IL102163A - Electric furnaces for heat-processing various ores - Google Patents

Description

A.. Mikulihsky Electric furnaces for heat-processing vatious ores ELECTRIC FURNACE FOR HEAT-PROCESSING VARIOUS ORES FIELD AND BACKGROUND OF THE INVENTION The present invention relates to an electric furnace, and particularly to one for heat-processing various ores. The invention is especially applicable for electric furnaces of the type used in the production of ferroalloys, calcium carbide, phosphorous, copper-nickel sulfides, in the production by vacuum of certain light metals, such as magnesium, calcium, potassium and sodium, and other materials, and is therefore described below with respect to such applications.

. Electric furnaces of the foregoing type are used to heat-process various ores, some while mixed with an electrically-conductive material such as' coke or coal, and others .while not so mixed. Such furnaces include at least two7electrodes , usually three electrodes, connectable to a source of electrical power, and a hearth for receiving the feed material in molten condition and for completing the electrical circuit through such feed material, and particularly the products resulting from the heating process, e.g., the melt, carbon bed, etc. In the conventional furnace, the electrodes are passed through the top of the furnace, and their lower ends are submerged in the feed material so as to establish ah electrical circuit from the electrodes through the feed material. The feed material is fed also through the top, and the resulting products, molten metal and slag, are tapped from the bottom, adjacent the upper surface of the hearth.

Electric furnaces of this type consume la- e amounts of power. The main problem is that when it is desired to increase the power, and thereby the heating energy applied to the feed material, the current magnitude increases proportionally - to the square, or even cube, of the voltage. This causes a lowering of the ohmic resistance and of the power factor. For this reason, most furnaces are supplied with electrical capacitors in order to permit an increase in the power (up to 70-80 MVA), but this technique also has a limiting factor since the capacitance magnitude increases much faster than the power of the furnace transformers. Moreover, the carbon in the feed material also lowers its ohmic resistance which therefore limits t!he quantity of the carbon that can be included in the charge. Therefore, various other means, such as the selection of the sort of carbonaceous reducing agent used, have been proposed to increase the ohmic resistance and thereby to enable the electrical power supply to the furnace to be increased. However, only very limited -increase ^n ohmic resistance have so far been achieved by such means.

The increase in the electric resistance of the furnace prevented the branching of the current between the upper electrodes. In addition, the carbonaceous electrodes are so porous that it is impossible to achieve in the furnace high pressures or high vacuum.

Current flow through hearth electrodes isolated from each other is known. In the furnace disclosed in Petersson (U.S. Pat. No. 971,782) besides the hearth electrodes, there .are electrodes in the side walls. The charge is fed from, below through an opening to prevent short-circuiting between the hearth electrodes. At the bottom of the furnace, over the brickwork, is disposed a layer of melted product of the processes of the furnace which partly found over the bottom of a lateral vessel. Submerging an electrode in the melted product ef ects the supply of the current from the submerged electrode, melted product and hearth of the furnace.

The furnace disclosed in Bunce {U.S. Pat. No. 1,922,274) includes a firebrick partition disposed between the hearths.

The structural mounting of these furnaces is such that their electrical resistance is lower than in the worked furnaces .

In the furnace described by Petersson, the products of reaction, namely, the slag and the metal, are generated on the entire surface of the section of the furnace, and, therefore, also on the opening. The liquid products contacted with the cold charge from the opening are quenched, forming a crust. The metallic portio of the crust closes the circuit between the hearths and results in a short circuit.

The furnaces of Bunce, as can be seen from the figures of the patent, the ratio of the distance between the axes of the hearths to the equivalent diameter of the hearths is equal for the two electrode furnace (1.68) and for three electrode furnace (0.9). Because of such proportions the current will flow mainly between the hearths and to a small degree through the stacks. This will inevitably bring about the melting down of the partition causing the resistance to be very small.

To start these furnaces it is necessary to effect the flow of current between the hearths to heat the charge.

The Petersson reference does not describe means for such heating.

The Bunce patent describes feeding material through a tube which is heated from outside by hot gases. However, it is impossible to use such a process for effecting a start since: (a) The contemporary metals for tube (ot. buncer) does not allow to heat the charge to temperatures capable of achieving the necessary conductivity for the most common furnace temperatures of 1400 to 1700 degrees; (b) It is impossible to warm up from outside the charge to the required temperatures in the amount of time it takes the charge to pass through the buncer, taking into account its diameter; (c) Heating from the outside eliminates the basic element of the electric furnace for heat processing ores, namely, the heat and mass exchanges between the charge and gases and -vapor, which moves from the lower zone to the upper zone. Without such exchanges the heat and material losses will be very great.

Petersson . suggests supplying the current to the hearth sections. The drawbacks of this suggestion are: (a) Interaction of the melted product with the brickwork, leading to shortened service life of the involved hearth section; (b) It is difficult to switch on the electrode when the furnace is started in the absence of melted product and after a long period during which the furnace was off, when the melted products have solidified and the contact between the products and the electrodes has been severed.

The Bunce patent does not suggest supplying current to the hearth sections.

An examination of the above-referenced patents . would lead to the conclusion ' that the use of furnaces having hearth electrodes leads: to a decrease of the electrical resistance and that it is impossible to start such furnaces and that, therefore, such furnaces are inoperable. . Such a conclusion could explain why the use of hearth electrodes has not been further developed in the more than 60 years which have elapsed since the publication of the above- referenced patents.

The second problem is achieving air-tightness for the purpose of creating in the, furnaces high pressures and high vacuum. The value of high pressure is proved by the practice of blast furnaces where a decrease of dust in the waste gases of 30 to 50% is achieved by working at a pressure of 2 to 3 atmospheres .

In addition, high pressures are useful in the reducing environment of the furnace in order to decrease the loss of volatile substances such as SiO or nO through the production of silicon o% manganese ferroalloys. However, because of the porosity of the carbonaceous electrodes in the working furnaces, a pressure of only several tens of water columns is achieved.

At the present time commercial furnaces are operating with upper electrodes which operate at pressures of 20 to30 mm Hg . This result is achieved by application of only a single water-cooled copper electrode. The advantages which would accrue were the furnace to operate with three carbonaceous electrodes are clear. , Electric furnaces of this type are generally also characterized by the further drawbacks of having a very complicated arch structure, high rate of electrode consumption, and considerable dust ejection.

OBJECTS AND SUMMARY OF .THE INVENTION ' 0 An object of the present invention is to provide an electric furnace having advantages in some or all of the above respects.

According to the present invention, there is provided an electric furnace for heat-processing a feed material, which furnace includes at least two electrodes connectable to a source of electrical power, and a hearth for receiving said hear£¾''.Includes a separate hearth section of electrically-conductive material for each of said electrodes; each of said hearth sections having a first surface in direct electrical contact- with its respective electrode, and -a second surface in direct electrical contact with the products of said feed-Material such that said feed material bridges said second surface of one hearth section with said second surface of the other hearth section -and thereby establishes a series electrical circuit for the flew of the electrical currant from one electrode, its respective hearth section, the feed material, the neartn section of the other electrode,' and said other electrode .' - wherein the spacing between the axes of two adja cent electrodes is a* least 2-5 tiures the e ≤EC±r:od'e equivalent diameter.- Claim 1 leads to the following advantages- - 1) decreasing of the frmace electrical resistance owing- o the lowering of the srectirn: and:, possibility of increasing the current partn length.. 2) achieving- high- prjsssurs or? gir. vaccuum in:, the furnace owing to the absence of uppe electrodes. listed below are a number of additional .advantages For achieving the goal of increasing the electrical resistance and of enhancing the reliability of the furnace, the flow of the current by means of the hearth is a necessary, but not- sufficient condition. It is also necessary to secure the following further requirement,-;: \ Ca-) The distance between the -axes of the hearth electrodes is to be .. more than. 2.5 equivalent diameters of the hearth electrode. When a lesser distance is used the current will- flow mainly between. the hearth 0 electrodes, . escaping the- flow through the stacks melting down, the partition. In this case the resistance will be very low. (b>) The electric furnace must include at least two control columns supported from the inside surface of the top 5 of the furnace and movable so 'as- to be immersed at different depths in the electrically-conductive feed material therein and thereby to secure the constancy of the strength of current and to allow inspection of the electrical resistance of the electrical circuit 0 through, the fe'ed material, carried out the definition of the . borders of -layers, the primary slag, carbonaceous" material, final slag and metal.

Preferably, there is a. control column for each of the hearth electrodes, and each column is non-circular in •25· · cross-section and rotatable alona its longitudinal axis to enable th&' column to effect, he loosening of the feed material.

CcO .Ensuring the operability of the start of the furnace when the charge is. cold and is..practically none-electroconductiv.e. The ensuring can he carried out:-.by-including an. inlet: port in the lower? end of - each stack for introducing air- or another gas sup- plied by tuyeres:, oir plasma generators-- · .to. additi¬ onally heat the feed', materials,.

For achieving the mentioned purpose i3 is necessary co carry oub ail of the mentioned requireme s, namely, to ° install hearth sections with a partition between them, to observe the. necessary distance between cr.e "earth sec cr.s , to install a column control and to ensure the operability ■of the start of t ^ furnace- 5¾rr- the partition.- the feed- material or? air refractory c-ouldv. be of use.. ^5 The auxiliary heating means is used for starting-up the furnace to bring the furnace close its operating temperature , at whic time the electric pnwer.-- sours is connected to the electrodes to supply the heat via the electrodes . The auxiliary heating means may also be used 20 during the- normal operatiOiL of thee furnace to control the processing; of the feed material and' to · save electrical energy ,. as.: well as- to pr.ey.ent clogging of the air; or gas inlets. Preferably ,: the auxiliary heating means; is operated during the normal operation: of the furnace .to- 25 supply from.. J to 4-5 %' of t&e heat required: in- the normal furnace pperation ,. the remaining- 95 to 55 £-beeng supplied " by the electric power" sours .

In . some preferred embodiments in the invention described below, the lower surface of each hearth section constitutes the first surface in direct electrical contact with ■ its respective electrode, and the upper surface of -each hearth section constitutes the -second surface in direct electrical contact with the molten products of the feed material.

In other described embodiments, one side of the upper surface of each hearth section constitutes the first surface in direct electrical contact with its respective electrode, and another side of the upper surface of the hearth section constitutes the second surface in direct electrical contact with the molten products of the feed material.

Reduction pr.oc.ess.. is- possible between: oxides: contained in. slag or charge , and carbon: of electrodes, resulting; in an considerably consumption; of electrodes. This: process may be pr_ov,ented by- creating a ermanent layer:- of molten metal or carbide over the surface of electrodes,, these- metal or carbide being nod o-ta: of processes taking.: place ίη· the furnace . This, layer is prov.id'ed by" a, su ficient spacing: between: the surface": of the electrodes andi the furnaraa-? tapping hole for the melt outlet.. This spacing^ shall be at least 50 mm,.

In some described embodiments , the furnace includes a common> jacket enclosin all the stacks . In other- embodiments the furnace includes an individual jacket , for each stack. The individual jackets allow further decrease of the section of the current path and through this to increase the electrical resistance. However, this construction is more complicated than for the furnace with a common outer jacket.

The foregoing features of the present invention enable the electrical power applied to the electric furnace to be substantially increased, without increasing the current, by increasing the ohmic resistance of the furnace. This is because the foregoing features permit the length of the current path to be increased by increasing the height of the ore and carbon in the stack, and/or by decreasing the cross-section of the stack and thereby of the current path.

The significance of such a large increase in the ohmic resistance will be appreciated when it is pointed out that previous investigations in various countries for reducing ohmic resistance, by the selection of the sort of carbonaceous reducing agent used, have resulted only in an 8-10% increase in the ohmic resistance, whereas in the present invention this increase can be 400-600% and even higher.

In addition, the foregoing features enable the carbon component of the feed material to be increased if desired. They also enable the arch construction to be greatly simplified because they obviate the need for passing the electrodes through the arch, and ■ . for a large number of feed chutes through the arch. The novel furnace may be operated under a relatively high pressure under the arch, and therefore decreases dust ejection or by vacuum and therefore has the possibility of producing a series of light metals.

The furnace also significantly decreases the electrode consumption leading to work with unexpensing electrodes because of the lack of direct physical contact of the electrodes with the feed material.

Still further, the electric furnace of the present invention, when used for extracting a product from ore, also substantially increases the product yield because it enables: (a) an increase in the pressure under the arch to thereby decrease the quantity of the product left in the slag (in many types of processes involving product extraction from ore); (b) an increase ih;; the height of the coke bed; and (c) an increase in the current density, and as a result, the temperature within the furnace.

Further features and advantages of the invention will be apparent from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is a longitudinal sectional view illustrating one form of electric furnace constructed in accordance with the present invention, Fig. 1a, 1b and 1c being transverse sectional view along lines a--a, b—b, c—c, respectively of Fig. 1 ; Fig. 2 is a longitudinal sectional view illustrating a second form of electric furnace constructed in accordance with the invention, Fig. 2a, 2b and 2c being transverse sectional views along lines a—a, b—b, c—c, respectively, of Fig. 2; Fig. 2d is a fragmentary view more particularly illustrating one of the three stacks in the electric furnace of Fig. 2, and Fig. 2e is a sectional view along line e—e of Fig. 2d; Fig. 3 is a fragmentary view illustrating another construction of one of the three stacks in the furnace of Fig. 2, Fig.3a being a sectional view along line a--a of Fig. 3; Fig. 4 is a transverse sectional view illustrating a further modification in the construction of a furnace according to Fig. 2, Fig. 4a being a sectional view along line a—a of Fig. 4; Fig. 5 is a transverse sectional view illustrating a complete furnace including three stacks each of the construction of Fig. 3; Fig. 6 is a fragmentary view illustrating one of the three stacks in a still further furnace construction in accordance with the present invention, Figs. 6a and 6b being transverse sectional views along lines a--a and, b--b, but of the complete furnace of Fig. 6; Fig. 7 illustrates a modification in the construction of the furnace stack according to Fig. 6; and Fig. 8 illustrates a still further construction of electric furnace in accordance with the invention, Fig. 8a being a transverse section along line a—a.

DESCRIPTION OF PREFERRED EMBODIMENTS The electric furnace illustrated in Fig. 1 is intended for producing various ferroalloys, calcium carbide, phosphorus, and a wide variety of other materials from their ores with (or without) the addition of carbon, such as coke or coal and for producing light metals such as magnesium, calcium, lithium, potassium and sodium. The illustrated furnace comprises an outer jacket 2 having an inner insulating lining 4 defining an 'internal chamber 6 divided into three main zones, namely a lower zone 6a, a middle zone 6b, and an upper zone 6c.

Disposed within the lower zone 6a are three electrodes 8 (see Fig. 1a) each in direct electrical contact with the lower surface of a hearth section 10. The electrodes 8, and their respective hearth sections 10 are all made of electrically-conductive material, such as carbon, and are electrically insulated from each other by a central partition 12 of electrically insulating material.

Partition 12 is of generally triangular configuration (Fig. 1a) and is formed, with semi- circular cut-outs at its three corners for accommodating the three electrodes 8 and their respective hearth sections 10. Partition 12 extends upwardly within the furnace interior 6 in the middle zone 6b and is capped at its upper end by a block 14 also of electrically- conductive material, e.g. carbon.

As shown in Figs 1a- 1c the furnace jacket 2 is also of generally triangular configuration. It conforms to the outer face of partition 12 except that at its lower end the jacket is open to provide access to the three electrodes and hearth sections 10. At these locations, jacket 2 is formed with flanges 16, for attaching insulated cover plates 18 with electrical insulation 19. The current flow to the hearth electrodes 8 is by means of clamping rings 20 I-and electric conductors 21. The air-tightness is achieved by stuffing gland seal 15 and insulating partition 19.

The upper end of jacket 2 is closed by a top wall 22 formed with feed chutes 24 for feeding the ore to be processed (with or without carbon) into the furnace. A further feed chute 26 is formed centrally of the top wall 22 for feeding carbon material (e.g., coke or coal) for passing electrical current therethrough. Top wall 22 is further formed with one or more pipes 28 for exhausting waste gasses formed within the furnace,insulating partition 12 thus electrically insulates each hearth section 10, as well as its respective electrode 8, from the others. It also defines a stack 30 for each hearth section extending from the lower zone 6a of the furnace to the upper zone 6c. The feed material, fed via the ore chutes 24 and the carbon chute 26, fills the three stacks 30 so that such materials are in direct electrical contact with the upper surface of the three hearth sections 10 and of the carbon block 14 within the middle zone 6b of the furnace. These electrically-conductive materials thus bridge the three hearth sections, and also the carbon block 1 4 which serves as an intermediate hearth section.

Thus, when electrical current, e.g. three- phase electrical current, is applied to the clamping rings 20 , serving as the electrical connection to the electrodes 8, a series circuit is established from each electrode 8, via its respective hearth section 1 0 , the feed material and the remaining two hearth sections and their respective electrodes.

The ohmic resistance of this circuit depends on the height of the stacks 30 filled with the feed material, and their cross-sectional areas. Accordingly, where it is desired to increase the ohmic resistance in order to increase the power, and thereby the rate of heating, without increasing the current or affecting the power factor, this may be done by merely increasing the length of the stacks 30 and/or decreasing their cross-sectional areas .

Each of the stacks 30 is further formed, at the lower end of the middle zone 6b , with inlet ports 32 for introducing air or gas supplied by tares or plasma generators to enhance the heating of the feed material within the furnace, with outlet ports 34 for tapping the molten slag, and with further outlet ports 36 for tapping the molten metal from the furnace.

The furnace may be operated in the following manner: Assuming the furnace is cold, the feed material, such as an ore to be processed, mixed with carbon, is introduced into the furnace via the feed chutes 24 until such material fills the three stacks 30 and rises to a level above carbon block 14 so as to bridge the upper surfaces of the three carbon hearth sections 10 and the carbon block 14. Hot air and/or plasma gasses are then applied via the inlet ports 32 at the bottom of each stack. Carbon material may be introduced via chute 26 to increase the conductivity of the feed material in the upper zone 6c.

After reaching the normal operating temperature, electrical power (e.g., three-phase) is applied to the electrodes 8, and the electrically- conductive material within the furnace completes a series circuit from each electrode 8 through its respective hearth section 10, the feed material, and the two remaining hearth sections and their respective electrodes. At this time, it is possible to decrease the amount of hot air or plasma gasses supplied via the inlet port. However, it is preferable not to completely terminate the supply of the hot air or plasma gasses in order to avoid clogging of the inlet ports.

During the normal operation of the furnace, the feed material is continuously introduced via chutes 24, and the carbon material is continuously introduced via chute 26 at the top of the furnace; whereas the resulting slag is tapped via outlet ports 34 and the molten metal is tapped via outlet ports 36 at the bottom of each of the three stacks 30.

During the normal furnace operation, the heating process can be controlled and optimized by controlling the rate of feeding the feed, material via chutes 24 , the carbon material via chute 26 , the hot air and/or gasses via the inlet ports 32 , and the current flow to the electrodes 8. In general the hot air and/or gasses fed via the inlet ports 32 should supply the furnace with about 5 to 45% of the total energy, whereas the remaining 95 to 55% should be supplied by the electrical current flowing through the materials inside the furnace.

The illustrated furnace enables the waste gasses produced during the furnace operation also to be used for heating the feed material in the furnace. These waste gasses -- carbon monoxide from the electric furnace -- may thus be directed to a heat-exchange, e.g., a Cowper stove, where in one chamber it is burnt with air, and in an adjacent chamber it is used to heat another oxygen containing gas which is burnt in the electric furnace by adding in it, for this purpose, carbonaceous material for interaction with the oxygen from the gas.

The furnace illustrated in Fig. 2 is of similar construction as that of Fig. 1 , and therefore the corresponding parts have been identified by the same reference numerals, except that in the furnace of Fig. 2 the outer jacket 1 02 and its insulating lining 1 04 also enclose each of the three stacks 1 30 . This is more particularly illustrated in the transverse sectional view of Fig. 2a^wherein it will be seen that each of the three stacks, therein designated 1 30 , is enclosed by a separate jacket section, therein designated 102, each having an inner liner 104 of insulating material. As also shown in Fig. 2a, the bottom of each stack 130 is provided with a plurality of hot-air or plasma inlet port 132, an outlet slag port 134, and an outlet molten-metal ports 136. Another change in the furnace construction illustrated in Fig. 2 is that the outer jacket 102 is cooled by a cooling jacket, shown at 103 in Fig. 2.

These modifications in the furnace illustrated in Fig. 2 permit the current density to be increased since the outer jacket is cooled.

Figs. 3 and 3a are fragmentary views, corresponding to Figs.- 2d and 2e, but illustrating a modification in the construction of the hearth and electrode portion of each of the three stacks, designated 230 in Fig. 3. ,Thus, whereas in the furnace illustrated in Fig.2. In the modification of- Figs.3 and 3a the auxiliary electrode, therein designated .208, is in direct electrical contact with the outer side of the upper surface of its respective hearth sec- tion 210. In this modification the molten material is in direct electrical contact with the inner side of the hearth section, as in the Figs. I and 2 construction . The electrode 208 is disposed in a hermetical vessel 231 , attached to the jacket 202 by means the flanges 216 and insulation 219. For retain a layer of melt on the surface of hearth section it is supplied by walls 223. The remainder of the furnace structure illustrated in the Figs.3 and 3a, is otherwise the same described above with respect to Figs. 1 and 2 , and therefore the corresponding parts have been identified with the same reference numerals .

An advantage in the construction illustrated in Figs .3 and 3a is that it facilitates the replacement of the electrodes 208 when they have been consumed.

For improving the electric contact between the end of the auxiliary electrode 208 ( 308 ) and hearth electrode 21 0 ( 31 0 ) and for increasing the service life of the hearth, it is necessary to cover it with a layer of metal so that the distance between the surface of the hearth and the outlet port 34 ( 1 34 , 234 , 334 ) must be no less than 50 mm. The metal which covers the hearth can be the reaction product of an introduced strong metal, such as iron.

Figs. 4 and 4a are fragmentary views illustrating another modification that may be included in the furnace. In this modification, the electrical conductors, therein designated 321 , for supply via the clamping rings 320 the electricity to the electrodes, therein designated 308 . These conductors are passed through the top wall 322 of the furnace and are accessible by removing from the top wall a cover 31 8 having electrical insulation 31 9 . In substantially all of the other respects, the furnace of Figs. 4 and 4a is constructed in the same manner as described above with respect to Figs. 1 - 3 , and therefore corresponding parts have been identified by the same reference numbers.

Fig. 5 illustrates a further modification that may be provided in the furnace construction. This modification concerns particularly the form of the jacket 402 and the insulating partition 41 2 defining the three stacks 430 . Thus, whereas the jacket ' 2 and partition 1 2 in the Fig. 1 construction are of a delta-configuration, in Fig. 5 they are of Y-configuration. The modification illustrated in Fig. 5 also includes the laterally-located electrodes 408 , as described above particularly with respect to Fig. 3 , but it will be appreciated the this Y-configuration could also include the arrangement illustrated in Figs. 1 and 2 wherein the electrodes are located below their respective hearth sections defining the bottom wall of the respective stacks 430 .

Fig. 6 illustrates a further modification that may be included in the electric furnace. The furnace illustrated in Fig. 6 is basically of the construction described above with respect to Figs. 1 and 2 . In the modification of Fig. 6 , however, each stack includes a control electrode 550 , of electrically-conductive material, such as carbon. Control electrode 550 is supported at the end of a rod 551 passing through the top of the furnace in each stack going past guide 552 and is movable- to various elevations in the upper and middle zones ( 6c , 6b , Figs. 1 and 2 ) so as to be immersed at different depths in the feed material therein. Thus, by controlling the position of the control electrodes 550 in the three stacks (Fig. 6a ) , the electrical resistance of the circuit through the feed material may be controlled to produce the optimum ohmic I resistance. In addition the movable, control electrodes 550 may be used for determining the location of the inter-face between the coke (carbon bed) and the melt.

The movable electrodes 550 may also be used for loosening the feed material. For this purpose, they are of non-circular cross-section, being shown as rectangular section in Fig. 6a, and are rotatable about their own longitudinal axes, so that when they are so rotated they loosen the feed material being heated within the furnace.

Fig. 7 illustrates a modification,' wherein each control electrode, therein designated 650, is mounted at an incline, rather' than vertically as shown in Fig. 6.

Figs. 8 and 8a illustrate a further modification, wherein each of the three .stacks , therein designated 730, extends for the complete height of the furnace. Thus, such a construction actually consists of three separate furnaces, each including a separate electrode, hearth section, top wall (722), and bottom wall (not shown) . The three sections are insulated from each other by insulating partitions 731 of Y-configuration . The construction illustrated in these figures has the advantage of minimizing the possibility of a. short circuit in the furnace.

In the working furnaces the- upper electrodes which passed through, th top. of the furnace carry cut the following functions: (a) supplying electric energy; (b). achieving the start by lowering the electrodes to the hearth in ..the period' of start; ( c-) · securing the control especially the security o the constancy of strength o current by movement upwards and downwards..

•By. · contrast. , in the ^furnaces according to. the present invention: a/- the electrodes carry out the supplying of eletrical energy b the hearth sections: b/ the start of the 'furnace -by introducing gasses : c/ the security the control by column electrodes.

The exclusion, of the upper electrodes ,. secure the" uniform dis ri t-inn o the aseg- which is . irp.p'drt nt when it introduce in the normal operation and set free place for the column electrodes.

In this is the interdependence between the hearth sections, introduction of gases and control.

Is—given a generalized scheme of interdependence of elements construction, methods and results.

The factors guaranteeing the increase in the electric resistance and the operability are: the separate hearth sections, ensuring the distance- of their axes, possibility of start and fulfilling of control.

The. increase the resistance and in connection with this the power supported the installation the Cowper stove in consequence of decrease the specific -investment.

The .elements if the scheme bring about 'the following advantages: ' (a) greatly increase the resistance (400 to 600 %)■-. (b) accordingl increase the power with exclusion of electric capacitors; „ lc) the possibility of working at pressures of 2 to 3 atmospheres _ or more, or using "vacuum of 0.1 to 30 mm Hg column; (d) decrease the consumption of electrodes right up to working with non-expenditured electrodes and exclusion the shoo for electrodes · oster arid preparation of the iron housing for electrodes; (e) effective use of the waste gases; These advantages are significant for the commercial viability of electrical furnaces for the heat-processing of ores . ' While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made. For example, the invention has been described with respect to heat-processing ores with carbonaceous.' materials (e.g., coal or coke), which latter materials are electrically-conductive and therefore form an electrically-conductive feed material with the ore The invention, however, could also be advantageously used in heat-processing ores without carbonaceous materials. Many other, variations, -^modifications and applications of the invention will be apparent.

Schema of interdependence of elements construction, methodes and results.

Claims (1)

1. WHAT IS CLAIMED An electric furnace for a feed which furnace includes at electrodes connectable to a source of electrical and a hearth for receiving melted products produced in the characterized in said hearth includes a separate hearth section of material for each of each of said hearth sections having a first surface in direct electrical with its respective and second surface in direct electrical contact with the of feed material such that said feed material bridges said second surface one hearth section with said second other section and thereby establishes a series electrical circuit for the flow of the electrical current from one its respective hearth the feed the hearth section of other and said other wherein spaicing between the axes two times e supported furnace 26 WHAT IS CLAIMED An electric furnace for a feed which furnace includes art electrodes connectable to a source of electrical and a hearth for receiving melted products produced in the furnace said hearth includes a separate hearth section of material for each of said electrodes each of said hearth sections having a first surface in direct electrical its respective and second surface in direct electrical contact with the of material such that said feed material bridges said second surface one hearth section with said second the other section and thereby establishes a series electrical circuit for the flow of the electrical current from one its respective hearth the feed the hearth section of other and said other electrode wherein spaicing between axes less times of electr control supported fiirnace z 27 in a control e c resistance of the electric furnace according to Claim wherein the lower end of each stack further includes an port introducing air or other supplied by tuyeres or ma generators to additionally the feed The electric furnace according to Claim wherein electrodes with their rings are situated air tight 5 electric furnace according to Claim the lower surface of each hearth section constitutes said first surface in direct with its tive electrode and upper surface of each hearth section constitutes said second surface in direct electrical contact the molten products of the feed electric furnace according to Claim wherein another side of the upper surface of each tion is laterally of said one side of upper surface of hearth section and is contacted by its respective rode vertically above the hearth section towards the top of the electric furnace according to Claim wherein a hermetically sealed vessel is to the by flanges and insulating partitions the said furnace rating also an electrically conducting the upper side partly in the the furnace partly in said the part the furnace is the 28 se c and is the in the vessel is wit electrode with its e rings extending towards to the top of 5 furnace according wherein furnace includes an at lower end of each stack for removing the molten wherein the between the surface of the hearth s and cutlet taps is no less than r electric furnace according to wherein there is an conductive at the upter end said electrical insulator he electric furnace according to Claim wherein the furnace includes a common outer enclosing all said furnace to Claim the furnace includes an individual enclosing each of said electric furnace according to Claim wherein said control electrodes are circular section and are ot at able about their respective longitudinal to effect loosening of the feed material in the z 3 ELECTRIC FURNACE FOR HEAT PROCESSING VARIOUS ABSTRACT OF THE An electric furnace for ore ning feed material includes a plurality ofalectrodes nectable to a source of electrical power and a separat e hearth section of material for each electrode Each hearth section has a first surface in direct electrical contact with its respective rode and a second surface in direct electrical contact with the molten products of the feed material such that the feed material bridges the hearth sections and thereby establishes a series electrical circuit for the flow of the electrical current from one electrode its respective hearth section the feed material and the other hearth sections and The spacing between the axes of two near situated said electrodes is no less than 5 times of the equivalent diameter of the electrodes To control the strength of the current there is a control which is movable so as to be immersed at different depths in the feed mat insufficientOCRQuality