US1675744A - Shaft-type electric furnace - Google Patents

Description

July 3, 1928.

4 Sheets-Sheet 1 T. F. BAlLY SHAFT TYPE ELECTRIC FURNACE F'lled July 19, 1927 5v Gnome July- 3, 1928.

- 1, 75,744 T. F. BAILY "SHAFT TYPE ELECTRIC FURNACE Filed July 19, 1927 4 Sheets-Sheet 2 lnom July 3, 1928.

T. F. BAILY SHAFT TYPE ELECTRIC FURNACE Filed July 19, 1927 4 Sheets-Sheet womtoz T 1 7 Baily a 6 b a a 1 aw July 3, 1928. v 1,675,744

T. F. BAILY SHAFT TYPE ELECTRIC FURNACE Filed July 19, 1927 4 Shets-Sheet 4 Ti? Bai /y Patented July 1928. v

PATENT OFFICE.

THADDE'US I. BAILY, OF ALLIANCE, OHIO.

SHAFT-TYPE ELECTRIC FURNACE.

Application filed July 19,

The invention relates to furnaces of the shaft type, and more particularly to electric furnaces of this general character in which an electrode is located at each end of the furnace, the charge forming a resistor between the electrodes to maintain the de-' sired temperature within the furnace.

The object. of the improvement is to provide a shaft type furnace arranged to be 1 charged at its upper end. the charge passing downward through the furnace to be discharged at the lower end, an electrode being located at each end of the furnace and the charge normally filling the entire furnace between the electrodes, forming a resistance through the charge between the electrodes for developing heat within the furnace; means being provided whereby. when working charges which in the re-action create a combustible gas, this gas may be bu'rned for preheating the charge before it enters the furnace shaft.

The improved apparatus, with slight modification. is adapted for the manufacture of synthetic pig iron, producing flake graphite as a by-product; for producing silicon direct from siO for producing silicon carbide from SiO and carbon; and for producing amorphous graphite from amorphous carbon.

The above and other objects may be attained by providing a vertical shaft type furnace having an electrode at its upper end and an electrode at its lower end, one or both of which electrodes may be in the form a ring through which-the charge passes, the charge which in some cases may be amorphous carbon substantially filling the shaft between the electrodes, whereby resistance is created through the charge to maintainthe desired furnace temperature.

Where it is desired to utilize the waste combustible gas from the re-action for preheating the charge, this waste gas may be taken off at the-top of the shaft and admitted to a preheating chamber, preferabl of the inclined rotary type, through whic the charge is passed for preheating before entering the shaft.

Various embodiments of the improved furnace are illustrated in the accompanying drawings, in which 1827. Serial K0. 806,885.

Figure 1 is a vertical sectional view through the improved furnace adapted for the manufacture of synthetic i iron from scrap and so arranged that aie graphite may be produced as a by-product;

igure 2, a similar view showing an adaptation of the improved furnace for the manufacture of silicon;

Fig. 3, a similar view showing the furnace adapted for the manufacture of silicon carbide, and

.Fig. 4, a vertical sectional view through the furnace adapted for the production of {:gnorphous graphite from amorphous car- Similar numerals refer to similar parts throughout the drawings.

Referring first to the form of the furnace illustrated in Fig. 1, it will be noted that a shaft type furnace is provided adapted to be charged with amorphous carbon such as coke, the scrap being melted in the to of the shaft and passed downward througi the coke and being discharged at the lower end of the shaft into suitable molds for casting pig iron, or into a ladle or the like.

By superheating the molten iron, as t passes through the coke, a su lus amount of carbon will be picked u y the iron which, upon cooling, will from the bath, in the form of flake graphite, thus producing the graphite as a by-product of the operation.

In this form of the furnace, the apparatus comprises broadly the melting chamber 1 communicating with the upper end of the shaft 2, the lower end of which communicates with the crucible 3.

The melting chamber may comprise the steel shell 4, supported in any suitable manner as by the structure including the I-beams 5 and standards 6. I

This melting chamber may be lined with thrown off any suitable material, such as fire brick, 7

shown at 7, and provided in its lower ortion with the linin 8, of carbon or the iike.

The roof 9, of t e melting chamber, may also be lined with fire brick, or the like, indicated at 10, and one or more electrodes 11 ma be su ported from the shell by brackets, sue as siiown at 12, and arranged to be vertically adjusted, within the melting chamber, as by the apparatus indicated generally at 13. v

The roof'has the central charging opening 14 through which scrap iron or other material to be melted may be continuously or intermittently charged into the melting chamber.

The shaft 2 is located beneath and ,communicates at its upper end with the lower open end of the melting chamber. This shaft comprises the steel shell 15, which may be lined with silicon carbide, or the like, as shown at 16.

The lower end of the shaft opens into the crucible 3, which may be provided with the steel shell 17 mounted upon the I-beams 18, sugported'from the uprights 6, and is provi ed with a lining 18, of fire brick or the like, and preferably has the discharge spout 19 at its lower end.

An electrode 20 extends up through the bottom of the crucible and is connected, as by the cable 21, with the three-phase circuit in which the upper electrodes 11 are also located.

In operating the furnace, to produce pig iron, the crucible, shaft and melting chamber are filled with amorphous carbon, which may be in the form of lump coke as indicated at 22, to a point slightly spaced below the upper electrodes. 11. i

Scrap iron is then charged through the.

charging opening 14 of the roof, upon the top of the bed of coke, and an arc will be produced between the scrap iron and the upper electrodes 11, rapidly melting the scrap down. As the iron melts it will trickle down through the coke and into the crucible.

The entire mass of coke, together with the scrap iron which is charged into the furnace, will form a resistor between the upper and lower electrodes, maintaining a high temperature throughout the stack and crucible as well as in the melting chamber,

thus keeping the metal molten as it passes downward through the furnace, after being melted by the.arc in the melting cham- When themetal has started to melt, the charging of scrap in the melting chamber will be substantially continuous and a continuous stream of molten iron will pour from the discharge spout.

A ladle or the like may be provided below the spout 19 to'receive the stream of molten metal, or the molten stream may be run directly into pig molds.

If it is desired to produce graphite, as a by-product of the iron, it is only necessary to run the furnace at a higher temperature, thus causing the molten iron to absorb a larger ercent of carbon from the coke charge in the furnace.

The molten stream of iron would then .be run from the discharge spout 19 into a ladle or the like and in cooling, the surplus carbon would be thrown out of the: bath, in

the form of flake graphite.

To compensate for the loss of carbon absorbed in the molten iron, carbon may be charged with the scrap iron from time to time.

. In Fig. 2. is illustrated an adaption of the veying waste combustible gases from the,

shaft into the preheating furnace. The rotary furnace comprises a cylindrical shell 28, which may be lined with beaux-- ite brick, as indicated at 29, and is mounted in a position slightly inclined from the hOllzontal as illustrated, being preferably provided with the rings 30 which rest upon the rollers 31. i

A ring gear 32 may be provided around the shell and .meshed with a pinion 33, driven from any suitable source ofpower, to

continuously rotate the preheating furnace at the desired speed.

A feed hopper 34 is supported upon any suitable structure as indicated at 35, and extends into the upper end of the rotary furnace.

When making silicon, SiO and carbon, in the proper proportions may be charged into the hopper 34, the carbon preferably being in the form of coke in fairly large lumps.

If desired, the SiO may be charged into the hopper while the coke may be charged directly into the-upper end of the shaft 26 by means of a bell hopper or the like.

When making ferro-silicon, either scrap iron or iron ore, in the desired proportions, may be charged into the hopper 34 with the Sic) and carbon. v

The shaft 26 comprises the vertical cylindrical steelshell 37, which may be lined'iwith beauxite brick,.' or the like, indicated at 38. This shell is supported above the floor level, as by the uprights 39', the upper end of the shell being supported by the structure, .in-

43 leading to one side of an electric circuit.

This clamp is preferably water cooled, as in-; dicated at 44, in order to compensate for the high temperature at which the electrode is necessarily operated.

An electrode 45 is located up through the lower end of the shaft and may be surrounded by the carbon ring 46, forming, with the electrode, the bottom of the interior of the shaft.

This lower electrode is provided with a clamp 47 for the purpose of connecting the same tow a cable 48 located in the other side of the electric circuit above referred to. A discharge spout 49 is provided in the lower end of the shaft.

In operating the furnace, the interior of the shaft is first filled with amorphous carbon, which may be in the form of lumps of coke, as indicated at 50, this coke extending from the lower electrode up through the upper electrode, thus forming a resistance element whereby the interior of the-shaft may be maintained at high temperature.

At the upper end of the shaft the hood 27 is provided, the lower end of the rotary furnace extending into said hood. This hood may comprise the steel shell 51, having a 'linlng 52 of any suitable insulation material. A pipe 53 may be located through the hood 27 and into the lower open end of the rotary furnace for furnishing air for combustion.

In operating the furnace to produce silicon, the rotary furnace may be charged with SiO and carbon as above described and the same may be initially melted by inserting a gas or oil burner into the rotary furnace.

The melted silica, with the coke floating thereon, will be continuously poured from the lower end of the rotary furnace through the annular electrode 41 and into the mass of coke in the shaft furnace.

This mass of coke in the shaft furnace will be heated by forming a resistance between the electrodes and will be maintained in an incandescent state, permitting the molten silica to trickle down through the same.

- v This molten silica will absorb carbon from the coke charge and will pass from the discharge spout 49 in a more or less continuous stream in the form of silicon.

If it is desired to produce ferro-sil'icon,

either ore or scrap iron in suitable quantities in the rotary furnace, thus making it unnecessary to continue the gas or oil burner after the reaction in the electric furnace has started.

An adaptation of the improved furnace to the production of silicon carbide is illustrated in Fig. 3. In this form of the furnace the rotary furnace 25, hood 27 and feed hopper 34 may be all as above described and as illustrated in Fig. 2.

The shaft 26 comprises the metal shell 37, having a suitable refractory lining 38 within which is located a carbon tube 38", it being preferable to locate a layer of lamp black between the carbon tube and the reend of the shaft and contacts with the lower end of the carbon tube, whereby at least a portion of the current passes through the carbon tube between the electrodes, producing a resistance. Each of the electrodes is connected by a cable 53 to an electric circuit.

In operating the furnace to produce silicon carbide, SiO and carbon, preferably in the form of crushed coke, would be charged in the rotary preheating furnace in about the proportions of one to .three.

This mixture may be initially heated to about 3000 F. to 3200 F. in the rotary furnace either by inserting a gas or oil burner or it may be initially heated by operating the electric shaft furnace.

This mixture of preheated SiO and carbon will be continuously fed from the rotary furnace into the shaft where it will be sub jected to approximately 3600 F.

The mass will form a more or less solid core whichwill slowly feed downward within the carbon tube, a portion at least of the current pasiing through this niass which becomes an electric resistance element.

This action will continue until the lower end of the core passes down through the lower annular electrode 45 and protrudes below the bottom of the shaft, in the form of a core of silicon carbide which may bebroken off from time to time and removed in order to not interfere with the continuous process.

In this case, as well as in the furnace for the production of silicon, the combustible gases generated by the reaction in the electric furnace will pass up through the hood and into the rotary furnace where they will be burned for preheating.

In Fig. 4 1s illustrated a modification of the furnace best adapted for the production of amorphous graphite from amorphous car bon. The shaft comprises the metal shell 55 lined with silicon carbide or the like as shown at 56.

This shaft is open at its upper and lower ends both and provided with the upper and These electrodes are connected, as by the cables 59, to an electric circuit whereby the coke charge shown generally at when entirely filling the shaft will act as a resistance element carrying the current between the electrodes. V

A rotary discharge hearth 61, preferably of substantially conical shape as illustrated, is located at the lower open end of the shaft and may be rotated in any suitable manner as by the gear 62 and pinion 63.

In operating the furnace to roduce amorphous graphite, the'shaft is fil ed with amorphous'carbon preferably in the form of finely pressed coke.

As this mass of coke contacts with both of the elect.rodes,the coke .will form aresistor between the electrodes, being maintained in an incandescent condition and preferably at a temperature of from 3600 to 5000 degrees F.

New coke is continually charged in the upper open end of the shaft while the amen phous graphite produced by the action of the furnace will be continuously fed out of i the lower end of the shaft by means of the rotary hearth.

From the above it wilibe seen that in each instance a vertical shaft'furnace is rovided with electrodes at opposite ends of t e shaft, means being provided for charging the shaft at its upper end and discharging at the lower end thereof, the charge contactin with both electrodes and forming a resistance element for producing the desired temperature in the furnace.

It should be understood that where the shaft is referred to throughout the specification and claims, this shaft need not be of the same hei ht or proportion as illustrated in the drawings but-need only be of suficient size to accommodate a proper amount of carbonaceous material to produce the results as described in the specification.

I claim:

1. A shaft type resistance furnace having an electrode at each end and a loose carbonaceous resistor within the furnace extending from one electrode to the other and means for melting a charge of material and passing the molten material downward through the carbonaceous resistor.

2. A shaft type resistance furnace having an electrode at each end and a loose carbonaceous material within the furnace adapted to carrycurrent between the electrodes and means for melting a charge of material and passing the molten material downward through the carbonaceous resistor.

ara-r44 *resistor within the furnace extending from .one electrode to the other and means for operating the upper portion of the furnace as an arc furnace and the lower portion as a resistance furnace for melting material in the upper portion of 'the furnace and passing the molten material downward through the carbonaceous resistor.

4. A furnace comprising an arc type melting chamber and a vertical resistance type electrically heated shaft below and communicating therewith, the shaft "containing loose carbonaceous resistance material through which material melted in the melting chamber is adapted topass.

5. Ashaft type resistance furnace having an electrode at each end, a loose carbonaceous resistance material within the furnace extending from one electrode to the other, a charging opening at the top of the furnace and a discharge opening at the bottom whereby material may be melted and continuously fed downward through the carbonaceous, resistance material.

6. In combination, an arc type melting furnace, and a resistance type reduction furnace communicating at its upper end with the lower end of the arc furnace and-having a loose carbonaceous resistor through which material melted in the melting furnace is passed.

7. A shaft type resistance furnace having an electrode at each end and a loose carbonaceous resistor between the electrode and means for operating the upper portion of the furnace as an arc furnace and the lower portion as a resistance furnace for melting material in the upper portion of the furnace and passing the molten material downward through the carbonaceous resistor.

8. A shaft type furnace having an electrode at each end. a loose carbonaceous resistor within the furnace between the electrodes and means for melting a charge of material at the upper portion of the furnace and passing the molten charge downward have hereunto. subscribed my name.

THADDEUS F. BAILY.

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