USRE20128E - Electrothermic seduction of - Google Patents

Description

Oct. 6, 1936. s. T. wlLEs Re. 20,123

y LECTROTHERMIC REDUCTION OF IRON ORES Original Filed Deo. 7, 1928 2 Sheets-Sheet 1 ETC.

'CHARGE or ORE.

WASTE, GASES.

BLEcrmcARc TURNACE was INVENTOR Buffoo Biecmumoc Corporation Assignee 0f Sydnqywos,vdoceosed, by Chorlesmnchofesidex.

vm ATTORNEYS Reissues ocr s, 192.6

Y Re. 20,128

ELECTBOTHEBMIC BEDUCT-ION. F IRON OBES Sydney T. Wiles, deceased, late of Bualo, N.r Y.. by Buffalo Electric Furnace Corporation, mesne assignee, Bullalo, N. Y.

Original No. 1,837,696, dated December 22, 1931,

'Serial No. 324,505, December '1, 1928. Application for reissue December 20, 1933, Serial No. 703.329 20 Claims. (Cl. 'l5-11) finely divided and homogeneously admixed -with is primarily effected by the reaction of hot carbon 5 a reducing agent such as charcoal and a uxing monoxide on' the raw ore. agent such as lime, and the mixture introduced During tbe past quarter century considerable into a closed tube leading directly into an electric serious study has been given to the electrothermic arc, the finely divided materials being protected reduction of iron ore,reduction of ore to metal i0 from blasts of waste gases until reduced to such by the heat of an electric arc or by means of a lo condition as to be substantially metalliferous in current of electricity owing through the coils of character when the'materials are elevated to a atransformer. Except for certain localities where temperature insuring complete reduction, and to economic conditions are favorable, these processes apparatus for utilizing this and similar processes. have not supplanted the blast furnace process. A

The extraction of iron from its ores is one of more extensve use has been found for such reduc- 1l the oldest of known metallurgical processes, 0f tion processes wherein the product sought was an the various methods that havebeen proposed, two iron alloy. Such as ferro-silicon, ferro-nickel. or in particular have survived and are now in use. the like. but the basic principles of the reducing one method, the blast, furnace method, which i; action for these auxiliary methods are substan-` universally employed, consists in feeding crushed .tially the Same l-S thse emlilOyed iii the electio- 20 iron ore, suon es hematite. rezos. or maenetite. thermio manufacture of nis iron- Accordingly, Fegol, (the nnhiraiiy occurring oxide; of iron) the latter manufacture may be` referred to for or ores converted into oxide form by roasting. exlnples sake. auch as the carbonate or suinde, into the iop of n Of the various proposals for. the utilization of as biagi; furnace, This apparatus consists of n di the electric arc in ore reduction, three may be 25 stack provided with means'at its lower portion for Glied heiii- The mOSt Satisfactory Process inthe introduction of n hinsi; of hot nir, Disposed in volves the reduction of the ore in a stack furnace, alternating layers with the ore are layers or the ore. carbon, and flux being fed into a tower. strata oi carbon in the form of coke and a uxing reacting with circulating blast of reducing material such as lime. The reactions of the re- Bases. and finally being treated in an arc furnace duction process are many and complex, but, in its disposed at the bOiilBOllll. of the tower. Like the essence, the action consists in burning the lower blast fi-iiiiie method. this Process depends 1111011 layers of coke with the hot air. to form carbon redliCtiOn by 83565 generated by the action of monoxide and carbon dioxide hot gage. which a blast of hot air on the carbon in the charge. ow upwardly through the charge to effecttheex- Another. and even more direct gaseous method traction of oxygen fromthe iron oxide,produclng 0f reduction, has been attempted ln the labora.-

, ultimately a layer or impure and molten iron tory by passing a current of carbon monoxide at (pig lroxr) at the bottom of the furnace, on an appropriate velocity and temperature over a which noats a. liquid layer of slag consisting of the batch of ore (and fluxing agent) contained in a o gangue of the ore, the fluxing agent. and various 'quartz tube- Essentially. this is not an electroo impurities of the ore which preferentially react thermic reduction, but may here be classed as with the lime. such because it originated from a study of such As stated, there are many individuni reactions actions. The product is not a reduced metal in occurring in the furnace, depending primarily the form 0f a uld pig. iron, but needs further on the temperature which varier from poggibiy "treatment in separate apparatus. Suchseparate 45 3000 F. at the base to 400 or 500 F. at the point alJDBl'BtU-S mi? be. (BCGOl'diDB t0 the reports 0f of exit of waste gases. At certain temperatures this method) Simiir'tO that employed in an carbon reacts directly with iron oxide. forming electrothermic method in which a pot, serving as metallic iron and carbon monoxide and carbon a furnace, is illled with crushed ore, carbon, and dioxide, while at other temperatures there are ilux, and subjected to the action 0f an electric 50 formed by the same ingredients another form of arc playing through the mixture. Fresh quanoxide of iron, FeO, and carbon monoxide. 'nie tities of charge may be added through a chute gases liberated in one portion of the stack move disposed over the furnace, entering in a cold upwardly, reacting both with carbon and ore, decondition. Waste furnace gases are not directly pending upon the specific conditions obtaining. utilized by them through the incoming This invention relates to a method vof and apparatus for the electrothermic reduction of iron ores or similar compounds, and it particularly relates to a method of reduction wherein the ore is The blast furnace method has been so extensively used and studied that detailed explanation would not be in order here, sulllce it to understand, from the foregoing comment, that the reducing action charge, being diverted from the furnace through a separate pipe. In this method, the reducing action is more essentially directly between elemental carbon and ore. As stated, the charge for this furnace may consist of the partially reduced material obtained by gas reduction, but the two methods are independent in principle and in type of apparatus employed.

Aside from economic factors, which are so variable as to permit of no positive statements here, it is Well known that all ofv these methods are open to criticism. With respect to the blast furnace method, it is recognized that the use of a blast of hot air is not entirely satisfactory. Expensive apparatus is required to preheat and feed the air. Of greater significance in the present connection is the fact that the use of a blast places a definite lower limit on the size of the ore lumps which may be used. Pieces about one inch in diameter represent the generally accepted lower limit, smaller pieces being unsuited for several reasons. Fine pieces of ore, or breeze, either fill the intersticesbetween the larger lumps of the charge, and so restrict the passage of the hot gases, or else they are swept away by the blast, being lost in the process and clogging the gas receiving apparatus. Another important factor is that the use of hot air, containing approximately '78 per cent of inert nitrogen, serves as a dilutent of the waste gases, reducing their heating value and limiting their application to other uses. It is also now commonly accepted that the nitrogen enters the molten metal to a limited extent, with deleterious results.

What has just been said of the blast furnace of course applies with equal force to the electro-l thermic method involving the use of a tower and hot blast. The direct gas reduction method, while not yet fully tested on a commercial scale, is obviously open to objection because of its admitted incompleteness, thenecessity for gas feeding mechanism requiring delicate control at high temperatures, and the further disadvantage that the size of the ore particules must be so large as to prevent their displacement by the hot blast. This last objection is apparent when considering the carbon pot furnace method, wherein the large size of the particles is again necessary and there is an ineiiicient utilization of heat and carbon.

The present invention contemplates, in so far as is known, a different procedure than any of those heretofore proposed, and one free from the foregoing noted objections. The reduction reaction of the present invention is not dependent upon the employment of a yblast of hot air nor the circulation of reducing gases, and so, at the outset, is to be distinguished from those methods noted which are predicated upon these features. The method which is contemplated involves a more direct action between carbon and ore and under such conditions as to permit of the utilization of extremely -nely divided particles of ore which are reduced to an agglomerated or semi-fluent state by use of the sensible heat developed in the action, either from the arc or the sensible heat of the waste gases, or both. Thereafter the charge is injected div rectly into the arc itself to effect a final reduction and melting of the resulting sponge iron and gangue. In these features the present invention cliiers materially from the carbon reduction f arated from the slag, in one ,set of operations and in a unitary apparatus, and not in the separated and individual apparatus units such as previously has been suggested for utilizing both gaseous and direct carbon reduction.

Without intending to suggest that the principles of the invention are confined to the following outline and without pausing here to point out the numerous advantages and utilities of the method and attendant apparatus, it may be said in a general way that the invention is practiced advantageously in the following manner: Ore of suitable grade is mined i'n the usual manner and otherwise subjected to the usual preliminary treatments as in any other case of reduction. The crushed ore is then further crushed, advantageously being ground to a ne or pulverulent form so that all of it will pass, for example, a 50 mesh sieve. The ore may be ground so as to pass a 250 mesh sieve but practical considerations such as economy of operation will usually necessitate considerable tolerance above this size. It is desirable to crush the ore to a flneness which will permit of a suiicient amount of contact with carbon to insure proper reduction.

The finely ground ore is then intimately admixed with carbon, which is advantageously in the form of powdered charcoal instead of coke. Such quantities of lime, also ground, as may be required to make the charge fluxing at the temperatures subsequently encountered are also added, and the mixture then stirred until a homogeneous mass is obtained. The ideal condition would exist when each minute particle of ore was` in direct contact with a similar carbon particle,

so that the direct reaction of reduction could be eiected with a minimum expenditure of energy. While theoretical conditions are not possible in usual practice, this homogeneity of mixture may be obtained to a sufllcient degree by the manner just outlined.

The homogeneous charge is then introduced by a suitable mechanical feeding device into a cold end of a hollow and practically impervious tube, which, in the preferred form of the apparatus for practicing the method, constitutes an electrode of an electric arc furnace. By means of the feeding device, the charge of ore is forced mechanically through the electrode, which is horizontally disposedfpassing from the cold end to the arc end, where its temperature is raised to the temperature of the arc, 4say 6000 F. During the passage, the contacting particles of ore and carbon are increased in temperature and enter into a direct reducing action, iron or the oxide, FeO, being formed, and more or less carbon monoxide and carbon dioxide being liberated. This liberated gas, of course, enters into other reducing actions with the ore, and also creates a decided pressure within the tube or electrode. The pressure of the gas tends to force the reduced charge out of the electrode and directly into the arc, into which it is discharged or ejected as a frothy, semimolten,.or spuming mass of ore in an advanced stage of reduction, spongy metallic iron, and calcareous matter which forms a slag as soon as it passes the arc and has an opportunity to collect in a pool beneath.

'I'here are certain precautions which must be taken, in view of the character of the reactions within the tube, in order to preserve one desirable advantage ofthe invention, namely, the utilization of nely ground ores. As previously noted, such ores are not suited for operations involving the use of a blast, as they are blown away faster than they-can be reduced. 'I'he liberation oi' gases within the tube would have the same effect, forcing the powdered ore into the arc with explosive violence and insufilcient treatment, if the tube were packed too tightly with charging material. Accordingly, enough void space should be provided. and the rate of feeding be so adjusted, and the proportioning of the charging ingredients be so regulated, as to prevent this explosive and premature discharge of the ore. which is useful in this connection, namely, the retention of the materials in the tube for. a sufficient length of time to insure a substantially com- 'plete reduction, (e. g., conversion of 90 to 95 per cent of Fe304 to Fe+FeO) is in making the charging opening terminate directly in the arc itself. The high temperature here encountered, and the approaching temperatures in the tube at adjacent points, effects a rapid reduction of the ore to its frothy condition, despite the increasing velocity imparted to it by the formation of waste gases. a

After passing through the arc, and so being reduced almost completely, the ore and fluxing agents fall to a hearth which is maintained at a high temperature by the arc above. Here a complete reduction is insured, the metal forming a liquid pool at the bottom of the furnace, and the slag floating above. The molten metal and slag may be tapped of! from time to time, and then utilized or further processed in known ways.

It has been pointed out that the present invention does not contemplate the use of an air blast, but on the contrary, the admission of atmospheric air is avoided as much as possible. However, the waste gases must be accommodated, and. in the preferred form of apparatus, the waste gases are led from the furnace through means serving to seal the furnace from ingress of air,

but not, however, until a certain portion of the sensible heat of the gases and their reducing power has been utilized. As previously noted, the reduced material falling to the hearth of the furnace is not necessarily completely reduced. 'Ihere is contemplated, in one form of apparatus, a revolving furnace, wherein, due to the revolution of the furnace, the molten mass of metal is constantly agitated and brought into contact with reducing gases in order to insure a com-.

plete reduction. These gases come from the products of reaction in the tube, and are constantly drawn oif through a manifolding device to maintain a more or less constant composition of the re.

ducing atmosphere. In passing out of the furnace, the gases flow around the hollow electrode or charging tube, giving up, by conduction, some Vof their sensible heat which is transferred through the tube wall to institute the reducing reactions. Thereafter, the gases are withdrawn under a sultable degree of suction which tends to draw the small amount of air leaking around the joints of the furnace into the waste gases, and so away from the molten metal. In this way the iron is protected from nitrogen.

The withdrawal of the gases may be controlled so as to provide a desired degree of pressure within the furnace.sufilcient to resist the explosive eifects of the gases generated within the tube, but insufficient to force the waste gases back through the tube and into the feeding mechanism of powdered ore.

In another way of reducing the ore, there may be utilized in the tube a small portion of 'the waste gases, not so much to serve as a reducing agent, but as a promoter or accelerator of the i direct reaction of reduction by carbon. In order to obtain the contemplated use of reducing gas fifi, 12B

Another factor v in this manner, it must be recalled that a large volume of gases is liberated inthe tube. and that blasts through the tube should be avoided if finely divided ore isnot to be displaced. Accordingly, in forming the charge, the voids are merely saturated between the particles with carbon monoxide and carbon dioxide, so as to provide a small quantity of reducing gas which serves to institute the reduction within the tube at a lower temperature than otherwise required. I'his saturation may be effected by stirring quietly the mixed materials in an atmosphere of gas, or permitting a trace of gas to ow in with the mixed materials as they are about to enter the tube. In another way, there is' added a little calcium carbonate or unburnt limestone to the charge, depending upon the breaking up of the carbonate at a low temperature into lime and C02 to provide the promoting agent. As stated, a promoter must be used with an appreciation of its purpose, which may otherwise be stated as a means to effect a more gradual development of the reaction to prevent the sudden formation of large volumes of gas having an explosive effect on the charge.

The apparatus may assume various forms, but the charging tube should be horizontal, or inclined to the horizon atan angle less than the angle of repose of the charge. The use of a revolving or oscillating furnace, to stir the molten charge, is-advantageous, but a stationary furnace may be employed. A rather long furnace may be used, with the waste gases owing around the charging tube, in order to utilize a greater amount of their sensible heat, and to eil'ect otherv economies in operation. Graphite electrodes have the longest life, but aI charging tube made of.

ilrebrick may be used and a carbon arc placed at its end. The charging tube should have a smooth bore, to prevent clogging, and a positive means should be employed to force the charge through the tube. Vertical tubes will not serve, as the charges would fall through them too rapidly to permit of any effective reduction.

A fuller understanding of the invention may be had by reference to the following description taken in connection with the drawings, wherein:

Fig. 'i is a view, partially in cross-section and partially in side elevation, of a revolving furnace suitable for reducing the ore according to the.

axially bored as indicated by the numerals I! and I6 to provide aligned openings. The side wall I2 is provided with a pair of spaced circumferentially continuous metal tracks I1 and I8 which rest in grooves formed in fixed support- --ing rollers mounted at either end and on opposite sides of the shell. One of these is illustrated and indicated by the reference numeral I9. A gear track 2l is also secured to the side wall I2 for engagement with a driving gear 22, by means of which the shell may be rotated or oscillated.

The shell ll is lined with a layer of fire brick 23 and a wall 24 of magnesite, or other suitable heat resisting material. These protective layers are discontinuous around the axial openings in l the end walls of the shell Il, to provide means for entering the interior of the furnace. Tap holes for the slag and molten metal are provided at suitable places in the lining and shell, in accordance with usual practice.

Projecting into the furnace through the openings I and I6 are graphite electrodes 23 and 23, each being suitably supported and capable of longitudinal adjustment, and also being provided with cooling means to maintain the outer ends of the electrodes at a low temperature. Each electrode is provided with a smooth hollow portion along its axis, as indicated by the numerals 21 and 23. 'Ihe charge is fed into the furnace through these tubes. 'I'he electrodes may be made of any desired length and be formed with male and female threaded ends, so that a fresh electrode may be attached to the outer end of an old electrode. There is shown in the drawings but one electrode section, but it will be understood that'more may be used. The extreme outer end of each electrode is provided with a threaded connection 23 for interengagement with a threaded end 3| of a feeding device to force the charge into the furnace. The device illustrated consists of a metal tube 32 having a bore` 33 in which is disposed a screw conveyor 34, driven by means` of a wheel 35 connected to a suitable source of power, not shown. A chute or hopper 33 is positioned on the top portion of the tube 32, and through it the charge may be fed to the screw conveyor, and so forced on through the electrode and into the furnace. 'I'he feeding device is of course rather schematically illustrated, and may assume a variety of forms.

Surrounding each electrode at its point of exit from the furnace is a cooling device which is also employed to remove waste gases from the furnace. The device consists of an annular metallic member 31 provided with an axial bore 3l for the reception of the electrode, and it is formed on its outer end with a gland that may be filled with packing material such as kieselguhr. The member 31 is mounted on a pedestal 4I which is longitudinally adjustable on a fixed base by means of a worm operated through a hand wheel 42. The member 31 may thus be moved with respect to the end walls of the furnace, and so form a very narrow gap through which air might seep into the furnace. 'I'his gap is further sealed by means of annular flanges 43 formed on the side walls I3 and I4 which surround the member 31. Packing rings of carbon may further be positioned between the members 31 and the anges 43.

'Ihe member 31 is formed with a-closed internal chamber 44 for cooling liquid which is introduced and removed through pipes 45 and 4l. Enclosed by the several portions of the chamber 44 is an annular chamber 41 which is open at its inner portions for direct communication with the openings in the furnace end walls. The chamber 41 is incommunication with a gas holder, scrubber, or similar device by means of a pipe line 43 leading through a suitable fan or like means for withdrawing gases from the furnace. During the course of operation, the waste gases liberated in the furnace are drawn into the chamber 41 and so on out of the system, being disposed of in a variety of economical ways. The flow'of gas through the openings Il and I3 induces a slightiiow of air through the narrow gap between the furnace wall and the member 31, and any air tending to leak into the furnace is accordingly diverted into the waste gas stream where it can do no harm. This slight suction action is desirable for the further reason that it prevents the escape of the flammable and poisonous waste gases into the air around the furnace. The cooling chamber 31, besides serving to prevent leakage of air into the furnace by virtue of its adjustability. also cools the electrode so that the outer end ls at room temperature. It will .be noted that with this arrangement, the reso that a greater resistance to the liberated gases is encountered, and explosive and premature discharge will not ensue. Thereafter, the regular line charge is used. As the charge comes into the zone of reaction at the furnace wall, the first stages of reduction occur, the gradually reducing charge being forced along the tube into regions vof higher temperature, and finally, as previously described,l being ejected in an advanced stage of reduction, into the furnace itself. As the furnace rotates, the growing layer of molten metal and slag at the lower side of the furnace is stirred and agitated, some portions of it being carried up with the furnace wall in thin layers where it is washed with the atmosphere of reducing gases maintained within the furnace.

The liberated gases are constantly being withdrawn by means of the suction apparatus, flowing around the electrodes as they leave the furnace to supply part of the heat necessary to eiect the initial reduction. These gases do not, howeVer, come into direct contact with the charge in the tube. The suction applied is so chosen as to prevent-the gases from back-firing through the ltube, but a pressure within the furnace which Iwill prevent explosive discharge from the tube 1s also maintained. The temperature or current consumption may be regulated by longitudinal adjustment of the electrodes 25 and 23, or by changing the voltage between them. Therate of feeding, and hence length of treatment in the tube, may also be adjusted by changing the speed of the screw conveyor 34; and, of course, it is obvious that the character of the charge itself may be varied over wide limits. 'I'his flexibility of adjustment and ease of control render the method and apparatus applicable to a wide variety of ores and for use in the manufacture of a number of products.

After the requisite amount of charging stock has been fed into the furnace the molten bath is laved in the reducing atmosphere to insure complete reduction and such degree of purication as may be desired. When the operation is complete the tap holes are knocked through the side wall of the furnace and the molten slag and metal run oil" separately to solidify. As soon as the reduced material is withdrawn the feeding may again be started, the furnace being rotated and freshquantities of charge being added. In some cases the rotation of the furnace need take place only after the feeding has ceased, the subsequent agitation or puddling being done on the complete molten charge to obtain a final purification.

It will of course be understood that much auxiliary apparatus other than that illustrated is employed in the operation of a commercial plant, but as such devices are known they need not be discussed in detail. here.

' move around I Due to the 'long length or the .'Ihe apparatus shown in Figs. 2 and 3 comprises a ratherlong furnace I similar in construction to the furnace shown in Fig. 1, exceptl that thisvfurnace is stationary. An arc is obtained over a furnace hearth 52 by passing current between a solid electrode 53 and a hollow electrode 54 through which the charge is fed in the manner previously described. The electrode 54 is supported at a suitable number of pointsV along its length by means of walls 55 which are so constructed as to deect gases passing from the hearth 52 to an exit pipe 56 positioned at the end of the furnace remote from the hearth. Bame walls 51, which are more or less angularly disposed to the axis of the furnace, are formed in the roof portion and, in association with the walls 55, providing means for causing the gases to the electrode 54 with a spiral motion.

electrode 54, an appreciable amount of the sensible heat of the waste gases is utilized in effecting a high temperature reduction within the electrode 5l. The material discharging from the tube 54 into the furnace arc 52 is practically all reduced, and the molten iron and slag may be tapped off in a continuous manner. If desired, an electrode may be vertically po tioned through the roof of the furnace 5I to create a deected arc acting upon the surface of the material on the furnace hearth.

In Fig. 4, there is shown rather schematically one means for introducing a trace of reducing gases into the incoming charge. Gases are withdrawn from the furnace 50 through a pipe 5| and are sent to a gas holder by means of a pump 62 and pipes 63 and Bl. Another pipe B5 provided with a needle valve 65 leads from the pipe 64 to the charging device 51. By proper manipulation of the valve 66 a limited amount of reducing gas may be stirred into the charge as it enters the cold end of the electrode 68. The charging hopper 59 is provided with a closed cover and the feeding is effected by means of one or more star wheels 1li positioned therein.

From the foregoing description of certain embodiments of the process and apparatus for practicing the same, it will be apparent that there is provided a novel system for treating ores or crude metals to effect their purification and reduction.

In view of the applicability of the principles of the invention to a variety of materials and for a number of special purposes, it will also be appreciated that the foregoing specifications are intended to be illustrative of the invention, and do not represent the Alimits thereof. understood therefore that the scope of the invention should be determined by the scope of the following claims.

What is claimed is:

1. The process of reducing iron ores which comprises homogeneously admixing ore, carbon, and uxing material, to form a charge, introducing said charge into a horizontally disposed closed tube, passing the charge through the tube and through a zone of the tube of gradually increasing temperature, maintaining the rate of passage through'the tube and the temperature at such values as to effect a substantial reduction of the ore prior to discharge from thetube, and maintaining the external pressure at the discharge end of the tube less than the pressure within the 2. In the electrothennic reduction of iron ores, the process whichA comprises feeding a charge of ore, carbon, and fluxing material into an elec- Vpresence of reducing gas,

It will be i tric arc furnace through a horizontally disposed hollow tube formed in a furnace electrode.

3. The process of reducing iron ores'to metallic iron which comprises nely dividing and homogeneously admixing iron ore, carbon, and a fluxing agent to form a charge, forcing said charge through a substantially horizontally disposed hollow tube into an electric furnace, and withdrawing gases generated in the ensuing actions from the furnace at a low pressure preventing the back ilow of said gases through the incoming charge.

4. The method of reducing iron ores which comprises finely dividing and homogeneously admixing iron ore, carbon and uxing material, enclosing the mixture in a horizontally vdisposed tube, moving the charge through the tube and simultaneously subjecting the mixture'to a gradually increasing temperature, thereby effecting a substantiall reduction ci the ore, discharging the so reduced material into a molten bath of iron and slag, stirring the molten bath in the removing the gas exteriorly of the tube and in contact therewith, and separately removing the molten iron and slag.

5. The process of reducing iron ores which comprises homogeneously admixing finely divided iron ore, carbon and uxing material, introducing the resulting charge into a horizontally disposed closed tube, heating the charge in the tube to a temperature at which reducing reactions will be instituted, moving the charge through the tube and simultaneouslyincreasing the temperature, and discharging the contents of the tube into an electric arc while maintaining the pressure at the discharge end of the tube less than the pressure within the tube.

6. The process of reducing iron ores which comprises homogeneously admixing finely divided iron ore, carbon and iiuxing material, further including in the mixture a limited supply of reducing gases, introducing the resulting charge into a horizontally disposed closedl tube, heating the charge in the tube to a temperature at which reducing reactions will be instituted, moving the charge through the tube and simultaneously increasing the temperature, and discharging the contents of the tube into an electric: arc while maintaining the pressure at the discharge end gfbhe tube less than the pressure within the '1. The process of reducing iron ores which comprises homogeneously admixing nely divided iron ore, carbon, and iiuxing material to form a charge, forcing the charge into a cold end of a horizontally disposed hollow tube, passing the material through the tube and out of a hot end thereof with gradual increase in temperature of the charge within the tube to effect the reduction of the maior portion of the ore, subjecting the charge to an intense heat at the discharge end of the tube, subjecting the discharged material to further heat to complete the reduction, separating the reduced iron from the slag formed in the reaction, withdrawing gases generated in the reduction from the charge exteriorly of the tube, and separately removing the reduced metal and slag from the region of final heating.

8. The process of reducing iron ores which comprises finely dividing and homogeneously admixing iron ore, carbon, and fiuxing material to form a charge, enclosing the charge in @a horizontally disposed hollow tube, moving the mass through the tube and into regions o'f progressively increasing temperature to effect a substantial reduction of the ore. simultaneously malntaining the chargeshielded from drafts of reducing gases formed by the complete reduction of the ore, discharging the partially reduced charge into an electric arc and into an atmosphere rich in carbon monoxide, heating the discharged mass in such atmosphere to effect a complete reduction of the ore to metal, and continuously withdrawing a major portion of the gases formed in the reducing reactions from the region of the arc.

9. In the preparation of ferriferous metals from ores, the process which comprises homogeneously mixing finely divided ore and a reducing agent, providing an electric arc *between horizontally disposed non-metallic electrodes formed with longitudinally extending bores, heating the inner portion of said electrodes progressively from the ends remote from the arc to said arc, forcibly feeding the said mixture through said bores from the cold ends of the electrode and through the arc, and controlling the rate of movement of said-mixture to efiect the reduction thereof.

10. The method of reducing iron ores which comprises striking an electric arc between a pair of horizontally disposed and hollow carbon electrodes, enclosing a portion of said electrodes within a refractory housing, heating the enclosed portions oi' the electrodes from the arc end toward the cold end, maintaining a reducing atmosphere around the heated portion of the electrodes, and forcibly feeding under controlled conditions a homogeneously mixed and finely divided charge of ore, carbon, and iiuxing agent and a limited quantity of reducing gas through said hollow electrodes from the exposed end to the arc ends thereof.

11. In the electrothermic ores. the process which comprises feeding a charge of ore, carbon, and fiuxing material into an electric arc furnace through a horizontally disposed hollow tube formed in a furnace electrode.

12. The process of reducing metallic ores to reduction of metallic metal which comprises finely dividing and homogeneously admixfng the ore, carbon and a fluxing agent to form a charge, forcing said charge through a substantially horizontally disposed hollow tube into an electric furnace. and withdrawing gases generated in the ensuing action from the furnace at a low pressure preventing the back fiow of said gases through the incoming charge.

13. The process of reducing metallic ores which comprises homogeneously admixing finely divided ore, carbon, and fluxlng material to form a charge, forcing the charge into a ,cold end of a horizontally disposed hollow tube, passing the material through the tube and out of a hot end thereof with gradual increase in temperature of the charge within the tube to effect a partial reduction of the ore, subjecting the charge to an intense heat at the discharge end of the tube, subjecting the discharged material to further heat to complete the reduction, separating the reduced metal from the slag formed in the reaction, with'- drawing gases generated in the reduction from the charge. and separately removing the reduced metal and slag from the region of final heating.

14. A method of propagating endothermic reactions in charges of solid material which comprises moving a charge of the solid material which has been finely divided through a substantially horizontal conduit formed in an electrode of an electric arc, and controlling the rate of movement of said charge through said electrode from the feeding end of the conduit relatively remote from the arc end of the electrode.

15. A method of propagating endothermic reactions which comprises creating an electric arc between substantially horizontally disposed electrodes, providing a conduit through at least one of said electrodes, introducing a charge of solid material into said conduit at the end thereof remote from the arc, forcibly feeding said finely divided charge through the electrode and into the arc, introducing a quantity of gas into the remote end of the electrode. and maintaining a pressure on said gas to insure its movement through the electrode with said charge.

16. A method of electrothermally treating chemicallyV reactive materials which comprises forming openings longitudinally through a pair of elongated electrodes normally arranged substantially horizontally in opposed relation, electrically energizing the electrodes to form an electric arc between adjacent ends thereof, feeding the reactive materials into the ends of the electrodes opposite the arc to maintain the last mentioned ends substantially closed by the reactive materials, and progressively conducting the reactive materials through the electrodes at such rate as to allow chemical reaction to take place before said materials reach the electric arc, thereby delining the zones of reaction inside the electrodes between the confining boundaries of the unreacted materials and the electric arc. e

17. The method of electrothermally treating chemically reactive substances which comprises forming an electrode with communicating entrance and exit openings therein, feeding the reactive substances through the electrode while the latter is in a substantially horizontal position, energizing a portion of the electrode by an electric arc to temperatures causing chemical reaction of the reactive substances inside the electrode, and discharging the reacted substances into the region of the electric arc.

18. The method of electrothermally treating reactive materials which comprises feeding charges of reactive materials through a carbonaceous electrode having entrance and exit openings communicating therethrough from one exy tremity to the other and into a space free from obstruction by any of the materials after they have been fed through the electrode, electrically energizing said electrode to heating arc at one end thereof, and coordinating the rate of feeding and intensity of the electric arc to insure reaction of the materials inside the electrode.

19. The method of propagating endothermic reactions in charges of solid material which comprises mechanically forcing a charge of solid material which has been finely divided through a conduit formed in a substantially horizontal electrode of an electric arc, and controlling the rate of movement of said charge through said electrode from the feeding end of the conduit relatively remote from the arc end of the electrode.

20. I'he method of propagating reactions at high temperatures in potentially reactive charges `of pulverulent 'solid material, that comprises intimately admixing particle` of the solid constituents of the charge, forcibl introducing the mixture into one end of a hollow substantially horizontal conduit so that it substantially fills the bore thereof in such relation that continued force is required to move the charge toward the discharge end of the conduit, discharging the mixture from the end of the conduit into a heated zone of an provide'a controlled amas 7 f electric arc furnace, maintaining intermediate portions oi! the conduit heated by the electric nrc oi' the furnace at elevated temperatures insuring the progress of reaction in the conduit, and feeding the pulverulent material by pressure along the bore of the conduit at `such rate as to permit the charge to react and become spumous, auch reaction being substantially complete before the charge LsA discharged from the conduit.

BUFFALO ELECTRIC FURNACE CORPORATION, Meana assignee ol Sydney T. Wiles, Deceased. 6

By CHARLES P. FRANCHOT,

President.

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