WO2006094283A2

WO2006094283A2 - Process and apparatus for manufacturing metal oxides

Info

Publication number: WO2006094283A2
Application number: PCT/US2006/008045
Authority: WO
Inventors: Peter Blonsky; Michael Kirksey; Romuald Drlik
Original assignee: Spheric Technologies, Inc.
Priority date: 2005-03-03
Filing date: 2006-03-03
Publication date: 2006-09-08
Also published as: WO2006094283A3

Abstract

Processes and apparatus for manufacturing a metal oxide product and byproduct hydrogen, in which sacrificial electrodes are covered by water in a reaction zone and an electrical potential is applied across the electrodes to form an electrical discharge plasma zone between the electrodes causing formation of the metal oxide and hydrogen at the plasma zone. A sol of the metal oxide product and byproduct hydrogen are withdrawn from the reaction zone.

Description

PROCESS AND APPARATUS FOR MANUFACTURING METAL OXIDES

This International Application, filed under the provisions of the Patent Cooperation Treaty, asserts convention foreign priority based on copending

International Application, filed under the provisions of the Patent Cooperation Treaty,

Serial No. PCT/US2005/006856, filed March 3, 2005, WIPO Publication 2005/089930; and USA Provisional Application, Serial No. 60/735,236, filed November 9, 2005.

The disclosures of said International Application PCT/US2005/06856 (WO

2005/089930) and said USA Provisional Application, Serial No. 60/735,236 are

hereby incorporated herein by reference.

As to the United States, this application is a continuation-in-part of said

International and Provisional applications.

This invention relates to processes and apparatus for manufacturing metal oxide products.

More particularly, the invention concerns an electrochemical process and

apparatus for practicing such process, in which the metal oxide is formed from at least

one sacrificial electrode and another electrode, sacrificial or not, immersed in water,

at an electrical arc plasma zone between the electrodes. In another and more particular respect the invention pertains to such processes,

and apparatus useful in practicing such processes, in which the electrical arc plasma

zone is continuously maintained and the metal oxide and byproduct hydrogen are continuously formed at the plasma zone.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other, further and more particular aspects of the invention will be apparent to those skilled in the art from the following description thereof, in which:

Fig. 1 is a flow sheet depicting the various steps of an embodiment of the

process and apparatus of the invention;

Fig. IA is a flow sheet depicting the various steps of an alternate embodiment of the process and apparatus of the invention;

Figs IB is a flow sheet depicting still another alternate embodiment of the process and apparatus of the invention;

Fig. 2 is a flow sheet depicting the presently preferred embodiment of the

process and apparatus of the invention; Fig. 3 illustrates the general features of a reactor for practicing the process of

Fig. 2.

FIELD OF THE INVENTION

There is an ever increasing commercial demand for metal oxides, especially high-purity finely divided products. For example, compounds such as cadmium oxide

and black nickel oxide are widely used in rechargeable batteries for industrial emergency instrumentation, as in power transformer stations, airport runways, railroad switching equipment, etc., and aluminum oxide has wide usage, for example, in the

food and chemical industries in manufacturing spark plugs, in industrial abrasives, etc. This invention pertains to processes and apparatus useful in manufacturing metal

oxide products and which also produce useful byproduct hydrogen.

THE PRIOR ART

Various prior processes for manufacturing metal oxides include calcining of

naturally occurring ores, chemical precipitation, electroexplosion, hydrothermal processes, etc., which require large, complicated and expensive fixed manufacturing

equipment and which have high raw material and operating expenses.

U.S. Patent 6,506,493 describes a process for manufacturing manganese oxide by laser pyrolysis of an aerosol of the oxide precursor. Published USA Application 20040009118Al describes producing metal oxide particles by generating an aerosol of the solid metal, injecting the aerosol into a

microwave plasma zone to vaporize the particles and then injecting the heated metal

particles into a cooler oxygen- containing zone where the metal is oxidized and then

condenses to form particles of the metal oxide product.

EP 1308417A3 discloses production of a metal oxide by controlled heating a metal salt of a carboxylic acid.

Published USA Application 20030167796A1 describes a thermal process for producing metal oxide by burning a flame formed from a combustible gas containing a metal oxide precursor.

U.S. Patent 5,789,696 discloses a method of propelling a projectile in which the propellant chamber contains water, an aluminum wire and powdered aluminum. The aluminum wire is exploded by an electrical pulse, thermally initiating a reaction

between the aluminum powder and the water, producing large quantities of hydrogen

which propels the projectile. This technology is not directed to the production of

metal oxides. A similar process, for production of hydrogen, is disclosed in U.S.

Patent 5,143,047.

Molten aluminum is reacted with water vapor in the process described in U.S. Patent 3,985,866. Kumar et al, J. Mater. Res. 3(6), Nov/Dec 1988 discloses a process for producing metal compounds in which a series of arcs are produced between sacrificial

electrodes submerged in a dielectric fluid. These arcs form "spark zones" or plasma

zones in a reactor. Part of the vaporized metal of the sacrificial electrodes is oxidized

in the plasma zone, forming colloidal metal oxide particles and part of the metal is

melted, forming relatively large spherical droplets which collect in the bottom of the reactor.

European Patent Specification 0 055 134 Bl discloses apparatus in which

metal oxide collecting on the reactive faces of electrodes is avoided by continuous relative movement of the electrodes to expose fresh unoxidized surfaces.

It would be highly desirable to provide manufacturing processes and apparatus

for preparing high-purity metal oxide products, using relatively simple processing equipment which has relatively low operating costs, using readily available relatively

low-cost raw materials. It would also be highly desirable to provide such processes

and apparatus in which the plasma zone is continuously maintained to minimize the

formation of melted metal droplets rather than conversion of the sacrificial metal to

the corresponding metal oxide. Also, such a process and apparatus would preferably

permit the colloidal particles, dispersed in the dielectric fluid, to be rapidly and conveniently removed from the reactor and separated from the dielectric fluid, would

preferably avoid masking of the reactive face(s) of the electrodes by a metal oxide

coating and, even more preferably, permit the inexpensive and convenient separation

of the metal oxide particles in the colloidal dispersion ("sol") from the dielectric fluid. I have now discovered such processes and apparatus, which are used to

manufacture high purity metal oxides and byproduct hydrogen by the electrical

plasma-phase reaction of an elemental metal vapor and oxygen, to produce the corresponding metal oxide product and byproduct hydrogen in which such desired

results are obtained.

BRIEF DESCRIPTION OF THE INVENTION

The Prior Art Processes

The prior art processes, which are improved by the present invention, include

the steps of introducing an aqueous dielectric fluid into a reaction zone, positioning an electrode pair in said reaction zone, at least one of which is a sacrificial electrode formed of the metal which is the metal moiety of the metal oxide product, applying an electrical potential between the electrodes sufficient to create an arc between them,

forming a plasma zone in the fluid between the electrodes and forming a sol of the

metal oxide product particles in the dielectric fluid in the locus of the plasma zone.

The Improvements of the Present Invention

hi one presently preferred embodiment of the invention, the improvement comprises,

in combination with the above-defined prior art steps, the steps of providing a reaction

zone having an upstream portion and a downstream portion; establishing a flow of sol

toward the downstream portion of the reaction zone; and withdrawing the sol from the

downstream portion of the reaction zone. In another presently preferred embodiment of the invention, the improvement comprises, in combination with the above-defined prior art steps, the step of directing

sonic energy to the reactive face(s) of the electrode(s) to prevent or substantially

reduce masking of the faces by metal oxide films.

In another presently preferred embodiment of the invention, the improvement comprises, in combination with the above-defined prior art steps, the steps of

withdrawing the metal oxide sol from the reaction zone; and spray drying the metal oxide sol formed at the plasma zone.

hi still another presently preferred embodiment of the invention, the improvement comprises, in combination with the above-defined prior art steps, the

steps of

(a) providing a reaction zone having an upstream portion and a downstream portion;

(b) establishing a flow of the dielectric fluid and sol toward the

downstream portion of the reaction zone;

(c) directing sonic energy to the reactive face(s) of the electrode(s) to

prevent or substantially reduce masking of the faces by metal oxide films; (d) withdrawing the metal oxide sol from the reaction zone; and

(e) spray drying the metal oxide sol formed at the plasma zone.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings like reference numerals identify the same elements in the

several views.

A fluid-tight reaction vessel 10 is provided with a pressure relief valve 11. Elongate sacrificial electrodes ("Me"), formed from the elemental metal moiety of the

desired metal oxide product (MeO) are axially fed into the vessel 10 by electrode feeders 12. Optionally, the inner opposed ends of the electrodes are also held spaced

apart a minimum distance by a ceramic grate 13 and immersed in water 14.

Electrical power ("P") 20 is supplied to a high-voltage, low-current power

supply 21 and a lower- voltage, constant current power supply 22. Power control circuitry 23 selectively feeds either high voltage-low current electrical power from the

power supply 21 or lower- voltage, high current electrical power from the power supply 22, thru circuit 24 to each of the sacrificial anodes in a manner hereafter

described in Figs. 2-4, to initiate and maintain an electrical arc plasma zone in the

space 25 between the inner opposed ends of the sacrificial electrodes.

The pressure in the reactor 10 is maintained at below the relief pressure of the

valve 11 by venting hydrogen gas through valve 30, through the conduit 31 to dryer

32, from which the dried hydrogen 33 is compressed 34 and accumulated in storage cylinder 35. A suspension ("sol") of the metal oxide formed at the plasma zone 25 in water is withdrawn through valve 51 and sent via conduit 52 to a filter 53 to separate the solid metal oxide 54 from the water 55. The metal oxide 54 is dried 56 and may be

subjected to optional sizing steps, etc. to produce the final metal oxide ("MeO")

product 57.

The water 55 separated from the mixed metal oxide- water suspension 52 may be cooled at cooler 58, sent to an accumulator 60 and then recirculated via conduits 50

to the reactor 10. Makeup water ("H₂O"), to maintain a sufficient level of water 14 in the reactor 10 covering the sacrificial electrodes is added via inlet line 59 to the accumulator 60. The pump 61 raises the pressure of the water in the lines 50 to a pressure sufficiently above the pressure in the reactor 10 to maintain the flow of

recirculated water 55 and makeup water 59 through the lines 50 into the reactor 10

and provide a water bearing around the electrodes 40 to assist moving them through the electrode feeders into the reactor 10. The axial position of the electrodes can be

automated by using suitable means known in the art, e.g., by using electrical step

motors, by using mechanisms similar to those employed in maintaining the axial

positions of carbon rods in carbon arc lamps or by mechanisms similar to those used in feeding arc welding machines.

Referring more particularly now to Fig. 1, in operation, the reactor 10 is

preferably maintained at superatmospheric pressure to minimize the water content of

the byproduct hydrogen and to increase the reaction rate at the electric arc plasma zone 25. The pressure relief valve is set to vent at pressures up to 900 psig and the pressure in the reactor 10 is maintained at up to approximately 800-850 psig. The exact reactor pressure is not critical and higher and lower pressures down to atmospheric pressure are operable.

The temperature of the liquid phase in the reactor 10 is maintained at below

the boiling point of water at the operating pressure selected. This temperature is maintained by cooling 56 the recirculating water 55 fed to the reactor 10 and, if

necessary, by cooling fins added to the reactor and associated water piping. For

example, when manufacturing black nickel oxide, it is preferred to operate the system

such that the temperature of the liquid in the reactor is reduced to about 13° C. For

each metal oxide product the temperature at the plasma zone is preferably maintained at between the melting point and boiling point of the sacrificial electrode metal. For

example, preferred temperatures of the plasma zone for various metals are set forth in Table 1.

TABLE l

Metal Plasma Temperature

Aluminum 1,859

Lithium 1,161

Magnesium 440

Nickel 1,458

Cadmium 446 To insure the purity of the metal oxide product, the water initially charged into

the reactor 10 and the makeup water added via inlet line 59 is preferably distilled

water.

The electrical power 24 applied to the sacrificial anodes is regulated by controller 23 to furnish an initial high voltage surge from the high voltage power

supply 21, on the order of 2,000 volts, so as to strike the arc between the sacrificial electrodes at a spacing of approximately 1/4 -1/2 inch. After the arc is established and the current spikes upwardly, the controller 23 switches the current from the high-

voltage supply 21 to the constant current supply 22, which continues to supply power to the sacrificial electrodes at a lower voltage and higher current on the order of 70

volts and 200 amps. Alternatively, electrical power can be generated by a DC

generator, the ouput voltage of which is controlled by the preselected rotational speed

of the generator. The resistance between the electrodes is measured and the resulting

signal is fed to a computer which shuts the generator down if the resistance indicates

that the electrodes are about to be welded together.

The elongate sacrificial electrodes are sized for convenient handling. In the

presently preferred embodiment of the invention the electrodes are cylindrically shaped, approximately 2 ¹A inches in diameter and 36 inches long.

If less than all of the electrodes are "sacrificial," i.e., formed of the metal

corresponding to the metal moiety of the desired metal oxide product, the other

electrode(s) is/are conveniently formed of a metal or other conductive material which will not unduly contaminate the metal oxide product or which is easily separated from the product. For example, in producing aluminum oxide product, the non-sacrificial electrode can be iridium or gold, as any contamination of the product aluminum oxide is easily separated from the product.

Referring now more particularly to Figs. 2 and 3, it will be appreciated by

those skilled in the art that various features of the process and apparatus of Figs 1, IA and IB would be employed in practicing the process of Figs. 2 and 3. For example,

details such as the construction of the electrode feeders, valves, electrical power

controls, etc. have been omitted or simplified for clarity illustration.

The process of Fig. 2 basically consists of conversion of the Me electrodes in the plasma zone 25 to a sol comprising MeO particles as the disperse phase and water

or other aqueous dielectric fluid as the continuous phase. The reactor (reaction zone)

10 has an upstream fluid inlet portion 201 and a downstream fluid outlet portion 202,

with the electrodes 40 positioned between the portions 201 and 202. A flow of the sol

formed at the plasma zone 25 is established to move the sol in the direction of the

arrows A toward and to and through the downstream portion 202 of the reaction zone

10 so that it collects in the vicinity (indicated by the cross-hatched portion of Fig. 3 of

a collector conduit 204. The collector conduit 204 is preferably an annular pipe with a

plurality of spaced inlet holes in the imier wall communicating between the exterior

and the interior of the conduit 204. A similar annular pipe, with spaced outlets in the

inner wall communicating between the interior and the exterior thereof, can be

employed to distribute incoming water evenly toward the plasma zone. As will be apparent, the flow rates of the inlet water and the outlet sol should be adjusted to

maintain substantially laminar flow through the reaction zone 10, to minimize mixing

the sol with the dielectric fluid below the plasma zone 25.

The sol is urged through the downstream portion 202 of the reaction zone 10 by any suitable technique. For example, introduction of water in the inlet portion 201

of the reaction zonelO and withdrawal of the sol through the collector conduit 204 at substantially the same volumetric rate will cause the desired direction of flow of the

sol to be established. This flow may also be enhanced by a thermal gradient established in the reaction zone 10, caused by heating of the sol at the plasma zone

and further enhanced by cooling the makeup water 59 and/or the condensed vapor

from the spray drier 205 exiting the condenser 206.

Referring more particularly to Fig. 2, the sol 207 is fed to a conventional spray

drier 205. Vaporized fluid 207 from the drier 205 is condensed and cooled 206, mixed with makeup water 59 and recycled to the inlet portion of the reaction zone 10.

The product MeO is collected and packaged for storage and sale. Any unoxidized

metal particles 208 are periodically removed from the reaction zone 10 and can be recast as Me electrode shapes and recycled to the reaction zone 10. Byproduct

hydrogen 208 is vented from the reactor and can be processed and stored as in Figs 1,

IA and IB.

Referring more particularly to Fig. 3, ultrasonic energy can be transmitted by

transducers 209 and focused upon the reactive ends of the Me electrodes in the plasma zone, to minimize the buildup of MeO on the reactive faces of the electrodes. This energy may also assist in establishing the flow of the sol from the plasma zone 25

toward the sol collector 204.

Fig. IA and IB depict alternate embodiments of the invention for purposes of illustration and are not intended as limitations on the scope of the invention, which is

defined only by the appended claims. As shown in Fig. IA, water 59 is distilled 101.

The distilled water is fed to the suction of a high pressure, e.g., 500 psi, pump and this

pressurized distilled water is then used to cool the electrodes. Additional distilled

water 103 is used to backflush the filter 53 Settling tank 104 and is provided to receive the filtrate water 106 from the filter 53. During backflushing, the backflush

water 107 is directed to another settling tank 105. Supernatant water 108 from the settling tanks 104 and 105 and makeup distilled water 111 is fed to the suction side of

a lower pressure , e.g., 90 psi pump 112. The wet underflow MeO product 109 is then

packaged for shipping or dried, for example, in a vacuum drier, depending on the intended use of the product. Byproduct hydrogen 113 passes through a pressure

control valve 11 which maintains the pressure in the reaction vessel 10 at a suitable

pressure, e.g., 90 psi. The byproduct hydrogen is then either vented 114 to the

atmosphere or pressurized by compressor 32 and loaded into storage cylinders for

shipment. In manufacturing certain metal oxide products, e.g., black nickel oxide, I

have found that it is preferable to inject an oxidizing agent 115 such as ozone or

hydrogen peroxide into the reaction vessel. An alternative embodiment of the invention is illustrated in Fig. IB, which is similar to the embodiment of Fig. IA, except that the water-product oxide slurry 52 is

sent successively to a pair of filters, first to a large particle filter 116 and then to a

small particle product filter 117. This embodiment is preferred when the slurry 52

contains relatively large particles such as melted portions of the sacrificial electrode or melted portions of the non-sacrificial electrode.

In the presently preferred embodiment of the process of the invention, the

electrical potential between the electrodes is regulated to continuously maintain the

current density of the arc, thereby continuously maintaining the plasma zone formed between the electrodes, and the metal oxide and byproduct hydrogen are continuously

formed at the plasma zone, thereby minimizing the amount of the unoxidized

electrode metal particles which is formed unoxidized in the reactor.

According to another embodiment of the invention the electrical potential between the electrodes is continuously pulsed to continuously vary the size of the

plasma zone between the electrodes, thereby displacing metal oxide formed on the

opposed surfaces of the electrodes. The pulsing can also be accomplished by

alternately touching the electrodes together and then bringing them apart, to

extinguish and then cause formation of the plasma zone, although this results in

formation of more melted, unoxidized metal particles. According to another aspect of the invention, apparatus is provided to

continuously manufacture a metal oxide product and byproduct hydrogen. The

apparatus of the invention includes a fluid-tight reaction vessel, a pair of electrodes, at

least one of which is an elongate sacrificial electrode, formed of the elemental metal

of the metal oxide product, positioned opposed in the reaction vessel; means for supplying water to the reaction vessel sufficient to cover the electrodes; means for maintain an electrical arc plasma zone therebetween; means for withdrawing a

mixture of the metal oxide product, formed at said plasma zone, from the reaction

vessel; and means for withdrawing the hydrogen byproduct, formed at the plasma zone, from the reaction vessel.

hi still another embodiment of the invention, automatic means are provided to

adjust the spacing between the electrodes, to continuously maintain the electrical arc

plasma. In the presently preferred embodiment of the invention, these means include an electrode carrier which is mechanically, hydraulically or electrically actuated to

control the relative positions of the electrodes. The electrode carrier is responsive to

control signals generated by a computer which, in turn is responsive to selected

process parameters such as pressure in the reaction vessel, temperature of the water- oxide mixture, electrode temperature, and the like, to optimize the oxide production

rate. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, in which like reference numerals identify the

same elements in the several views, Figures 1, IA₃ IB and 2 are flow sheets which illustratively depicts various items of processing equipment and the interrelationships of these items in practicing the processes of the invention.

A fluid-tight reaction vessel 10 is provided with a pressure relief valve 11.

Elongate sacrificial electrodes ("Me"), shown in greater detail in Fig. 2, formed from

the elemental metal moiety of the desired metal oxide product (MeO) are axially fed into the vessel 10 by electrode feeders 12. Optionally, the inner opposed ends of the

electrodes are also held spaced apart a minimum distance by a ceramic grate 13 and

immersed in water 14.

Electrical power ("P") 20 is supplied to a high-voltage, low-current power supply 21 and a lower- voltage, constant current power supply 22. Power control

circuitry 23 selectively feeds either high voltage-low current electrical power from the

power supply 21 or lower- voltage, high current electrical power from the power

supply 22, thru circuit 24 to each of the sacrificial anodes to initiate and maintain an

electrical arc plasma zone in the space 25 between the inner opposed ends of the

sacrificial electrodes. The pressure in the reactor 10 is maintained at below the relief pressure of the

32, from which the dried hydrogen 33 is compressed 34 and accumulated in storage

cylinder 35.

A suspension of the metal oxide formed at the plasma zone 25 in water is withdrawn through valve 51 and sent via conduit 52 to a filter 53 to separate the solid metal oxide 54 from the water 55. The metal oxide 54 is dried 56 and may be

product 57.

The water 55 separated from the mixed metal oxide- water suspension 52 may

be cooled at cooler 58, sent to an accumulator 60 and then recirculated via conduits 50

to the reactor 10. Makeup water ("H₂O"), to maintain a sufficient level of water 14 in the reactor 10 covering the sacrificial electrodes is added via inlet line 59 to the

accumulator 60. The pump 61 raises the pressure of the water in the lines 50 to a

pressure sufficiently above the pressure in the reactor 10 to maintain the flow of recirculated water 55 and makeup water 59 through the lines 50 into the reactor 10

and provide a water bearing around the electrodes 40 to assist moving them through the electrode feeders into the reactor 10.

In operation, the reactor 10 is preferably maintained at superatmospheric

pressure to minimize the water content of the byproduct hydrogen and to increase the reaction rate at the electric arc plasma zone 25. The pressure relief valve is set to vent at pressures up to 900 psig and the pressure in the reactor 10 is maintained at up to

approximately 800-850 psig. The exact reactor pressure is not critical and higher and lower pressures down to atmospheric pressure are operable.

The temperature of the liquid phase in the reactor 10 is maintained at below the boiling point of water at the operating pressure selected. This temperature is

maintained by cooling 56 the recirculating water 55 fed to the reactor 10 and, if

necessary, by cooling fins added to the reactor and associated water piping. For example, when manufacturing black nickel oxide, it is preferred to operate the system

such that the temperature of the liquid in the reactor is reduced to about 13° C. For each metal oxide product the temperature at the plasma zone is preferably maintained at between the melting point and boiling point of the sacrificial electrode metal. For

example, preferred temperatures of the plasma zone for various metals are set forth in

Table 1.

TABLE l

Metal Plasma Temperature

Aluminum 1,859

Lithium 1,161

Magnesium 440

Nickel 1,458

Cadmium 446 To insure the purity of the metal oxide product, the water initially charged into the reactor 10 and the makeup water added via inlet line 59 is preferably distilled

water.

The electrical power 24 applied to the sacrificial anodes is regulated by

controller 23 to furnish an initial high voltage surge from the high voltage power supply 21, on the order of 2,000 volts, so as to strike the arc between the sacrificial

electrodes at a spacing of approximately 1/4 -1/2 inch. After the arc is established and the current spikes upwardly, the controller 23 switches the current from the high-

volts and 200 amps. Alternatively, electrical power can be generated by a DC generator, the ouput voltage of which is controlled by the preselected rotational speed

signal is fed to a computer which shuts the generator down if the resistance indicates that the electrodes are about to be welded together.

If less than all of the electrodes are "sacrificial," i.e., formed of the metal

corresponding to the metal moiety of the desired metal oxide product, the other

electrode(s) is/are conveniently formed of a metal or other conductive material which

will not unduly contaminate the metal oxide product or which is easily separated from

the product. For example, in producing aluminum oxide product, the non-sacrificial

electrode can be iridium or gold, as any contamination of the product aluminum oxide is easily separated from the product. Figs 1, IA and IB, depict alternate embodiments of the invention for purposes

of illustration and are not intended as limitations on the scope of the invention, which

is defined only by the appended claims.

As shown in Fig. IA, water 59 is distilled 101. The distilled water is fed to the

suction of a high pressure, e.g., 500 psi, pump and this pressurized distilled water is

then used to cool the electrodes. Additional distilled water 103 is used to backflush the filter 53 Settling tank 104 and is provided to receive the filtrate water 106 from

the filter 53. During backflushing, the backflush water 107 is directed to another settling tank 105. Supernatant water 108 from the settling tanks 104 and 105 and

makeup distilled water 111 is fed to the suction side of a lower pressure , e.g., 90 psi pump 112. The wet underflow MeO product 109 is then packaged for shipping or dried, for example, in a vacuum drier, depending on the intended use of the product.

Byproduct hydrogen 113 passes through a pressure control valve 11 which maintains

the pressure in the reaction vessel 10 at a suitable pressure, e.g., 90 psi. The byproduct hydrogen is then either vented 114 to the atmosphere or pressurized by

compressor 32 and loaded into storage cylinders for shipment. In manufacturing

certain metal oxide products, e.g., black nickel oxide, I have found that it is preferable

to inject an oxidizing agent 115 such as ozone or hydrogen peroxide into the reaction

vessel.

An alternative embodiment of the invention is illustrated in Fig. IB, which is

similar to the embodiment of Fig. IA, except that the water-product oxide slurry 52 is

sent successively to a pair of filters, first to a large particle filter 116 and then to a small particle product filter 117. This embodiment is preferred when the slurry 52

contains relatively large particles such as melted portions of the sacrificial electrode or

melted portions of the non-sacrificial electrode.

Having described the invention in such terms as to enable those skilled in the

art to understand and practice it, and, having identified the presently preferred

embodiments thereof, the invention claimed is:

Claims

1. In a prior art process for manufacturing a metal oxide product, which

includes the steps of introducing an aqueous dielectric fluid into a reaction zone, positioning an electrode pair spaced apart in said reaction zone,

at least one of the electrodes in said pair, being a sacrificial electrode

formed of the metal which is the metal moiety of said metal oxide product,

applying an electrical potential between said electrodes sufficient to create an arc therebetween, forming a plasma zone in said fluid between said electrodes and

forming a sol of said metal oxide product in said fluid in the locus of

said plasma zone, the improvement comprising the steps, in combination with the steps of said prior art

process, comprising:

(a) providing a reaction zone having an upstream portion and a

downstream portion;

(b) establishing a flow of sol toward said downstream portion of said

reaction zone; and

(c) withdrawing said sol from said downstream portion of said reaction zone.

2. In a prior art process for manufacturing a metal oxide product, which

includes the steps of introducing an aqueous dielectric fluid into a reaction zone,

positioning an electrode pair spaced apart in said reaction zone, at least one of the electrodes in said pair, being a sacrificial electrode

formed of the metal which is the metal moiety of said metal oxide product,

applying an electrical potential between said electrodes sufficient to create an arc therebetween,

forming a plasma zone in said fluid between said electrodes and forming a sol of said metal oxide product in said fluid in the locus of said plasma zone,

the improvement comprising the step, in combination with the steps of said prior art process, comprising:

reducing the formation of a metal oxide film on the faces of said electrodes by

directing sonic energy to said electrodes.

3. In a prior art process for manufacturing a metal oxide product, which

at least one of the electrodes in said pair, being a sacrificial electrode

formed of the metal which is the metal moiety of said metal oxide

product, applying an electrical potential between said electrodes sufficient to create an

arc therebetween,

forming a plasma zone in said fluid between said electrodes and

forming a sol of said metal oxide product in said fluid in the locus of said plasma zone,

the improvement comprising the steps, in combination with the steps of said prior art

process, of:

(a) withdrawing said sol from said reaction zone, and

(b) spray drying said withdrawn sol.

4. In a prior art process for manufacturing a metal oxide product, which

at least one of the electrodes in said pair, being a sacrificial electrode

formed of the metal which is the metal moiety of said metal oxide

product, applying an electrical potential between said electrodes sufficient to create an arc therebetween,

the improvement comprising the steps, in combination with the steps of said prior art process, comprising:

(a) reducing the formation of a metal oxide film on the faces of said

electrodes by directing sonic energy to said electrodes;

(b) providing a reaction zone having an upstream portion and a

downstream portion;

(c) establishing a flow of sol toward said downstream portion of said reaction zone;

(d) withdrawing said sol from said downstream portion of said reaction

zone; and

(e) spray drying said withdrawn sol.