US3918956A

US3918956A - Reduction method

Info

Publication number: US3918956A
Application number: US054427A
Authority: US
Inventors: Jesse J Baum
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-11-04
Filing date: 1970-07-13
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A system and method for the direct reduction of iron by utilizing powdered hard grade, high melting point coal tar pitch that does not become soft and maintains its dry state at ambient temperatures in the formation of compact briquettes under high pressures and the reduction of such briquettes to metal.

Description

United States Patent 1191 1111 3,918,956

Baum 1 Nov. 11, 1975 [5 REDUCTION METHOD 2.876.094 3/1959 Lusby 75/111 2.911319 11/1959 M H b t 75136 [76] Inventor: Jesse 10419 K6150 Dnve- 3.053.648 9/1962 st hinf 75/3 'W 85351 1351.459 11/1967 M1115 75/3 [22 Filed: Jul. 3 1970 3374.085 3/1968 Stone 75/3 [2 [1 Appl' 54427 Primary E.t'ami11er-Hylz1nd Bizot R l t d U A li i Assistant E.\'uminerPeter D. Rosenberg [63] Cntinua1tion-in-palr1 of Ser. No. 591.997. Nov. 4 Agwm fl Byrne; Edward E.

1966. abandoned.

15:} us. 01. 4. 75/3; 75/4; 75/43; [57] ABSTRACT [5 H 1m. C2) 1/08. Cslb 1/78. C7 w??? A system and method for the direct reduction of iron [58] Field of segrch h 75H by utilizing powdered hard grade. high melting point d 37 coal tar pitch that does not become soft and maintains h 1 its dry state at ambient temperatures in the formation [56] References Cited of compact briquettes under high pressures and the UNITED STATES PATENTS reduction of such briquettes to metal 2.650.160 11/1953 Totzek /29 9 C|aim$- 17 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 #8 3,918,956

Wk. M32. 193. wmmwza 312'.

US. Patent Nov. 11, 1975 Sheet 2 0f 8 US Patent Nov. 11, 1975 Sheet 3 of8 3,918,956

Sheet 5 of 8 manna.

Nov. 11, 1975 U8. Patent US. Patent Nov. 11, 1975 Sheet 6 of8 3,918,956

U.S. Patent Nov. 11, 1975 Sheet 7 of8 3,918,956

US. Patent Nov. 11,1975 Sheet 8 of8 3,918,956

FIG. 15

REDUCTION METHOD This application is a continuation-in-part of my copending application Ser. No. 591,997, filed Nov. 4, 1966, and now abandoned, which is based on my Philippine applications Ser. Nos. 6872, filed Nov. 18, 1965, 7330, filed May 16, 1966, 7385 filed June 7, 1966, and 7427, filed June 29, 1966, for which priority is claimed under 35 USC 119 for the subject matter disclosed in said parent.

This invention relates to method for preparing briquettes of iron ore and or other oxide ores, furnace and component constructions and the direction reduction of iron ore and or other oxide ores and apparatus for reducing iron ore and other metallic oxide ores. More particularly, this invention relates to methods and apparatus for producing iron by direct reduction of oxides or iron ores such as Fe,o,, (Hematite), Fe O (Magnetite), and FeO such as mill scale, and oxide ores of chromium, manganese, and copper. Specifically, this invention also relates to a novel method for preparing briquettes of such oxide ores, which briquettes may be subsequently reduced in a continuous process with the manufacture thereof or may be sold as articles of commerce.

Generally, the technology of the invention described herein is related to methods, apparatus, and techniques for producing a light porous iron commonly known as sponge iron; however, as will appear hereinafter, this invention contemplates a directly reduced metal product which has very significant and unexpected characteristics which distinguish the product and the process from conventional sponge iron production.

The present invention relates to a shaft furnace, generally a vertical or slanted shaft, which is used to process a charge of iron ore and a reductant such as coal or oil at a high temperature in the approximate range of 1,900 P. to 2,200F. to produce iron. When 1 refer to iron, I mean the product obtained by removing the oxygen from various oxides of iron ore to be processed such as Fe,o,,, Fe O and FeO such as mill scale, the resultant product after processing being mainly high density concentrate iron.

One object of this present invention is to change or convert iron ore directly to the metal without causing the ore to go through the molten phase. The present invention requires much less heat energy than other methods such as the blast furnace because it removes oxygen from the ore without changing the physical characteristics of the ore. This makes for lower cost of production.

Another important objective of this invention is to provide a crucible tube having an inner liner of graphite and an outer liner of silicon carbide.

In systems of the type involved herein it is known to use a coal tar pitch as a reductant binder. The reductant herein is of a type to match the particle size of the concentrated granular or powdered ferrite material. The two are mixed together with a small amount of moisture of approximately 6 percent so they will hold together for briquetting. A still further objective of this invention is to provide a mixture for forming briquettes where approximately 50 to 90 percent of same passes through a 325 mesh.

1n the invention described herein, vertical or slanted tubes are utilized to reduce the labor involved. An angle of recline of the tubes is utilized so that a briquette will move through the tube aided by gravity.

One of the important contributions of this invention is in the use of high-frequency induction electricity for iron reduction purposes. There are two principal types of reduction methods described herein. One, the indirect method, uses a tubular retort or crucible wherein portions thereof are of a material such as graphite or heat resisting alloy which will heat when subjected to a medium or high frequency electric field and this heat is transferred to the briquettes by conduction and/or radiation. The other method is to provide briquettes with a sufficient conductive quality that they in themselves will convert the high frequency field into heat. In the latter case, the tubular crucible is of a relatively non-conducting type, such as silicon carbide. Another method contemplates a situation wherein the retort is first heated and after a certain amount of reduction takes place, the briquettes are sufficiently conductive to be further reduced as a direct result of the electromagnetic energy.

A still further objective of this invention is to provide a binder of coal tar pitch which can be pulverized to a fine powder at ambient temperatures. Although the prior art has used coal tar pitches as a binder reductant, it did not realize the significance of using a type which can be pulverized to pass through a fine grade mesh. Such pitches, because of their low content of volatile matter, does not cause swelling upon the heating thereof. In fact, substantial shrinkage of the briquette occurs during its reduction.

Another important objective of this invention is to provide a briquette which can be made of any convenient size for handling by utilizing vertical or slanted tubes in which a great many moving parts are eliminated.

A still further objective of this invention is to provide a system wherein electric and carbon fuels are economically used for reduction purposes.

Another important objective of this invention is to utilize medium to high-frequency energy from 10,000 to 14,000,000 cycles of induction electric power by way of a coil surrounding a refractory retort which contains bounded briquettes. The advantage of utilizing this type of energy is that briquettes can be converted directly by way of a single step from iron ore or other oxides into a liquid iron or steel or other metals.

A further objective of this invention is to provide means for utilizing an induction powered medium to high frequency water-cooled coil surrounding a conducting type cylinder such as graphite containing a non-conductive charge, or a non-conductor type such as silicon carbide alundum-zircon, etc. within which a conductive type briquette charge is contained. When the briquetted ore is of a conducting type such as Magnesite or copper oxide, a nonconductor tube such as silicon carbide may be used. When the briquetted charge is non-conductive, such as chromite or manganese oxide then the tube will be conductive such as graphite, to the electric field.

Another object of this present invention is to accomplish the reduction of iron ore withthe aforementioned type briquettes, to the metallic state with a minimum of capital investment. When the liquid phase is avoided (as by direct reduction of the solid iron ore) it is possible to build a plant at lower capital cost.

More specific objects of this invention are as follows:

The provision of a vertical shaft iron ore reduction furnace including a means for charging the furnace with iron ore mixed with a reducing agent, a means for heating the upper part of the vertical shaft with induction electricity, a water seal at the bottom of the furnace, and a conveyor to remove the reduced iron, ash, unburned coal and other reductants, the conveyor comprising at one end a magnetic pulley to separate the magnetic reduced iron from the ash and other discharge.

The provision of an iron ore reduction furnace including a means for charging, wherein the reducing agent may be other than coal such as gas, oil, bunker oil, Naptha, charcoal or coke. The liquid reductant may be injected into the furnace through pipe lines through the wall of the furnace.

The provision of an iron ore reduction furnace wherein the atmosphere of the furnace may be, for all practical purposes, sealed from and excluding the outside air or atmosphere, thus obtaining a positive control over the inside atmosphere.

An iron ore reduction furnace wherein the upper portion is heated by an induction electric coil powered by a source of electric power such as 60 cycle, medium frequency such as 180 cycle, or higher frequency such as 1,000 cycles or higher and where the cold portion of the stack or chamber is insulated from the upper portion and water cooled so that the upper portion can be maintained in the range of about 1,900F. to 2,200F. while the lower portion is cooled by a water sheet and is immersed in a water cooling tank for the purpose of sealing the air from entering the chamber.

The provision of an iron ore reduction furnace where the reduced ore cools in the lower portion progressively until it is quenched in a water tank and removed on a conveyor and over a magnetic pulley so it can be separated by magnetic means from the ash and other products of combustion.

In addition, a highly and most significant feature of the present invention is the provision of vanes cast integrally with and extending inwardly from the cylindrical shell around which the induction coil is located. An important object in transferring the necessary heat into the ore being reduced is to transfer the heat uniformly and rapidly across the entire section of the stack so that the reduced ore reaches the reaction temperature as quickly as possible. In general terms, this object is accomplished by the electric power from an induction coil heating first a heat resisting alloy or graphite shell and vanes which extend inwardly therefrom. The large surface area provided by the interior surface of the cylindrical shell and by the vanes helps to transfer the heat into the charge quickly. Also, as the ore begins to reduce to the metallic form, the electro-magnetic field set up by the induction coil generates heat directly within the partially reduced iron ore as the latter becomes conductive. The overall objective is to obtain as much heat as possible from the reactions between the reductants and the oxides using a minimum of heat from the inductive electric power because electric power may be more expensive than equivalent exothermic heat obtained from common reductants such as pitch, asphalt, coal and coke. The heat energy provided by the induction coil, even though it is held to a minimum to keep the cost down, is absolutely necessary to initiate and to trigger off the reactions required to reduce the ore.

The provision of a method whereby oxygen or air is injected into the downcoming charge at a point above the reaction zone or just below the charging area. This oxygen reacts with the reducing gases or materials in this area to generate supplementary heat which makes it possible to reduce the consumption of electricity from the induction coil and to preheat the downcoming charge faster so that when it enters the reaction or induction heating zone the ore will reduce more quickly.

The present invention also contemplates a process for the direct reduction of ore and the melting thereof in one combined operation and a furnace for carrying out the indicated process. ln the combination process iron ore is reduced directly to metal and then the metal is melted, both steps being performed in a single furnace and in a combined operation, although the individual steps are performed separately. Thus, refined steel is produced by casting the resultant product into billets, ingots or slabs which may then be sold to steel mills where they will be rolled into rods, bars, sheets, plates and shapes. This latter form of raw product, billets, ingots or slabs, will generally command a much higher price than synthetic scrap (direct reduced iron) because it is refined steel ready to roll. This refined metal may also be a high grade pig iron in which the carbon is much higher than steel, for example from 3 to 4 percent carbon.

The present invention also relates to a method for direct reduction of high concentrate iron ore or other oxide ores in the form of briquettes (2-12 approx.) or lumps from approx. two inches in size or diameter and under as it comes from an ore crusher and, in the same furnace or direct reduction stack, melting the reduced iron ore so that the product will be liquid iron or steel which may be cast into ingots, pigs or billets, or may be passed on to another furnace for refining or further processing. In general, this object is accomplished by the use of a vertical or slanted stack in which fine iron ore mixed with a carbonaceous thermosetting reductant binder, such as coal tar pitch or gilsonite or where lump iron ores physically mixed with coal, coke, gas, asphalt, pitch or other reductants, is first heated to reduce the metal and then, in a separate part of the furnace, melted, both heating steps being accomplished by induction electricity. Ores which may be used include iron ore, copper oxide concentrates, chromium ore concentrates, or manganese ore concentrates. Such ore concentrates usually will be briquettes with five to 12 percent coal tar pitch as a binder reductant, but it also may be handled as loose fine ore or lump ore mixed with a reductant such as coke, coal, etc., in the range of 5 to 20 percent by weight.

In contrast with one embodiment of the present invention, there are many possible applications where it is advantageous to conserve the residual heat in the reduced briquettes and, instead of cooling these reduced metal briquettes by passing them through a water seal, the present embodiment contemplates the replacement of the water seal in the lower cooling section of the furnace with an electric induction melting furnace similar to the standard types being much used as remelting furnaces in industrial areas of the world. Thus, it is possible to exclude the outside air because the bottom of the stack is completely sealed (except for tapping holes in the melting crucible which are closed when liquid metal is not being removed).

Thus, another object of this species of the invention is to conserve the residual heat in the reduced briquettes, then melting them while they are still hot (about l,900 to 2,200F.). ln this way, by combining both the direct reduction and the melting operation, it is possible to reduce the overall cost of the product.

Further and more specific objects of the present species of the invention are:

The provision of a method of processing oxide type ores, for example, iron ore, copper ore, manganese ore, and chromium ore, wherein such ores are mixed with a reductant or carbonaceous type thermosetting reductant binder" such as coal tar pitch or Gilsonite, such materials being of a hard grade high melting point type and charged into a vertical stack sealed from air except at the top, passing the charge down through an induction heated zone where it is reduced without being cooled, passing the charge into an induction electric heated melting zone at the bottom of the same furnace where the reduced iron or other metal is melted or refined, and tapping the liquid metal or draining it from the furnace crucible to be cast into primary forms such as ingots, billets and pigs.

A method for processing briquettes of finely divided concentrated oxide ore mixed and bonded together with powdered high melting point hard grade coaltar pitch whereby the ingredients are briquetted, and then passed through a furnace stack containing a reduction zone operated at about at about 1,900 to 2,200F. and into a melting zone operated at about 2,600 to 3,000F. and thence into molds or into other furnaces for further refining.

The provision of a method for the direct reduction of iron ore and the subsequent melting and refining of reduced ore into various alloys wherein a vertical stack is used, the top being open for charging the raw materials and the bottom being closed so that the products of combustion of carbon and hydrogen with oxygen in the ore passes out the top of the stack, it being impossible for air or oxygen to enter the fumace except as desired through injection valves into a preheating zone, which may be above the reduction zone and just below the charging zone, where the amount of air or oxygen injected is measured and where an electric induction melting furnace is located at the bottom, which fumace may be stationary or non-tilting, and wherein another induction electric heating coil is located around the outside of the vertical stack above the melting furnace about midway to the top of the stack, wherein the ore passes through the upper coil after discharge into the top of the stack where it is heated to about l,900 to 2,200F. to reduce the ore directly without melting, the ore being contained in a heat resisting alloy or graphite lined stack which heats up by induction, and wherein the reduced ore is melted at the bottom by an induction electric melting coil surrounding a refractory crucible thereby making it possible to charge raw materials into the top of the stack and draw off liquid refined metal at the bottom. Since the stack is open only at the top and since below the top the entire stack is an enclosed chamber, including both reducing and melting zones, the entire reduction and the melting operation takes place in the absence of air; the lower part of the stack being air-tight and the evolution of hot gases at the top preventing entry of air into the top of the stack.

The present invention also relates to a method for mixing finely divided iron ore (or other ores) with finely divided reductant materials such as powdered coal tar pitch, and similar compounds such as Gilsonite and then compacting such mixtures into dense briquettes up to about 4,000 psi after which the briquettes are heated to a comparatively low temperature of about 350 to 525F. for thermosetting, caramelizing or hardening after which the briquettes are processed into direct reduced iron by passing them through a direct reduction furnace where they are heated for approximately 15 minutes to about four hours at l,900 2,250F. in the absence of air or of oxygen.

A further object of the invention is the provision of a method for producing a shrunken briquette which is relatively non-porous and in which the reduced iron particles are coagulated or welded together into one dense coherent mass. Contrary to the usual direct reduced sponge iron these dense reduced briquettes do not reoxidize when exposed to the air.

Additional and more specific objects are as follows:

The provision of a method of preparing a briquette or other solid or compressed form of fine mesh oxide ore such as iron ore concentrate. copper oxide, manganese oxide, chromium oxide, with a fine mesh binder reductant binder such as coal tar pitch, Gilsonite and similar materials of low volatile matter content by mixing the materials intimately together and then compressing under relatively high pressures the combined powder into a compact briquette after which the briquette, or similar form, is hardened by low temperature baking and then reduced or deoxidized by passing it through a furnace or in a direct reduction process whereby the oxide ore in the briquette is reduced free of oxygen, the resultant product being a dense chunk of metal or shrunken briquette.

The provision of a method for preparing briquettes of fine iron ore mixed with fine coal tar pitch, the latter comprising 1 to 15 percent by weight, after which the briquette is heated to about 350F. to about 550F. to caramelize or harden the pitch binder so that it may be handled without breaking for the purposes of direct reduction of the iron ore to metallic iron.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings wherein:

FIG. 1 is a side elevational view in partial crosssection showing the overall arrangement of a preferred form of the induction heated shaft reduction furnace of this invention;

FIG. 2 is a cross-sectional view in expanded scale of the wall construction of the furnace of FIG. 1 showing the joint between upper and lower sections;

FIG. 3 is a side elevational view in partial cross section of a modified and improved version of the furnace of this invention showing the system and means for utilizing the recovery system to preheat briquettes;

FIG. 4 is a side elevational view in partial crosssection of the furnace of FIG. 3 showing the details of the furnace construction in enlarged scale;

FIG. 5 is a detail in cross-section and in larger scale of the joint between a lower cooled section of the furnace and an upper susceptor section of the furnace;

FIG. 6 is a detail of the joint construction between the susceptor section of the furnace and the preheat section of the furnace;

FIG. 7 is a detail of the joint between the preheat section of the fumace and the ore input bin of the furnace;

FIG. 8 is a cross-sectional view of the furnace taken in the direction of the arrows as indicated in FIG. 4;

FIG. 9 is a detail of the wall construction of the susceptor section of the furnace of FIG. 4;

FlG. 10 is a side elevational view in partial crosssection of a modified version of this invention showing the combination of an inductively heated reduction and inductively heated melting furnace.

FlG. ll is partially diagrammatic end view of a direct reduction fumace;

FIG. 12 is a cross-section along the line l2l2 of FIG. 11;

FIG. 13 is a perspective of a briquette for use with the fumace of FIG. 1;

FIG. 14 is an embodiment of a reduction system wherein cylindrical retorts are utilized and heating is accomplished by heating the retorts via electrical energy.

FIG. 15 is a cross-section along the lines l5l5 of FIG. 14 showing a retort construction;

FlG. 15A is a cross-section along the lines of 15-15 of FIG. 14 of another embodiment of a retort constructron.

FIG. 16 is a partially diagrammatic, longitudinal cross-section of another embodiment of the invention.

FIG. 1 shows an inductively heated shaft furnace comprising a generally vertical cylinder 20 which further comprises an upper susceptor section 22 which preferably is composed of a heat resisting alloy such as 25 percent chrome, 20 percent nickel alloy with iron, or any other suitable alloy or heat resistant conductive material such as graphite or silicon carbide. The wall of susceptor section 22 is preferably one half to about two inches in thickness. Susceptor section 22 is surrounded by an insulating cylinder 24 which is preferably composed of A1 0 foam insulation or insulating brick having a thickness of from 1% to 4 /2 inches. A water cooled copper tube 26 is helically wound around the insulating cylinder 24 to form an induction coil surrounding the susceptor 22 and separated therefrom by the heat insulating cylinder 24 surrounding the susceptor cylinder.

A conductive cylinder 28 is secured below susceptor cylinder 22 and is separated therefrom by an annular insulating disc 30, which is shown in greater detail in FIG. 2. The lower conductive cylinder 28 is cooled by an encircling blanket of downwardly flowing water 32 which is provided by an inwardly and downwardly sloping annular member 34 which cooperates with cylinder 28 to form a water containing trough; the bottom of the annular member being spaced from cylinder 28 to form an annular discharge port surrounding the conductive cylinder 28.

Since sometimes it is desirable to add gaseous or liquid reducing agents to the furnace, an input conduit 36 and a control valve 38 are provided for injecting a reducing fluid, such as a liquid or gaseous hydrocarbon, into the lower portion of the furnace through conductive wall 28. Gases may be withdrawn from the upper portion of the furnace, or oxidizing gases injected, through an exit conduit 40 which is controlled by valve 42.

Ore is supplied to the fumace by means of a skip hoist 44 which comprises a leading bucket 46, which, at its lower end, may rest in excavation 48 for loading, is carried on a frame 50 by means of cable 52 along a track 54 which is curved at the top to discharge the contents of bucket 46 into surge bin 56. The skip hoist is shown only in a generalized way since it is conventional and frequently used for charging blast furnaces and other types of furnaces. Such skip hoists as may be used with this invention are described by Baumeister, MECHANlCAL ENGINEERS HANDBOOK, 6th Ed. 1958, McGraw Hill, New York, Chapter Ten, and pages 10 and 13 to 14 in particular. Ore material handling devices which are conventionally used in relation to charging furnaces may be used in this invention. Such devices are described in Zimmer, MECHANI- CAL HANDLING AND STORAGE OF MATERIAL, Crosby, Lockwood & Son, London 1922, and more particularly, in the chapter on Fumace Hoists therein.

The loose unbriquetted ore which may be in the form of finely divided oxides or small lumps, such oxides mixed with finely divided reducing materials such as coke or coal in the reduction zone and in the furnace. Thus, a very simple means for controlling the reduction time and overall throughput of the furnace is provided. While not a necessary feature of this invention, it is preferred that one end of the continuous conveyor for controlling the discharge rate of ore from the cylinder to thereby control the furnace throughput and for conveying the reduced ore to a remote point exteriorly of the body of liquid as shown in FIG. 1. It will be realized that while a continuous belt conveyor is illustrated as exemplary of the invention, any other continuous conveyor capable of controlling the rate of discharge of the reduced ore from the furnace may be used.

While this invention is primarily intended for the reduction of iron, it may be used to reduce other ores such as chrome ore, and manganese ore in a manner similar to that used for reducing iron ore.

As illustrated, a preferred embodiment of this invention consists of a vertical cylindrical shaft or chamber with a skip hoist commonly used for cupolas and blast furnaces. A mixture of iron ore and coal or coke are charged into the top through a double bell feeder, of the type which is commonly used to charge blast furnaces. The top portion of the shaft or stack is heated to the reaction temperature by induction electricity. The electric current passes through a spiral watercooled copper tube coil which surrounds the top half of the furnace and heats up the alloy steel or graphite shell. This metal which operates at high temperature is a heat resisting alloy such as 25 percent chrome, 20 percent nickel, with the balance mostly iron, or other suitable alloy or refractory conductive material such as graphite. The shell is a susceptor because it is initially heated and in turn it transfers the heat to the charge. This entire operation is based on the fact that when iron ore is subjected to high temperatures about l,900 2,250F. in the presence of a carbonaceous reducing agent such as coal tar pitch or coke in the absence of free oxygen or air, this ore will be reduced. In one embodiment, briquettes of ore and reducing agents will be described. The ore passes from surge bin 56 to a weigh-batch hopper 58 and therethrough a double bell valve 60 into the furnace. Such ore charging devices are well known in the art and are described, for example, in US. Pat. Nos. 670,322; 1,865,476; and 2,408,945.

The ore charge passes under the force of gravity, downwardly through the cylindrical furnace sections 22 and 28. The ore is heated to its reaction temperature by heat conducted from the inner surface of susceptor section 22 which, in turn, is inductively heated by currents induced from induction coil 26. Electric energy for induction coil 26 may be provided by direct connection to an ordinary AC power line of proper voltage or from any of numerous commercial induction generators or static conversion units. Such equipment is described in the trade journal FOUNDRY of October, 1962, and devices of the type which may be used in this invention to provide the electric energy to the induction coil are manufactured and distributed by Inductor Therm Corporation, Rancocas, NJ. As the ore is partially reduced to the metal, the reduced portions of the ore become conductive to the electrical field and may then be directly inductively heated in the known manner. The reduced metal, commonly iron, passes downwardly through a cooling zone inside the cooled conductive section 28. Reduced iron then passes into a body of liquid 62 and is carried therefrom by a continuous conveyor 64 which may include a magnetic outer pulley 66 to separate the reduced portions 68 from the slag, ash, and unreduced portions 70. An important feature of this invention is the ability to control the throughput of the furnace merely by controlling the speed of the conveyor 64. It will be realized that control of the conveyor also controls the residence time of the ore at temperature, such as 1,900F. to 2,200F. for from minutes to about four hours in the absence of free air and in the presence of reducing agents such as coal tar pitch binder carbon, carbon monoxide, and hydrogen, the oxygen will leave the ore and combine with a reducing agent. A sample of this type of reaction is:

F6203 T CO2 2P6 Among the outstanding points of the invention are the following:

A closed chamber with an iron ore and reductant charge is heated by an induced electrical field. This is the only known practical means for heating a closed chamber. If it were heated by the usual means, as described in the prior art, it would be necessary to have an opening in the furnace and the furnace would no longer be sealed from the outside air. In addition, in the present process only one stack is required. The only refractory is a coating of from 1 k to 4 /z inches of alumina (M 0 insulator on the outside of the upper portion of the stack between the inductor coil and the stack or susceptor which is a conductor as alloy steel or graphite. Of course, alumina bricks may be used.

The heat loss is small because the hot portion is covered with an insulator. The lower portion is insulated by a separating heat and electrical insulator annulus from the upper half. This pennits the lower half to be 'cooled by a flowing sheet of water which is drained off into a body of water in a water tank at the bottom and which may be recirculated through a cooler and repassed over the lower portion of the stack.

FIGS. 3 and 4 illustrate another embodiment of the present invention. Generally, the furnace 120 of this embodiment is similar to furnace as previously described, and comprises an upper susceptor section 122 which is surrounded by an insulating cylinder portion 124 around which helical water cooled copper coils 126 are wound to fon'n an inductiJn coil. A lower cooled conductive section 128 is secured to susceptor section 122 and separated therefrorr by an annular insulating disc 130. An encircling blanket of downwardly flowing water 132 is supplied from annular member 134 which cooperates with conductive section 128 to form a trough, similar to the manner previously described with respect to furnace 20. Means for injecting a reducing fluid into the lower portion of the furnace 136 comprises, in furnace 120, a manifold communicating at a plurality of points with the inside of cooling cylinder 128. A metering pump 138 may be provided to control the inflow of reducing liquids or gases through manifold 136 to the furnace 120. A plurality of conduits 140 extend through the susceptor section 122 and open in a zone above the induction coil for injecting oxidizing gas into the furnace at a point above the reducing zone therein for reacting with reducing materials to preheat the ore in the top portion of the furnace.

A skip hoist 144 having a bucket 146 which, in its lowered position may rest in depression 148 and which is guided by frame 150 and lifted by cable 152 along guide track 154 where the ore is discharged into a surge bin 156. After reduction, the ore is discharged into a body of water 162 and carried therefrom by a conveyor 164 which may include a magnetic separator 166, in the manner described with respect to the furnace 20. The ore is then dumped into a container 172 where it may be transferred to a melting furnace, sampled, or otherwise handled or stored.

Significant differences exist between the furnace 120 and furnace 20 as described previously. The connection between susceptor section 122 and conductive section 128, which is shown in enlarged detail in FIG. 5, and which may include a bolt 131, is generally similar to the connection of the susceptor 22 and conductive section 28; however, an additional preheat section is connected, by means shown in enlarged detail in FIG. 6, to the top of susceptor section 122. The preheat section may comprise a preheat cylinder 174 surrounded by an insulating cylinder 176 which is connected by a bolt, or other fastening means, directly to susceptor section 122. The surge bin 156, which in the present embodiment is surrounded by insulating member 180, is connected by a bolt 182, or other convenient fastening means, to the top of heater section 174, as shown in greater detail in FIG. 7.

FIG. 8 shows in cross-section the internal constructional features of susceptor 122. It will be seen that a plurality of vanes 184 and 186 are secured to the inner surface of the susceptor cylinder 122. The vanes extend radially inwardly to the reduction zone in the susceptor cylinder. In a preferred embodiment, susceptor section 122 may be built up of a plurality of cylinder segments 188 which may be secured to each other by a weld bead 190, as best shown in FIG. 9.

Referring again to FIG. 3, the furnace of this embodiment may comprise a mixer and feed bin 192 for iron or other oxide ore plus binder or other reductant. The mixed ore and reductant are fed to a briquette machine 194 and are conveyed through a heating zone 196 by a conveyor 198 which may be of any conventional type. Heat is supplied from an enclosure 200 which is secured to the top of the vertical cylindrical furnace for collecting the gases expelled therefrom and passing them through conduit 202 to the heating zone 196. The heated gases may be propelled by a gas pump 204, in conduit 202, which may be of any convenient type. Thus the heat from the furnace is recovered and used to preheat briquettes which have been formed by briquette machine 194. The preferred temperature in heating zone 196 is in the range of 350 to 550F., preferably about 525F. It may be necessary or desirable to supplement the heat from the furnace for regulation purposes. Supplemental heat may be provided by any convenient means, such as an electrical resistance heater or a gas fired heater adjacent the heating zone 196.

The hard caramelized briquettes, which may be of the type described hereinafter, are carried by skip hoist 144 to the top of the furnace. As these briquettes pass downwardly through the furnace they may be preheated by the injection of air or oxidizing gas into conduits 140, which are located above the reduction zone. The oxidizing gas reacts with part of the reducing material associated with the briquettes to preheat the briquettes to a point just below their reduction temperature. As they pass downwardly through the furnace, the heated briquettes contact vanes 184 and 186 which efficiently transfer heat to the briquettes. Vanes 184 and 186 induce current and heat flow radially inwardly from the susceptor section 122. It will be understood, of course, that the vanes are composed of a high temperature resistant susceptor material. In this manner the briquettes are preheated economically by using abundant carbonaceous fuel and the precise temperature required for most efi'icient reduction is controlled by induction heating. This combination of preheating and induction heating is highly desirable for high efficiency. A spacer support 206 of any non-conductive material may be used to position coil 126.

The embodiment of the furnace as described is particularly advantageous in that it permits a continuous process including the interrnixing of ore and reducing agent, the formation of briquettes from the intermixture of ore and reducing agent, preheating the green briquettes to harden, or caramelize them to permit handling, and the reduction of these briquettes, after preheating, by carefully controlled inductive heating.

In order to further increase the efiiciency of the reduction furnace, vanes have been provided which are, in a preferred embodiment, integral with and extending inwardly from a cylindrical shell around which the induction coil is located. In this manner, heat is transferred efficiently to the ore being reduced, and is transferred unifonnly and rapidly across the entire section of the stack so that the reduced ore reaches the reaction temperature quickly. The large surface area provided by the interior surface of the cylindrical shell, and increased by the inwardly extending vanes, helps to transfer the heat into the charge quickly. In addition, as the ore begins to be reduced to the metallic form, the electro-magnetic field set up by the induction coil generates heat directly within the partially reduced iron ore as the latter becomes conductive.

While the furnace has been shown in a generally vertical plane; it will be realized that it is necessary only that the fumace be oriented upwardly from the horizontal to permit gravity feed through the furnace, or, if the furnace is horizontally oriented, to provide means for conveying the ore through the fumace. It will also be noted that in the embodiment of the furnace just described, furnace 122, the top of the furnace is partially open to the atmosphere. While it is generally desirable to maintain the to of the fumace stack closed to prevent loss of heat and valuable reducing gases, it will be understood that the furnace may be operated with an open top, the flow of exiting reducing gases preventing entry of oxidizing gases into the furnace.

The temperature of the furnace may be precisely controlled by the use of induction heating, and the reducing atmosphere in the fumace is controlled by the amount of reducing agent intermixed with the ore and is further controlled very precisely by the selective addition of reducing liquids or gases by injecting means 136. Of course, by careful preparation of the ore intermixture with reductant, it is not necessary to supplement the reducing material. The temperature of the briquettes as they enter the reducing zone may be carefully controlled by varying the amount of oxidizing gas which is injected into conduits 140.

While an experienced operator can make the necessary adjustments in throughput by varying the speed of conveyor 164, in oxidizing or reducing conditions by varying the input of reducing or oxidizing materials through injecting means 136 and 140 and in the temperature of the ore in the furnace by controlling the power input to induction coil 126 by merely observing the color of the exiting flame, it will be realized that the control process may be also automated as a function of the exhaust gas which may be extracted or sampled through an output conduit 208. Thus an automatic sampler and control system, such as those built and designed by Minneapolis-Honeywell and by Leeds and Northrop may be used to automatically control the furnace.

In a specific embodiment, the susceptor section 122 may be a 29% inch o.d. cylinder having a wall thickness of one inch and having vanes 184 extending inwardly to the circumference of a 13% inch circle and vanes 186 extending inwardly to the circumference of a six inch circle. The susceptor cylinder 122 may be made of nickel chrome alloy or other refractory type conductor such as graphite and may be eight feet long. The preheating zone may be of the same diameter, without vanes, and may be two feet long, below a three foot long surge bin. The cooled conductive cylinder may be of the same diameter and 10 feet in length. Conduits 140 are conveniently /2 inch diameter pipes and may be composed of a heat resistant alloy. FIGS. 3 and 4 are shown generally to scale with respect to the above dimensions and it is believed that one skilled in the art of furnace design and construction would have no difficulty in carrying out the invention.

FIG. 10 discloses a combination reduction and melting furnace which provides means for utilizing the heat generated during and prior to the reduction step. This furnace may be of the type described with reference to furnace 20 or may be of the improved type described with reference to furnace and comprises a top part 301 where the ore is preheated, a middle part 302 for induction electric heating coils 303, either shell or susceptor 304, which is made of heat resistant alloy, and a lower part 305 which consists of an induction electric melting furnace lined on the inside with refractory material 306.

The ore is charged in at the top by skip hoist 307, or by other means, and the stack is maintained completely full of charge ore and reductant at all times while in operation. In the embodiment shown, the top is usually open but it may be partially closed to exclude outside air. A tapping spout 308 at the bottom of the lower section of the melting furnace is used to empty the furnace of liquid metal. There is also a relatively vertically lo cated tapping spout 309 located at a higher level to remove slag which accumulates on top of the liquid bath.

While the furnace of FIG. has been described in rather general terms, it will be understood that the same constructional features and equipment which have been described hereinbefore and which are used in the prior art may be utilized in this combination furnace.

In the embodiments of the furnace previously described, reduced iron or other metal briquettes for sale as synthetic scrap and for melting in the usual melting furnaces, such as direct are or open hearth, LD oxygen, induction or other furnaces, to primary forms of steel or iron such as ingots, billets or pigs have been described. in the present invention, however, has been found advantageous to conserve the residual heat in the reduced briquettes and, instead of cooling these briquettes, to pass them directly into an induction electric melting furnace similar to the standard types used as remelting fumaces.

For the relatively small amount of induction heat required both in the reduction section and in the melting section it is convenient to use a 60 cycle current from the usual standard type power source, such as a distribution transformer, or other frequencies such as 180 cycles from a stationary frequency changing transformer or 1,000 cycles from a high frequency generator.

In using briquettes bonded with pitch, as will be described more fully hereinafter, the mixture of fine ore and pitch would first be briquetted and then hardened by heating at about 350 to 525F., then charged in the top of the furnace, which is kept filled. As the liquid metal is tapped from the induction electric crucible which forms the bottom of the stack, the charge descends by gravity in the stack thus continually feeding the reduced briquettes into the molten bath from which the molten metal is tapped off for further processing. In using loose lump or fine iron ore, not briquetted, the same operation is followed except the lump or fine ore is not bonded with the pitch but instead is mixed by mechanical means with reductant such as coal, coke or charcoal and then charged into the top of the stack.

The outstanding points of the invention may be enumerated as follows:

Direct reduction and melting in the same production unit is combined.

The advantages of mixing fine hard pitch with fine high grade ore, in briquettes as described hereinafter, thus obtaining an accelerated reaction by utilizing maximum surface contact area between ore and reductant and then melting the reduced ore without letting it first cool down is obtained with the resulting efficiency therefrom.

The product, a refined metal ingot or billet, free of excess slag or oxide, is suitable for rolling directly to the final product, or if it is in the form of pig metal, is suitable for sale directly as a synthetic steel scrap or pig iron.

While other direct reduction processes for iron ore give a product which is light or of low density and does not easily melt and which usually has about 10% of oxide and slag material, such as Si0 and A1 0 by the present apparatus and process these impurities are floated off as slag, and a refined metal product wherein the iron content is about 98 to 99.9 percent iron or metal is produced.

The electric power required to melt the red hot reduced briquettes is much less, about one-half, than is required to melt cold scrap or metal briquettes.

The present process does not require huge plants in the usual sense, such as hundreds or thousands of tons per day which require huge capital outlays. Plants of the type described can be economical in any size from a few tons, such as ten tons, up to hundreds or thousands of tons per day. One small stack can make ten tons per day, a large stack can make 50 tons per day and, for increase in size over 50 tons, multiple stacks may be used. For example, ten stacks may be used to make 500 tons per day.

By using the method reducing iron ore and melting the resultant product all in a single combustion furnace unit in a highly reducing atmosphere, there is less oxidation and therefore all the metal in the ore is recovered, whereas in other usual steel making processes such as the open hearth, LD oxygen, electric arc, or in any other melting furnaces where the molten bath is exposed to the oxygen of the air, there is considerable loss of the metal due to oxidation.

By the present method and apparatus it is possible to produce many different kinds of iron or steel, high carbon, low carbon, alloy steel and alloy cast irons. This is made possible and is subject to very close control because, first, a highly reducing atmosphere not only in the reduction zone but in the melting zone is utilized, and secondly, the final analysis of the alloy is determined and controlled to the desired composition by varying the composition of the charge going into the furnace. For example, if a chrome alloy is desired, chromium, ferrochrome or chrome ore may be added to the charge. In this manner, it is possible to make stainless steel, for example 18-8 or similar analysis, by using a charge made up of chrome ore, nickel and iron ores.

While the furnaces hereinbefore described are highly versatile and may be used with a large variety of ore and reductant combinations and ores in a large variety of forms, a particularly advantageous and preferred process has been developed and is carried out utilizing the furnaces of the present invention. Generally, this invention consists of taking a finely divided ore concentrate and mixing it with a finely divided carbonaceous reductant binder, preferably powdered coal tar pitch. The mixing takes place in the dry state, using an ordinary paddle or concrete bath type mixer whereby the mixing machine, by rotation or by mechanical agitation, obtains a thorough, intimate and uniform mixture throughout. The combined materials are then pressed into hard compact briquettes on an ordinary molding or briquetting machine. At this stage the green briquettes must be handled with care. They are put through a warm oven of about 350 to 525F. where the pitch is caramelized (hardened) and the briquette becomes hard and tough and may safely be handled by conventional means. The briquette may then be dipped or immersed in liquid asphalt, or otherwise coated with liquid asphalt, and, as it is extracted from the asphalt, powdered coal or coke is dusted onto the sticky asphalt in a manner similar to stuccoing of a finely divided hard material on a fresh plaster wall. This briquette is then ready to charge into the direct reduction furnace so that the ore may be converted directly with or without melting, into metals such as iron, copper, chromium, manganese or other metals.

In carrying out the process, the fine ore is mixed with a finely divided carbonaceous thermosetting reductant binder such as coal tar pitch or Gilsonite. When finely divided iron ore, for example 325 mesh, is mixed with finely divided coal tar pitch of about the same mesh, using about 1 to 15 percent pitch, and the balance, the finely divided and concentrated iron ore (by weight) and the mixture is formed by pressure into briquettes of about two inches to about 12 inches in diameter by about two inches to eight inches in height and the briquettes are heated to approx 350 to 525F. to thermoset or caramelize the pitch, the briquettes are hard and tough and may be handled without breaking.

When these hard, tough briquettes are heated in a highly reducing atmosphere to approximately 1,900 to 2,200F. the oxygen of the ore is removed by the pitch, which is a combination reductant-binder, and an iron briquette in shrunken form consisting of relatively solid metal iron with a slight amount of gangue material, such as silica and alumina, is produced. Quite unexpectedly, this shrunken briquette, about one half the former volume, is different from the usual sponge iron in that it is relatively non-porous. As the oxygen was re moved, the remaining reduced iron particles coagulate or weld together into one dense coherent mass. This is distinctly more valuable and useful than the usual porous low density form of sponge iron produced with the binder reductants of the prior art. The product herein does not have characteristics of ordinary sponge iron because it is highly dense. Thus, it will not soak up wa' ter, is not easily reoxidized in the air, and when fed into a molten bath it sinks readily and is easily melted whereas the usual low density sponge iron or reduced iron pellets lie on the surface of a molten bath of iron or steel, reoxidize and do not readily melt in.

In its most comprehensive form, the process of this invention contemplates the machining or hot forming by forging, of the solid, dense, shrunken metal bri quettes into useful articles, such as nuts and bolts.

While coal tar pitch is a highly preferred material, other materials may be used as a partial replacement for pitch, for example, powdered coke and gilsonite (a natural form of pitch). A combination of pitch with these materials may be used, such as five percent powdered pitch, five percent powdered coke, and five percent fine powdered coal or asphalt.

Binder materials used to make pelletized iron ore are usually clays, such as bentonite, or water glass. These are expensive and are ultimately wasted since they have no reducing power. On the other hand, my invention provides for materials like coal tar pitch which serve both as binder and as reductant and thus have dual or double function and avoid the waste inherent in the use of bentonite and similar non-reductive binders. In addition, these non-reductive binders increase the nonmetallic gangue content.

A pitch of the type which has been found satisfactory was obtained from the J. S. McCormick Co. of Pittsburgh, Pa., and has an approximate analysis as follows:

Melting point 300 to 320F.

Carbon 93.7%

Sulfur 0.5%

Hydrogen 4.1%

Nitrogen 1% Oxygen 0.6%

Ash 0.1%

The melting point must be sufficiently high so that the block pitch will be ground to a fine mesh at ambient temperatures without gumming" and also so it will mix dry with the fine ore concentrate. Iron ore concentrates with at least percent iron, and preferably from to about percent iron, are most advantageously used in the present process. Briquettes composed of such iron ore and pitch, bonded in the manner described in the process as reduced, do not tend to sinter or hang up in the furnace as has been a problem heretofore. There is no problem at all with bridging in the reducing or melting furnace with the briquettes of this process, especially briquettes which have been dipped in asphalt and stuccoed with powdered coal or coke. These desirable results occur in part from shrinkage of the briquettes during reduction.

The invention additionally encompasses the use of coal tar pitch-ore briquettes in novel crucible tubes heated by conventional fuels as well as by medium to high frequency inductive electric energy. Referring now to FIG. 11, the numeral 410 indicates furnaces of a different type which can be used in the invention. The furnace 410 is comprised of an outer wall 412 of a refractory material. Such furnaces can be electrically heated or can utilize conventional fuel such as gas, oil, coke or coal as is well known in the art. In the FIG. 11 embodiment, the fuel or heat is charged into the furnace by way of a conventional means, for instance, such as a gas line from burner 414. The furnace has the capacity to reach operating temperatures in the range of 2,350F. A thermocouple 416 is utilized as a sensor and control mechanism. The furnace is equipped with a vent 418 to allow the gases of combustion to escape.

The

end walls

420 and 422 of the furnace are also of a refractory material. Disposed within the furnace are a plurality of crucible tubes 424. These tubes are normally comprised of sections which are sealed together with a refractory at joints 425. The tubes are placed at a slant of approximately 25 to 40 and extend from an upper feed opening 427 in the wall 422 to a lower discharge opening 426 in wall 420. In the end elevation of FIG. 1 1, it can be seen that a pair of furnaces of the 410 type can be disposed with their walls 422 in spaced opposing relation on either side of a platform 427. At its upper end, retort 424 is enclosed by a door 428 and at its lower end a door 430. Supports 432 support the tubes in their sloping positions. The tubes are adapted to be charged by briquettes of a type indicated by the numeral 436. The briquettes can be brought to the loading area of platform 437 by way of the chute assembly 439. Sets of perhapd twenty retorts, ten on either side of the platform, can quite efficiently be fed from a single chute. The chute can be loaded at the end of the platform and, while horizontal, moved to a position over a retort.

A cross section of tube 424 is shown in FIG. 12. The dimensions of the tube and the dimensions of briquetted charges 436 are dependent on the practical consideration of easy handling. The briquettes 436 are formed with a plurality of holes 440 for gases to egress during reduction.

The inner lower surface of retort 424 is lined with graphite layer 438. The graphite layer supports the charges 436 and presents a surface of lesser friction than a refractory material such as silicon carbide.

In operation, a charge of briquettes is loaded into chute 431 and brought to a position adjacent a retort to be filled. Door 428 is opened and door 430 is closed. By a simple tilting manipulation of the hoist means 431, the chute is loaded into the retort. Door 428 is then closed. The charge is then subjected to heat from burner 414. The retort 424 can be of a material such as graphite or of a material such as silicon carbide. There are advantages to a retort having an inner liner of graphite and an outer layer of silicon carbide. The graphite is resistant to the abrasions of the briquettes and to the conditions within crucible. The silicon carbide, on the other hand, resists the high temperatures and other abrasive conditions in the furnace itself.

Another embodiment of a furnace is shown in FIG. 14. In this embodiment, a crucible or retort 446 is surrounded by a water-cooled induction coil 447 capable of operating at from 4,000 to 14,000,000 cycles per second. This invention encompasses two different methods of utilizing this structure. One uses a conductive refractory tube such as graphite with a relatively non-conductive briquette charge and the second uses a conductive charge with a relatively non-conductive refractory tube such as silica carbide. The crucible tube 446 can be vertical or slanted and is made of a combined silicon carbide graphite material.

In FIGS. 14 and 15 there is shown an embodiment wherein heat is supplied to the charge via coils 447 about the retort. The coils extend the length of the retort 446. In this embodiment the retort is manufactured of an inner liner of graphite 449 and an outer layer of non-conducting material such as a refractory 448. As in the FIG. 1 1 embodiment, the tube is heated and the charges are reduced via conduction and radiation from the retort.

A variation of the retort is shown in FIG. 15a. Here there is an inner layer 450 of silicon carbide, a graphite layer 449 and an outer insulating layer 447 of a refractory material. The coils 447 are about the layer 448. This variation is used with a frequency generator 458 means capable of producing frequencies of a level capable of inducing heat in the briquettes themselves. The briquettes become increasing conductive as they begin to reduce and this reduction will accelerate as a result.

in FIG. 16 there is shown a vertical refractory retort 460 which can receive a disoriented charge of briquettes. At its lower end, the retort is formed with a restriction orifice 462 substantially less in size than any single briquette. A coil assembly 464 adapted to emit ultra high frequencies from 4K to 4.5 megacycles, surrounds the refractory retort 460. With such a frequency source, heat of sufficient intensity first reduces and then melts the ore. As the metal liquifies, it flows through the orifice 462 to a holding melting fumace 465 for further processing. Coils 466 of more conventional induction frequencies maintain the liquid metal at desired temperatures.

In a general manner, while there has been disclosed an effective and efiicient embodiment of the invention, it should be well understood that the invention is not limited to such embodiment as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the pres- *ent invention as comprehended within the scope of the accompanying claims.

I claim:

1. A process for producing molten metal for casting purposes comprising the steps of,

forming a mixture of finely divided metal ore concentrate with a coal base pitch,

compressing said mixture into soft briquettes ranging in size from 2 to 12 inches in diameter and 2 to 8 inches in height,

thermosetting said soft briquettes to form hard briquettes at a temperature ranging from approximately 350F. to 550F.

continuously passing a multiplicity of said hard briquettes downwardly under the force of gravity through an elongated reducing zone,

excluding substantially all oxygen from said reducing zone,

reducing said hard briquettes in said reducing zone by heating said hard briquettes to a temperature ranging from approximately 1,900F. to approximately 2,200F. so that a relatively non-porous, shrunken briquette is formed that is substantially reduced, and

passing the briquettes from the reducing zone into a melting zone to produce a supply of molten metal, thereby conserving the residual heat in the briquettes from the reducing zone.

2. The process of claim 1 wherein said mixture comprises approximately 1 to 15 percent coal base pitch and to 99 percent finely divided metal ore concentrate by weight.

3. The process of claim 1 wherein said briquettes are reduced in said reducing zone by at least percent.

4. The process of claim 1 further including the step of injecting a fluid carbonaceous material onto the briquettes below the reducing zone while the briquettes retain residual heat from the heating step.

5. The process of claim 1 further comprising the steps of continuously passing a multiplicity of hard briquettes through a preheating zone prior to passing said briquettes through the reducing zone,

conducting gases produced in the reducing zone into the pre-heating zone,

introducing oxygen into the pre-heating zone for reaction with the gases from the reducing zone to utilize the residual and chemical energy in the gases from the reducing zone to pre-heat such hard briquettes, and

continuously passing such multiplicity of hard, preheated briquettes downwardly under force of gravity into the reducing zone.

6. The process of claim 5 wherein heating the briquettes during passage through the reducing zone comprises encircling the reduction zone with a susceptor material, and

inductively producing current flow in the susceptor material to resistively heat the susceptor material. 7. The process of claim 6 further comprising the steps of conducting the induced current flow radially inward into the reduction zone at a plurality of points; and

conducting the heat from the encircling susceptor material radially inward into the reduction zone at a plurality of points.

8. The process of claim 1 wherein heating the briquettes during passage through the reduction zone comprises the steps of encircling the reduction zone with a susceptor material, and

19 i 20 inductively producing current flow in the susceptor into.the reduction zone at a plurality of points; and material to resistively heat the susceptor material. conducting the heat from the encircling susceptor 9. The process of claim 8 further comprising the steps material radially inward into the reduction zone at of a plurality of points.

conducting the induced current flow radially inward 5

Claims

1. A PROCESS FOR PRODUCING MOLTEN METAL FOR CASTING PURPOSES COMPRISING THE STEPS OF, FORMING A MIXTURE OF FINELY DIVIDED METAL ORE CONCENTRATE WITH A COAL BASE PITCH, COMPRESSING SAID MIXTURE INTO SOFT BRIQUETTES RANGING IN SIZE FROM 2 TO 12 INCHES IN DIAMETER AND 2 TO 8 INCHES IN HEIGHT, THERMOSETTING SAID SOFT BRIQUETTES TO FORM HARD BRIQUETTES AT A TEMPERATURE RANGING FROM APPROXIMATELY 350*F, TO 550*F. CONTINUOUSLY PASSING A MULTIPLICITY OF SAID HARD BRIQUETTES DOWNWARDLY UNDER THE FORCE OF GRAVITY THROUGH AN ELONGATED REDUCING ZONE, EXCLUDING SUBSTANTIALLY ALL OXYGEN FROM SAID REDUCING ZONE, REDUCING SAID HARD BRIQUETTES IN SAID REDUCING ZONE BY HEATING SAID HARD BRIQUETTES TO A TEMPERATURE RANGING FROM APPROXIMATELY 1,900*F. TO APPROXIMATELY 2,200*F. SO THAT A RELATIVELY NON-POROUS, SHRUNKEN BRIQUETTE IS FORMED THAT IS SUBSTANTIALLY REDUCED, AND PASSING THE BRIQUETTES FROM THE REDUCING ZONE INTO A MELTING ZONE TO PRODUCE A SUPPLY OF MOLTEN METAL, THEREBY CONSERVING THE RESIDUAL HEAT IN THE BRIQUETTES FROM THE REDUCING ZONE.

2. The process of claim 1 wherein said mixture comprises approximately 1 to 15 percent coal base pitch and 85 to 99 percent finely divided metal ore concentrate by weight.

3. The process of claim 1 wherein said briquettes are reduced in said reducing zone by at least 90 percent.

5. The process of claim 1 further comprising the steps of continuously passing a multiplicity of hard briquettes through a preheating zone prior to passing said briquettes through the reducing zone, conducting gases produced in the reducing zone into the pre-heating zone, introducing oxygen into the pre-heating zone for reaction with the gases from the reducing zone to utilize the residual and chemical energy in the gases from the reducing zone to pre-heat such hard briquettes, and continuously passing such multiplicity of hard, pre-heated briquettes downwardly under force of gravity into the reducing zone.

6. The process of claim 5 wherein heating the briquettes during passage through the reducing zone comprises encircling the reduction zone with a susceptor material, and inductively producing current flow in the susceptor material to resistively heat the susceptor material.

7. The process of claim 6 further comprising the steps of conducting the induced current flow radially inward into the reduction zone at a plurality of points; and conducting the heat from the encircling susceptor material radially inward into the reduction zone at a plurality of points.

8. The process of claim 1 wherein heating the briquettes during passage through the reduction zone comprises the steps of encircling the reduction zone with a susceptor material, and inductively producing current flow in the susceptor material to resistively heat the susceptor material.

9. THe process of claim 8 further comprising the steps of conducting the induced current flow radially inward into the reduction zone at a plurality of points; and conducting the heat from the encircling susceptor material radially inward into the reduction zone at a plurality of points.