, mining residues such as those from ore concentration flotation processes, sea sand and other like waste materials having desired compositions.

In the methods of the present invention, one of the processing stages comprises a pneumo-gravitational separation technique to separate out the mineral content such as metal and metal oxide concentrates from the raw material stock. Another stage of the process comprises a chemo-thermal treatment of a raw material stock or, in a preferred embodiment, an effluent stream derived from the pneumo-gravitational separation stage utilizing plasma separation techniques to extract essentially pure mineral

SDBSπiϋfESHEET values therefrom and to yield further by-product effluents which may be utilized separately or in combination with other residual effluents derived from the pneumo-gravitational stage to provide building material end products such as cement-like products, binder materials and the like.

In a preferred embodiment, the method of the present invention includes the stage of introducing mineral containing particulate material having a radial particle size of less than about 0.1 mm. into a pneumo-gravitational separation apparatus to be described hereinafter having a flotation chamber with at least one inlet port and multiple outlet ports formed therein. Means are provided such as a fan, a blower or similar device to introduce air into the chamber and to cause an air flotation stream to flow from at least one of the inlet ports to at least one of the outlet ports and the particulate material is contacted with this air flotation stream at a predetermined air flow velocity. The air flow velocity must be sufficient to cause the particulate material introduced into the chamber through at least one inlet port positioned a predetermined longitudinal distance from the location of air introduction into the chamber and at a predetermined angle relative to the axial air flow path through the chamber to separate into a mineral value fraction which precipitates out from the air flotation stream. This mineral value fraction precipitates out from the stream in response to gravitational settling of the fraction frβm the stream based on the weight of the mineral values in the fraction leaving an unprecipitated residual granular fraction in the flotation stream.

SUBSTITUTE SHEET The unprecipitated residual granular fraction from the flotation stream is collected for further treatment in order to produce valuable building materials including advantageous cement-like compositions or binding compositions and the like. Also, in a preferred form of this invention, the precipitated fractions which are collected contain such materials as aluminum oxide (alumina) , titanium oxide, chromium and iron salts, as well as elemental forms of such minerals and a variety of other compounds and elemental constituents derived from the diversity of particulate raw materials which may be treated by the methods of this invention. Considerable improvement in the purity of the resulting mineral values recovered are achieved from this pneumo-gravitational separation stage although it is preferred to subject the recovered values to further processing either by further pneumo-gravitational separation or some other extraction technique in order to enhance the purity of the recovered mineral values. In construction, the flotation chamber of the pneumo-gravitational separator may be rectangular, square, circular or any other appropriate shape in cross-section and the assembly is structured so that air for the air flow stream is introduced at an inlet port at one end of the chamber and flows through the chamber to an outlet port positioned at the other end of the chamber. A separate inlet port is provided for introducing the particulates into the chamber and is positioned a distance from the outlet end of the chamber sufficient to provide optimum separation of the mineral values in the treated particulates as will be discussed in greater detail hereinafter.

SUBSHΓ:^ HEET Further ore, it is preferred to wet the particles with a sulfuric acid solution prior to introduction into the chamber in order to react the active particles with the acid whereby the density of the particles increase and these heavier particles have less likelihood to clog or agglomerate within the chamber as they are blown therein. Also, the particulates should be introduced into the chamber at an angle ranging from 12° to 75° relative to the axial direction of laminar air flow through the chamber from one end to the other and the air flow velocity in the chamber should be maintained in a range of from about 2 meters/second for lighter weight particles up to about 25 meters/second for heavier particles such as lead oxide having a density of about 13 g/cm . Flow velocities below about 2 meters/second have been found to provide no separation of particles.

In a preferred embodiment of the invention, means are provided for tilting the chamber in order to enable adjustment of the angle presented between the essentially horizontal direction of the laminar flow of air in the chamber and the longitudinal axis of the chamber. This angular adjustment controls the time and distance the particles will fall before being contacted by the air stream and is set, preferably, in a range of from about -60° to about 0^β (horizontal) to accommodate lighter weight particles by increasing the time and distance before the particles are engaged by the air flow and from about +60° to about 0^β (horizontal) to accommodate heavier weight particles by decreasing the time and distance before the particles are engaged by the air flow.

After the pneumo-gravitational separation stage, it is particularly preferred within the method of the present invention to combine the precipitated mineral value fractions collected therefrom and to introduce such combined particulate fractions into a chemo-thermal processing stage utilizing a plasma reactor apparatus to be described in detail hereinafter wherein the combined fractions are subjected to plasma separation to further separate the mineral values in the fractions from impurities. This further processing stage results in the extraction of essentially pure mineral values from the treated fractions.

During the plasma separation stage of the present method, the mineral value fractions in particulate form are introduced into a reaction chamber of a plasma reactor. Preferably, the average radial size of the mineral value particles to be treated is less than about 0.1 mm. A stream of plasma gas is also introduced into the reaction chamber and the gas is ionized to produce a plasma arc in a reaction zone formed in the reactor between a cathode and a multi-segmented anode wherein the temperature is raised to a level of about 10,000° K. The reactor is structured and dimensioned in a manner such that the plasma arc is caused to rapidly revolve about the segmented anode and the particulate fractions are subjected to this motion whereby the particles are caused to pass through the plasma in a desired spiral flow.

In preferred embodiments of this invention, the anode employed in the reactor includes from six to ten segments and, most preferably, eight segments in order to achieve plasma rotation preferably greater than about 15,000 revolutions per minute (RPM) and, most preferably, in a range of about 15,000 - 30,000 RPM. More particularly, the plasma reactor of this invention is constructed to produce a rotating plasma arc discharge between two stationary electrode structures. When a voltage of sufficient magnitude is impressed across the electrode pair (i.e., the cathode and anode), a plasma

SDBSTHϋπ. 52EET arc discharge occurs. In an exemplary embodiment, the anode is a segmented annular ring with each of the anode segments electrically isolated from the others. Each anode segment is electrically connected to a region of constant potential or ground through a pair of solenoid coils arranged on either side of the anode segment at a 90° angle. The axis of each such solenoid coil is parallel to a line drawn from the center of the reaction chamber to the anode segment to which it is connected. A plasma discharge from the cathode to a particular anode segment and then to ground thus energizes the corresponding pair of solenoid coils. The magnetic field thus produced tends to rotate the plasma arc to the adjacent anode segment. The process is then repeated which results in a rapidly rotating plasma arc.

Also in accordance with the present invention, a coaxial solenoid coil encircles the periphery of the reaction zone and is coaxial with the path from cathode and anode. The coaxial coil produces a second magnetic field to further increase the rotational velocity of the plasma arc by converting radial velocity of the plasma arc to circumferential velocity.

Appropriate plasma gases for use in generating the plasma arc depend on the composition of the particulate raw material being treated but include various oxidizing gases such atmospheric air or oxygen, reducing gases such as hydrogen and inert gases such as argon or other noble gases.

Thus, as the particles pass through the arc, they are heated to a temperature exceeding the melting temperatures thereof thus causing the particles to liquify. The reactor of this invention is further structured and dimensioned to provide a cooling zone so that as the liquid exits from the plasma reaction zone, it passes

SUBSTITUTE SHEET through various declining temperature gradients during which time the desired mineral values in essentially pure elemental or compound form cool and agglomerate into relatively dense particulate form. Also, the heated residuals in the originally fed particles either crystallize and form dust-like particles of low relative density in the cooling zone or evaporate and form gases in such zone as a result of the plasma treatment and the subsequent cooling. Additionally, the reactor construction includes a countercurrent flow zone into which the liquid, dust and gas materials pass as they exit from the cooling zone. In this flow zone, these materials are subjected to a countercurrent flow of air in a manner and utilizing apparatus to be described in detail hereinafter such that the desired liquid mineral values pass through the countercurrent air flow and are collected in their essentially pure particulate form while the residual dust-like and gaseous components are removed from the desired mineral values by virtue of the countercurrent flow of air and are separately collected.

Thus, as a result of the chemo-thermal separation of particulates utilizing the plasma reactor of the present invention, essentially pure mineral values having purity levels exceeding 95% are extracted from the raw material treated therein. Additionally, depending on their composition, the residual dust-like and gaseous components separated from the collected mineral values may be further processed to provide other desirable essentially pure fractions. Alternatively, the collected residuals may be utilized in certain instances as valuable by-products of the process.

Accordingly, it is a general object of the invention to provide improved methods for extracting essentially pure mineral fractions, such as aluminum oxide (alumina)

SDBSiπUISSHEET and titanium oxide from mineral containing raw materials, preferably waste materials such as fly ash, flue dust, industrial slag, foundry or metallurgical processing residues, mining residues, sea sand and the like. Another object of this invention is to provide an economically feasible and environmentally advantageous method for extracting essentially pure mineral fractions in a commercially successful manner.

A further object of this invention is to provide methods for extracting commercially advantageous by-products in addition to essentially pure mineral fractions from raw materials, preferably waste materials such as fly ash, flue dust, industrial slag, foundry or metallurgical processing residues, mining residues, sea sand and the like.

A still further object is to provide a method for the recovery of aluminum oxide, and titanium oxide, iron, chromium, nickel, cobalt, lead, zinc, copper, zirconium and other elemental mineral values and other valuable by-products from waste raw materials derived from foundries; power plants, waste disposal facilities, environmental pollution abatement sources such as sea bed cleansing programs and the like in a manner such that the initial environmental concerns relative to the raw materials are eliminated and essentially no additional environmental pollution problems are presented as a result of the practice of the method.

A more specific object is to provide a single stage method for extracting mineral values from mineral containing particulate raw materials by introducing and treating the raw materials in a pneumo-gravitational separation apparatus. A companion object is to provide the pneumo-gravitational separation apparatus for performing such extraction process.

SUBSΠTCTESHEET Another specific object is to provide a single stage method for extracting mineral values from mineral containing particulate raw materials by introducing and treating the raw materials in a chemo-thermal reactor utilizing plasma separation techniques. A companion object is to provide the chemo-thermal reactor for performing such extraction process.

A still further specific object is to provide a multiple stage method for extracting mineral values from mineral containing particulate raw materials by subjecting the raw materials to pneumo-gravitational separation in a first stage followed by a second stage separation in a chemo-thermal reactor utilizing plasma separation techniques. Other objects of the invention, in addition to those set forth above, will become apparent to one skilled in the art from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flow diagram illustrating the method of the present invention employed to extract mineral values from a dry fly ash raw material source;

FIG. 2 is a schematic flow diagram similar to FIG. 1 illustrating the method of the present invention employed to process a galvanization residue raw material source; FIG. 3 is a schematic flow diagram illustrating the method of the present invention for processing a metallurgical slag waste material from a ferro-chrome treatment process; FIG. 4 is a schematic flow diagram illustrating the method of the present invention for processing sea sand;

FIG. 5 is a schematic side view of a preferred apparatus for performing the pneumo-gravitational separation step in the method of the present invention;

SQBSΪIΪϋΣi_ SHEET FIG. 6 is a schematic side view of a preferred plasma reactor apparatus for performing the chemo-thermal separation step in the method of the present invention;

FIG. 7 is a schematic top view projecting downwardly from the cathode to the multi-segmented anode assembly in the plasma reactor apparatus of FIG. 6; and

FIG. 8 is a detailed schematic view of the cathode and segmented anode arrangement of FIG. 7 with broken cross-sections of parts thereof.

DETAILED DESCRIPTION FIGS. 1-4 are schematic flow diagrams showing various embodiments of the methods of the present invention including process options depending on the composition of the raw material source and its physical condition, its inherent mineral content and other like considerations. The embodiment of this invention depicted in FIG. 1 utilizes a freshly produced, dry fly ash derived from the combustion of power plant coal. In this regard, it should be noted that the fresh ash employed herein was soft enough to be used as dust without grinding into particulate form. However, if an ash had been utilized which had been obtained from a reserve pile or mountain which has been collected over an extended period up to a period of years, it would have been necessary to grind the raw material ash into an appropriate particle size in order to provide adequate results in the method of the present invention.

The composition of the dry fly ash utilized in this method may vary somewhat depending on the fuel burned.

However, the main elements in the fly ash are silicon and aluminum and the minor elements therein include calcium, iron, titanium and magnesium. Trace amounts of lead, mercury, silver, manganese and chromium may also be

SDBSETϋϊESHEET included. A fly ash employed in the method normally contains the following compounds present in amounts (on a weight basis) as follows:

Si 0₂ 50 - 56% ^A1 ₂°₃ ^{21 " 28%}

Ca 0 2 - 4%

^Fe2°3 ^{7 " 12%}

Ti 0₂ 1 - 1.7%

Mg 0 2 - 3% In one operating example of the present invention, a

10 Kg dry fly ash dust sample freshly produced from coal as part of the daily output from a power plant was collected. This 10 Kg sample had the following composition on a weight percentage basis: si 0₂ 51.5%

A1₂0₃ 26.6%

Ca 0 2.6%

Fe₂0₃ 11.3%

Ti 0₂ 1.2% Mg 0 2.1%

Other 4.7%

This fly ash sample was introduced into a flotation chamber of a pneumo-gravitational separation device of the type illustrated in FIG. 5. As the fly ash was being introduced into the chamber, it was treated with 1 liter of 5% sulfuric acid solution and the ash reacted with the acid to form a sulfate particle fraction of higher density to promote settling out of the active particles on further processing.

In the pneumo-gravitational separation device, the particles were contacted by a laminar air flotation stream flowing through the chamber from an inlet port at one end thereof to an outlet port at the other end thereof. The

SDBSTHUΪBSHEET air velocity was about 2 meters/second and as the particles were blown through the chamber, the higher weight particles including Al_0₃ and Ti 0₂ precipitated out of the flotation stream as a result of gravitational settling while the lighter weight particles essentially remained suspended in the flotation stream. The particulate mineral value fraction which precipitated out of the flotation stream weighed 3.08 Kg and had the following composition on a weight percent basis:

This precipitated particulate fraction was collected and transported for further processing in a chemo-thermal separation stage to extract higher purity mineral values from the product obtained from the pneumo-gravitational separation stage.

With regard to the residual particles which remained in the flotational stream, these particles were separately collected and weighed 6.92 Kg. The composition of this residual fraction was as follows on a weight percent basis:

A1₂0₃ 2.80% A1₂(S0₄)₃ .87%

Si 0₂ 69.30%

Fe₂0₃ 13.20%

Fe₂(S0₃)₃ 1.15%

Ca 0 3.00%

Mg 0 ) 2.89%

Mg S0₄)

Other 6.79%

SUBSTIT These residual particles have been found to be valuable by-products of the method suitable for further processing for use in the production of cement-like building compositions or binder and filler materials of excellent quality.

In the chemo-thermal separation stage, the precipitated particulate fraction from the pneumo-gravitational separation stage was introduced into a plasma reactor of the type illustrated in FIG. 6 wherein a plasma having a temperature of about 10,000°K was generated employing air as the plasma generating gas and the plasma arc was caused to rotate about an eight segmented anode at a rate of about 30,000 RPM which resulted in the separation of a mineral value fraction having a weight of 2.53 Kg based on the original 3.08 Kg sample of particulate material introduced into the reaction chamber. This separate fraction had a composition on a weight percentage basis of: 1₂0₃ 95.0% Ti 0₂ 2.7%

Impurities 2.3%

Thus, a 97.7% pure fraction of A1₂0₃ and Ti 0₂ are obtained from this two stage process by melting the A1,0₃ and Ti 0₂ in the plasma and collecting the unseparated, agglomerated particles which settle to the bottom of the reactor chamber of the reactor device of FIG. 6. The remaining .55 Kg residual fraction from the original 3.08 Kg sample introduced into the reactor is removed from the reactor as described in regard to the device depicted in FIG. 6. For example, the predominant portion of magnesium, iron and silicates in the 3.08 Kg sample were melted in the plasma and crystallized forming dust-like particles which were blown out of the reactor. Also, the sulfates evaporated in the plasma forming a gas

SUBSTITUTESHEET which likewise were blown out of the reactor. The entire

.55 Kg residual fraction including the dust-like particles and the gases was available for collection and further processing, if desired. Fig. 2 illustrates another embodiment of this invention wherein a metallurgical slag derived from a foundry producing ferro-chrome products was employed as the particulate raw material. In this regard, it should be noted that slag derived from mining operations has also been employed as the mineral containing particulate for use in the methods of this invention.

In this example of the present invention, a sample of metallurgical slag from a foundry blast-furnace was collected from a reserve pile or mountain of slag. The slag sample was screened to remove over size particulates and then the resulting particulates were subjected to a magnetic separation technique whereby magnetic particles having average radial particle size of greater than 250 mm were separated from the remainder of the raw particulate material stock. This separated fraction with 250 mm or greater radial size contained 75% (by weight) iron and 25%

(by weight) chromium compositions. A 10 Kg sample of the remaining smaller particle size raw material had the following composition on a weight percentage basis: Si 0₂ 25%

A1₂0₃ 3%

Ca 0 45%

Fe₂0₃ 7%

Mg 0 8% Chromium )

Chromium oxides ) 12% Chromates )

SUBSTITUTESHEET ISA/EP This 10 Kg sample was then subjected to a crushing or grinding operation wherein the particles were reduced in size to an average radial particle size of about .1 mm to about 2 mm. These ground particles were introduced into a flotation chamber of a pneumo-gravitational separation device of the type illustrated in Fig. 5. In the pneumo-gravitational separation device, the particles were contacted by a laminar air flotation stream flowing through the chamber from an inlet port at one end thereof to an outlet port at the other end thereof. The air velocity was about 10 meters/second and as the particles were blown through the chamber, the particles precipitated out in a first and a second fraction based on particle weight. As a result of gravitational settling, the first fraction contained the heavier weight particles while the second fraction contained the lighter weight particles. The first particulate mineral value fraction which precipitated out weighed 5.75 Kg and was collected and subjected to known magnetic separation techniques in order to separate an iron and chromium rich portion weighing

3.27 Kg from a second portion weighing 2.48 Kg. The iron and chromium rich portion was collected.

The 2.48 Kg second portion had the following composition on a weight percent basis: ^A12°3 6.05%

Ca 0 66.52%

Si 0₂ 26.21%

^Cr2°3 ^,41%

Fe₂0₃ .40% Mg 0 .41%

SUBSTITUTE SHEET ISA/EP Additionally, the second fraction obtained from the pneumo-gravitational separation stage weighed 4.3 Kg and had the following composition on a weight percent basis:

^A12°3 3.49% Ca 0 32.60%

Si 0₂ 39.56%

Cr 0₃ 5.80%

Fe 0₃ 4.65%

Mg 0 13.90% The 2.48 Kg second portion was combined with the 4.3 Kg second fraction to provide a 6.78 Kg combined sample which was transported for further processing in a chemo-thermal separation stage to extract higher purity mineral values from the product obtained from the pneumo-gravitational separation stage.

Sufficient coal particles were added to the combined 6.78 Kg sample in order to achieve a mixture having about 0.72 Kg of its weight as carbon and the resulting particulate mixture weighing 7.50 Kg was then introduced into a plasma reactor of the type illustrated in Fig. 6 wherein a plasma having a temperature of about 10,000°K was generated employing air as the plasma generating gas and the plasma arc was caused to rotate about an eight segmented anode at a rate of about 30,000 RPM which resulted in the separation of a mineral value fraction weighing .28 Kg having a composition on a weight percentage as follows:

Chromium mixture 85%

Iron mixture 14% Impurities 1%

Thus, 99% pure mineral values were extracted from the raw particulate materials by the two stage-process including a high percentage of elemental chromium and iron (i.e., about .27 Kg). The remaining residual fraction

SUBSTITUTESHEET ISA/EP collected from the chemo-thermal reaction stage as described in regard to the removal of residuals from the reactor of Fig. 6 weighed 6.5 Kg and was employed for producing valuable by-products such as a Portland Cement-type product.

In the embodiment of this invention illustrated in FIG. 3, the residue obtained from the galvanization process for producing high quality steel was utilized as the mineral value containing raw material for use in practicing the method. From the galvanization process, a waste residue or sediment was collected having a composition including chromates, sulfate and chloride salts, ferric and ferrous compounds as well as silicates. In particular, the sediment included a high percentage (greater than 50% by weight) of chromium salts.

Initially, this residue was subjected to hot air treatment in order to dry the material. Then, the dried material was ground into particles having an average radial size not in excess of 2 mm. This particulate material was transported to and introduced as a 10 Kg sample into a pneumo-gravitational separator of the type illustrated in FIG. 5 and which was operated as described in reference thereto. The air velocity of the laminar air flow in the flotation chamber was 5 meters/sec. and a 4.5 Kg particulate fraction precipitated out from the flotation stream while the remaining 5.5 Kg fraction remained suspended in the flotation stream.

The precipitated particulate fraction from the pneumo-gravitational separation stage including a predominance of chrome salts, chromates and ferric and ferrous compounds, was then collected and transported for further processing in a chemo-thermal separation stage to extract higher purity mineral values from the product obtained from the pneumo-gravitational separation stage.

SUBSTITUTESHEET With regard to the residual particles which remained in the flotational stream, these particles were separately collected and have been found to be valuable by-products of the method suitable for use as binding or filler materials for use in mines.

In the chemo-thermal separation stage, the precipitated particulate fraction from the pneumo-gravitational separation stage was introduced into a plasma reactor of the type illustrated in FIG. 6 wherein a plasma having a temperature of about 10,000°K was generated employing methane as a reducing plasma gas and the plasma arc was caused to rotate about an eight segmented anode at a rate of about 30,000 RPM which resulted in the separation of essentially pure elemental chromium and chromium salts as well as elemental iron.

This mixture of chrome and iron materials was subjected to an electromagnetic separation step in order to extract the essentially pure chromium materials from the essentially pure iron. The embodiment of this invention depicted in Fig. 4 utilizes sand dredged from the bottom of a body of water such as an ocean, sea or lake as the raw material mineral value source. Preferably, the sand for use herein which will be referred to as "sea sand" is collected from a location in close proximity to a mining operation or an industrial plant which disposes wastes into the body of water. In the illustrated example, a 10 Kg sample of particulate sea sand was employed as the raw material mineral value source. The sea sand sample had a mineral value content which was present in the form of the

SUBSTITUTESHEET following mineral containing compositions on a weight percentage basis:

The 10 Kg sea sand sample was initially introduced into a magnetic separator having a weak magnetic field of up to about 5 Kilogaus in order to separate a highly magnetic fraction of predominantly ferrous materials from the non-magnetic and less magnetic components of the sample. The highly magnetic fraction thus separated weighed 2.8 Kg and contained 97% Ilmenite and 3% of such mineral containing compositions as Garnet, Amphibole, Epidote and Tourmaline. This magnetic fraction was then introduced in particulate form into a plasma reactor of the type illustrated in FIG. 6 and this particulate material was subjected to the chemo-thermal processing technique as described in regard to the operation of such reactor whereby 98.6% pure iron and 99.4% pure Ti 0_ was extracted from the treated Ilmenite rich fraction.

The remaining non-magnetic and less magnetic fraction weighing 7.2 Kg was transported from the magnetic separator and was subjected to an electrostatic separation process with the positive potential up to 50 kV. This electrostatic separation caused the treated fraction to separate into two portions. The first portion constituting the conductive materials weighed 2.9 Kg and the second portion constituting the dielectric and non-conductive materials weighed 4.3 Kg.

SUBSTITUTESHEET ISA/EP The first conductive portion included such mineral containing materials as Garnet, Amphibole, Epidote, Tourmaline and Rutile and was further treated in order to separate "semi-magnetic" materials therein from the non-magnetic fraction by subjecting the 2.9 Kg sample to magnetic separation in a strong magnetic field of up to 16 Kilogaus. The separated semi-magnetic material represented the residue from the process weighing 1.6 Kg. The remaining separated material weighing 1.3 Kg was collected and cleaned by a subsequent electrostatic separation treatment whereby any remaining dielectric materials were removed as residue and the conductive materials weighing 7 Kg and constituting a 96% Rutile concentrate along with 4% impurities predominantly including Garnet as well as Zircon, Amphibole, Epidote and Tourmaline was collected for further processing in a plasma reactor of the type illustrated in FIG. 6 which was operated in accordance with details provided relative thereto. The resulting composition extracted as a result of such chemo-thermal processing in the plasma reactor contained 99.8% pure Ti 0_.

Additionally, the 4.3 Kg dielectric and non-conductive second portion referenced above was collected and subjected to magnetic separation in a strong magnetic field of up to 16 Kilogaus resulting in two additional fractions being separated. One such fraction included the magnetic minerals in the portion and weighed 0.5 Kg. This magnetic material fraction comprised 98% Monazite along with 4% impurities such as Zircon, Garnet, Amphibole, Epidote and Tourmaline. This 98% Monazite fraction was collected and treated in the plasma reactor in order to obtain 99.3% pure lanthanum oxides.

SUBSTITUTESHEET ISAEP With regard to the non-magnetic fraction of the above referenced two fractions, this fraction weighing 4.15 Kg was transported for further electrostatic separation whereby a Zircon concentrate was obtained as the dielectric output of the electrostatic separation with the conductive residue separated therefrom. The Zircon concentrate weighed 2.1 Kg which contained 97% Zr Si 0. and 3% impurities comprising mainly Rutile and small quantities of other materials such as Garnet, Amphibole, Epidote and Tourmaline. This Zircon concentrate was also treated in a chemo-thermal processing stage by introducing the particles into a plasma reactor of the type described and illustrated in FIG. 6 in order to obtain 99.5% pure Zi 0₂ and 99.8% pure Si 0₂. T e conductive material weighing 2.05 Kg was separated and represented the residue from the process. This residue was combined with the residue from the prior stages for disposal.

In FIG. 5, a pneumo-gravitational separation apparatus 50 is schematically illustrated which is suitable for use in extracting mineral values from mineral containing particulate raw materials introduced therein. The apparatus 50 has a longitudinally extending housing 52 which is rectangular in lateral cross-section. The housing 52 includes a flotation chamber 54 therein and has an inlet port 56 with an adjustable chute 58 such as a vibrating conveyor or the like depending therefrom and extending into the chamber 54 for introducing the particulate materials into the chamber 54 at a desired angle of entry. Another inlet port 60 is provided in

SUBSTITUTESHEET ISA/EP housing 52 for allowing air to be introduced into the chamber 54 via operation of a fan or blower 62 fixedly positioned proximal to a first end 64 of the housing 52. The housing 52 also includes at least one outlet port, which as illustrated is represented by ports 66 and 68 which are positioned to enable recovery of precipitated mineral value fractions resulting from treatment of the particulate raw materials input into the chamber 54. An outlet port 70 is provided at a second end 72 of the housing 52 distal from the first end 64 for enabling recovery of an unprecipitated fraction of residual mineral containing particulate materials from the treatment of the particulate raw materials.

In a preferred embodiment, the inlet port 56 is positioned longitudinally from the outlet end 72 of the chamber 54 a distance determined by the formula:

C H V in 9

L = F d² 2f_t

wherein L is the longitudinal distance of the inlet port through which the particles are introduced into the chamber from the end of the chamber through which the particles exit from the chamber; C is a constant which is calculated on the basis of Reynold's No. and, in the case of a laminar flow of air in the chamber, has been determined to be 18; V is the velocity of gas (e.g., air) flowing through the chamber; m is the dynamic viscosity of the gas; F is the cross-sectional area of the chamber; d is the average diameter of the particles being introduced into the chamber through the inlet port; ^_c is the specific weight of the particles and H is the height of the chamber.

SUBSTITUTESHEET ISA/EP In operation, air is blown into the chamber 54 by fan 62 and creates a laminar air flotation stream along a fixed horizontal axis 74 extending from the exit nozzle 76 of the fan 62 to the distal end 72 of the housing 52. The particulates are introduced into chamber 54 through port 56 and chute 58 is adjusted to provide a desired angle of entry for the particles (angle o( ) into the chamber 54. Angle ok may be varied in a range of between about 12° and about 75° relative to the axis 74 in order to accommodate differing weight raw materials. Preferably, chute 58 is structured to vibrate or oscillate in a manner such that the particles exiting therefrom and entering chamber 54 will be shaken sufficiently to avoid agglomeration of the particles. Legs 76 and 78 are provided for supporting housing 52 in a stable condition removed from the floor 80. Standard control mechanisms 82 and 84 for adjusting the height of the legs 76 and 78 are positioned on the legs 76 and 78, respectively. These mechanisms 82 and 84 are independently operable to raise or lower the housing 52 in order to tilt the flotation chamber 54 in the housing 52, if desired, and to thereby adjust the angle (angle _ ) between the fixed horizontal axis 74 and the longitudinal axis of the chamber. In this manner, the distance which the particles entering the chamber 54 must fall before coming into contact with the flow of air may be adjusted as required to accommodate various weight raw material particles. In practice, it has been found that for best results this angular adjustment should range from about -60* to 0^β (horizontal) for lighter weight mineral value particles and from about +60° to 0° (horizontal) for heavier weight mineral value particles.

In FIG. 6 there is shown schematically a plasma reactor 100 suitable for processing particulate raw

SDBSIIϊϋlE S3BET materials such as the unprecipitated mineral containing fractions recovered from a pneumo-gravitational separation stage utilizing an apparatus as illustrated in FIG. 5 or any other such particulate mineral raw materials. The reactor 100 includes a plasma head 102 having a plasma gun or torch 104 vertically mounted therein. The plasma gun 104 is structured and dimensioned for introduction of a suitable plasma gas for purposes of establishing a downwardly directed, central plasma arc or stream 105 extending from a cathode 106 to a multi-segmented annular anode assembly 108 positioned in a reaction chamber 110 downstream of the head section 102. The plasma head 102 has channels 116 formed therein which extend upwardly and are in communication with dispensing equipment or metering devices (not shown) for introducing particulate mineral containing raw materials into the reaction chamber 110. Positioned downstream of the reaction chamber 110 is a cylindrical cooling chamber 112 which leads vertically downward to a conical section 114 wherein a countercurrent flow of air is introduced through an inlet port 138 for purposes of blowing certain residual cooled materials descending from the chamber 110 out through an outlet port 140 as will be described in detail below. in operation, once the particles are introduced into the chamber 110, they are contacted by the plasma arc 105 and the particles are heated to a high temperature in an environment wherein the plasma arc 105 is revolving or circulating as shown by arrow A in FIGS. 7 and 8 at greater speeds than can be attained with previous methods and devices.

FIG. 7 is a schematic illustration of a particular embodiment of the plasma reactor of the present invention looking downwardly from the cathode 106 toward the anode

SUBSTITUTESHEET 108 along the path of the plasma arc 105 in the reaction chamber 110. The region between the cathode and anode will be referred to herein as the reaction zone 118. The reaction zone 118 normally contains a gas suitable for plasma formation when a sufficient voltage from an external source (not shown) is applied between the anode 108 and cathode 106. The path of the plasma arc 105 from cathode 106 to anode 108 will be referred to herein as the axis of the reaction zone. As illustrated, the plasma arc 105 is directed from the cathode 106 to a segmented annular anode 108 having eight separate segments electrically insulated from one another to which the plasma arc is sequentially directed resulting in a rotating plasma arc. A segmented anode having up to six segments has previously been described in U.S. Patent No. 4,361,441 which is hereby incorporated by reference into the present disclosure. In the apparatus described in the '441 patent, sequential activation of the anode segments causes the arc to move in a circular fashion at a velocity up to about 6,000 RPM according to the frequency at which the separate segments are activated. Electrical switching means are used to effect the sequential activation of the anode segments. To assist in rotating the plasma arc, the '441 apparatus also uses a rotating magnetic field which, owing to the charged nature of plasma, causes the arc to experience a force perpendicular to the applied magnetic field and the velocity of the arc. An array of solenoid coils arranged around the periphery of the plasma arc path and sequentially energized by an external source is used to generate the rotating magnetic field.

As noted above, the present invention also employs a segmented anode 108. However, unlike the '441 apparatus, the present invention employs no electrical switching circuitry to cause the plasma arc to jump from one anode

SDBSmUII. SHEET segment to another. Rather, as described in detail below, magnetic fields are used to rotate the plasma arc 105 from one anode segment to the next as depicted by arrow A. This means that the rotational velocity of the plasma arc is not dependent on any frequency at which electrical switching elements can be activated. Much greater rotational velocities of up to about 30,000 RPM, therefore, can be attained than has been possible with such prior devices. Referring to FIGS. 7 and 8, the annular segmented anode 108 has a plurality of solenoid coils 120 arranged around its periphery. Each coil 120 is wrapped around a low reluctance annular core 122 with its axis oriented perpendicular to the axis of the reaction zone 118. In a preferred embodiment, there are two such coils 120 for each anode segment located 90° on either side of that anode segment. Thus the total number of coils 120 equals twice the number of anode segments. FIGS 7 and 8 show an eight-segmented anode with the segments separated by insulating material 124. For simplicity, however, only four coils 120 are shown in FIG. 7, designated 120a, 120a', 120b, and 120b'. Anode segment 108a is electrically connected to coils 120a and 120a' while anode segment 108b is electrically connected to coils 120b and 120b*. Coils 120a and 120b are wrapped around the same portion 126 of core 122 in opposite directions. Coils 120a¹ and 120b' are similarly wrapped around the opposite core portion 122. Each of the coils 120 is also connected to an electrical ground, designated 130. Thus, each anode segment is maintained at a constant electrical potential by two paths to ground in which is interposed a solenoid coil 120 located on the periphery of the reaction zone 118 and oriented so that its longitudinal axis is parallel to a line drawn from the center of the annular anode 108 to

SDKIKUIE SϋEEf the particular anode segment to which it is connected. When a plasma arc discharge 105 takes place between the cathode 106 and a particular anode segment, an electrical current flows between the anode segment and ground which thus energizes the two solenoid coils associated with that segment (e.g., coils 120a and 120a'). The purpose of the coils 120 is to generate a magnetic field oriented radially and pointed toward (or away from) the anode segment conducting the plasma discharge. As shown in FIG. 7, the pair of coils 120a and 120b arranged on opposite sides of the periphery of the arc's path when energized produce a radially oriented magnetic field vector B_j. The magnetic field B₁ therefore causes the plasma arc 105 to experience a circumferentially directed force at right angles to B₁ which is proportional to the arc's axial velocity along the path from cathode to anode.

The plasma reactor 100 of the present invention thus operates as follows. All of the anode segments are connected to ground (or other constant potential) through separate pathways each of which includes a solenoid coil 120. When the cathode is initially energized, a plasma discharge occurs between the cathode 106 and one of the anode segments 108 when the breakdown potential of the gas within the reaction chamber is reached and a conductive plasma pathway is formed. If no other forces were present, the resulting plasma discharge would either remain stationary or jump from anode segment to anode segment at random. The magnetic field B-, however, forces the arc circumferentially and causes it to jump to the adjacent anode segment. That anode segment in turn energizes another pair of solenoid coils which further rotates the plasma arc to another adjacent anode segment and so on. In this manner, the plasma arc is made to rotate continuously at a rate independent of any electrical switching frequency.

SDBSlill'IESHEET In order to impart even more angular velocity to the plasma arc, the present invention employs another solenoid 132 wrapped around the periphery of the reaction zone 118 and coaxial with the axis of the reaction zone 118. The coaxial solenoid 132 when energized by an external power source thus causes another magnetic field B_≥ directed axially along the plasma arc path as depicted in FIG. 8. The field B₂ therefore causes any charged particles moving with a radial or circumferential velocity component to experience a force directed perpendicularly to that velocity component. The plasma arc is given a radial velocity component by the segments of the annular anode being arranged near the periphery of the arc path which tends to cause the plasma arc to bend radially outward. The magnetic field B₂ thus converts the radially directed linear momentum of the charged particles into angular momentum and causes the arc to rotate. Furthermore, the resulting circumferential velocity component of the rotating plasma arc (caused by both magnetic fields B_t and B₂) is acted upon by the field B₂ which tends to draw the arc radially inward. This provides the centripetal force necessary to maintain rapid rotation.

Previous methods of imparting angular momentum to the plasma arc, such as disclosed in the '441 patent cited previously, have relied exclusively on the rotation of an external magnetic field rotated by electrical switching means and the sequential activation of anode segments also by electrical switching means, to cause rotation of the plasma. This means that the angular velocity of the plasma can be no greater than the frequency of the electrical switching. The present invention, in contrast, suffers from no such limitation and is therefore able to impart a much greater rotational velocity to the plasma arc.

msmπz. SΉEET Thus, in the practice of the method of the present invention, atmospheric air or oxygen has been employed as the plasma gas to produce essentially pure aluminum oxide and titanium oxide from a precipitated particulate fraction derived from the pneumo-gravitational separation of fly ash. The temperature generated in the reaction chamber 110 of the plasma reactor 100 was about 10,000° K and the arc was caused to revolve or rotate about an eight segmented anode 108 at a velocity of about 16,000 RPM. The particulates were introduced into the top of the vertically aligned reactor chamber 110 through channels 116 at a rate such that they descended in a spiral through the plasma arc.

As the particles descend through the arc in the reaction chamber 110, the desired mineral values therein (such as, aluminum oxide and titanium oxide) melt while the remaining constituents of the introduced particles such as magnesium either crystallize or evaporate. Thus, as the treated materials exit from the reaction chamber 110 through anode 108, they enter cylindrical cooling chamber 112 and descend through temperature gradients therein as the melted mineral values agglomerate into relatively dense particles, the crystallized residuals form dust-like particles and the evaporated components form gases. Then, as the resulting cooled components reach the lower section of the cooling chamber 112, they contact a product guide or collector plate 134 which is positioned centrally within the chamber 112 for purposes of causing the relatively denser agglomerated mineral value particles such as aluminum oxide and titanium oxide to separate out from the other descending materials. Furthermore, plate 134 acts to direct or guide the separated mineral value particles in a proper downward direction through conical section 114 to enable collection thereof at the bottom end 136 of the conical section 114.

SUBSTITUTESHEET In section 114, a countercurrent flow or swirl of air is directed from an inlet port 138 upwardly to an outlet port 140 in order to cause the dust-like particles and the gases accompanying the agglomerated minerals to separate out from the agglomerates and to be blown out of the reactor 100 through outlet pipe or tube 141 associated with outlet port 140.

In construction, an air inlet pipe or tube 142 is associated with inlet port 138 and the axis 144 of pipe 142 is aligned at an angle X relative to a horizontal axis 146 through the mid-point or center of port 138. Therefore, angle X essentially defines the angle of entry of air into the conical section 114 of the reactor 100. In a preferred embodiment of this invention, the angle X should be about 15°. However, the appropriate dimension of angle X for any particular treatment depends on a variety of factors including the speed or velocity of the air being introduced through port 138, the specific weight or density of the material being treated and the angle of the cone (angle Y as illustrated) . In this regard, it should be noted that angle X may be increased as high as 90° (i.e., air will be introduced from the bottom of the cone) for very high density materials.

The preferred angle of the cone (angle Y) is about 30°. However, as a result of experimentation, it has been found that for processing of raw materials having a high concentration of iron and chromium therein such as those derived from foundries, angle X should range from about 0° to about 37° and angle Y should range from about 10° to about 30°. For raw materials having a high concentration of copper, nickel or cobalt such as those derived from mines or foundries, angle X should range from about 5° to about 30° and angle Y should range from about 15° to about 40°. For treatment of raw materials having a high

SDBSΠΓCTESHEET concentration of zirconium such as those derived from sea sand, angle X should range from about 0° to about 15° and angle Y should range from about 30° to about 40°. For raw materials having a high concentration of aluminum oxide and titanium oxide, angle X should range from about 0° to about 30° and angle Y should range from about 20° to about 40°.

In order to accommodate such varying angular alignments for treating various raw material sources, in .one embodiment of the present invention the conical section 114 of the reactor is provided as an interchangeable part so that variously configured piece parts may be installed onto the body of the reactor 100 as desired. Another important feature in the construction of the conical section 114 of the reactor 100 is the positioning of the port 138 and its accompanying air inlet 142. In this regard, it has been found that in a preferred embodiment, the mid-point of the port 138 should be a height h, above the bottom end 136 of the conical section 114 of about 1/4 of the total height h of the section 114. The height h for any embodiment of the section 114 may be calculated as a function of the cone angle Y employing the equation:

h 5 - 1/2 d5_β (tangent Y)

wherein d_s is the diameter of the cone 114 at the horizontal top edge 148 of the section 114. In this regard, the diameter d of the cone 114 may be calculated from the further equation:

SUBSTITUTESHEE? wherein d is the diameter of the cylindrical cooling chamber 112.

A further important feature in the construction of the reactor 100 is the provision of an appropriately angled wall section 150 positioned horizontal bottom edge 152 of the cylindrical cooling chamber 112 and the horizontal top edge 148 of the conical section 114. The wall 150 circumferentially interconnects and seals the chamber 112 and the cone section 114. In a preferred embodiment of this invention, the wall 150 is positioned at an angle Z relative to the horizontal top edge 148 of the conical section 114 such that the air introduced into the section 114 through inlet port 138 at angle X will be directed by wall 150 in a desired upward direction in order to contact the descending materials exiting from the cooling chamber 112 and to cause the relatively lower density materials therein such as the dust-like particles and the gases to ascend through a centrally located tube or funnel arrangement 154 to contact the descending particles and to direct the lower density materials to the outlet port 140 where they exit through outlet pipe 141 and are collected as residuals of the method of this invention.

In preferred embodiments of this invention, angle Z may range from about 35° to 60°, and most preferably should be about 45°. However, angle Z may be varied as desired to achieve optimum aerodynamic conditions within the conical section 114 for guiding and directing the air introduced at port 138 to the outlet port 140 either in a direct air flow pattern or in a swirling, spiraling or revolving flow stream.

If desired, a ventilation device (not shown) may be associated with outlet pipe 141 to assist in the collection of residual materials.

SUBSTITUTESHEET The velocity of the air being introduced into the conical section 114 is a further important factor to be considered in regard to the operation of the reactor 100 of this invention. For example, it has been found that in general, the velocity of the air being introduced into section 114 through port 138 should be in the range of about 1 to 20 meters/second. The speed of air is regulated depending on the density of the mineral values being extracted with higher speeds generally being employed for the heaviest or most dense particles such as ferro-chrome, while lower speeds are employed for less dense materials. For example, when a fly ash raw material particulate is treated in the reactor, it has been found that air velocity of about 1.7 meters/second should be introduced into the conical section 114 through port 138. Additionally, it has been found that provision of an electromagnet 156 annularly encircling the lower section of the cylindrical cooling chamber 112 may be desirable for certain applications of the reactor 100. Specifically, in order to perform certain separation treatments on the plasma treated materials derived from metallurgical slag or foundries, operation of this electromagnet 156 may be of value in separating the mineral values from the residuals. However, for processing fly ash particulates, such eletromagnetic operation normally is not required.

Although the invention has been described in its preferred forms with a certain degree of particularity, it is to be understood that the present disclosure has been made by way of example only. Numerous changes in the details and operational steps of the method and in the materials utilized therein will be apparent without departing from the spirit and scope of the invention, as defined in the appended claims.

SUBST_ITUTESHEET

Claims

I Claim:

1. A method for chemo-thermal separation of mineral values from mineral containing particulate material comprising: introducing said particulate material and a plasma gas into a reaction chamber of a plasma reactor and ionizing said gas to produce a rotating plasma arc discharge in a reaction zone between two stationary electrode structures in said reactor when a sufficient voltage is impressed across the electrode structures, one of said electrode structures being a cathode and the other of said electrode structures being a multi-segmented annular anode with each anode segment electrically isolated from the remaining segments, said arc rotating about the segmented anode at a rate of at least 15,000 RPM; subjecting said particulate material to said rotating plasma arc in said reaction zone to heat the mineral values in said particles to a temperature exceeding the melting temperature of said mineral values causing said mineral values to liquify; and transporting said liquified mineral values from said reaction zone through a cooling zone in said reactor wherein said liquified mineral values agglomerate into relatively dense particulate form for collection in essentially pure form.

2. The method of claim 1 wherein said agglomerated particles are transported from said cooling zone through a countercurrent flow zone in which said agglomerated particles are subjected to a countercurrent flow of air such that said agglomerated particles pass through said flow of air and residuals associated with said agglomerated particles are separated therefrom for collection separately from said agglomerated particles.

SUBSTITUTESHEET

3. The method of claim 2 wherein said countercurrent flow zone comprises a conical section having an inlet for introducing air into said conical section and an oulet for removing said residuals with said air from said conical section.

4. The method of claim 1 wherein said particulate material has a radial particle size of less than about 0.1 mm.

5. The method of claim 1 wherein said raw material is selected from the group consisting of fly ash, flue dust, slag, coal, foundry waste materials, mining residues, sea sand and mixtures thereof.

6. The method of claim 5 wherein the foundry waste material is a metallurgical slag produced in a ferro-chrome manufacturing process.

7. The method of claim 5 wherein the fly ash is produced from a blast furnace slag.

8. The method of claim 1 wherein said collected essentially pure mineral values are selected from the group consisting of aluminum oxide, titanium oxide, iron, chromium, nickel, cobalt, lead, zinc, copper, zirconium and mixtures thereof.

9. The method of claim 2 wherein said collected residuals are subjected to further processing to produce a cementitious building material.

10. A plasma reactor for use in separating mineral values from mineral containing particulate material comprising:

SUBSTITUTESHEET a first stationary electrode; a second stationary electrode of annular shape divided into a plurality of segments electrically insulated from one another; a reaction zone positioned between the first and second electrodes through which a plasma arc traverses when sufficient voltage is applied across the two electrodes, the longitudinal axis of the reaction zone being a vertical line from the first electrode to the center of the annular second electrode; and, a solenoid coil connected between each second electrode segment and a region of constant potential, the coil being positioned at a point around the periphery of the second electrode 90° from the electrode segment to which the coil is connected and being oriented so that the longitudinal axis of the coil is parallel with a line from the center of the second electrode to the electrode segment to which the coil is connected.

11. The plasma reactor of claim 10 wherein each said second electrode segment is connected to a region of constant potential through a path containing two solenoid coils arranged around the periphery of the second electrode located 90° on either side of the second electrode segment to which the coils are connected and being oriented so that the longitudinal axes of the coils are parallel with a line drawn from the center of the second electrode to the second electrode segment to which the coils are connected.

12. The plasma reactor of claim 10 wherein the solenoid coils around the periphery of the second electrode are wrapped around a low reluctance annular core.

_SUB_STITUTESHEET

13. The plasma reactor of claim 10 including a coaxial solenoid coil which encircles the periphery of the reaction zone, said coaxial solenoid coil having its longitudinal axis coincident with the axis of the reaction zone for producing an axially oriented magnetic field when the coaxial solenoid is energized.

14. The plasma reactor of claim 10 wherein a cooling zone is provided in said reactor positioned vertically below said reaction zone for receiving materials heated in said reaction zone and for allowing said materials to cool therein before being collected.

15. The plasma reactor of claim 14 wherein a countercurrent flow zone is provided in said reactor positioned vertically below said cooling zone into which said cooled materials are transported from said cooling zone and wherein said materials are subjected to a countercurrent flow of air such that desired materials pass through said flow zone and are collected at the bottom of said zone while residual materials are removed for collection at a location remote therefrom.

16. The plasma reactor of claim 15 wherein said countercurrent flow zone is a conical section and said countercurrent flow of air is directed upwardly from an inlet in the conical section to an outlet therein.

17. The plasma reactor of claim 16 wherein the angle of said cone is in a range of about 0° to about 40°.

18. The plasma reactor of claim 17 wherein the angle of entry of air into said conical section is about 15°.

SUBSTITUTESHEET

19. The plasma reactor of claim 16 wherein the mid-point of said inlet is positioned about 1/4 of the total height of the conical section measured from a bottom edge of said conical section.

20. The plasma reactor of claim 16 wherein an angled wall section circumferentially interconnects said cooling zone and said conical zone, said wall section being angled at an angle of about 35° - 60° relative to a horizontal top edge of said conical section.

SUBSTITUTE SHEET