US3340566A

US3340566A - Apparatus for the production of metal particles

Info

Publication number: US3340566A
Application number: US541405A
Authority: US
Inventors: William P Woosley; John S Connor; Jr Vincent E Furnas
Original assignee: Reynolds Metals Co
Current assignee: Reynolds Metals Co
Priority date: 1962-08-16
Filing date: 1966-01-18
Publication date: 1967-09-12
Anticipated expiration: 1984-09-12

Description

Se t. 12, 1967 W. P. -'WOOSLEY ETAL 3,340,566

APPARATUS FOR. THE PRODUCTION OF METAL PARTICLES 3 Sheets-Sheet 1 Original Filed Aug. 16, 1962 INVENTORY s. ON%%% NT E.FURNAS,J'R. w; WW

ATTORNEYS Sept. 12, 1967 W AP 1VV'OOSI' EY E 3,340,566

APPARATUS FQ Rfik IE PRODUCTION OF METAL PARTICLES I Original Filed Aug.- 16, 1962* 1 3 Sheets-Sheet 2,

' INVENTORS WILLIAM F. WOOSLEY JOHN S CONNOR VINCENT EF'URNAS, JR.

ATTORNEY:

Sept. 12, 1967 WYPQW QSLEY ETAL 3,3

APPARATUS FOR THE-:PRODU CTiON OF METALPARII-CLES I I v 3Sheets-Sheet 3 Original Filed Aug. 16, 19 2 INVENTORS WILLIAM PWOOSLEIY JOHN s. CONNOR VINCENT E. FURNAS'JR.

' ATTORNEYJ Patented Sept. 12, 1967 3,340,566 APPARATUS FOR THE PRODUCTION OF METAL PARTICLES William P. Woosley, John S. Connor, and Vincent E.

Furuas, Jr., Jefferson County, Ky., assignors to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Original application Aug. 16, 1962, Ser. No. 217,414.

Divided and this application Jan. 18, 1966, Ser. No. 541,405

9 Claims. (Cl. 182.5)

ABSTRACT OF THE DISCLOSURE Apparatus for the production of fine spherical metal particles, including a first chamber adapted to receive molten particles for cooling thereof in a controlled atmosphere and a second chamber to effect controlled oxidation of the particles. A spiral conveyor for use in the second chamber is provided with discontinuities to permit material rnoving upward on the conveyer surface to fall back to a lower surface, and means are included adjacent such discontinuity for subjecting the falling particles to the action of a treating gas.

This application is a division of prior copending application Ser. No. 217,414 (now US. Patent 3,293,333).

This invention relates to the production of metal powders composed of particles spherical in shape. More particularly, the invention concerns apparatus for the continuous manufacture of fine spherical aluminum particles by atomization of the molten metal with an inert gas and subsequent exposure of the atomized metal to an inert gas providing controlled oxidation of the metal surface. The invention is especially concerned with spherical aluminum powders.

Finely divided metal powders, such as, for example, aluminum, magnesium, copper and tin powders, have numerous industrial applications, including powder metallurgy, pyrotechnics, flares, and solid fuel components. In these and other applications, it has been a general objective to obtain powders which are free-flowing, possess a high packing density and smooth surface, and which are desirably spherical in shape.

One of the known methods of producing finely divided metal powders is that of atomizing the molten metal by means of a gas inert to the metal, into a closed chamber. In metal atomization as carried out in this fashion, the art had laid considerable stress on the necessity of avoiding surface oxidation of the molten metal, the thought being that the usefulness of the finished powder was greatly impaired when the powder particles became coated with oxide. It was also believed by those skilled in the art that the production of spherical metal powders from molten metal by atomization with inert gases which might contain small amounts of oxygen and nitrogen Was impeded by formation of metal oxides and nitrides by chemical reaction, causing clogging of the atomizing nozzle and other difliculties. Accordingly, elaborate purification systems were proposed to remove impurities such as oxygen and nitrogen, especially from argon or helium inert gas media, the purified inert gas then being recirculated to the main circulatory system.

In accordance with the present invention, it was found, surprisingly and unexpectedly, that the presence of small amounts of oxygen during formation of particles from the molten metal is not detrimental, provided that the degree and/or rate of oxide formation on the surface of the molten metal is controlled. Control of the degree and/0r rate of oxide formation, according to the invention, is accomplished by atomizing the metal into an inert gaseous atmosphere in which solid particle formation takes place, said atmosphere containing a small amount of available oxygen, suflicient to achieve a degree of surface oxidation which will protect the metal from ignition or detonation, but insufiicient to interfere with the normal surface tension forces tending to draw the molten metal particle into spherical shape.

As employed herein, the term available oxygen means oxygen which is present in the free, uncombined state, as well as oxygen made available by the decomposition of gaseous oxygen compounds which may be present by the molten metal.

When molten metal is atomized, the particle initially formed is elongated in shape owing to the action of the high velocity gas stream which tears it away from the stream of molten metal issuing from the atomizing nozzle. If oxygen or moisture is present in suflicient amount, an oxide envelope immediately forms, preventing the normal surface tension forces within the molten metal particle from pulling the particle into a spherical shape, the shape having the minimum surface area. If the metal does not form an oxide film, the initially formed metal particle will draw itself into a sphere, providing it remains molten and not subject to external forces greater in magnitude than its own surface tension forces for a period of time sufiicient to permit sphere formation.

Atomization breaks the metal into small particles and maintains it in molten condition long enough to form spheres. Small particle size is a factor favoring sphere formation.

The apparatus of the invention is adapted for the production of spherical metal powders generally, including such metals as copper, magnesium and aluminum and their alloys. For purpose of illustration of the novel principles of the invention, aluminum and aluminum base alloys, including alloys of aluminum with copper, tin, and magnesium, will be referred to herein.

The invention permits the production of spherical aluminum and aluminum alloy powders in improved yield, with greater economy, and having desirable characteristics of spherical shape, smooth surface, high packing density, and free flowing properties.

In accordance'with one aspect of the invention, there is provided a method for the formation of fine spherical metal particles which comprises forming a body of molten metal, subjecting said body of molten metal to the action of a high velocity stream of a gas inert to said metal to disintegrate the metal into fine particles, and discharging said molten particles and said inert gas stream into an enclosed cooling zone comprising an atmosphere of a gas inert to the metal and containing available oxygen in an amount insufficient to interfere with normal surface tension forces within the molten metal particles causing sphere formation.

The atomizing gas may itself be either a gas inert to the metal and containing no oxygen, or it may be a gas inert to the metal-andcontaining a limited amount of available oxygen, identical with or similar in composition to the atmosphere of the cooling zone.

The inert gas containing limited amounts of available oxygen is preferably produced by an exothermic reaction, and is customarily known as an exothermic gas. As produced, for example, by the controlled combustion of natural gas in a gas generator, a typical exothermic gas composition is:

CO 11-12% by volume. H O u Saturated at discharge temperature. Combustibles (CO-j-Hz-l-CILQ 0.5% maximum. Less than about 0.3%. N Balance.

In accordance with another aspect of the invention, there is provided a multistage method, which is adapted for continuous operation, for the production of spherical metal powders. In this method, the formation of spherical particles from molten metal is divided into two stages, with controlled access of oxygen to the metal in each stage, thus providing for progressive oxidation.

In the first stage, a body of molten metal is subjected as before to the action of a high velocity stream of a gas inert to the metal to disintegrate the metal into fine particles, the molten particles and said gas stream being discharged into a first zone comprising an atmosphere of the inert gas. The inert gas contains available oxygen in an amount insufiicient to. interfere with normal internal surface tension forces in the particles causing sphere formation. The spherical particles are partly cooled, collected and transported to a second zone in which further oxidizing and cooling takes place in the presence of an atmosphere with a controlled amount of free or available oxygen, the amount of the oxygen being below that which will support ignition. The amount of oxygen that may cause difliculty in this regard may be between about 5% and about but this will depend upon particle size and other factors.

The single stage method may be performed as a batch operation, utilizing an apparatus providing an enclosed cooling zone in the form of a closed chamber into which the gas and molten particles are discharged, the velocity of the molten particles being rapidly diminished upon entry into the chamber. The chamber is filled with the inert gas containing a limited amount of available oxygen. Cooling and sphere formation take place, the metal particles collecting at the bottom of the chamber on a suitable conveyer. The initial atmosphere in the chamber may be replaced by an atmosphere of an inert gas containing a controlled amount, e.g. about 5%, of free oxygen, to complete oxidation of the particle surfaces in the same chamber. The conveyer transports the finished particles out of the chamber to a suitable collecting system.

The preferred embodiment of the invention comprises a two-stage method and apparatus, whereby the metal is atomized into a first or cooling zone formed by a chamber provided at the bottom thereof with a horizontal type vibratory conveyer, upon which the spherical metal particles collect and are transported to a second chamber, which serves a further cooling and oxidizing zone. Both the first and second zones are thus separated and each is provided with means for supplying inert gas containing available oxygen. A slight pressure is maintained inside to prevent leakage of outside air.

The two-stage method is especially adapted for continuous operation, the metal particles moving progressively through the first cooling and sphere formation zone containing an inert gas having a limited amount of oxygen, as previously described, thence to a second cooling and oxidizing zone containing an inert gas having about 5% oxygen, and thence to a collecting system where the particles become exposed to the outside air.

In the second zone, the metal particles, while mechanically agitated, are moved continuously through the zone, and are subjected at intervals to a mechanical cascading or tumbling step, in order to expose the particle surface fully and effectively to the action of the oxygen containing gas in the second zone. During these intervals the cascading particles are subjected to the action of streams of the oxygen containing gas. This cascading action is preferably accomplished, in accordance with the invention, by means of a spiral conveyer, described more fully below. The particles passing upwardly in this conveyer, which is of the vibratory type, periodically traverse portions of the spiral at which there is provided a steplike interruption in the helical conveyer surface. Thus, the particles are at intervals subjected to a downward movement during which they form a cascade, and the cascading particles are subjected to the action of a stream of inert gas containing available oxygen, said gas stream being applied in a direction transverse to the direction of the falling particles.

Accordingly, the objects of the invention include the provision of a method for the production of spherical metal powders by atomization and subsequent controlled oxidation of the metal particle surface by intermittent exposure of a cascade of the particles to the action of an inert gas containing a small amount of available oxygen.

Another of the objects of the invention is the provision of an apparatus for the production of fine spherical metal powders including means for the exposure of an atomized metal to the action of an inert gas containing a controlled amount of available oxygen.

Still another object of the invention is the provision of an improved conveying means whereby the metal particles are periodically exposed to the action of an inert gas containing available oxygen during their passage through the conveyer.

These and other objects will be apparent from the detailed description below, reference being made to the accompanying drawings, in which:

FIG. 1 is a side elevation, in cross-section, of a single chamber apparatus suitable for batch operation;

FIG. 2 is a vertical sectional view, taken along the line 2-2 of FIG. 1;

FIG. 3 is a side elevation, partly in cross-section, showing a multi-chamber apparatus, suitable for continuous operation;

FIG. 4 is an enlarged cross-sectional view along the line 4-4 of FIG. 3, showing the detail of the gas treatment means;

FIG. 5 is an enlarged fragmentary detailed sectional view of a portion of the helical conveyer, showing the step construction; and

FIG. 6 is an enlarged detailed sectional view taken along the line 66 of FIG. 4.

As shown in FIG. 1, the single chamber apparatus includes a chamber 1, made of any suitable material, such as steel sheet, and of any desired shape, preferably rectangular shape. Chamber 1 is provided with said

walls

2 and 3, a closed top 5, and a hopper type bottom shown generally at 6. The chamber is supported on legs 4. In sidewall 2 there is located in the center portion thereof a flared outwardly projecting portion 7, having a terminal member 8 serving as a means of mounting the atomizing assembly 9. The lower portion of the chamber 1 terminates in a recessed channel section 10, in which there is suitably mounted a conveyer, which may be of any suitable type, such as a belt conveyer, as shown, or a vibrating type conveyer. Channel section is provided, at the end opposite to the side wall containing the atomizing assembly, with a discharge chute 14, by means of which metal powder collecting on the conveyer is discharged to the atmosphere. Driving means (not shown) for the conveyer cause movement of the upper portion of the conveyer belt towards the discharge chute. The conveyer is not in operation during a run.

The atomizing assembly includes an atomizing nozzle 15 which may be a metal pipe lined with a thin ceramic layer, and which is provided with a ceramic tip 16 from which the molten metal from a source not shown is fed into chamber 1. Surrounding the atomizing nozzle 15 is a jacket 17 whereby inert gas, which is preferably preheated, is fed into the atomizing assembly under pressure, causing disintegration of the molten metal. Inlet 19 provides for introduction of replacement gas.

In the operation of the embodiment shown in FIGS. 1 and 2, molten metal, such as molten aluminum, is fed into atomizing nozzle 15, while a stream of an inert gas containing a limited amount of available oxygen, such as an exothermic gas previously described, is fed into the surrounding jacket under pressure suflicient to cause disintegration of the molten metal stream into small particles, which discharge into the interior of chamber 1. The metal particles, under the action of surface tension forces, draw into spherical shape, fall and collect on the upper surface of the conveyer belt located at the bottom of the chamber, when a run is completed, the conveyor is operated causing the spherical metal powder to be discharged through chute 14 into a suitable receiver. The batch operation may be carried out using either an inert gas containing no oxygen, or a gas containing a limited amount, for example 0.2% by volume, of oxygen, as the atomizing gas. The chamber may be initially filled with an inert gas containing a limited amount of available oxygen of the same type as used for atomization, such as an exothermic gas. In order to complete the oxidation of the metal particles in the same chamber, the gas initially present, and the gas introduced into the chamber via the atomizing nozzle, may be replaced by blowing into the chamber a fresh supply of an inert gas containing a slightly larger amount of available oxygen, such as, for example, about 5% by volume, and the oxidation completed in the chamber by exposure of the metal particles to the cooling and oxidizing action of the replacement gas. When the run is completed, the conveyer is operated to discharge the particles to the outside.

The preferred embodiment of the invention is the multichamber system shown in FIGS. 3 and 6 inclusive.

Referring to FIG. 3, the apparatus comprises an atomizing chamber 20 provided with

walls

21 and 22 and closed top 23. In the central portion of wall 22 there is mounted the atomizing assembly, on an outwardly flared projecting wall portion 22a, including an atomizing nozzle 24 which may be a metal pipe lined with a thin ceramic layer, and which is provided with a ceramic tip 25 from which molten metal is fed, from a source not shown,

charges into adjacent chamber 31 through communicating discharge opening 29.

into chamber 20. Surrounding the atomizing nozzle 24 is a jacket 26 whereby inert gas, which is preferably preheated, is fed into the atomizing assembly under pressure, causing disintegration of the molten metal. Inlet 49 provides for introducing additional gas.

Located in the bottom portion of chamber 20 is a vibratin'g conveyer 27, comprising a trough 28 having a general-1y flat central configuration, upon which the falling metal particles collect. The trough may be either horizontal or inclined at a slight angle toward the discharge opening 29 located at the lower end of wall 21 of the chamber. The conveyer 27 is actuated by a series of electromagnetic vibrators 30 which are of conventional type including an electromagnet and armature. The action of the conveyer depends upon the principle that under controlled vibration .a loose bulk material will travel over a surface by itself, with its speed and degree of vibration unit. The action is that of pulling the trough downward and backward, leaving the load momentarily suspended in space. .It then falls vertically, landing slightly, up to about /s ahead of its earlier position, producing an effect of almost continuous flow, which can be increased by sloping the trough a few degrees toward the discharge. The conveyer projects a short distance and dis- Chamber 31 houses a vertical helical vibratory conveyer 32, which may be of any suitable type, such as disclosed, for example, in US.

Patent

2,6 5 8,-28 6. In the arrangement shown in FIG. 3, the helical or spiral conveyer consists of a spirally arranged conveyer trough 33 mounted on a central tube 34 and extending from the lower end to the upper end of tube 34. The lowermost trough portion is provided with an annular trough 35 for receiving bulk feed material. Located to the upper portion of the conveyer, is an actuating means shown generally at 36, which includes a pair of symmetrically mounted electromagnetic reciprocating motors energized by current impulses, which impart their magnetic forces to the conveyer .to reciprocate it in such manner that the vibrations cause the material to flow in a circular path about the axis of the central tube 34 and up the inclined path provided by the helical or spiral trough. The top of the uppermost conveyer flight is provided with a laterally extend ing or tangential discharge trough 37 which discharges the material into an exit trough or tube 38, whereby it is transported to collecting means not shown, located outside chamber 31.

Chamber 31 functions as a further cooling and oxidizing chamber, and is accordingly provided with means for introducing a supply of suitable treating gas, such as, for example, an inert gas containing a limited amount of available oxygen. The means for introducing gas comprises an inlet 39, connecting with a vertically extending central supply pipe or header 40, located inside chamber 31, and running parallel to the central conveyer tube 32. Located at suitable intervals is a series of nipples 41, positioned opposite lengths of pipe 42, fastened to central tube 32 and extending laterally therefrom, said pipe lengths being of approximately the width of the conveyer trough 33. Each pipe length contains a horizontal slot 43 through which the gas issues under slight pressure. The slotted pipes are connected to the nipples by flexible connectors 44 so that the vibratory action of the conveyer will not affect the gas supply system, by causing loosening of connections, leakage, and the like.

In accordance with a novel feature of the invention, there are provided at intervals in the conveyer trough 33, discontinuities 45, in and extending across the upper surface thereof over which the ascending material falls in the form of a cascade 46, as shown in FIG. 6, the distance of fall depending upon the depth of the step formed by the discontinuities. The pro-file of the discontinuity in the helical trough is shown in FIGS. 5 and 6. The discontinuity 45 is forrned by a portion of the spiral trough which overhangs the continuing portion 47 of the trough, upon which the cascading material falls to resume its upward journey. The height of the cascade is slightly greater than the. outside diameter of the slotted pipe 42. The latter is positioned in a recess slightly greater than the outside diameter of the slotted pipe 42, and formed by wall 48 which extends from the edge of trough position 47 to the under surface of the preceding portion of the trough. The slotted pipes 42 extend across the under surface of the trough positioned just behind and in a direction parallel to the edge of the discontinuity 45, with the slots 43 positioned so that the gas issuing therefrom will traverse the cascade of falling particles 46, thus cooling, oxidizing and further agitating of said particles. 3

In the embodiment shown in FIG. 3, there are four cascades and corresponding sets of slotted gas treatment pipes.

tI-t will be understood that the principle upon which the embodiment shown is based may be similarly applied in other types of spiral conveyers, including those operating with a downward flow of material under gravitational forces. Thus, a conventional gravity spiral conveyer can be adapted for the purpose of the invention by providing discontinuities at intervals in the trough thereof, in conjunction with a slotted pipe gas treatment system of the character described.

In the continuous operation of the embodiment shown in FIGS. 36 molten metal, such as aluminum, is supplied to the atomizing nozzle and inert gas containing either no oxygen or a limited amount of available oxygen, such as exothermic gas, is supplied to the surrounding jacket, serving to disintegrate the stream of molten metal into small particles which draw into spherical shape in the first or cooling chamber 20. The particles collect on the conveyer by means of which they are continuously moved to chamber 31. Treating gas comprising an inert gas containing about 5% oxygen by volume is introduced into chamber 31 via the slotted pipe system, or additionally by direct introduction into the chamber, under slight pressure to prevent leakage of outside air. The gas envelops the material moving upward on the spiral conveyer, and also contacts the material descending in the respective cascades formed by the discontinuities in the trough surface. The cooled and oxidized metal particles are then discharged into suitable collecting devices and stored in any desired manner.

The choice of operating conditions will depend upon the metal being atomized, size of nozzle orifice, gas temperatures and pressures, and other factors. For purposes of illustration, but not of limitation, in the case of aluminum, nozzle temperatures may range from about 1300" to 1700 F. Gas temperatures in the first chamber may range between about 600 and about 1200 F., but these figures are indicative only, and are subject to wide variation. In the second chamber, the gas temperature may be in the range 600 to 900 F., again with wide variations.

What is claimed is:

1. Apparatus for the production of fine spherical metal particles from molten metals, comprising a substantially closed spherical metal particle forming and cooling first chamber contiguous to and in communication with a substantially closed metal particle cooling and oxidizing second chamber, means supported on a wall of said first chamber for forming fine molten metal particles and discharging them into said chamber, means located at the bottom of said first chamber for collecting and transporting the spherical metal particles to said second chamber, means located in the interior of said second chamber for receiving and transporting a stream of the metal particles between the lower and upper portions of said chamber while interrupting said particle stream at intervals to produce a downward cascading thereof, means for subjecting the downwardly cascading particles to the action of a treating gas in a direction transverse to the direction of fall of the cascade, and means for removing the treated spherical particles.

2'. Apparatus for the production of fine spherical metal particles from molten metals, comprising a substantially closed spherical metal particle forming and cooling first chamber contiguous to and in communication with a substantially closed metal particle cooling and oxidizing second chamber, means supported on a wall of said first chamber for forming fine molten metal particles and discharging them into said chamber, means for introducing a supply of treating gas into said first chamber, conveyer means located at the bottom of said first chamber and extending into said second chamber for collecting and transporting the spherical metal particles to the second chamber, means located in the interior of said second chamber for receiving and transporting a stream of the metal particles from the lower portion to the upper portion of said chamber comprising a vertically disposed rigid helical conveyer, the upper surface of said conveyer being provided at intervals with discontinuities forming a step over the edges of which the ascending particles fall in a cascade to the next lower continuing conveyer surface, means rapidly reciprocating said conveyer producing vibrations to cause particles to move up the conveyer surface,

means for subjecting particles cascading over the discontinuities to the action of a treating gas in a direction transverse to their direction of fall, and means for discharging the treated particles.

3. Apparatus for the production of fine spherical metal particles from molten metals, comprising a substantially closed spherical metal particle forming and cooling first chamber contiguous to and in communication with a substantially closed metal particle cooling and oxidizing second chamber, means supported on a wall of said first chamber for forming fine molten metal particles and discharging them into said chamber, a vibrating conveyor located at the bottom of said first chamber and extending into said second chamber to collect and transport spherical metal particles to said second chamber, a vertically disposed rigid helical vibrating conveyor positioned in the interior of the second chamber and extending from the lower to the upper portion thereof, said conveyer being actuated by a plurality of electromagnetic reciprocating motors energized by electric current to impart reciprocating vibratory motion thereto to cause the particles to move up the conveyer surface, said conveyer including a series of turns about a central axis and having inlet and outlet means to receive and discharge material, and having at intervals discontinuities in its surface extending radially from said central axis and across its width forming a step over the edge of which the ascending particles fall in a cascade to the next lower continuing conveyer surface, means for sup-plying a treating gas to said second chamber, means for distributing said gas Within said chamber to points slightly below the edges of said discontinuities, means parallel to said edges and positioned beneath and adjacent thereto for subjecting particles cascading over the discontinuities to the action of treating gas in a direction transverse to their direction of fall, and means for collecting the treated particles.

4. The apparatus of claim 3 in which the gas distributing means comprises a vertically disposed header conduit spaced apart from and extending parallel to the axis of the conveyer, having at intervals a series of flexible conduits extending therefrom connecting with a set of rigid conduits mounted on the central conveyer axis extending radially therefrom immediately beneath said discontinuity edges, and having openings parallel to said edges to permit the passage of treating gas.

5. The apparatus of claim 3 in which the discontinuity in the conveyer surface is formed by a portion of the helical surface which overhangs the continuing portion of the conveyer positioned beneath it, said continuing portion extending underneath and to the rear of the overhanging surface and terminating in a vertical wall to provide a recess to receive said gas treating means.

6. A vibratory helical conveyer adapted for gas treatment of material moving thereon comprising, in combination, a vertically disposed rigid helical conveyer including a series of turns about a central axis, a plurality of electromagnetic reciprocating motors energized by electric current to impart reciprocating motion thereto to cause material to move up the conveyer surface, inlet and outlet means to receive and discharge material, said conveyer having at intervals discontinuities in its surface extending radially from said central axis and across its width forming a step over the edge of which ascending material falls in a cascade to the next lower continuing conveyer surface, said continuing portion extending underneath and to the rear of the edge and terminating in a wall to provide a recess adapted to receive a gas treating member, and a gas distributing system terminating in a set of rigid conduits mounted on said central axis extending radially therefrom and positioned in said recess, and having slotted openings facing in the direction of the edge of the discontinuity and of the falling particles.

7. A vibratory conveyer having a helical conveyer surface including a series of turns about a central axis, said surface being interrupted at intervals toprovide a dis 9 10 continuity forming a step to permit material moving up- References Cited Ward on the conveyer to fall to a lower conveyer surface, UNITED STATES PATENTS and means for subjecting the falling material to the action 373 766 11/1887 Bosworth 5 Of a "eatmg 2,199,087 4/1940 Drill et a1. 1825 X 8. Apparatus aecordmg to cla1m 7, mcluding an inlet 5 2 274 948 3/1942 Ahlmann 34 147 pipe extending laterally beneath each step to in ro 2358900 9/1944 Zettel I 5 X said treating gas, each pipe having a lateral outlet direc- 2:688807 9 /1954 Gimme; n ting the gas through the falling material. 9 129 7 19 0 Carri 34 147 X 9. Apparatus according to claim 8, in whi h e c pip 3,024,133 3 19 2 whit 19s 220 X has an outlet slot extending substantially parallel to the 10 adjacent step. WILLIAM J. STEPHENSON, Primary Examiner.

Claims

1. APPARATUS FOR THE PRODUCTION OF FINE SPHERICAL METAL PARTICLES FROM MOLTEN METALS, COMPRISING A SUBSTANTIALLY CLOSED SPHERICAL METAL PARTICLE FORMING AND COOLING FIRST CHAMBER CONTIGUOUS TO AND IN COMMUNICATION WITH A SUBSTANTIALLY CLOSED METAL PARTICLE COOLING AND OXIDIZING SECOND CHAMBER, MEANS SUPPORTED ON A WALL OF SAID FRIST CHAMBER FOR FORMING FINE MOLTEN METAL PARTICLES AND DISCHARGING THEM INTO SAID CHAMBER, MEANS LOCATED AT THE BOTTOM OF SAID FIRST CHAMBER FOR COLLECTING AND TRANSPORTING THE SPHERICAL METAL PARTICLES TO SAID SECOND CHAMBER, MEANS LOCATED IN THE INTERIOR OF SAID SECOND CHAMBER FOR RECEIVING AND TRANSPORTING A STREAM OF THE METAL PARTICLES BETWEEN THE LOWER AND UPPER PORTIONS OF SAID CHAMBER WHILE INTERRUPTING SAID PARTICLE STREAM AT INTERVALS TO PRODUCE A DOWNWARD CASCADING THEREOF, MEANS FOR SUBJECTING THE DOWNWARDLY CASCADING PARTICLES TO THE ACTION OF A TREATING GAS IN A DIRECTION TRANSVERSE TO THE DIRECTION OF FALL OF THE CASCADE, AND MEANS FOR REMOVING THE TREATED SPHERICAL PARTICLES.

7. A VIBRATORY CONVEYER HAVING A HELICAL CONVEYER SURFACE INCLUDING A SERIES OF TURNS ABOUT A CENTRAL AXIS, SAID SURFACE BEING INTERRUPTED AT INTERVALS TO PROVIDE A DISCONTINUITY FORMING A STEP TO PERMIT MATERIAL MOVING UPWARD ON THE CONVEYER TO FALL TO A LOWER CONVEYER SURFACE, AND MEANS FOR SUBJECTING THE FALLING MATERIAL TO THE ACTION OF A TREATING GAS.