US2057554A

US2057554A - Method of and apparatus for the reduction of oxide ores

Info

Publication number: US2057554A
Application number: US627340A
Authority: US
Inventors: James D Bradley
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-08-03
Filing date: 1932-08-03
Publication date: 1936-10-13
Anticipated expiration: 1953-10-13

Description

Oct. 13, 1936.

J. D. BRADLEY 2,057,554

METHOD OF AND APPARATUS FOR THE REDUCTION OF OXIDE ORES Filed Aug. 5, 19.32

4 Sheets-Sheet 1 lNgENTOR y aw mflmww Oct. 13, 1936. J. D. BRADLEY METHOD OF AND APPARATUS FOR THE REDUCTION OF OXIDE QRES Filed Aug. 3

INVENTOR Oct. 13, 1936. J. D. B'RADLEY 2,057,554

METHOD OF AND APPARATUS FOR THE REDUCTION OF OXIDE ORES INVENTOR Oct. 13, 1936. E 2,057,554

METHOD OF AND APPARATUS FOR THE REDUCTION OF OXIDE ORES Filed Aug. 3, 1932 4 Sheets-Sheet 4 which is highly reactive Patented Oct. 13,1936

UNITED STATES METHOD OF AND A REDUCTION 0 James D. Bradle Application August 3,

20 Claims.

This invention relates to the recovery of metals from their ores, and more particularly to the re-- covery of metals wherein the ore is in the nature of an oxide either naturally or by conversion from its natural state to the oxide state.

Various attempts have been made to reduce ores. particularly iron ore, directly from the oxide to a metallic form without first reducing the ore in a blast furnace and then purifying the resultmetal in an open hearth or other purification furnace, but. for various reasons such methods have not proved to be highly practical from a commercial standpoint. Such methods as have heretofore been most successful have been characterized by the mixing of the ore with coal or coke and heating the mixture in a reducing atmosphere, the iron oxide giving up its oxygen to the adjacent carbon particles, leaving the iron in a metallic state. This is often referred to as "sponge iron".

The present invention is characterized by a method and appartus in which the ore may be maintained out of contact at all times with solid reducing agents and in a reducing atmosphere with the ore through the exclusion of atmospheric air. With the present invention the reduction is effected at a relatively low fuel cost per pound of metal secured and the practice of the invention yields combustible gas which may be employed for various purposes externally of the reducing plant.

The invention may be readily understood by reference to the accompanying drawings, which are more or less diagrammatic, and which are intended to merely show one embodiment of my invention, such details as are old and well-known in the art being omitted or only schematically illustrated.

In the drawings:

' Figure 1 is a schematic view showing a side elevation-of a complete plant for the practice of the invention;

Figure 2 represents a transverse vertical section through the retort and reducing apparatus detached from the various auxiliary equipment shown in Fig. 1;

Figure 3 is a staggered longitudinal vertical section substantially in the plane of'line IIIIII of Fig. 2; I

Figure 4 is a transverse horizontal section in the plane of line IV-IV of Fig. 3; and

. Figure 5 is a detail view showing one arrangement for the melting of the processed ore.

According to the present invention, the ore to be treated is first preferably preheated and then introduced into a reducing chamber, preferably PPARATUS FOR THE F OXIDE ORES y, Pittsburgh, Pa.

1932. Serial No. 627,340

of the type in which the ore is kept continuously agitated and in which the ore may move progresto the coal on the interior. The distillation of the coal yields hydrocarbon vapors, particularly the CH4. As before stated, the spent gases, or partially spent gases, from the reducing chamber, are conducted from admission of atmospheric air, the CO2 is broken down to form an increased volume of CO(C+CO-.-=2CO). The water vapor 35 is broken down to form CO and hydrogen (H2O+C=CO+H2). These gases formed in the hot coke bed of the retort mingle with the products of distillation from the green coal to produce the reducing atmosphere above described. According to the preferred method of carrying out the process, the reducing gases, after leaving the retort, are cooled and treated to remove tar and sulphur and then forced by a compressor into a storage tank. Part of this gas is 46 led from the storage tank to a preheater and after being preheated is introduced into the reducing chamber for contact with the heated ore. Another portion of this gas can be used to fire the retort. Still another portion of it may be used 50 for melting the deoxidized ore to eflect removal of slag and other contained impurities, and any further excess of the combustible reducing gas can be used as may be desired.

In carrying out this process, it will be observed, 55

material do not comeinto contact except where the carbon is in a gaseous state. A second thing to be noticed is that the system is a substantially closed circulating system which excludes atmospheric air. The reducing gases, therefore, are not diluted with atmospheric nitrogen, with the result that they have a much higher ailinlty for the oxygen of the ore, it being well understood that dilution with inert substances reduces the rapidity and the efliciency of most chemical reactions.

In carrying out the method, I prefer that the system be operated at a pressure above atmospheric pressure, say a pressure of one atmosphere, so as to exclude atmospheric air, and because of this pressure and the fact that the gases are not diluted with nitrogen, the efficiency of the process is further increased.

.A further point of merit'in the system is the manner in which available heat units are used, with the result that the ore may be reduced at a relatively low fuel cost. In this connection it may be pointed out that the preheating of the reducing gas after it leaves the storage tank can be accomplished, and in the preferred practice of the invention, is accomplished by utilizing excess heat from the retort. In like manner excess heat from the retort is utilized in maintaining the ore at the reaction temperature and for preheating the ore. The heat from the reducing gases and products of distillation from the retort may be used for generating steam to supply the retort where additional water vapor is desirable.

In the process, the deoxidized ore may be obtained in its divided form and used in such commercial operations as require a sponge iron of this nature. For the production of metals, however, the process further contemplates the introduction of thetreated ore, preferably before it loses its heat, into a bath of molten metal and preferably in a state of diffusion, together with reducing gases, whereby any particles that have been only partially deoxidized may be completely deoxidized in this bath. The slag forming impurities are released from the particles and float to the top of the metal while the metal may be tapped from time to time from the bottom of the bath.

Because of. the fact that the process may be carried out without bringing the ore into contact with solid carbon particles, those impurities of coal and coke which form the ash of coal or coke are not mixed with the ore, with the resultthat the metal is not contaminated from the fuel and the metal which results is very low in carbon, and, moreover, the bulk of reduced ore does not have to be treated for the removal of carbon and coal or coke ashes. Since, moreover, the process may be effected without having the coal or coke in contact with the ore, the ore itself may be broughtmore rapidly to the reaction temperature than where there is a relatively large mass of comminuted coal or coke and comminuted ore, all of which has to be heated to the reaction temperature. The reaction temperature with high grade ores can also be higher because of the absence of those slagging impurities provided by coal or coke. This is desirable because the reaction of course takes place more effectively when the ore is highly heated, and it also takes place where the particles of the ore do not tend to cling together and agglomerate as they do if the temperature is too high and there are too many slag forming ingredients present.

first, that the ore and the carbonaceous reducing.

The process may be further and better understood and the novel apparatus will be described by reference to the accompanying drawings. Referring first to Fig. l, A designates the retort or reducing gas producing unit and B designates the ore treating unit. The letter C designates the melting. The various gas treating and gas storage units of the system are designated generally as D.

The unit A, shown in more detail in Figs. 2 and 3, comprises an outer wall structure 2 within which is a retort 3 having a distillation chamber 4. The walls. 2 of the structure are preferably formed of a heat insulating refractory, while the retort walls 3 are preferably formed of a heat conducting refractory such as silicon carbide. In the bottom of the unit A is a pit 5 adapted to hold a body of water 6, and the lower end of the retort 3 projects into this pit so as to be sealed by the water. It is supported on piers] at its bottom. It is also provided with an ash pan 8 having a screw conveyor 9 therein for the removal of ashes from the bottom of the retort. In the retort above the water line there is a grate III for supporting the coal and coke in the distillation chamber 4. The walls ofthe retort I are spaced inwardly from the outer walls 2 in order to provide a combustion space H at each side of the retort. The combustion spaces H are closed at their bottoms above the level of the wall seal by refractory partitions II. The retort 3 is of a generally rectangular shape, the combustion spaces Ii being provided only at opposite sides of the retort, while the ends of the retort are closed by the refractory walls l3, as shown in Fig. 3.

Located near the lower ends of the combustion spaces II are gas burners ll. At the top of the retort 3 there is a roof to, and this roof has one or more extensions 31) projecting through the top l5 of the unit A. Mounted above these extensions are feed hoppers to having feed chutes 3d delivering into the extensions 3b and provided with the conventional bell type closures Is for permitting the material to be fed from the hoppers into the retort while sealing the retort against the escape of gases through the hoppers.

The unit B for the deoxidation of the ore comprises a refractory structure which is above the unit A and offset laterally with respect thereto. As illustrated, it has side walls I6 and end walls [1 which enclose a vertical chamber l8. Leading from the top of the unity A is a flue passage ID that opens into the bottom of the chamber II. The chamber I8 is provided with a refractory baille 20, the arrangement being best shown in Fig. 3 where it will be noted that the passage l9 opens into the chamber It at oneside of the chamber. The baille 20 divides the interior chamber into a lower passage Ito and an upper compartment l8b. The baiiie 20 has an opening at 2| at that end which is opposite the flue I! so that the gases from the unit A flow first along the passage or compartment l8a, then through the port 2|, and in the opposite direction along the upper compartment l8b. In the upper part of the compartment lab there are two heat exchangers placed side-by-side and designated 22 and 23. They are of sheet metal construction, being formed of a heat resistant metal.

At the end opposite the baille opening 2| these heat exchangers provide a vertical passage ll between them so that the gases entering the compartment lab through the port it iiow longitudinally through this compartment into the vercharges into the storage tank ll.

spams ticalportorpassagell. Thepassageminturn,

opens into a horizontal passage it formed between upper and lower parts of the two exchanger units 22 and a. This horizontal passage in turn a terminatesinaverticalpassageltleadingtoa stack 21.

In the upper compartment llb there is an ore preheater which may conveniently comprise a heat resisting metal cylinder It having a receiving spout 2! at one end thereof which is turned upwardly and which communicates with a feed chute It leading from a hopper II. the

chute til being provided with feeding bells 82 of the conventional type. permitting the ore to is be fed into the preheater 28 while preventing the escape of gas from this unit. At the opposite end of the drum is is a downwardly turned gepipe It andin thedrum II is ascrew conveyor 84 for progressively moving the incomso ing ore from one end of the drum to the other.

The ore discharging from the outlet 38 delivers into the inlet extension 88 of the reducing chamber, which is in the lower compartment Ila of the chamber II, and which is designated It.

as This reducing chamber may conveniently comprise a drum formed of heat resisting metal having a screw conveyor 81 therein for agitating the ore and for causing it to travel from one end of the drum to the other, although obviously any so other suitable agitating and conveying means may be used.

On the end of the drum ll opposite the intake II is a discharge pipe 30. The screw conveyors l4 and 31 may be operated by common gearing 85 which, in turn, is geared to a driving motor It.

Referring again to Fig. 1, the distillation chamber of the retort has one or more outlet pipes 40 leading from a point near the top of the distillation chamber and preferably above the nor- 40 mal coal level in the retort. This pipe it conveys the gases from the retort to a cooler or heat exchanger 4| which is conventionally'illustrated and which may be of any well-known type. I

have shown a heat exchanger in which there is a water boiler 42 by means of which the gases from the ret rt can heat water to generate steam,

the boiler having an inlet pipe ll and a steam outlet pipe 44. The heat exchanger 4| has a gas discharge pipe 48 leading to a tar extractor 50 is of any known or preferred construction, and

which is only conventionally illustrated, such elements being well-known in the coal distillationindustry and forming no part of the present invention. From the tar extractor the gases are passed through pipe 41 to a desulphurizer 4., which is also conventionally illustrated, being a devicewell-known and commonly employed in the coal distillation industry, which serves to remove sulphur containing products from the gases. Q0 The gas is now cooled sumclently so that it can be handled by a compressor. Leading from the desulphurizer 48 there is a pipe 49 which goes to a compressor It, the compressor being conventionally illustrated. The compressor dis- The pressure storage tank Ii has a gas outlet e 52 coupled into a line it. One branch of this line leads through a pressure regulator conventionally indicated at It, to a circulating pump 56. Leading from the circulating pump 65 is a pipe which goes into the top of the heat exchanger unit 28. Leading from the bottom of the heat exchanger unit 23 is a pipe U which opens into the reducing drum It (see Fig. 3). 75 By reason of this arrangement the reducing gas from the storage compartment is preheated in the preheater It and then d in its heated state into the ore reducer where it travels through the ore in direction of movement of the ore andwhile the ore is being constantly stirred and agitated. These gases, upon leaving the reducer, enter the a direction counter to the ore preheating unit 2|, again traveling through I the ore in a direction counter to the flow of the ore, and they are removed from the unit It through pipe II. The pipe it (see Fig. 1) opens into the distillation chamber 4 of the retort above the grate. I ii, at the point designated. It. in Figs. 2 and 3. The steam pipe 44 may Join to the pipe It. as shown in Fig. 1, so that steam can be introduced into the retort along with the spent reducing gas.

The burners it are connected by a pipe til through which a combustible mixture is supplied to them. The pipe It may have a branch ti leading to any suitable gas generator (not shown) for supplying gas in the initial operation of the system. After the system has been operated and. 1 gas is available from the storage tank I, it may be conveyed to the pipe 60 through pipe II, and blower II. The blower is designed to handle a mixture of gas and air, and the air is supplied through pipe 64 leading from the preheater unit 22. The air enters the preheater unit 22 from atmosphere.

The deoxidized ore discharging from the outlet 38 of the unit It may be conveniently carried directly through a pipe or chute into the unit C which may be arranged as shown in Fig. l for the ore to go into the bottom of the unit, being blown in by a blast of reducing gas supplied through pipe II and pump 61 which is connected to the pipe 82. This unit C is heated from the burners It arranged around the top of the unit C and suppliedfrom the manifold 69 connected to a pipe It with the pipe It so as to receive the combustible mixture from the blower t3. Preferably, however, the unit C is of the construction shown in Fig. 5 in which the chute 65' has a feeder 1i therein of any preferred or conventional type. I have shown the feeder H or casing extends down point adjacent the bottom thereof. The burners ll serve to heat the interior of the structure and enter the structure through the top thereof.

a refractory plug, as shown. Spaced above the floor oi the melting chamber there is another opening or port 18 through which slag may run oil. when the metal and slag reaches a predetermined depth in the melting chamber.

Opening into the well or casing 14 at the top of the melting chamber is a pipe it corresponding to pipe It shown in Fig. 1, and which leads to a source of reducing gas. Burned gases are led out of the chamber" through a flue 11.

The operation of the system may now be followed. Coal is charged from the hopper to into the coking retort until the retort is nearly full.- As previously stated, the operation permits or the use of an interior grade or coal where this is the cheapest material obtainable. The invention also makesit commercially practicable to use a low grade of ore. Heat is applied to the retort through the combustible mixture introduced into the chamber ll through the burners l4. The heat of this combustion is transmitted through the walls of the retort to effect distillation-of the coal while the highly heated gases are conducted from the combustion chambers ll through the passage l9 and to the lowermost compartment lila of the chamber l8. They flow along this compartment, heating the ore reducing chamber 35, then flowing along the upper compartment i8b, preheating the ore in the preheater 28. From this point they flow through the

heat exchangers

22 and 23, heating the air for combustion in the heat exchanger 22 and heating the reducing gases for the reduction of the ore in the heat exchanger 23. The gases from the retort, on the other hand, pass through the pipe 40 into the heat exchanger 4|, where they are cooled, thence to the tar remover, and from there into the desulphurizer, after which they are forced by the compressor into the storage tank I. From the storage tank some of these gases are led to the burners i4. Other gas is led'to the heat exchanger 23 and from the heat exchanger through the pipe 51 into the ieducingunit 36. Here the reducing gases flowing across and through the heated ore react with the ore to remove oxygen from the ore. Leaving the reducing unit, they are conducted through the ore preheating unit 28 where they may have some effect in the initial reduction of the ore. They are removed from the ore prehcater and conducted through the pipe 58 back to the bottom of the retort. After a period of operation the retort contains a bed of glowing coke in the lowermost zone thereof. As previously explained, the spent gases from the ore reducing unit, comprising principally carbon dioxide and water vapor, are broken up to form carbon monoxide and free hydrogen. Carbon monoxide and free hydrogen together with hydrocarbon gas which is driven off from the distribution of the coal comprises the reducing gas which is circulated through the reducing unit 36, the gases having been cleaned of, tar and sulphurous compounds before being introduced into the reducing unit.

There is thus maintained a closed circulation of gases from the retort to the reducing unit and back to the retort, with the result that atmospheric air is not drawn into the system and the reducing gases are thus not diluted. Since there is a constantly increasing volume of gas being generated through the conversion of carbon dioxide and water vapor generated in the ore reducing unit to carbon monoxide and hydrogen, plus additional gases of distillation in the retort, an excess of gas is available for the burners I4 and 68. l a

The ore, after it has been deoxidized, discharges into the unit C through the central well or casing I4 into which there is being blown at the same time a volume of the reducing gas. The ore particles are thus again brought into intimate contact with reducing gas and are heated from the burners 68 at the same time. There is preferably at all times a residuum of molten metal in the bottom of the chamber 13 which accelerates the melting of the ore particles with the liberation of entrapped slag and impurities. In

this final diflusion o! the reducing gas and the heated ore particles in the presence of the molten metal, particles which have not been completely deoxidized are thereby completely deoxidized.

An important advantage of bringing the treated ore into intimate contact with molten metal, or blowing it through the molten metal, is that the fines and dust-like particles are immediately and completely absorbed, whereas in the ordinary ore reducing processes the fines are blown out as flue dust.

The metal which accumulates in the unit C, which is tapped ofl from time to time tobe cast into molds, or to be further treated, as may be desired, has been i'ound to be oi! a very pure quality, low in carbon, and low in those impurities which are normally found in pig iron from blast furnaces.

While I have, in the foregoing description, mentioned iron ore specifically, the invention is not confined to the reduction of oxides of iron, but is applicable to the reduction oi! various other metallic oxides. Due to the concentration of the reducing .gases and the exclusion of inert gases, the reducing operations are effected at temperatures considerably below those at which it has heretofore been thought practical to reduce ores, which is an advantage not only from the standpoint of the heat saved, but from the fact that the equipment and refractories are not disintegrated so rapidly at the lower temperatures at which the process can be effected. It is for the same reason that ores of other metals than iron, such for instance, as chromium, have been successfully reduced to a metallic state with this: process.

Where the ore -is a sulphide ore, or contains a percentage of sulphide, the sulphur will combine with the reducing gas. In such instances, it may be necessary to circulate the spent reducing gas, through water or other treating apparatus to absorb any sulphuric .or sulphurous acids that are formed before the gases are returned to the retort.

It will also be appreciated that while I have described in considerable detail one specific system with particular apparatus that various changes and modifications may be made in the construction and disposition of the various parts within the contemplation-of my invention and under the scope of the following claims.

I claim:

1. The herein described method which comprises heating a retort containing a body of coal to effect distillation of the coal, utilizing excess heat from such heating operation to heat a mass of ore, circulating the gases from the retort over the heated ore, and then returning them to the retort andreducing them.

2. The herein described method which comprises heating a retort containing a body of coal to effect distillation of the coal, utilizing excess heat from such heating operation to heat a mass of ore, circulating the gases from the retort over the heated ore, then returning them to the retort and reducing them, and cooling, cleaning and again heating the gases after they leave the reexterior or the reducing unit for heating the to the reducing unit, and means for conveying gases from the reducing unit back to the retort.

4. An apparatus oi the class described comprising a retort, a combustion chamber around the retort, an ore reducing unit, means for conveying hot gases oi combustion from the combustion chamber to the exterior oi the reducing unit for heating the same, means for circulating gases from the retort to the reducing unit, and means for conveying gases from the reducing unit back to the retort, said reducing unit comprising a chamber having means for agitating the ore.

5. An apparatus 01 the class described comprising a retort, a combustion chamber around the retort, an ore reducing unit, means for conveying hot gases of combustion from the combustion chamber to the exterior or the reducing unit for heating the same, means for circulating gases from the retort to the reducing unit, means for conveying gases from the reducing unit back to the retort, said reducing unit comprising a drum having means for receiving the ore at one end, means for discharging the ore at the other end, and means for conveying the ore therethrough from one end to the other.

6. An apparatus 01' the class described comprising a retort, a combustion chamber around the retort, an ore reducing unit, means for conveying hot gases or combustion from the combustion chamber to the exterior of the reducing unit for heating the same, means for circulating gases from the retort to the reducing unit, means for conveying gases from the reducing unit back to the retort, said reducing unit comprising a drum having means for receiving the ore atone end, means for discharging the ore at the other end, means for conveying the ore therethrough from one end to the other, an ore preheating unit also heated from the gases of combustion and out the retort and comprising an enclosed chamber having conveying means therein, one end or the preheating unit discharging into the receiving end 01' the reducing drum, and means for feeding ore into the other end oi! the preheating unit, said i'eeding means including means for preventing the iree escape of gas from the ore preheating unit.

7 An apparatus of the class described comprising a system having a retort, an ore reducing unit, a common means for heating the retort and the ore reducing unit, means for conveying gases from the retort to the ore reducing unit, means for returning gases from the ore reducing unit to the retort, said system comprising the retort and ore reducing unit being substantially closed against the introduction of atmospheric air, the means for conveying gases from the retort to the ore reducing unit including a heat exchanger, a gas cleaning means, a compressor, a storage tank, and a gas preheater between the storage tank and the ore reducing unit.

8. An apparatus of the class described comprising a system having a retort, an ore reducing unit, a common means for heating the retort and the ore reducing unit, means for conveying gases from the retort to the ore reducing unit, means for returning gases from the ore reducing unit to the retort, said system comprising the retort and ore reducing unit being substantially closed against the introduction of atmospheric air, the means for conveying gases from the retort to the ore reducing unit including a heatexchanger, a gas cleaning means, a compressor, a storage tank,

and a gas preheater between the storage tank and the ore reducing unit, the gas preheater being adjacent the ore reducing unit and receiving heat from the same means as the ore reducing unit.

9. Apparatus for the reduction of metal from ore, comprising an ore reducing unit, means for circulating reducing gas through the unit, including a gas generator, the reducing unit being substantially closed against atmospheric air, means for conveying reduced ore from the ore reducing unit to a melting unit and terminating below the normal level of molten metal in the melting unit, and means for mixing reducing gas in intimate contact with the deoxidized ore before the reduced ore has been completely melted.

10. An apparatus oi the class described, comprising amelting receptacle having burners therein, a common conduit through which reducing gas and comminuted ore are introduced into said receptacle, said conduit terminating adjacent the bottom oi the melting unit an ore deoxidizing unit closed against the free circulation of air therethrough discharging into, said conduit, means for circulating heated reducing gases through said deoxidizing unit, and means in the deoxidizing unit for agitating the ore and conveying it to the conduit.

11. A system of the class described comprising an ore reducing unit having means for continuously conveying ore therethrough, means for feeding ore to said unit while substantially excluding the escape of gas therefrom, a retort, means for continuously supplying coal to the retort, a combustion chamber outside the retort, means for conveying gases from the combustion chamber around the reducing unit to heat the ore in the reducing unit, a gas cleaning and storage system into which the gases from the retort are passed, means for receiving gas from the cleaning and storage system, preheating it and conveying it to the reducing unit, said reducing unit being substantially closed against the escape of gases to the atmosphere, and means for conveying the gases from the reducing unit back to the retort.

12. A system of the class described comprising an ore reducing unit having means for continu ously conveying ore therethrough, means for feeding ore to said unit while substantially excluding the escape of gas therefrom, a retort, means for continuously supplying coal to the retort, a combustion chamber outside the retort, means for conveying gases from the combustion chamber around the reducing unit to heat the ore in the reducing unit. a gas cleaning and storage system into which the gases from the retort are passed, means for receiving gas from the cleaning and storage system, preheating it and conveying it to the reducing unit, said reducing unit being substantially closed against the escape of gases to the atmosphere, means for conveying the gases from the reducing unit back to the retort, burners in the combustion chamber for heating the retort, and means for conveying gases from the cleaning and storage system to said burners.

13. A system of the class described comprising an ore reducing unit having means for continu ously conveying ore therethrough, means for feeding ore to said unit while substantially excluding the escape of gas therefrom, a retort, means for continuously supplying coal to the retort, a combustion chamber outside the retort. means for conveying gases from the combustion chamber into which the gases from the retort are passed, means for receiving gas from the cleaning and storage system, preheating it and conveying it to the reducing unit, said reducing unit being substantially closed against the escape of gases to the atmosphere, means for conveying the gases from the reducing unit back to the retort, burners in the combustion chamber for heating the retort, means for conveying gases from the cleaning and storage system to said burners, and means heated by gases from said combustion chamber for preheating air and supplying it to said burners.

14. The method of reducing ore which comprises agitating the ore in a receptacle substantially closed against atmospheric air, heating the ore while it is being agitated, passing a reducing gas substantially free of atmospheric air through the chamber during heating and agitation of the ore, thereafter reducing any gases which have been oxidized by contact with the ore and recirculating them, and enriching the gases so circulated with additional hydrocarbon gases.

15. An ore-reducing and gas-generating appa ratus comprising an externally heated gas producing retort, a reducing unit where gas and oxygen-containing ore are brought into intimate contact, means including gas cooling, cleaning and storing equipment for conducting gas from the retort to the reducing unit, means for reheating the gas before it enters the reducing unit after leaving the storing equipment, and means for conveying spent gas from the reducing unit back to the retort.

16. The method of reducing ore and generating gas which comprises subjecting a, mass of carbonaceous material to heat and generating a reducing gas therefrom, cooling and storing the reducing gas, conveying some of the gas which has been cooled into intimate contact with a mass of heated oxygen-bearing ore to reduce the ore, returning the used gas to the heated carbonaceous mass, maintaining the gases and the carbonaceous mass and the ore during the operation substantially out of contact with atmospheric air, and utilizing waste heat from the heating of the carbonaceous mass for supplying heat to aid in reducing'the oxygen-containing ore.

17. The method of treating ore to recover metal therefrom, which comprises subjecting the ore to the action of a reducing gas and out of contact with solid carbonaceous material and at a temperature below which appreciable melting of the resulting metal particles takes place, then discharging the treated ore into a molten metal and slag bath below the surface of said bath. and simultaneously discharging a reducing gas into the bath below the surface thereof to further react on unreduced ore particles, the metal in said bath comprising metal' recovered from the ore.

18. The method of treating ore to recover metal therefrom, which comprises subjecting the ore to the action of a-reducing gas and out of contact with solid carbonaceous material and at a temperature below which appreciable melting of the resulting metal particles takes place, then discharging the treated ore into a molten metal and slag bath below the surface of said bath, and simultaneously discharging a reducing gas substantially free of atmospheric nitrogen into the bath below the surface thereof to further react on unreduced ore particles, the metal in said bath comprising metal recovered from the ore.

19. Apparatus for the reduction of ore and generation of gas, comprising a gas producer and an ore-reducing unit and, a gas circulating system connecting the two and arranged to transfer gas from the producer to the ore-reducing unit and from the ore-reducing unit back to the producer, the entire system being substantially closed to entrance of atmospheric air, the system including means for cooling and storing the gas after it leaves the producer and before it is returned to the reducing unit and for reheating it by waste heat from the producer after it leaves the storing means and before it enters the reducing unit.

20. Apparatus for the reduction of ore and generation of gas, an ore-reducing unit and a gas circulating system connecting the two and arranged to transfer gas from the producer to the ore-reducing unit and from the ore-reducing unit back to the producer, the entire system being substantially closed to entrance of atmospheric air, the system including means for cooling and storing the gas after it leaves the producer and before it is returned to the reducing unit, the producer being of the heated retort type, and means whereby excess heat from the reducing unit.

the producer is utilized in JAMES D. BRADLEY.

comprising a gas producer and-