US2755325A

US2755325A - Electric shaft furnace

Info

Publication number: US2755325A
Application number: US491599A
Authority: US
Inventors: Brugger Wilhelm
Original assignee: TH Goldschmidt AG
Current assignee: Evonik Operations GmbH
Priority date: 1954-03-05
Filing date: 1955-03-02
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17

Description

July 17, 1956 w BRU 2,755,325

ELECTRIC SHAFT FURNACE Filed March 2, 1955 4 Sheets-Sheet l w am J.

INVENTOR. 7407/? elm 3 2 998 ,flizorney,

July 17, 1956 w. BRUGGER ELECTRIC SHAFT FURNACE 4 Sheets-Sheet 2 Filed March 2, 1955 INVENTOR. 14 27 I'm/m ,Er'a9j er July 17, 1956 w. BRUGGER 2,755,325

ELECTRIC Si-IAFT FURNACE Filed March 2, 1955 4 Sheets-Sheet 3 jt zrney July 17, 1956 w. BRUGGER ELECTRIC SHAFT FURNACE 4 Sheets-Sheet 4 Filed March 2, 1955 INVENTOR. Mil/helm Bragg?" BY 9 3 7 6 0 M W W 2 W 5 n06 w w x00 L G 1 MW w .2. %/y 5 .5 m

United States PatentO ELECTRIC SHAFT FURNACE Wilhelm llrugger, Essen, Germany, assignor to Th. Goldschmidt A. G., Essen, Germany, a German company Application March 2, 1955, Serial No. 491,599 Claims priority, application Germany March 5, 1954- 14 Claims. (Cl. 1323) This invention relates to electric shaft furnace; and it comprises a shaft furnace which is particularly adapted to be used in the halogenation of oxidic ores, metallic oxides and the like, comprising a metallic furnace jacket, an acid-resistant refractory lining inside said jacket, a replaceable cylindrical insert of an electrically-conducting, heat-resistant carbon material, selected from the class consisting of amorphous carbon and graphite, mounted inside said lining, a screen of said carbon material mounted horizontally inside said insert and serving to divide the interior into a lower melting zone and an upper reaction zone, a graphite electrode having a central bore mounted centrally inside said insert, an electrically-conducting heat-resistant carbon material making surface contact only with the lower end of said electrode for supporting the same above said screen and for conducting electric current therefrom to said screen and said insert, means for controllin the pressure of the electrode against the elec trode supporting means thereby to control the contact resistances between the electrode and the insert, means for charging the reaction zone with oxidic material to be halogenated, means for passing a gaseous halogen through the bore of said electrode into the bottom of the furnace just above said screen, means for tapping off molten halides collecting in said melting zone, means for collecting gaseous products from the top of said insert, and means for passin an electric current through said electrode, through said screen and through said insert; all as more fully hereinafter set forth and as claimed.

It has long been known that various metal oxides can be reacted with carbon and chlorine at high temperatures to form anhydrous chlorides. Thus, for example, aluminum chloride can be produced from aluminum oxide, carbon and chlorine in accordance with the following equations:

In practice highly reactive oxides of aluminum and magnesium are mixed in the ground state with coal dust, pulverised charcoal and a binder, pressed into briquettes or other granular shapes, and then used as starting materials for the direct chlorination with chlorine gas.

The practical performance of direct chlorination or halogenation of oxidic materials however constitutes such a difficult problem with respect to corrosion that hitherto only relatively pure and intensely reactive oxides, such as alumina and magnesia, have been used as starting materials for the production of anhydrous chlorides on an industrial scale. Compounds such as silica, zirconium oxide, beryllium oxide, and various other oxidic ores, however, are far less reactive, so that extremely high reaction temperatures are required for their reaction with carbon and chlorine. This applies to compounds of different oxides with one another, for example to silicates such as orthite, cerite, zirconium sand, and so on, and also to ores having a high content of impurities, such as bastnaesite. In order ot obviate these difliculties, for example in the known production of zirconium tetrachloride from zirkon Patented July 17, 1956 sand, the zirkon sand is first reacted with carbon to form zirconium carbide and/or zirconium cyanonitride and volatile silicon monoxide, and the zirconium carbide or zirconium cyanonitride is reacted with chlorine to form zirconium tetrachloride only in a second stage. it has also already been proposed, for other difiicultly producible anhydrous chlorides, first to produce the sulphides and to convert these into the corresponding chlorides by direct chlorination.

The particular ditficulties which occur in the direct chlorination or halogenatio-n of difficultly reactive oxidic materials with carbon and chlorine or halogen on an industrial scale are caused by the high reaction temperatures required, namely about 1200 to 1500 C., since in this temperature range the metal oxide components of refractory bricks of conventional industrial chlorination furnaces are themselves converted into anhydrous chlorides in the region of the reaction zone. Since quartz or porcelain bricks also constitute an oxidic material, these are also chlorinated under these conditions. Lining the inner furnace shaft with carbon or graphite bricks also fails to provide satisfactory protection for the chlorinating furnace, since at the high reaction temperatures these materials are gradually oxidized by the oxidic starting material. Renewal of the inner brick layers of chlorination furnaces or reactors is difficult or practically impossible.

in the present invention i provide a furnace construction in which the above described difficulties are substantially overcome. My furnace can be operated successfully at extremely high temperatures. Corrosion is minimized and those parts which are subject to corrosion or erosion can be readily replaced.

in my furnace I provide the conventional furnace jacket of iron or the like and this is lined with a refractory, such as fire clay or acid-resistant brick, in the conventional manner. But inside the refractory lining I provide a replaceable cylindrical insert of amorphous carbon or graphite which is spaced from the refractory lining a slight distance and which in effect forms an inert inner lining for the furnace. This spacing, l have found, substantially increases the life of both the refractory and the insert. Chlorine or other halogen is conducted into the bottom of the furnace through a central graphite electrode. A screen of graphite is mounted horizontally inside the insert and serves to divide the interior into a lower melting zone for collection of molten halides and an upper reaction zone in which the halides are formed. A layer of granulated coke or other heat-resistant electrically-conducting granular carbon material, such as graphite or amorphous carbon, is placed on top of the screen. This granular layer has the function of dispersing and distributing the halogen before it is passed through the furnace charge and in addition this layer passes at least part of the electric current from the electrode to the insert. Numerous points of contact resistance are provided where the granules of coke touch each other and these resistances, being in the path of the current, cause heating to be produced in the zone of this layer of coke. In one modification the central electrode rests on top of the coke layer and a spring suspension means is provided to suspend a controlled fraction of the weight of the electrode from above thereby altering the sum of the contact resistances and hence the temperature of the furnace. In another embodiment the graphite screen is supported on the shoulder of a graphite post while the central electrode rests loosely on top of the post which protrudes above the layer of coke. Here again the weight of the electrode resting on the post controls the sum of contact resistances in the path of the current passing from the electrode to the post and then partly through the layer of coke but mostly through the screen to the insert. Means are provided for collecting the gases evolved from the furnace and for charging the furnace without permitting escape of the gases. Means are also provided for tapping off the molten halides which collect in the bottom of the furnace. The charge, which consists of shaped pieces of a mixture of oxidic material, such as a metal oxide ore, carbon and combustible binder in conventional proportions, is charged on top of the layer of coke.

My invention can be explained in greater detail by reference to the accompanying drawing which shows, more or less diagrammatically, an operating embodiment of my shaft furnace. In this showing,

Fig. 1 is a front elevation of my furnace and superstructure with part broken away in the furnace proper to show details of the electrically conducting insert and screen,

Fig. 2 is an enlarged vertical section through a modified insert showing a removable screen and its support,

Fig. 3 is an enlarged partial vertical sectional view through the furnace hood and upper part of the furnace, the partial section being taken between the lines 33 of Fig. 1,

Fig. 4 is a similar sectional view through the top of the central electrode of the furnace, extending between the lines 44 of Fig. 1,

Fig. 5 is a similar sectional view through the suspending means for the furnace, taken between the lines 5-5 of Fig. 1,

Fig. 6 is a side view of the suspending means for the central electrode,

Fig. 7 is a partial vertical section on an enlarged scale showing the construction of the ceramic tubes in the central electrode which are used for conducting the chlorine gas into the furnace, taken along the line 7--7 of Fig. 4,

Fig. 8 is a horizontal section looking downwardly through the central electrode taken along the line 3-8 of Fig. 4,

Fig. 9 is a plan view of the top of the electrode taken along the line 99 of Fig. 4,

Fig. 10 is a plan view of the furnace hood taken along the line 10-10 of Fig. 3, while Fig. 11 is a vertical sectional view looking downwardly taken along the line 11-11 of Fig. 4.

In the various views like parts are designated by like reference numerals. Referring first to Fig. l the main parts of my shaft furnace comprise the furnace proper shown generally at 1, the hood shown generally at 2, the electrical connection and cooling means for the central electrode 5, shown generally at 3, and the spring suspen sion means for the central electrode, shown generally at 4. As shown in Fig. 1 the furnace has an iron jacket 6, a lining of refractory material 7, which may be acid resistant bricks, and is provided at its bottom 3 with a tapping means 9. Inside the refractory lining of the furnace an annular replaceable insert 10 is positioned which in effect forms a corrosion-resistant lining but it is spaced a slight distance from the refractory lining. The lower portion of the insert, which is the only portion subjected to the maximum temperature reached in the furnace, is constructed of graphite and the space between the graphite insert and the refractory ensures a long life for the latter. The entire insert can be constructed either of graphite or amorphous carbon, if desired, or the insert can be made in two or three interfitting parts, as shown in Fig. 2 where the central portion 11 is constructed of amorphous carbon which has the advantage of having a lower thermal conductivity than graphite thus causing the maximum heat to be concentrated in the lower part of the furnace. But it is advantageous to provide an upper contact ring 12, Fig. 2, of graphite where the insert makes electrical contact with the iron contact plate 13; see Fig. 3.

The graphite or carbon insert 16 of Fig. l is provided with an integral horizontal plate or screen 14 having vertical holes 15 through which the molten chlorides or halides formed in the furnace pass to the bottom of the furnace from which point they can be tapped through the tapping means 9. On top of the screen 14 a layer 16 of granular heat-resistant conductive material, such as coke, is placed and the central electrode of graphite 5 rests on the top of this coke layer. The electric current passes from the central electrode through the layer of coke, then to the screen 14 to the graphite or carbon insert 10 and finally out through the top of the insert to the contact plate 13. This contact plate is provided, as shown in Fig. 11 with 18 contact elements 39 symmetrically arranged about its periphery. All or any of these can be connected to a source of electricity by means of contact plugs 17; see Figs. 1, 3 and 11. The heating is produced by the contact resistance between the central electrode and the coke layer as well as between the individual granules of coke. The graphite insert 19 is supported a slight distance above the furnace bottom 8 by means of graphite discs 13 so that the anhydrous molten halide which collects on the bottom of the furnace can readily flow to the tapping hole.

In the modification shown in Fig. 2 the screen 14a is formed as a separate part and has a sliding fit in the insert 10a and is supported by means of a central post 19 of graphite which rests on the bottom a of the furnace. The upper part 20 of the post is reduced in diameter where it passes through the screen leaving an annular shoulder 21 on which the screen rests. In this embodiment the post has a head 22 having a cone-shaped top surface which is provided with several grooves or rccesses 23 which form passageways for the chlorine or other halogen which is passed downwardly through the central bore 24- of the electrode 5, through the recesses and then upwardly through the briquetted charge 25 of ore or the like to be halogenated. The bottom surface of the electrode conforms in shape to the shape of the top surface of the post where these surfaces engage. This ensures good electrical contact. it will be seen that the furnace charge rests on top of the coke layer 16 which in turn rests on top of the screen 1411. The top of the post rises slightly above the layer of coke so that the electrode 1t) rests on top of the post. in this embodiment the electric current passes from the central electrode to the head of the post and then partly through the layer of coke but mostly through the post to the screen and/or to the insert, heating being due to the contact resistances in the path of the current.

Owing to the high heat conductivity of the graphite insert sufiicient heat is diverted both upwardly and downwardly from the layer of coke and the screen so that the entire reaction chamber, that is, the melting chamber below the screen and the reaction chamber above the screen, is heated adequately to cause the chemical reaction to take place and to keep the molten halidc in the bottom of the furnace in fluid condition so it can be readily tapped. As compared with graphite the heat conduo tivity of amorphous carbon is low so that, in the modification of Fig. 2 the upper part of the furnace remains cooler than in the modification shown in Fig. 1. Heat losses are therefore smaller. if desired the several parts of the insert of Fig. 2 can be screwed or otherwise secured together. Otherwise they may be supported loosely on each other as indicated in the figure.

In order to protect the amorphous carbon portion 11 of the insert of Fig. 2 from corrosion by volatile chlorides, such as ferric chloride, aluminum chloride, zip.

conium chloride etc., this portion of the insert can he impregnated with an alkali metal silicate solution or with a concentrated solution of phosphoric acid. This caution is not necessary with all-graphite inserts the graphite conducts the heat upwardly sufiiciently so that the temperature of the insert remains above the condensation temperatures of the gaseous halides.

The construction of the upper part of my furnace is shown best in Figs. 3, l0 and 11. It will be seen from Figs. 3 and ll that the contact plate 13 is annular but that on three sides bracket plates 26 are welded thereto,

these forming in effect extensions of the contact plate.

Each of the bracket plates is provided with a vertical strengthening fin 27 and mounting plates 28 are attached by bolts 29 to two of the bracket plates, the mounting plates in turn being mounted on a foundation, not shown, 5 which may be used to support the furnace. At the outer ends of the bracket plates tightening bolts 39 are provided. The lower ends of these bolts are pivoted at 31 to lugs 32 welded to the top of the furnace jacket 6. When the bolts 3d are tightened this prc s the contact plate i3 against the top of the conducting insert to improve the electrical contact between these elements. The contact plate can be cooled by passing water through annular water jacket 3", introducing it through inlet tube 33 and discharging it through outlet tubes 34 (Fig. ll).

The space (Pig. 3) between the conducting insert it and the refractory lining 7 of the furnace is sealed off at the top by means of a layer 36 of acid proof cement. Another layer 37 of a thermosetting resin, such as asplit or coumarone resin, can be introduced above the cement 20 layer, this resin layer being cooled by water passing through the lead tubing 33, if desired. The conducting insert can be replaced easily when required by removal of the cement and resin seals.

The furnace proper is surmounted by the hoodstructure shown generally at 2. The hood structure is cement d tightly to the iron contact plate 13 by means ll g of asbestos or acid proof cement. T he hood is provided with a covered cleaning hole and with a exhaust fine A charging funnel as the top of the hood structure.

of which has a charging aperture clc ed and by the conventional charging valve mechanism &5 (P 3) operated by valve handles The oper structure of the charging valve mechanism are believed to be evident from the drawing which shows that openings 4'7 in top plate are opened to permit entry into the funnel of the briquettes to be charged only when the charging apertures 4d are closed. This pre .ts cs cape of gases during the charging operation. The hood structure can be insulated from the central electrode by insulation shown at 49, if desired.

The electrical connections for the central electrode are shown best in Figs. 4- and The contact clamp dd is made in two parts which fit around the electrode 5 and are clamped together with bolts 51. Vertical grooves 52 are provided in the inside surface of the cl mp, where the central bore of the electrode, as shown best 7. The outer tube 55' serves an imp ins list-- ing for the bore, While the halogen is passed through the central tube A stuffing box or packing gland g asbestos or other packing *eals oil the end of tube 1d prevents tl'e halogen from upwardly. Means must be provided to tighten the packing gland owing to the different rates of thermal expansion of the various parts. For this purpose I provide at the top of the electrode 5 a threaded bore into which is screwed a threaded nipple 5'8 which extends a short distance above the top of the electrode. An iron plate 59 is screwed to the top of the nipple. Four screws 59 are threaded into the top of the iron plate. These screws pass through holes drilled in a second iron plate d1. This upper plate has a 75 central bore which i s just large enough for the inner ceramic tube 56 to pass therethrough. The plate therefore rests on the upper end the outer ceramic tube 55, the plate being counterbored from below to receive the upper end of this tube. It is evident that when the nuts 62 on screws 60 are tightened, this presses the outer ceramic tube downwardly thereby compressing the packing in the gland 57. It will be noted from Fig. 7 that the central bore 24 of the electrode is provided with

shoulders

63 and 64. The inner ceramic tube 56 rests on shoulder 63 while the shoulder 64 supports packing gland 57.

The inner ceramic tube 56 passes upwardly through the iron plate 61 and extends for a short distance above this plate. A hose 65 of rubber or plastic is attached to the top of the tube and this hose supplies gaseous halogen to the furnace.

The central electrode is advantageously supported by means for controlling the downward thrust of the electrode against the layer of coke 16 (Fig. l) or the post head 22 of Fig. 2. This downward thrust controls the contact resistance between the lower end of the electrode and the conducting insert 16 and therefore the resistance of the furnace. Such a controlling means is shown generally at 4 in Fig. 1 and in more detail in Figs. 5 and 6. As shown in these figures the bars Eda extend upwardly above the central electrode and at their upper ends they are provided with a notch 66 which is adapted to receive a horizontal suspending rod 67. This rod has a central vertical bore which receives with a sliding fit a sleeve or bushing 63 of insulating material. A threaded rod 69 extends through the central bore of this sleeve and flanged nut 69a is threaded on the lower end of the rod while at its upper end the rod terminates in a suspending loop 78 above a horizontal flange 71 which rests on the upper end of the insulating sleeve which at this point has an integral flange 72 which rests on top of the suspending rod. An insulating washer 73 is mounted on the insulating sleeve directly below the suspending rod and a coil compression spring 74 is mounted between the flanged nut 69a and the washer 73. It is evident that, when loop '76 is engaged with a fixed support, not shown, and when flanged nut 6% is a tightened, this tends to raise the suspending rod 67 and therefore the vertical bars 5 5a and the central electrode 5. This would increase the resistance of the furnace. Thus the spring suspension which has been described can be used to control the resistance and hence the electric current passing through the furnace, i. e. to control the furnace temperature. This makes it possible to heat up my furnace rapidly even though the insert it? should consist of a single tube of amorphous carbon.

The weight of the central electrode resting on the layer of coke (Fig. l) or on the head of the contact post (Fig. 2) was found sufficient to loa er the contact resistance in one furnace to the point where adequate heating was provided when the furnace was operated at from 19 to 25 volts and at from about lOOO to 2500 amps. This ft nace has a graphite insert havin an outer diameter of 500 mm. and an inner diameter of 300 mm. resting on three graphite discs serving as feet. The inner diameter of the furnace shaft (refractory) was 520 mm. The graphite screen had a thickness of ll); lit) him. while the head of post of 2 ex 'ifid about 159 mm. above the screen. The central electrode had a diameter of about mm. and a bore of about 15 mm. diameter. The screen of Fig. 2 may have a diameter of 295 mm.

In a furnace having the construction shown in Fig. 2 a controllable fraction of the current passes through the molten halides at the bottom of the furnace and hence these halides can be maintained readily in molten condition. This construction has the further advantage that the amount and temperature of the melt can be judged to a certain extent by the readings of the electrical instruments connected into the electrical circuit since all of the electrical conductors inside the furnace have a strongly negative temperature coefiicient of resistance.

"When inserts comprising amorphous carbon are employed it is always an advantage to provide an upper section of graphite where the insert contacts the iron contact plate 13 in order to provide a better electrical contact with the plate. This graphite section may have a length of from 100 to 150 mm. for example. In the absence of such a section difiicult electrical contact conditions may develop at the point of contact between the contact plate and the insert if the furnace is operated on a high load.

The construction of the furnace hood may be varied in accordance with the disposal to be made of the gases evolved. When fusible salts are to be produced in the furnace the volatile halides, which may then be produced in small amounts, may be without value and the gases evolved can then be merely collected, chemically decomposed and neutralized. In case valuable fusible and volatile halides are produced simultaneously. however, a tightly fitting furnace hood is required so that the volatile halides can be recovered from the furnace gases. Further treatment would follow conventional practices.

A particular advantage of the hereindescribed shaft furnace is that it can be operated at very high reaction temperatures. The upper limit for the reaction temperature required is determined by the fact that the boiling points of most of the molten chlorides lie below 2000 C. The throughput through the aforedescribed chlorination furnace is high. With a shaft diameter of 300 mm., about 50 kg. of zirconium sand or 50 kg. of bastnaesite or 60 kg. of cerite oxides, in the form of coal-ore briquettes, can be reacted per hour to form the corresponding chlorides or halides. The upper limit of the furnace throughput is determined by the gas speed, because if this limit were exceeded the briquetted starting material would be blown out of the furnace.

Another advantage of my furnace construction is that no electrical leads are passed through the ceramic lining of the furnace. My electrical connections are made above the furnace proper where they can be readily inspected and replaced if necessary. The connections for the gaseous halogen are also above the furnace. Only a very small amount of electric current passes through the briquetted charge on account of the low furnace voltage. In contrast the layer of coke and the graphite parts in the bottom of the furnace are highly conducting. Intense heating is therefore produced where it is required and no arcing is produced even at very high temperatures. This is extremely important since arcing could produce intense local over-heating, volatilization losses etc.

While I have described what I consider to be the most advantageous modifications of my furnace it is obvious, of course, that various details of construction can be varied without departing from the purview of the invention. Thus the carbon used in the briquettes of the charge can be pulverized coal dust, carbon black, coke or charcoal. The construction of the composite conducting insert of Fig. 2 can be varied considerably. Thus the separate parts may be threaded, as at '75, and screwed together or they may merely rest loosely on top of each other, as shown at 76. Water cooling of the various furnace parts may be employed where desired or required. And, of course, various means can be used to control the downward pressure of the central electrode against its support, thereby controlling the contact resistance and indirectly the temperature of the furnace. Other modifications of this invention which fall within the scope of the following claims will be immediately evident to those skilled in this art.

What I claim is:

1. An electric shaft furnace adapted to be used in the halogenation of oxidic ores, metallic oxides and the like, comprising in combination a furnace jacket, an acid-proof refractory lining inside said jacket, a replaceable cylindrical insert of an electrically-conducting, heat-resistant carbon material, selected from the class consisting of amorphous carbon and graphite, mounted inside said lining, a screen of said carbon material mounted horizontally inside said insert and serving to divide its interior into a lower melting chamber and an upper reaction zone, a graphite electrode mounted concentrically inside said insert, an electrically-conducting, heat-resistant electrodesupporting means making surface contact only with the lower end of said electrode, supporting the same above said screen and adapted to conduct electric current from the electrode to the screen and to said insert, means for controlling the pressure of the electrode against the electrode-supporting means thereby to control the contact resistances in the path of the current from the electrode to the insert, means for charging the reaction zone with oxidic material to be halogenated, means for passing a gaseous halogen into the reaction zone just above said horizontal screen, means for tapping 0d molten halides collecting in said melting chamber, means for collecting gaseous products evolved from the furnace charge, and means for passing an electric current through said electrode, through said screen and through said insert.

2. The furnace of claim 1 wherein the cylindrical insert is formed in sections, the lowest section being of graphite while an upper section is of amorphous carbon.

3. The furnace of claim 2 wherein the top section of the insert is of graphite and wherein a metallic contact ring is in electrical contact with the graphite section to conduct current therefrom.

4. The furnace of claim 1 wherein said screen of carbon material is integral with the insert.

5. The furnace of claim 1 wherein said screen of carbon material is a separate element fitting inside the insert and is supported on a graphite post resting on the bottom of the furnace.

6. The furnace of claim 5 wherein said graphite post extends above the screen and the central electrode rests on top of the post, the post constituting the supporting means for the electrode.

7. The furnace of claim 1 wherein the electrode is provided with a central bore for conducting gaseous halogen into the reaction zone of the furnace.

8. The furnace of claim 7 wherein the central bore of the electrode is lined with a ceramic tube above the furnace level and an electrical conductor is attached to the electrode at this point so that the conductor is protected from corrosion by gaseous halogen which in the absence of the ceramic tube would diffuse through the wall of the electrode.

9. The furnace of claim 1 wherein the electrode has a central bore for conducting gaseous halogen into the reaction zone and is supported on a graphite post which rests on the bottom of the furnace and extends a short distance above the screen and wherein one of the contact surfaces between electrode and post is provided with re cesses to conduct the gaseous halogen from the bore into the charge in the furnace.

10. The furnace of claim 1 wherein said insert is unitary and constructed of graphite.

11. The furnace of claim 1 wherein said insert is unitary and constructed of amorphous carbon.

12. The furnace of claim 1 wherein said electrode supporting means is a shallow layer of granulated coke.

13. The furnace of claim 1 wherein said pressure controlling means comprises a spring support for the electrode and means for changing the tension on the spring.

14. An electric shaft furnace adapted to be used in the halogenation of oxidic ores, metallic oxides and the like, which comprises in combination a furnace jacket, an acidproof refractory lining inside said jacket, a replaceable insert of an electrically-conducting, heat-resistant carbon material, selected from the class consisting of amorphous carbon and graphite, mounted inside and spaced a short distance from the refractory lining of the furnace, a screen of said carbon material mounted horizontally inside said insert and serving to divide its interior into a lower melting chamber and an upper reaction zone, a graphite electrode 9 having a central bore mounted inside said insert, an electrically-conducting, heat-resistant electrode-supporting means making surface contact only with the lower end of the electrode, supporting the same above said screen and adapted to conduct electric current between the electrode and said insert, means for controlling the pressure of the electrode against the electrode-supporting means thereby to control the contact resistances in the path of the current between the electrode and the insert, means for charging the reaction zone with briquettes of carbon and oxidic material to be halogenated, means for passing a gaseous halogen to and through the central bore of the electrode to a point in the reaction chamber just above the screen, means for tapping oif molten halides collecting in said melting chamber, hood means for collecting 10 gaseous products evolved from the furnace mounted above with a gas-tight connection to said insert, and electrical contact means mounted above the furnace for attaching a source of electricity to said electrode and to said insert.

References Cited in the file of this patent UNITED STATES PATENTS 815,016 Heroult Mar. 13, 1906 1,463,970 Pope Aug. 7, 1923 1,562,684 Brown Nov. 24, 1925 1,901,524 Moschel Mar. 14, 1933 2,447,809 Miguet Aug. 24, 1948

Claims

1. AN ELECTRIC SHAFT FURNACE ADAPTED TO BE USED IN THE HALOGENATION OF OXIDIC ORES, METALLIC OXIDES AND THE LIKE, COMPRISING IN COMBINATION A FURNACE JACKET, AND ACID-PROOF REFRACTORY LINING INSIDE SAID JACKET, A REPLACEABLE CYLINDRICAL INSERT OF AN ELECTRICALLY-CONDUCTING, HEAT-RESISTANT CARBON MATERIAL, SELCTED FROM THE CLASS CONSISTING OF AMORPHOUS CARBON AND GRAPHITE, MOUNTED INSIDE SAID LINING, A SCREEN OF SAID CARBON MATERIAL MOUNTED HORIZONTALLY INSIDE SAID INSERT AND SERVING TO DIVIDE ITS INTERIOR INTO A LOWER MELTING CHAMBER AND AN UPPER REACTION ZONE, A GRAPHITE ELECTRODE MOUNTED CONCENTRICALLY INSIDE SAID INSERT, AN ELECTRICALLY-CONDUCTING, HEAT-RESISTANT ELECTRODESUPPORTING MEANS MAKING SURFACE CONTACT ONLY WITH THE LOWER END OF SAID ELECTRODE, SUPPORTING THE SAME ABOVE SAID SCREEN AND ADAPTED TO CONDUCT ELECTRIC CURRENT FROM THE ELECTRODE TO THE SCREEN AND TO SAID INSERT, MEANS FOR CONTROLLING THE PRESSURE OF THE ELECTRODE AGAINST THE ELECTRODE-SUPPORTING MEANS THEREBY TO CONTROL THE CONTACT RESISTANCES IN THE PATH OF THE CURRENT FROM THE ELECTRODE TO THE INSERT, MEANS FOR CHARGING THE REACTION ZONE WITH OXIDIC MATERIAL TO BE HALOGENATED, MEANS FOR PASSING A GASEOUS HALOGEN INTO THE REACTION ZONE JUST ABOVE SAID HORIZONTAL SCREEN, MEANS FOR TAPPING OFF MOLTEN HALIDES COLLECTING IN SAID MELTING CHAMBER, MEANS FOR COLLECTING GASEOUS PRODUCTS EVOLVED FROM THE FURNACE CHARGE, AND MEANS FOR PASSING AN ELECTRIC CURRENT THROUGH SAID ELECTRODE, THROUGH SAID SCREEN AND THROUGH SAID INSERT.