US1134817A - Electric furnace. - Google Patents

Description

J. W. BROWN. ELECTRIC FURNACE.

APPLICATION FILED JAN-8, 1912.

PatentedApr. 6, 1915 INVENTOR trod/V BRam N BY W T SSES ATTORNEY I Cuyahoga,

vented new and useful Improvements in Electric Furnaces, of which the following IS electric furnaces in use,

I: required to .produce high temperatures, on account of carbon having'a negative tem- 50 furnace are JOHN W. BROWN, LAKEWOOD, OHIO,

OF CLEVELAND, OHIO, A

AssIGNon r o NATIONAL CARBON COMPANY, CORPORATION or NEW JERSEY.

ELECTRIC FURNACE.

Application filed January 8, 1912. Serial o. 670,070.

To all whom it may concern:

Be it known that I, YJOHN W. BROWN, a resident of Lakewood, in the county of in the State of Ohio, have ina clear and exact description. This invention relates to an electric arc furnace of the continuous type, and 1s espe- 1' cially adapted to the calcination of carbon and to the manufacture of graphite. This type of furnace, however, is adapted to the heating of all granular or pulverized ma- 7 terial that will flow freely therethrough.

At present there are two general typesof one in which the current .is sent through the body of the material to be-treated, or is sent through a resistor surroundedby the material, and

20 another in which the material is treated by heat radiating from an electric-arc. When the current is sent through a resistor, or "through the charge itself a large current 15 perature coefficient of resistance, certain parts of the charge may carry nearly all the current. In an arc furnace however, intense temperatures can readily be produced with small currents and the heating zone can not shift. Hence, when a uniforml heated product is desired an arc type of urnace is sometimes .preferable.

Other advantages will appear in the followin descri tionarticular reference g P P being had'to'f the drawings in which:

Figure 1 represents a sectional elevation of a type of furnace in which the electrodes are incased in a carbon box at right angles to the 2 line of movement of the charge. Fig. 2 is a sectional elevation of a modified type in which the electrodes are parellel to the line of movement of the charge. Fig. 3 is a sectional elevation of the electric'heating zone of another modified type of furnace. Fig.

4 is a sectional elevation of the electric heating region. of another modified type of furnace. I

Referring to Fig. 1, the outer walls of the denoted by 1, and may be composed of firebrick or any other heat insulating material. Inside of the furnace there is a channel 2 preferably composed of car bon. If only temperatures below thatof graphitization are to be reached in the fur- Speciflcation of Letters Patent;

Patented Apr. 6, 1915.

nace the inner walls or channel need not be made of carbon, but may be made of carborundum or firebrick. The cross-section of this furnace islpreferably circular, although it may be rectangular or in the shape of any polygon. A cover 3 rests on the outer walls 1, and closes the furnace at the top. A conveyer 4: feeds'material in at the top and the conveyers5, 6 and 7 move it out at the base of the furnace. Extending through the furnace is a box-like part 8 formed of carbon. Within this box-like member the electrodes 9 extend from each side of the furnace. Theelectrodes are removed a short distance from each other so that an arc is produced. These electrodes are formed of carbon and are to be connected to any source of E. M. F. either direct or alternating, single or polyphase.

In operation the furnace works as follows: Material is fed in at the top by conveyer 4., and part of it passes down the central channel in'closed by the walls 2. When it reaches the neighborhood of the electric arc it becomes intensely heated and is converted into graphite, and passes down through the furnace and is removed by the conveyer 6. charge brought in by the conveyer'4: passes down the space between the outer wall 1 and the inner wall 2, and receives the heat radiating from the hot material inside the channel 2 in the region of the electric arc,

The remaining part of the,

and also receives heat from the material,

or it can be taken out into the air and used 7 for commercial purposes. Carbon baked to a temperature below that of graphitization is useful for various purposes. Itfmay be advisable to, put water pipes 10 throughout the lower part of the furnace to cool the graphite and the material in the outer channel.

Fig. 1 is shown'broken awayabove and below the electric heating region, but this is only for the purposes of illustration. It will be understood that the electric furnace will be built of a height depending upon circumstances.

From an inspection of the drawing it will be apparent that all of the heat radiating from the electric arc passes into the material in the central channel, excepting that portion that may radiate through the space between the carbon casing 8 and the electrodes 9, in a direction parallel with the electrodes. The outer ends of this box may be closed by silicon carbid or any other heat resisting material that is a nonconductor of electricity. It will thus be seen that the electric furnace will be very efiicient, and by controlling the conveyers 4, 5, 6 and 7 the material can be passed through the furnace at any desired rate so that the temperature within the furnace will be under control of the operator in chargeof the furnace.

Fig. 2 shows another type of furnace in which the electrodes are in a'vertical position. The outer walls 1 may be made of firebrick or any other heat insulating material. Inside of the furnace there is a carbon channel 11, extending down from the electric heating region to the base of the furnace and another channel 12 extending from the electric heating region to the top of the furnace. One electrode 13 extends through the furnace cover 3 and the channel 12, while the other electrode extends through to the center of the furnace and then upward axially of the furnace so that an are between the two electrodes can be drawn. The lower electrode has the form of a right angle and is preferably screwed together or they may be fastened together in any other well known way.

The material is fed in at the top of the furnace and is removed from the bottom of the furnace by screw conveyers as in Fig. 1.

The operation of the furnace is as followsz The material brought in by the upper con- ,veyer passes down the channel between the outer walls 1 and the inner channel 12, until it gets to the end of the latter channel, where part of it will pass into the channel 11 and be removed by the conveyer 6. The other part will pass down the space between the outer walls 1 and the channel 11, and be re moved by the conveyers 5 and 7 The material that flows through the channel 11 will pass in close proximity to the electric arc and will be intensely heated in a very short time so that graphitiz'ation will take place. Channel ll'can be made of small diameter so that practically all the material that passes therethrough will be quickly heated to substantially the same temperature so that the product willv be uniform. The material that passes between the walls 1 and the channel 11 will be heated by radiation from the hot graphite in the vicinity of the arc, and also by the graphite in the region below the electric heating zone and the conveyer 6. 1t

' desired height.

will be evident that the material outside of the channel 11 will cool the graphite at the same time that it is itself heated so that two purposes are served. Also water pipes may be run through the lower part of the furnace to cool the two materials to any temperature desired.

By regulating the screw conveyers the material can be fed in and taken out at any desired speed and it can be passed through the two channels at the same rate or at different rates by controlling the individual conveyers at the bottom of the furnace. Thu's material may be taken down very slowly through the channel 11 and at a greater rate through the outside channel or vice-verse. All this would be under the control of the furnace operator.

The material fiowingpast the electric arc would assume a definite angle depending upon the coefiicient of frictionof the carbon particles on each other/ upper electrode 13 it may be kept out of the furnace charge itself so that the charge will not conduct the current. This can also be controlled by adjusting the member 12 through the cover 3.

If the charge used has a considerable proportion of ash, the carbon channel 12 will serve another useful purpose. The ash will be volatilized by the heat of the arc and will condense in the channel and adhere thereto. It is not desirable to permit the ash to condense in the descending charge for it would then become more and more contaminated and the furnace would eventually be clogged up. -The channel .12 can be taken out at periods to remove the condensed material.

In Fig. 3 is shown only a section of a furnace in the electric heating zone. It will be understood that this furnace will be equipped with the conveyers at the top and bottom as in the furnace shown in Figs. 1 and 2, and that the furnace may be of any Extending through the outer walls 1 are two or more cases 16 which may be formed of carbon towithstand the intense heat of the electric arc. Within these cases the electrodes 17 and 18 are placed so that an arc can be formed in the center of the furnace. These electrodes are supported in any manner, not shown, and can be adjusted asthey are consumed. The outer ends of the cases may be closed by firebrick 16' or any other heat insulating material that is a non-conductor of electricity. A water jacket may also be used to cool the outer ends of the is an outercarbon channel formed of a cylindrical section 19 which extends to the base of the furnace. On top of this cylindrical section is placed a funnel shaped sec- Ahove this is shaped carbon tion 20 also made of carbon. placed an inverted funnel By adjusting the electrodes. There I 'or may extend through the member to bear upon lugs in the wall 1 This is to furnish a support for the member 26 without impeding the progress of the materials flowing down between the channel 19 and 24. Above the arc is placedanother funnel shaped member 28 which has no opening at the top. This member rests on the, carbon cases 16 and also has legs 29 which bear upon the member 25 to support it. The 'operation of this type of furnace will be as follows: The material fed in at the top of .the furnace will descend until it reaches the line 30 where'part of it will proceed through the opening in the member 26. This part will spread out around over the cone shaped member 28 and flow between the supports down below the electric arc assumin the natural slant depending upon the coe cient of friction of the particles on each other,

and then on down into the channel 24 where it is-withdrawn by a conveyer. The material descending through this route may be converted into graphite due to its being in close proximity to the electric arc, or carbon baked at any temperature below that of 'graphitization may be obtained, however, by controlling the rate of flow of the material.

Part of the material in the region of the line 30 will pass outside of the member 26 and inside of member 21 and descend between members 25 and 20, and 24 and 19. The material will not be substantially impeded by the legs 27 in traveling this route. This material will not be heated directly by the heat of the electric arc. However, it will absorb the;- heat radiating throng the member 28 and member 26, and also, y the heat radiating through the charge 1n the members 25 and 24. It will be finally withdrawn from the bottom of the furnace by another conveyer.

Another part of the materlal leavmg the line 30 will pass outside of the member 21 and will flow between the supports or legs 23 and 22; and then flow between the outer walls 1 and the channel 19. Itwill beheated by the heat radiating through the ad acent inner charge and will be removed at the bottom' ofthe furnace by "a separate'com.

veyer. From the foregoing it will beevident that a material heated to a very high temperature can be taken from the channel;

It is evident that there will be very littleheat lost in'this type of furnace and hence it Wlll be more eflicient than the usual types of electric furnaces.

Fig. 4 shows a portion of an electric furnace 1n the region of" the electric arc. In

this type of furnace the electrodes extend in a direction'parallel with the axis of the furnace, as in Fig. 2. The members 25, 26, and 29 are shaped similar to those of Fig. 3, and have been similarly numbered. These will not need further description. Within the member 26 and above the region ofthe electric arc is a funnel shaped member 31 formed ofcarbon. This member may be supported at various points in its circumference by legs which extend to the member 25 as in Fig.- 3. On top of this member 31 rests a tubular member 32 extending to the top of the furnace. The electrode 13 extends through the tubular member 32. The electrode 14 extends into the furnace as in Fig. 2. Between these two electrodes the arc is formed. A baflie'member 33 is supported above the arc in any appropriate manner asby the electrode 13 or by legs, not shown, -which extend from 1 various points of its circumference to rest upon the member 25. In the latter case the electrode 13 would pass freely through it and not contact therewith. In operation the mate rial would pass within themember 26 andspread out over the cone shaped member 31 and flow with its natural slant over the member 25 'and pass down member 24. The heat of the arc will radiate directly into'the charge in the neighborhood of the natural slant referred to, and may convert it into graphite. The baflie member 33 is'for intercepting heat rays and reflecting them onto the material below. Any heat radiating through the baflie and the member 31 will be intercepted by, the material and hence it will be preliminarily heated before it has passed into the region of the electric arc, The space above the bafiie member also servesas a condenser to condense the volatile materials arising from the heating zone. The modification shown in Fig. 4 could be used alone in which case it would be surrounded by the desired thickness of firebrick, or it may be used as in.Fig. 3, being surrounded by the descending charges which tially vertical, and means for removing the tamer AVAlLAELfi COPY &

absorb the heat radiating through it. By controlling the rate of flow, the material in channel 24 of Fig. 4 may be heated to anytemperature below that of the electric arc. In Figs. 3 and 4 the various carbon channels, as 24, 25 and 26, for instance, canbe formed and united in any way, or these members may be formed or pressed into an integral part or they may be pressed or formed into two or more vertical sections which placed together will form the channel. In the arrangements shown inFigs. 2 and 4, the lower electrode may be dispensed with and the are formed between the upper electrode and thecharge itself. One terminal could then be connected to the channels 11 and 24 respectively. The current after leaving the arc would then travel through the charge to the carbon channel. This would furnish a resistance to steady the arc. However, if the resistance is too great to maintain an arc the lower electrode may be made short so that it will not quite reach to thesurface of the charge.

Having described my invention, what I claim is:

1. In an electric arc furnace having stationary walls, electrodes for producing an electric are one of which is insulated from the furnace charge and means whereby the furnace charge is caused to descend past the are on all of its sides.

2. In an electric arc furnace, inclosing walls, electrodes for producing an arc, and

means for removing the treated charge be-. low the electrodes whereby the charge is caused to descend past the are on all of its' sides. 1

3. In an electric arc furnace, inclosing walls, an upper and a lower electrode for producing an are one of which is substantreated charge from below the lower electrode.

l. In an electric arc furnace, an upper and a lower electrode, a condensing chamber surrounding the upper electrode for condensing volatile matter arising from the heated charge and means whereby the charge is caused to descend around. the

. chamber and tne lower electrode.

In an electric arc furnace, an upper electrode insulated from the charge and a lower electrode, a condensing chamber surrounding the upper electrode and means, whereby the charge is caused to descend around the chamber and the lower electrode.

6. In an electric arc'furnace, an upper and a lower electrode, means surrounding said upper electrode to space it from the charge, said means also to condense volatile matter arising from the charge and means whereby the charge is caused to descend around the chamber and the lower electrode.

7. In an electric arc furnace, inclosing walls, a channel extending downward within the walls, a lower electrode, an upper electrode extending through the said channel and means whereby the charge is caused to descend around electrode.

the channel and the lower.

. 8. In an electric arc furnace, inclosing H walls, a channel extending downward within the walls, an upper electrode extending through the channel, a lower electrode and means whereby the charge iscaused to descend around the channel and the lower f an arc and means'for causing part of the furnace charge to pass between the outer walls and the channel, and part to pass through the channel. I

11. In an electric arc furnace, outer walls, inner walls, electrodes for producing an are within the inner walls, means for feeding the, charge into the furnace and means for causing the charge to flow in the two channels formed by said walls. I

12. In an electric arc furnace, outer walls,

' an inner channel extending downward within the said walls, an electrode extending through said channel, a second electrode, a, second channel surrounding said second electrode'andmeans to'cause part of the furnace charge to pass adjacent the arc and downward through the second channel and part to pass between the second channel.

13. In an electric arc furnace, outer walls, an electrode extending downward within said walls, a sec'ondelect'rode, a channel surrounding said second electrode and means the outer walls and .for condensing volatile matters arising from the heated charge, and means to cause the charge to How part'through'the said channeland part between the channel and the outer walls. I

In testimony whereof signed name.

I have hereunto JOHN w. BROWN.

Witnesses:

F. D. LAURENCE, R. W. HANEY.

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