US319945A

US319945A - Electric smelting-furnace

Info

Publication number: US319945A
Authority: US
Publication date: 1885-06-09
Anticipated expiration: 1902-06-09

Description

(No Model.) 2 Sheets-Sheet l.v

E. H. & A. H. OOWLES.

ELECTRIC SMELTING FURNACE.

No. 319,945. Patented June 9, 1885.

(No Model.)

2 Sheets-Sheet 2.

E. H. & A. H. COWLES.

ELEGTRIO SMELTING FURNACE.

FIG-

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UNITED STATES PATENT @rrice.

I EUGENE I-I. (JOYVLES AND ALFRED H. CO'WLES, OF CLEVELAND, OHIO.

ELECTRIC SMELTING-FURNACE.

SPECIFICATIUN forming part of Letters Patent No. 319,945, dated June 9, 1885.

(No model.)

To all whom it may concern:

Be it known that we, EUGENE H. CowLE and ALFRED H. CowLns, citizens of the United States, residing at Cleveland, in the county of Guyahoga and State of Ohio, have invented certain new and useful Improvements in Electric Smelting- Furnaces; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification. I

The object of the present invention is to provide an apparatus by means of which metallurgical operations and chemical operations which require an intense heat can be carried on with electricity as the heat-producing agent, operating on the incandescent principle.

Numerous experiments have demonstrated that the electric arc cannot be successfully used for metallurgical and smelting purposes on a scale of any considerable magnitude, for the reason that the heat, though intense, is localized, and cannot be evenly distributed over any considerable area. Moreover, it is very diiiicult to maintain with an are a constant resistance when used for such a purpose; but by means of an incandescent furnace we have been able to secure most favorable results, and to maintain a high temperature for a long period of time.

The present invention consists of the furnace or apparatus by means of which this improved process can be carried out, and the same will be fully described, and then set forth in the claims.

Figure I of the accompanying drawings is a vertical longitudinal section through a retort designed for the reduction of zinc ore according to our process, and Fig. II is a front elevation of the same. Fig. Ill is a perspective view of a furnace adapted to withstand a very high temperature, and Figs. 1V andV are respectively longitudinal and transverse sections of the same. Fig. VI illustrates a modification in the construction of the core.

This retort consists of a cylinder, A, made of silica or other non-conducting material, suitably embedded in a body, B, of powdered charcoal, mineral wool, or of some other material which is not a good conductor of heat. The rear end of the retort-cylinder is closed by means of a carbon plate, 0, which plate forms the positive electrode, and with this plate the positive wire of the electric circuit is connected. The outer end of the retort is closed by means of an inverted graphite crucible, D, to which the negative wire of the electric. circuit is attached. This graphite crucible serves as a plug for closing the end of the retort. It also forms a condensingchamber for the zinc fumes, and it also constitutes the negative electrode. The term electrode is used in this case as designating the terminals of the circuit proper, or that portion of it which acts simply as an electrical conductor, and not with the intention of indicating the ends of a line between which there is no circuit-connection. The circuit between the electrodes, so called, is continuous,being established by means of and through the body of broken carbon contained in the retort A. There is no deposit made on either plate of the decomposed constituents of the material reduced. The mouth of the crucible is closed with a luting of clay, or otherwise, and the opening (I, made in the upper side of the crucible, near its extremity, comes entirely within the retort, and forms a passage for the zinc fumes from the retort-chamber into the condensing-chamber. The pipe E serves as a Vent for the condensingchamber. The zinc ore is mixed with pulverized or granular car bon, and the retort charged nearly full through the front end with the mixture, the plug D being removed for this purpose.

Electric-light carbon is preferably employed to form the incandescent body of the charge, as it possesses the necessary amount of electrical resistance, and is capable of enduring any known degree of heat, when protected from oxygen, without disintegrating or fusing; but crystalline silicon or like material can be employed for the same purpose. A small space is left at the top, as shown. After the plug has been inserted and the joint properly lutcd the electric circuit is closed, and the current allowed to pass'through the retort, traversing its entire length through the body of mixed ore and carbon. The carbon constituents of the mass become incandescent.

generating a very high degree of heat, and being in direct contact with the ore the latter is rapidly and effectually reduced and distilled. The heat evolved reduces the ore and distills the ZlIlC, and the zinc fumes are condensed in the eondcnsingchamber, precisely as in the present method of zinc-making, with this im portant exception, that aside from the reaction produced by heating carbon in the presence of zinc oxide, the electric current in passing through the zinc oxide has a decomposing and disintegrating action upon it, not unlike the effect produced by an electric current in a solution. This action accelerates the reduction and promotes economy in the process.

' It will be observed that the intimate mixture of incandescent carbon and ore affords the most effective utilization of all the heat evolved; none of it is lost by transmission through any intervening bodies or spaces. Moreover, the maximum degree of heat generated by the furnace is within the ore body, and the retort and furnace receive only the heat which is transmitted outward from the ore and carbon contained within; consequently the retort or the furnace is not subjected to the highest degree of heat, as is the case in the Belgian and English methods of zinc-smelt ing, and the life-time of a retort is thus mate rially increased. It is proposed to use a number of these retorts in the same circuit in series or multiple are, as desired.

Another form of furnace embodying our in vcntion is illustrated by Fig. III, which is a perspective view of a furnace adapted for the reduction of ores and salts of non volatile metals and similar chemical compounds. F1 IV and V are longitudinal and transverse sections, respectively, through the same, illustrating the manner of packing and charging the furnace.

The walls and floor L and L of the furnace are made of fire-bricks, and do not necessarily have to be very thick or strong, the heat to which they are subjected not being excessive. Near each end of this fire briek box there are plates M, attached to rods M, which extend through the end walls of the furnace, and have the circuit-wires m attached to their projecting extremities. These plates are preferably made of carbon, as being the material best adapted for this purpose, and for convenience will be designated as carbon plates. These carbon plates are smaller than the cross-section of the box, as shown, and the spaces between them and the end walls are packed with fine charcoal.

The furnace is covered with a removable slab of fireclay, N, which is provided with on 01- more vents, a, for the escaping gases.

The space between the carbon plates constitutes the working part of the furnace. This is lined on the bottom and sides with a packing of fine charcoal, O, or such other material as is both a poor conductor of heat and clectrieityas, for example, in some cases silica or pulverized corundum or well-burned limeand the charge P of ore and broken, granular, or pulverized carbon occupies the center of the box, extending between the carbon plates. A layer of granular charcoal, 0, also covers the harge on the top. The charge thus forms a core extending lengthwise of the box, in contact with the carbon plates M at the ends, and incased on all sides by thejacket of fine charcoal. Fine charcoal, as is well known, is a very poor conductor of heat, and the charcoal packin confines the heat within the core, protects the walls of the furnace, prevents them from fluxing down and miir gling with the charge, thereby introducing deleterious matter, and it forms a dcoxidizingshell for the charge. The protection of the charge from the introduction of deleterious matter by the fluxing down of the walls is a very important matter, and the protection afforded therefrom by the charcoal packing immediately surrounding the charge is complete. It is also a much inferior conductor of clec tricity than the carbon used in the core, and hence it operates as an insulating-jacket for the charge and confines the current to its path through the charge, besides confining the heat. The protection afforded by the charcoal ja ck ct as regards the heat is so complete that, with the covering-slab removed, the hand can be held within a few inches of the exposed charcoaljacket; but with the top coveringof charcoal also removed and the core exposed the hand cannot be held within several feet. The charcoal packing behind the carbon plates is required to confine the heat and to protect them from combustion, as they would be con sumed very rapidly if exposed to the air. As it is, the extremities of the rods M become very hot, and have to be kept cool with wet cloths or otherwise. i

In charging the furnace the-box is first filled with the packing material, and then a trench is dug between the end plates, leaving a wall of charcoal or other material 011 each side, and a floor ofthe same; or the trench may be formed by packing the charcoal in around a patterncore temporarily suspended within the box. The trench is then filled to the top of the plates with a charge of ore and carbon, and covered over with granular charcoal, to allow the es cape of the gases, and the covering-slab put on and luted around the edges. A small space is left between the top of the charcoal and the slab.

It will be observed that the body of ore and carbon is comparatively shallow in depth, and has its longest dimensions in a horizontal. direction. The object of this is to allow the gases evolved during the process of reduction to escape with facility. It has been demonstrated that when a deep and narrow body of ore and resistance material are treated in a furnace the gases generated near the bottom of the charge, being confined by the material above them, which does not sometimes allow them to escape as fast as generated, exert great ICC expansive force, sufficient at times to throw off the top of the furnace, and even to eject part of the charge. WVhen, however, the charge is spread out so as to have comparatively little depth, the gases or vapors readily force a passage to the surface through the interstices of the charge and pass off without acting detrimentally on the charge or furnace. When coarse carbon is employed,fine carbon is mixed with the coarse carbon at the ends of the core, where they abut against the plates M, as indicated at p .p,in order to secure a general contact and prevent an undue heating of the plates. This may be done by sifting fine carbon in between, the, interstices of the coarse carbon, close to the inner faces of the. plates, as the charge is being packed into the, furnace. The same resultmay be accomplished by fiaringthecore out at the ends, making it of larger cross-section 'at the extreme ends than at the center, as illustrated by Fig. VI, so as to make more points of contact between the carbon particles of the core and the plates than would otherwise be made. In either case there are a larger number of points of contact between the particles of carbon in a cross-section of the core taken at the ends close to the plates than in a cross-section taken at the middle part of the core, and hence the resistance is less at the ends, and less heat is there generated.

The electric current is now turned on, and the reduction of the ore takes place. The liberated gases escape through the vent-holes a, and burn with great vigor. The changes that take place in the appearance of the flames as the reduction progresses afford a means of determining when the reduction is complete. The reduced metal is found, at the close of the operation, filling the interstices between the particles of carbon mixed with it, and plated, as it were, onto the same; and when the carbon is very coarse it works down through it and collects in the bottom of the charge on the charcoal floor.

\Vith this furnace aluminium can be reduced direct from its ores,and chemical compounds from corundum, cryolite, clay, 820., and silicon, boron, calcium, manganese, magnesium, and other metals are in like manner obtained from their ores and compounds. The reduction of ores according to this process can be practiced, if circumstances require it,without any built furnace. For example, a floor of charcoal can be prepared, the carbon plates set upon it at the proper distance apart, with the circuit-wires attached thereto, the charge packed in between the carbon plates, and the whole covered over with charcoal, and on top of all earth. The mound thus formed will be not unlike a heap for burning charcoal in external appearance.

\Ve do not herein claim the method of conducting metallurgical operations above described, as the same forms the subject-matter of a prior application, filed December 24, 1884.

We are aware of the existence of a carbonizing apparatus consisting of a muffle or case adapted to contain a filling of pulverized carbon,in which the articles to be carbonized are embedded,and provided with an electrode at each end,to which the wires of an electric circuit are connected, one of the electrodes having a movement lengthwise of the muiile, to preserve the contact between the electrodes and the contents of the muffle as the carbonization progresses. In such apparatus the muffle stands in a vertical position,and the movable electrode fits the same in such a manner that it can descend by its own weight, and space is left between it and the walls of the muffle. An apparatus thus constructed is not adapted for the reduction or smelting of metals, since it lacks some of the essential rcquisites fully set forth in the foregoing description of our apparatus.

We also are aware that an electric heatingfurnace has been devised in which the walls of a vertical chamber are lined with a solid electrical resistance material and provided with oppositely-located electrodes of graphite, to which the wires of an electric circuit are connected. Such chamber is accessible through a top lid,and is designed to receive a crucible containing the material to be fused. In such apparatus it is the lining of the chamber that is heated by the electric current, and there is no provision for the escape of gases that would be evolved if metallurgical operations were performed therein, and hence it is not adapted for the reduction of metals, which is the chief aim and object of our invention; but

WVhat we do claim as our invention, and desire to secure by Letters Patent, is-

1. In an electric smelting or reducing apparatus, a chamber or casing having its long est dimension in a horizontal direction, and adapted to contain a charge of ore and electrical resistance material previously pulverized and mixed together, the oppositely-located. electrodes in conductive relation to the charge, but otherwise insulated from one another, and an exit for the escape of the gases and vapors evolved from the charge during the process of reduction, substantially as herein set forth.

2. In an electric smelting or reducing apparatus, the smelting-chamber formed of side and bottom walls of closely-packed pulverized or granular material and the permeable top wall formed of a layer of granular non-heatconducting material, and the electrodes opposiiely located at the ends of the core or smelting chamber, substantially as herein set forth.

3. In an electric smelting or reducing furnace, the combination of a chamber or casing, the side and bottom layers of closely-packed pulverized or granular material, and the top covering of similar material, made permeable for the escape of gases and vapors, with the electrodes oppositely located at the ends of the chamber or casing and surrounded by the packing or filling which incloses a charge of carbon and ore, substantially as herein set forth.

4. In an electric smelting or reducing apparatus,a smelting-chamber formed of closelypacked granular or pulverized material of a nonheat-conducting nature and of lesser elec trical conductivity than the charge to be smelted in the furnace, with two electrodes arranged at the opposite ends of said chamher, for conducting the electricity to the said charge, substantially as herein set forth.

5, In an electric furnace, a body or core of pulverized, granular, or broken resistance ma terial interposed between two electrode-plates, substantially as described, having a greater number of points of contact in a cross-section of the body taken close to the plates than in a crosssection of the same taken at intermediate parts thereof, whereby there is less resistance and consequently less heat at the ends of the core than at other parts thereof.

6. In an electric furnace, a body or core of pulverized, granular, or broken resistance material interposed between two electrode-plates, substantially as described, with fine carbon filling the spaces between the particles of coarse carbon at the ends only of the core abutting against the plates, whereby there is less resistance and consequently less heat at the ends of the core than at other parts thereof.

7. In an electric smelting or reducing apparatus, a smelting-chamber formed of closelypacked pulverized material of 'non-heat-conducting nature and oflesser electrical conductivity than the charge to be smelted within it, a layer of similar material, permeable for the escape of gas,forclosing the said chamber,

and two electrodes arranged at the opposite ends of the said chamber, for conducting electricity to the charge, substantially asset forth.

In testimony whereof we affix our signatures in presence of two witnesses.

EUGENE H. OOW'LES.

ALFRED H. OOW'LES, \Vitnesses:

EDWIN COWLES, E. H. PERDUE.