US1852583A - Apparatus and process for treating materials such as metal powder - Google Patents

Description

J. H. LUCAS prifi 5, 132.

APPARATUS AND PROCESS FOR TREATING MATERIALS SUCH AS METAL POWDER Filed March 10, 931

INVENTOR Jam )5. Lawn.

BY HIS ATTORNEYS Patented 5, 1932 JAMES H. IBUCAS, OF ELMHUBST, NEW YOBK, ASSliGNOR 'IO NICHOLS COPPER COM- PANY, OF NEW YORK, N. Y A CORPORATION OF NEW YORK APPTUS AND PROCESS FOR TREATING MATERIALS SUCH AS METAL'POWDEB Application am March 10, 1981. ser al'mi, 521,548.

This invention relates to an apparatus and process for drying and if desired otherwise treating materials such as'metal powder.

Metal powders whose properties are injured by oxidation, require careful handling to avoid injury in this way.. Heating of metal powder e. g. copper powder to even moderate temperatures, for example 100 C. in the presence of air will result in oxidation, which may injure the electrical and other properties of thepowder, particularly where the heating continues for a few minutes.

Such powder if made by a wet process must ordinarily be dried inpreparing it for sale. Copper powder for example prepared in accordance with my copending application Ser. No. 484,540, filed September 26, 1930, is obtained by electrolyzing a solution of copper sulfate with sulfonic acid under conditions to produce a spongy mass on the rotating cathode. This spongy mass is scraped OE and washed away by a stream of electrolyte, which latter is then removed by washing the powder. This wet powder I formerly proposed to dry by a vacuum dryer in ac cordance with the process described in the copending application of Eugene Fitzpatrick et a1. Ser. No. 287,033 filed June 20, 1928.

I have found that this process'of drying is capable of producing a satisfactory product but the vacuum apparatus employed isexpensive to install and requires more labor.

for operation than necessary.- In addition when copper is deposited on rods in a well-v known manner, instead of rotating cathodes as I prefer, it is the usual practice to grind and otherwise treat it after drying. This has required a separate grinder or other ap; paratus. For example for grinding a Raymond mill has been used. Such powder,

however, after grinding contains a relatively large percentage of rejects (particles ofimproper size) and in addition the density of the copper is increased substantially, which for some purposes is a disadvantage.

The principal object of this invention accordingly is to provide an apparatus and process for treating metal powder and particularly copper powder which shall besimple in construction, inexpensive to install and novel apparatus and combinations thereof, as

well as the novel processes and steps of processes which may be carried out in such apparatus, specific embodiments of which are described herein by way of example only and in accordance with the manner in which I now prefer to practice the invention.

In carrying out the" process of my invention, I take a wet metal powder such as copper powder as produced for example by the invention of my copending application above referred to and place it 1n a confined space preferably an airtight chamber. The chamber is preferably vented to allow air and steam to be driven off from the inside upon heating. The powder as introduced into the chamber is preferably combined with sufficient water so that oxidation at room temperature of the metal particles is substantially prevented. The chamber with the copper powder therein is then heated to a temperature to form steam and. the steam is allowed to drive out the air contained in the chamber. While the heating of the powder is continued an atmosphere substantially free from air is maintained by the steam. The heating is continued until a temperature above the boiling point of water is attained,

which will be reached when all of the water has been driven off from the copper powder.

Unless a heat-treatment of the copper is decelerate the drying. If desired, by the introduction of steel or other slugs, grinding of the powder as it dries may be carried on.

In case it is desired to heat treat the copper afterit has been dried, the temperature may be raised to about 400 C. and maintained there fob three or four minutes. Under these conditionsan annealing effect is obtained and the copper powder is thereby rendered less brittle. The mobility, that is, the ease of flow when the copper powder is poured for example may be improved also by heat-treatment, for example the copper is heated in the above, where the copper powder was pro-' duced on rods and then ground in a Raymond mill, the number of round particles produced was increased but also the density of the copper was considerably increased. In addition in grinding with the Raymond mill, quite a high proportion of rejects,that is, copper particles of improper size were formed tending to increase the expense of this process.

After drying, and carrying out one or more of the other steps as indicated above, the copper powder is discharged from the chamber, cooled, sieved if desired and packaged for the market.

An apparatus which I prefer to use in car- ,rying out the process of my invention. is shown in the accompanylng drawings forming part of this application in which Fig. 1 is an elevation partly in section of the apparatus.- Fig. 2 is a transverse sectional view of the drying cylinder taken on the line 22 of Fig. 1 and Fig. 3 is a diagrammatic plan view of the apparatus with the upper hood' removed.

Referring now more particularly to the drawings, the numeral 1 designates a firebox built preferably of firebrick or other refractory material, and mounted near the lower portion thereof is an oil burner 2 projecting through the side wall thereof. This oil burner is used as a source of heat for drying or heat-treating copper powder 3 contained in the airtight horizontal metal drying cylinder 4; The cylinder -4 is one of a battery of drying cylinders shown more clearly in Fig.- :3 and all heated in the same firebox. A description of one drying cylinder will suffice for all. Each drying cylinder is mounted in the upper portion of the firebox, being sup ported by a short solid shaft 5 at one end and a short core or hollow shaft 6 at the opposite end. These shafts are in turn sup- 7 ported respectively by bearings 7 and 8 which lie respectively in slots 9 and 10 in the opposite walls of the firebox. The upper end of these slots is open so that the entire drying cylinder when uncoupled, as mentioned beheater mentioned.

low, may be removed from the firebox for discharge of the copper powder.

The shaft 5 has a worm gear 11 fixed to the outer end thereof which is driven by a worm gear mounted on shaft 12 by an outside source of power not shown. The hollow shaft 6 is connected by a packed coupling 13 with a pipe 14 which preferably leads to the electrolyte heater shown in my copending application mentioned above. Located between the packed coupling and the pipe 14 is a thermostatic Valve 15 which is of any desired type and which may be set to close at a predetermined temperature. I prefer to set this valve to close at a temperature above the boiling point of water say at about 240 F. The hollow shaft 6, packed coupling 13 and thermostatic valve 15 provide a through passage from the interior of the drying cylinder 4 through the pipe line 11 to allow passage of air and steam from the dryer to the pipe line and away to the electrolyte The valve may be a motor driven valve of the Arco type with the current to the motor thermostatically controlled by the usual mercoid control.

switch placed in the electric circuit from the mercoid control to the Arco motor valve will open with an arm operating the motor driven valve. The circuit is then to be closed only by manual operation. The electric signal bell can be operated by placing the contacts therefor in a position such that the arm on the Arco motor valve at the time of closing closes the circuit operating the signal valve.

On the interior of the rotating dryer is placed a series of slugs 16 preferably of hard material suitable for grinding, such as steel. Upon rotation of the dryer these slugs grind the copper powder in the manner of a ball mill. The drying cylinder is provided with a hinged door 17 which extends substantially for the length thereof and which is provided with a clamping means comprising a rotatable bolt -member 18 which is threaded 7 through a nut 17 mounted on the door and the lowenend of which is provided with a lug 20 whlch passes under a ledge 21 located on the drum at the door opening. Gaskets 22 of heat-resisting material make tight joints between the ad aCent faces of the dryer and the faces ofthe door. lVhen the door of the dryer is open in order to discharge the copper powder the lugs 16 are prevented from discharge with the powder by means of a wide meshed screen 22 placed over the door openmg as shown more clearly in Fig. 2, the mesh being sufliciently large to permit the powder to pass freely therethrough but to-retain the slugs.

In Fig. 1 I have shown in the lower part of the fire-box a car 23 containing a load of copper castings 24 which are in process of cooling and which may be employed to substitute or supplement the heat from the oil' burner if desired. A hood 25 provided with a stack outlet 26 is provided above the dryers to carry oflf the exhaust heating gases. Lifts 27 consisting of strips of metal attached to the sides of the drying cylinder are employed to raise the material upon rotation of the cylinder and to allow it to drop back to the bottom thereof.

In operating the apparatus the dryer 4 is charged with wet copper powder 3 up to a height below that of the supporting shafts 5 and 6. Steel slugs 16 are placed therein. The door 17 is clamped down to make the dryer substantially airtight and it is then lowered through the slots 9 and 10 to a horizontal position so that the worm'wheel 11 is in contact with the worm drive12. The coupling 13 is then coupled. The oil burner 2 is then set in operation and is supplemented if desired by the heat from the copper castings 24 and rotation of the dryer is commenced. Steam is generated inside the dryer by the heat rising around the rotating cylinder. This steam drives out the air through the hollow shaft 6,. coupling 13, thermostatic valve 15 and pipe 14: to the electrolytev heater, and the steam is conducted from the chamber at a rate to maintain an inert atmosphere about the powder until substantially dry. The heating is continueduntil the thermostatic valve closes to exclude air from the outside from passing into the chamber. This valve may operate a bell or other signal in order to indicate when it is closed at which time the operator will be advised that the powder is dried and a predetermined temperature, e. g. 240 F. has been reached. If a further heat-treatment is desired the heat may be adjusted to give a higher temperature and rotation may be continued for a desired interval. During the rotation the slugs 16 grind the copper powder and this grinding, as indicated above, may be carried out for any desired interval. A check valve or similar valve 15a is preferably placed as shown in the drawings adjoining coupling 13' to prevent air from returning into the drying chamber.

Although I have described the invention as applicable to copper powder, it will be understood that other metallic powders may be employed therein and other inert vaporizable liquids than water may be employed in drying. r

The process and apparatus described are simple and eficient in operation, require little attention and have a high daily output.

The product'resulting may have-its characteristics varied as required, that is, it may be more or less brittle and more or less mobile. The product produced has been found to be substantially free from oxygen content, containing about the same or alittle less oxygen than produced by the vacuum method men.- tioned above.

VVhat- I claim as new and desire to secure by.

Letters Patent is I 1. In a drying apparatus in combination a 'drying chamber for receiving metal powder containin a liquid capable of producin a vapor substantially inert to the pow er, means to heat the chamber to produce vapor from the liquid and vapor exit means for said chamber, said chamber being closed except for said exit nqeans, and means to substantially preclude air from the powder upon its becoming substantially dry.

2. In a drying apparatus in combination a drying chamber for receiving metal powder such as copper powder containing a liquid capable of producing a vaporsubstantially inert to the powder, means to heat the chamber to produce vapor from the liquid, and. a conduit to conduct the vapor from the chamber, said chamber being closed except for said conduit and a valve for closing the conduit to prevent the entrance of air therethrough. a a

3. In a drying apparatus in combination a drying chamber for receiving metal powder containin 'a liquid capable of producing a vapor su stantially inert to the powder,

means to heat the chamber to produce vapor from the liquid, and a vapor exit, said chamber being closed except for said exit, and a valve for closing said exit at a predetermined temperature.

4. Ina drying apparatus in combination a drying chamber for receiving metal powder containing a liquid capable of producing a vapor substantially inert to the powder, means to heat the chamber to dry the powder and vaporize the liquid and a vapor exit for said chamber, said chamber being closed except for said exit, and a thermostatic valve to close said exit at a temperature somewhat above the boiling point of water and means for moving said drying chamber to remove the dried metal owder therefrom.

5. In an apparatus for removing water from copper powder, in combination, a heatmg chamber,a source of heat therein, an airfor conducting moisture generated on heat ing said copper powder, and a thermostatic valve to close said pipe and prevent admiszoo sion of air into-said cylinder-when the temperature of the copper powder has risen somewhatabove the boiling point of water.

6. A process for drying metal powder which comprises, heating moisture-containing powder in a chamber to a temperature to convert the moisture into vapor, driving out air from the chamber by the vapor and maintaining by the vapor an atmosphere substantially free from air while continuing the heatmg.

7. A process according to claim 6 in which the heating is continued until the temperature of the powder is above the boiling point of water and thereafter closing the-chamber to substantially prevent entrance of air thereinto.

8. A process according to claim 6 in which the powder is kept in agitation during the drying.

9. A process according to claim 6 in which after drying copper powder it is subjected to a heat-treatment in such chamber for annealing the powder at a temperature above the boiling point of water.-

10. A process for removing water from copper powder which comprises heating the wet powder in a chamber to a temperature to form steam, driving out air from the chamher by the steam, maintaining by the steam an atmosphere substantially free from air while continuingthe heating and proceeding with the heating until the temperature is above the boiling point of water and thereafter closing the chamber and then discharging the dried-copper powder.

In testimony whereof I have signed my name to' this spe ification.

JAMES H. LUCAS.

CERTIFICATE 015 CORRECTION.

Patent No. 1,852,583. a

. Gama Apr-5,1932, m

mms u; Lucas.

- It is hereby certified thaterrorr appears -i'nthe printed specification of the above numbered patent requiring correction as follows: Page 1, line 19, for the word "sulfonic" read sulfuric; pa2e-3, liine46, tor "drawings" read-drawing; and that the said Letters Patent should he read with these corrections therein that the slmemay conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of lime, A D. 1932,

(Seal M. L no ore,

Acting Commissioner of Patents.

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