US1004924A - Electric-resistance furnace. - Google Patents

Description

W. A. SMITH. ELECTRIC RESISTANCE FURNACE. I ABIPLIOATION FILED DEC. 20, 1910. RENEWED AUG. 12, 1911. 1,004,924.

Patented Oct. 3, 1911 UNITED STATES-PATENT. orator.

WILLIAM ACHESON' sMrrrr, or NIAGARA name, new roux; AssrGNoR To INTERNA- rIonAL-Ac EsoN GRAPHITE COMPANY, or NIAGARA FALLS, NEW YORK. I

. nnncrmc-nnsrsranonrunniion.

Sp'ecificatio n of Letters Petent. Patented Oct, 3,1911,

Application filed December 20, 1910, Seria1 No..598,3G1. Renewed August 12, 1911. Serial No. 645,779.

. To all whom it may concern:

Be it known that I, WIL AM AoHnsoN' SMITH,- a citizen of the United States, 'residing at Niagara Falls, in the county of Niagain and State of New York, have invented certainnw and useful Improvements in I Electric-Resistance Furnaces, of which the I followingisa specification.

This invention relates to electric resistance furnaces, the object of the invention being the provision of a-furnace of this type whichshall be. capable of continuous or 'substan tially continuous operation for the treatment of such charges as do not undergo a substantial reduction'of bulk as a result of the heating operation; An exampleof a charge of this character is'carbonin its commercial forms, such as gas-coke, petroleum coke', an-

thracite coal, etc.,' which when heated undergoes a series of successive modifications dependentynot only uponthe temperature but upon the duration of the heat treatment,

without however undergoing any marked. change n bulk such as ischaracterlsticofmost meta lurgi'cal or reducing operations. For example moderate heating or heating for a briefperiod to a high temperature, results in the expulsion of volatile hydrocarbons; by longer heating at sutiicient temperatures suchiinpurit-ies'as silica, alumina, lime, oxids of iron, etc., are' driven off, and the carbon undergoes a progressive increase in density and electrical conductivity and becomes polyinerized, and maybe converted ultimately. into graphite. I

For many industrial uses, as. for example electrode compositions, battery fillers, etc., a

close adjustment of time and temperature'is required to convert a given raw material into a product of the desired character; and for the performance ofoperations of this kind the'intennittently-operated furnace. is always employed in practice. In all cases where it has beeii sought to render the operation of electrically heating carbon con-' tinuous, so far as I ain'aware, the electric current has been caused to traverse the body of the carbon or carbonaceous material constituting the charge, in a direction'transverse to the direction of movement of the charge, that is to say, either at right angles or in other angular relation thereto, there, .sult.in all cases being that the charge fails to. receive the I prolonged treatment under substantially uniform temperature conditions which is essential to securing the best re- 'sults, whether the object'be to. shrink, purify, polymerize or graphitize the charge.

A furthendefectofprioroperations in' for the purposes in am; The conductivity .of carbon increases with the temperature,

and the current tends therefore to follow indirect and irregular paths which include the more highly heated portions of the charge. For the same reason there is a strong tend- -ency forthecurrent tofollow restricted paths between the electrodes witlifthe result that whereas a portionof the carbon vmay be heated to an unc0ntrollably high temperature, other portions thereof traverse the furnace without adequate or proper. heating, The resulting lack of uniformity in the product renders it quite unsuitable for any technical use.

In the furnace which forms the subject? matter of the present invention the electric current for heating is passed either through the body of the charge as a resistor, or'

wholly or in part through a resitenindependent of the charge, between terminals 'whichare comparatively widely spaced ;.'and

the charge is progressively advanced either continuously or intermittently, in a direction a which is substantially parallel to the lines of flow of the electric current. In this way the charge may be subjected for such period v as may be desired, depending upon the, rate of advance of the charge, to substantially uniform temperature conditions; and it is 'found that by controlling the factors of time and temperature the desired product may be obtained with certainty and uniformity. This principle may be carried into effect in various wa s, it being essential in all cases that such ocalization of t-he current as would result-1n uneven or irregular heating should be avoided.

Certain forms of apparatus embodying the invent-ion are shown in the accompanying drawing, wherein: [F gure 1 1s a central vertical section of ing means may lip axially of the furnace by the discharge device,

one form of electric furnace; and Fig. 2 is a slmilar view of a slightly modified construction.

In said drawing, 1 represents the wall of a furnace of the vertical shaft type, having a bottom discharge mechanism comprising a horizontal disk or slightly coned hearth '52,

mounted. for slow rotation by means of a worm gear 3, and adjustable relatively to the base of the'furnace so that the material-is discharged over the periphery of the hearth onlywhile the same is being rotated.

4 indicates a space in the furnace walls adjacent the heating zone, said space communicating by inclined apertures 4 both with the heatingchamber and the external air, in order that the furnace gases may readily escape from the heating zone, and that a mantle of such gases may be burned within the furnace wall to economize heat.

5 indicates cooling means, represented as a system of Water pipes,between the heating zone and the discharge hopper. I The cooldisposed in the path of the charge as Figfl or in the furnace walls as in Fig. 2, the former construction being regarded as preferable.

In the construction illustrated in Fig. 1 the furnace charge is intended to serve as the heating resister, interposed between vertically 1 alined, axially arranged upper and lower terminals or electrodes 6 and 7, which are of carbon or graphite. The working end of the upper'electrode 6 is embedded in the charge 8, as is also the lower electrode 7. The lower electrode is shown as supported a hollow metal bar or casing 9 carried by the furnace walls; water maybe circulated through this electrode support by means of appropriate connections 10. 11, 12 represent the electrical connections to the upper and lower electrodes respectively. 4

Instead of the hollow electrode support 9 shown in Fig. 1, I may use a graphite bar 13, Fig. 2, into which the lower graphite electrode 7 is screwed or to wise secured.

In Fig. 2 I have illustrated a resister l t in the form of a carbon or graphite rod extending between the terminals 6 and 7, this construction being particularly useful when the charge, in its unheated state, is a comparatively poor conductor of electricity.

In either construction the lower electrode is so supported that the downward move ment ofthe charge is not substantially impeded, such movement being controlled by which is of such character as to afford a regulated downward movement of the charge, whereby all portions of the charge may receive a practically even heat-treatment. Obviously, the single -carbon pencil constituting the upper electrode may be replaced by a group of such 'tions may require.

which it is other pencils but in such case it is advisable to provide suitable means for securing a substantially even distribution of the heating.

effects from the several electrodes. This may be accomplished by known methods, as for example by making the several pencils the terminals vof the polyphase heating circuit,

by the provision of suitable automatic regu lators for the individual pencils, etc.

In operation, the furnace is filled with carbon or carbonaceous material in a suit- ',ably subdivided state and the electric cir' cuit is closed, an independent resister or starting core bemgused or not as the con-(tr- The portion of the char between the electrodes is heated to a high and substantially uniform temperature, and as the heating proceeds is advanced, either continuously or by stages. The movement of the charge is in a direction substantially parallel to the lines of current fiow, and the charge is subjected. to substantially equa-ble temperature conditions for a period which is dependent upon. its rate of advance, the actual temperature being controlled by the quantity of current passing. By proceeding in this way, all factors being under control of theoperator, it has been found possible so' to regulate the operation that a substantially uniform product of the desired character is obtained.

I claim:

1. An electric resistance furnace comprising a shaft, a terminal or terminals arranged near the upper end thereof, a second terminal or electrode axially located intermediate the ends of the shaft and supported in such manner as to permit free passage of the charge and means for-causing a regulated downward movement of the charge.

2.- An electric resistance furnace comprising a shaft, a terminal or electrode arranged near the upper end thereof, a second terminal or electrode axially located intermediate the ends of the shaft and supported in such manner as to permit free passage of the charge, means for causing a regulated downward movement of the charge and cooling means for the charge below said terminals.

3. An electric-resistance furnace comprising a shaft, a terminal or electrode arranged near the upper end thereof, a second terminal or electrode axially located intermcdiate the ends of the shaft and supported in such manner as to permit free passage of thecharge, vmeans for causing a regulated downward movement of the charge, a com-- minal or' electrode axially located interrac-

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