US2701761A - Integrated cyclic process for producing metallic iron from iron oxide-containing material - Google Patents

Description

' H. CROWLEY Feb. 8, 1955 2,701,761 INTEGRATED cycuc PROCESS FOR PRODUCING METALLIC IRON FROM IRON OXIDE-CONTAINING MATERIAL Filed May 5, 1951 I 3 Sheets-Sheet 1 4 INVENTOR .fimrg L (raw/2y ATTORNEY MR E ma. \h

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8, 1955 H. L. CROWLEY 2,701,761 INTEGRATED CYCLIC PROCESS FOR PRODUCING "ETALLIC IRON FRO IRON OXIDE-CONTAINING MATERIAL Filed lay 5, 1951 3 Sheets-Sheet 2 I Ih M 4| h 3x+ z em vi INVEIN'I'OR flkary L llwv/eq BY PM J paw/W I ATTORNEY x Q n m BE 2.3.3

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' ORE m United States Patent INTEGRATED CYCLIC PROCESS FOR PRODUC- ING METALLIC IRON FROM IRON OXIDE-CON- TAlNlNG MATERIAL Henry L. Crowley, South Orange, N. 1., assignor, by mesne assignments, to Henry L. Crowley &'Company, Inc., West Orange, N. J., a corporation of New Jersey Application May 5, 1951, Serial No. 224,770

8 Claims. (CI. 75-34) The present invention relates to an integrated cyclic process for producing metallic iron from ironoxidecontaining material. More particularly, the present invention relates to a balanced process by which iron oxide-containing material may be processed, without going through the usual blast furnace and open hearth processes for the recovery of iron therefrom, and by resorting to more strictly chemical methods, the process being adapted to raw materials which are leaner or poorer in iron content than those required for use in present commercial ferrous-metallurgy methods.

In the present process for the treatment of lIOIl ores in the blast furnace to make cast iron and subsequently in an open hearth to refine this cast iron to eliminate many of the known impurities thereof, large amounts of heat are required as well as othermaterials such as limestone in order that the gangue portion of the ore be fluidized and separable as such from the molten iron. As such, these known processes are practically restricted by economic limitations to handling ore having a substantially high iron content, for example, an iron content approaching or exceeding 50%. Such iron ores are used up in the course of time, at least in any given locality, so that that locality is forced to use lower grade ores, which may still be available in abundant supply, but are useful in accordance with conventional processes, only at a considerably higher cost per ton of H011 produced. The lower grade ores may, however, provide the raw material for some new and essentially different process. The present invention provides such a new and different process. This new process is practicable when applied to relatively low grade sources of iron, as it operates to lift the iron out of the accompanying nonvolatile material or gangue, in a manner which is substantially independent of the relative amounts of iron and gangue in the ore.

Certain of the detailed steps of the present process form the subject matter of separate applications, which will be referred to particularly as the present description proceeds. The present process, however, covers the entire cyclic process, which is so integrated together as to the several steps, re-cycling of some of the materials used, control of the flow of materials from one step to the next, etc. that the process as a whole is practicable, not only from a technical point of view, but also from an economic point of view to compete successfully with the known process aforesaid in the production of metallic IIOH.

Summarizing the present process, it comprises the steps of introducing an iron oxide-containing material, which may contain FczOs, Fea04 and/or FeO in any desired proportions as between each other and as compared with the total material present (including gangue) and may also contain relatively small amounts of metallic iron, into a chloridizing zone. introduced into the chloridizing zone and remains in the solid phase throughout this zone. The chloridizing zone may be constituted by one or more such part zones arranged at different portions of a single piece of equipment, or arranged as a succession of the same or different types of pieces of equipment. In the chloridizing zone, whether this zone is considered as a single zone or one or more part zones, the solid material aforesaid is brought into contact with a chloridizing gas, which contains as essential ingredients, HCl and hydrogen. This gas may also contain more or less inert gas, such as nitrogen, and may also (in some special instances) in- This material is solid as elude some one or more reducing gases, such as carbon monoxide. In any event, the gaseous mixture which is brought into contact with the solid material in the chloridizing zone must include HCl and hydrogen, irrespec'-' tive of whether or not it includes some one or more other gases.

The next step is to pass the solid material from the chloridizing zone, and at a rate which is preferably adjustably controlled into a vaporizing zone. in this vaporizing zone the temperature is sufficiently high so that ferrous chloride is vaporized and in this way is lifted out of the gangue and/or any remaining non-volatile materials. The gases including vaporized ferrous chloride are thus separated from the remaining non-volatile materials in the vaporizing zone; and the non-volatile materials, irrespective of their proportion in the original raw material, may be discarded or used for any other desired purpose, forming no part of the present invention. It is noted that this solid material is never melted during the process thus far described, so that much heat is saved in this respect as compared with prior art processes.

The ferrous chloride vapor from the vaporizing zone is then conducted into a reducing zone and there brought into contact with a gas or gaseous medium, the essential active ingredient of which is hydrogen. In this reducing zone, a reaction takes place between the ferrous chloride vapor and hydrogen, resulting in the production of metallic iron, which is the desired product of the process. This metallic iron may then be separated from the remaining gaseous materials and the separated gaseous materials recycled in the process.

Two methods of separation of the products of the reducing reaction are included in the present invention. First, there is contemplated a hot separation, that is, one in which the gases are separated, while still quite hot, from the metallic iron. Under these circumstances, any ferrous chloride, which is not completely reduced to iron in the reducing zone, will remain in the vapor phase and may be recycled, along with any unreacted hydrogen and with the HCl which is produced as one product of the reducing reaction, to the chloridizing zone. In this hot separation cycle, ferrous chloride returned to the chloridizing zone with the recycled gases as aforesaid will be condensed in that zone, due to the lower temperatures maintained therein, and thereafter will be recycled through the process.

Any excess hydrogen included in the gases being recycled from the reducing zone will also pass through the chloridizing zone and may there be used to some extent in reducing any trivalent iron to bivalent iron. The HCl contained in these recycled gases will be used in the chloridizing zone to convert the iron therein to ferrous chloride.

In the cold separation phase of the process, the products from the reducing zone will be cooled to the point where not only metallic iron, but also any remaining ferrous chloride will condense out in solid form. There will then be a separation effected between solid materials resulting from this condensation and gaseous materials, particularly including hydrogen and HCl, and possibly also including any inert gases which may be present. It is preferable, even under these circumstances, that the temperature of the gases be kept sufiiciently high, so that any water vapor present therein will not condense out. The gaseous material resulting from this separation may then be returned to the chloridizing zone to react in that zone in the same way as described in connection with the hot separation cycle. The solid materials resulting from this cold condensation of the products from the reducing zone may then be separated from each other, for example, by leaching out the ferrous chloride from the iron by use of a suitable solvent, followed by evaporation of the solvent; or other separation may be effected as between solid iron and the solution of ferrous chloride. In the event that some organic solvent is used to dissolve the ferrous chloride at this stage of the process, a suitable solvent recovery system is contemplated for use, so that the solvent may be recycled in the process and the ferrous chloride discharged for such use as may be desired therefor, or, alternatively returned to the cycle, for example, to the chloridizing zone or to the vaporizing zone.

vertical section taken on the line The objects of the invention will be apparent from the chloridizing zohe due to the presence of hydrogen in this foregoing. While the principal features of the invention zone as hereinafter particularly set forth. which this purging of the solid material is etfected are The means by not particularly shown, as any suitable means may be used for this p se. 1

In both l igs. land 2 of theaccompanying drawings, the chloridizing'f 'zone consists of two chloridizers, the first of which is shown at I1 and the second of which is shown at 17. 'I-hechloridizing zone may generallybe comprised by one or more indepe" dent pieces of apparatus with provision for moving the solid material there- Fig. 3 is aforeshortened view, with parts principally in central section, illustrating a device which can be used to provide a chlorodizing zone or part zone;

Fig. 4 IS a fragmentary view, principally in transverse of Fig. 3;

Fig. 5 is a view, principally in central vertical section and somewhat diagrammatic, illustrating an apparatus usable to provide a vaporizing zone for the process; and

Fig. 6 is a diagrammatic view of apparatus usable to provide a reducing zone for the process.

In considering the particular process contemplated in accordance with the present invention, the first point to consider is the composition of the raw material supplied to the process. ally as an iron oxide-containing material. The iron oxide content of this material may be in any one or more of the forms FezOs, Fe3O4 or FeO. There may also be present relatively small amounts of metallic iron. The remainder of the material may be of any desired composition, so long as this composition does not substantially interfere with any of the processes contemplated for use in accordance with the present invention. Such other material may, therefore, be earthy or rock-type material, such as silica, which is completely inert. This other solid material mayalso include, for example, oxides of one or more other metals, such as calcium or magnesium, which could react with the HCl in the chlorodizing zone to form the corresponding chlorides, but wherein the chlorides would not be volatilized in the vaporizing zone along with the ferrous chloride, but would pass out in the gangue afid non-volatiles. It is further contemplated, that if desired, an original raw material or ore could be pre-treated in some way, for example, for reducing the iron content thereof to a ferrous state with carbon monoxide, so that iron oxide-containing material as supplied to the present through and preferably with independent control for the temperatures at difierent portions thereof, although the last is not absolutely essential.

As shown in Figs. 1 and 2, the chloridizers 11' and 17 are substantially identical. Again, this is not essential This material is herein desgribed generprocess may include a part or all the iron in ferrous form.

The raw material supplied to the process of the present invention should preferably be sufficiently comminuted so that a desired intimate gas-to-solid contact reaction can take place without having some of the iron oxide or iron physically protected from contact with the gases by surrounding solid material- For this purpose, it is preferred to comininute the raw material in any suitable way to a particle size, probably about 48 to 50 mesh or smaller. It is alsopreferred to have the raw material substantially dry as it is supplied to the chlorodizing zone in order to facilitate proper handling of the solid material and to avoid the expenditure of any heat which otherwise might have to be used in evaporating water therefrom.

As shown in Figs. 1 and 2 of the accompanying drawings, this iron oxide-containing material is supplied in any suitable way, forming no part of the present invention, to a suitable supply hopper 10. From this hopper the material is supplied at a desired and preferably conas the same.or difi'erent'types. of apparatus rriay be used .in any desired sequence and may collectively constitute a chloridizing zone. I As shown inthese two figures, the solid material from the first chloridizer 11 is passed through a suitable passage 18 to a screw feed chamber 19 provided with a helical feed member 20 driven by a. suitable prime movei', such as a variable speed motor 21.

In each of the chloridizers 11 and.17, there is illustrated a substantially helical material feeding and agitat ing means22, each of which is driven by a suitable prime mover, again illustrated as a variable speed motor 23. Surrounding each of the chloridizers 17 and 22 is a temperature controlling jacket 24 through which atemperature controlling fluid may be passed for controlling the temperatures in the different portions of the chloridizing zone. Each jacket 24 is provided with inlet and outlet passages 25 and 26.

In starting up the apparatus, it is necessary to bring up the temperature of the solid material in the chloridizing zone by the addition of'heatto this zone. In some instances, however, after the chloridizing operation is progressing in a continuous manner, no further heat addition is necessary as the chloridizing reaction is exothermic, and in some cases, some heat may have to be withdrawn and dissipated. This may be done by suitable control of the fluid circulated through the jackets 24.

The temperatures to be maintained in the various portions of the chloridizing zone are generally from about 500 F. to about 1200 F. In some cases, it may be desired to operate with a progressively increasing temperature gradient, following the teachings of the Graham et al. application, Ser. No. 127,428, filed November 15, 1949, now Patent No. 2,665,191, issued January 5, 1954. In other instances; it may be desired to carry on the chloridizing at'a substantially constant temperature.

In general, the rate of the chloridizing reaction is in- I creased with higher temperatures, although the equilibrium trollable rate into a chloridizing zone here generally inwhich is arranged a helical screw feed member 13, driven by a variable speed motor 14 or other suitable source of power, the speed of which is preferably controllable'. From the housing 12, the raw material may then pass through a passage means generally indicated at 15 under control of a suitable means such as a star valve 16 to prevent the outflow of gases from the chloridizing zone through the solid material input passage means 15 and 12. If desired, means may be provided to purge the incoming solid material of included air or oxygen-containing gases, as by passing through some selected part of the solid material feeding system above described an inert purging gas, such as nitrogen.

This will prevent to which this reaction proceeds may be more desirable under one set of temperature conditions than under another, as particularly discussed in the Graham et al. Patent No. 2,665,191 aforesaid.- In a preferred embodiment of the invention which follows the cycle set forth in the Graham et al., application aforesaid, the temperatures for the solid material are progressively raised during its passage through the chloridizing zone starting, for example, in a temperature range from about 500 F. to about 800 F. in the first chloridizerll, and rising to temperatures in the range of about 800 F. to about 1200 F. in the second or last chloridizer 17. This may advantageously be effected by passing heated gases into the jackets 24 of each chloridizer adjacent to the exit end thereof and exhausting such gases from the jackets adjacent to the ends of the chloridizers through which the solid material enters. These gases may be controlled as to their temperature at or'before they are introduced into for example, by diluting them with air from the at- 'mosphere at one or more selected points along the jackcts, in a manner not shown, but which will be obvious to those skilled in the art from this description.

Each or either of the chloridizers 11 and 17 may, for example, be substituted bya device constructed as particularly illustrated in Figs. 3 and 4.. In these figures there is shown a substantially cylindricalhousing' 27, which is provided at its ends with suitable bearing. means (not shown), in which is journalled a central, rotating shaft 28. The shaft 28 may also be journalled jin a suitable bearing 29 mounted on a rigid structure'fadjathe formation of a combustible gaseous mixture in" the cent to but outside the chloridizer. The shatt 28"is pro- Alternatively, the housing 27 may be inclined downwardly to some extent from the inlet end toward the delivery end, for the solid material, so that the agitation of this material by longitudinal blades, without a helical twist to the blades 31, may be effective in conjunction with gravity to move the solid material from the inlet to the outlet end of the housing 27. Surrounding the housing 27 is shown a substantially cylindrical jacket 32, which is provided in a manner not particularly illustrated with inlet and outlet means, through which a heated fluid, such as products of combustion, 'maybe circulated for controlling and maintaining the temperatures of the materials within the housing 27.

While there is illustrated and described in a general way two more or less similar types of equipment which may be used to provide a chloridizing zone, it will be understood that the other gas-to-solid contact equipment capable of withstanding the chemical effect of HCl gas, the erosive effect of the solid material flowing therethrough, and the temperatures involved as aforesaid, may be used in' lieu of either or both types of equipment herein illustrated and particularly described.

In the chloridizing zone, the solid material is brought into contact with a gaseous mixture, the essential active ingredients of which are HCl and hydrogen. The other gases which may be present in this mixture include inert gases such as nitrogen, and under certain special circumstances some carbon monoxide, as has been discussed hereinabove in the general summary of the invention. For the purposes of the present application, only two gases are essential as constituents in the chloridizing zone, namely, HCl and hydrogen.

In the chloridizing zone, iron in oxide form as FeO may be converted to ferrous chloride; and further if the iron is introduced into the chloridizing zone in a trivalent condition as F6203, it must also be reduced to a bivalent condition. In the event that some or all the iron is introduced as trivalent iron oxide such as FezOa or FeaO4, then the reduction of the iron to a bivalent condition preferably taltes place substantially simultaneously with the chloridizing thereof, or immediately prior to such chloridizing as to any particular portion of the iron. This also is discussed to a substantial extent in the Graham et al. Patent No. 2,665,191 aforesaid. A relatively small amount of iron introduced into the chloridizing zone in metallic form and any metallic iron formed therein by reduction of any of the iron oxides by the reducing gas present (as hydrogen) may be converted to ferrous chloride by reaction with the HCl present in the gases. In the event that reduction of the iron is required, hydrogen is present to effect such reduction. The HCl is present to effect a conversion of the iron to ferrous chloride. In the usual case, it is contemplated that the gases supplied to the chloridizing zone will pass therethrough in a direction substantially countercurrent to the flow of solid material through this zone. Here again, this is-not essential, but is usually desirable and is the process illustrated in the drawings, Figs. 1 and 2.

The constituents of the entering gas, which have been described aforesaid as to their essential ingredients, may now be described as to proportions. In these gases there should be about 2% to about 35% and preferably from about 5% to about 25% HCl based on the total of hydrogen and HCl. There may, in addition, be more or less diluent gases, the proportions of which to the combined hydrogen and HCl total is not particularly critical as long as there is sufficient HCl brought into contact with the solid material to chloridize the amount of iron which it is desired to chloridize. Usually, this will be all the iron content of the raw material, even though in some instancesall this iron may not be 100% chloridized in practice. 1

There are several ways in which the chloridizing step of the process may be operated. If it is desired to use up all the HCl in the gases, so that the gases leaving the chloridizing zone will contain substantially no HCl, then the rate of supply of the solid material supplied to the chloridizing zone may be maintained high in respect to the amount of gases passing therethrough and particularly the HCl content thereof. Under these circumstances, the HCl eficiency of the entire process may be kept at a maximum, even though at the cost of losing some iron, which will be discharged with the gangue, usually as unchloridized iron oxide, but possibly includrng some metallic iron reduced from the oxide by the hydrogen present in the gases.

On the other hand, if it is desired to operate the process so as to recover the maximum amount of iron, while possibly losing some HCl, then the amount of raw material will be relatively less in respect to the rate of supply of HCl in the gases to the chloridizing zone. In this 'way, little or none of the iron will be lost in the gangue, although the gases leaving the chloridizing zone may have some substantial HCl content. It is contemplated that some compromise between these two extremes of operation may be preferred as by using a plurality of chloridizers such as 11 and 17 as shown in Figs. 1 and 2 with a substantially countercurrent flow of solid material and gases. In this way it is possible to use up almost all the HCl while converting almost all the iron to ferrous chloride.

It is further contemplated'that more than two individual chloridizers could be used if desired. Under such circumstances, for example, three or more units could be provided with appropriate piping connections and material handling connections, so arranged that some one, or any one chloridizer, could'be by-passed for inspection or repair while using the remaining chloridizers. For example, if a third chloridizer were used, it could be operated in a temperature range of about 1000 F. to

about 1200 F. following the two chloridizers shown in the drawings, the third chloridizer being connected .to the second chloridizer 17 in the same way that that chloridizer is connected to the first chloridizer 11. Under such circumstances, HCl concentrations in the entering gases should be relatively high in order that the hydrogen presentin this gas will not serve to reduce the ferrous chloride formed to metallic iron, which is undesired at this stage of the process. If under these circumstances, there IS sufliclent I-ICl present in the gases, any metallic iron, which may have been formed in the earlier portions of thechloridizing zone, may be converted to ferrous chloride.

Thus, in general, the first chloridizer 11 or the first portion of the chloridizing zone from the. point of view of solid material maybe said to be effective to remove the last portions of the HCl content of the gases by provtdmg an ample amount of unchloridized iron oxide; the second or central section of the chloridizing zone is effective for suchreduction as may be necessary and chloridization in a relatively rapid manner; while the last portion of the chloridizing zone or a third chloridizer, if such a third chloridizer be provided, is usable to obtain a relatively high yield of FeClz from the iron present by contacting the solid material with a gas havmg a relatively high percentage of HCl, and also for chloridizing any metallic iron formed by reduction of a compound of iron in any previous portion of the chloridizing zone to form FeClz.

The solid material from the chloridizing zone is then supplied through to a suitable storage point indicated In Figs. 1 and 2 as a hopper 33. This is shown only diagrammatically in these figures; although in practice the solid material will be moved by gravity or bythe' use of suitable conveyor means fromthe chloridizing zone into the hopper 33. Suitable means, such as a star valve 34, may be provided for preventing gases from the chloridizing zone passing into the hopper 33.

While the chloridized material is in the hopper 33, suitable means (not shown) may be provided for purgmg therefrom any hydrogen in the solid material, so that when the ferrous chloride is vaporized from the solid material in the vaporizing zone, there will be no hydrogen present to react with the ferrous chloride vapor in this zone. This purging is normally effected by the use of an inert gas, such as nitrogen.

The next principal operation in the process is the vaporizing of the ferrous chloride to lift it out of the non-volatile material, including any gangue, which may have been present in the original raw material, and any non-chloridized oxides of iron. In order that there be a control of the rate of supply of ferrouschloride vapor to the reducing zone, which will be hereinafter described in detail, it is preferred that the vaporization of ferrous chloride from the solid material supplied to a vaporizing zone be quite rapid, if not instantaneous. In this way, it is possible, by controlling the supply of solid material to the vaporizing zone, to effect a control of the rate of supply of ferrous chloride vapor to the reducing zone.

As shown in Figs. 1 and 2, the material is supplied by gravity from the hopper 33 through a feeding means 35 to a vaporizer 36. The feeding means 35 may be provided as shown with a helical screw feeding device 37, which may be driven by any variable speed source of power, such as a variable speed motor 38. The solid material may pass from the feeding device 35 by gravity into the left hand end, as seen in Figs. 1 and 2, of a tubular member 39, and be moved through this tubular member by any suitable means such as a ram 40, driven by any suitable source of power (not shown) in a manner which will now be obvious to those skilled in the art. In the diagrammatic showing of the vaporizer 36 in Figs. 1 and 2, there is illustrated a jacket 41 surrounding the tubular member 39 and provided with inlet and outlet passages 42 and 43 for a heating fluid such, for example, as hot products of combustion. Alternatively, any suitable and available source of heat may be provided for the vaporizing zone, which in this instance, comprises the tube 39.

In Fig. there is shown a tubular member 44 located in a furnace generally indicated at 45. Heat may be supplied to the furnace by combustion therein. For this purpose there is illustrated a plurality of fuel burners 46 supplied from a common supply line 47, products of combustion leaving the furnace through a stack 48. The material may be moved through the vaporizing zone by a ram 40, which is reciprocated in a conventional manner by any suitable means (not shown). Solid materials may be supplied to the tube 44 through a passage 49. Ferrous chloride vapor may leave the tube 44 through a means indicated at 50 and pass thence to the reducing zone hereinafter described. Solid material from which the volatile portions have been vaporized may pass through to the right hand end of the tube 44, as seen in Fig. 5, and move by gravity through a passage 51, which may be provided with means for permitting the removal of this solid material without introducing any diluent gas or permitting the escape of gas from the vaporizer. Such means in the present instance comprises a portion of the passage means 51 provided-with spaced apart valves 52 and 53. The solid material may then be taken to any suitable disposal point and used for any desired purpose for which it is adaptable.

While it is contemplated that ferrous chloride could be distilled out 'of'solid material by a simple distillation operation and thereby be lifted away from this solid material, it may be desired to pass a carrier or sweep gas through the vaporizing zone. Such a gas will normally be an inert gas, as nitrogen, and will be supplied through the vaporizing zone in a manner not particularly illustrated, but which will now be obvious to those skilled in the art. Due to the partial pressure of this carrier gas, the vaporization point temperature of the ferrous chloride will be somewhat less than it would otherwise be. Thus, there is attained a minimum heat supply requirement for the vaporizing zone by reason of the lower temperature required to be maintained in this zone. This will result in corresponding savings in various parts of the process as will be-obvious to those skilled in the art.

Between the vaporizing zone and the reducing zone, the ferrous chloride vapors are preferably purified by removing therefrom any entrained solid particles. The means for accomplishing this purpose are not shown in the drawings as such means are substantially conventional whenever relatively pure gases are required. These means may, for example, take the form of one or more conventional filtering means.

The gas from the vaporizing zone having as' its essential ingredient, ferrous chloride, is then conducted to the reducing zone and there contacted with a reducinggas, having as its essential reducing ingredient, hydrogen. This will result in the reduction of the ferrous chloride to give as final products, metallic iron and HCl. This reaction and the'process of carrying it on are set forth in substantial detail in the copending application of Crowley et al., Serial No. 214,632, filed March 8, 1951, now Patent No. 2,663,633, issued December 22, 1953.

The reduction reaction when carried on in the vapor 8 phase in accordance with the present invention, is ex-. othertmc in character. Thus, the reducing zone, which is provided by an apparatus 54, shown only diagrammatically in Figs. 1 and 2, should be provided with suitable temperature controlling means by which it may initially be brought up to a desired temperature or in a desired temperature range; and thereafter excess heat may be dissipated, so that the temperature may be maintained at a desired point or in the desired range.

The reaction occurring in the reducing zone, may be expressed by the equation:

This reaction is a reversible one, which proceeds to an intermediate equilibrium. It is substantially impossible,

from a practical point of view, to carry on this reaction.

to a completion.- It has been found, for example, that while the reaction proceeds more rapidly from left to right as above set up when higher temperatures are used, the equilibrium end point of the reaction is nearer to 10.0% in the direction desired at relatively lower temperatures. For this reason, it may be preferred to carry on the reaction for a period at a higher temperature and then bring it to an equilibrium point nearer to 100% completion at a relatively lower temperature. This type process may be carried on in the device shown in Fig. 6, which is a structural showing of the reducing zone generally indicated at 54 in Figs. 1 and 2. As shown in Figs. 1 and 2, ferrous chloride vapor from the vaporizing zone (the vaporizer 36) is conducted through a passage 55 to the reducing zone or reducer as it is labeled on the drawings. A gas containing a substantial proportion of hydrogen is also supplied into the reducing zone. Means (not shown) are preferably provided for preventing premature contact between the ferrous chloride vapor and this gas in the reducing zone, so as to prevent the reaction occurring at a place such that the iron produced will tend to clog up the inlet passages for the ferrous chloride vapor, the hydrogen-containing gas, or both. Such means are not shown in the accompanying drawings as they form per so no part of the present invention.

Turning now to Fig. 6, there is illustrated a furnace indicated generally at 56, surrounding a structure 57, which provides the reducing zone and to which hydrogen I and ferrous chloride vapor are supplied through passage means generally indicated at 58 and 59 respectively. It will be understood that the passage means 59 of- Fig. 6 will be connected to the pipe 55 of Figs. 1 and 2. The furnace 56 surrounding the structure 57 which, as shown, may be in theform of a vertical cylinder, is preferably divided into upper and lower combustion chambers 60 and 61 by a diaphragm or wall 62. Each of the combustion chambers 60 and 61 is provided with means for the independent control of the temperatures within the structure 57; and for this purpose, each is provided with one or more independently adjustable burners as shown at 63 for the upper combustion chambers 60 and 64 for the lower combustion chamber 61. Independently adjustable valves 65 and 66 may be provided for controlling the passage of fuel to these two sets of burners. Separate independently dampered stack means 67 and 68 may be provided as shown for the combustion chambers 60 and 61 respectively.

The products resulting from the reaction in the reducing zone may then be treated in either of two ways: (A) by hot separation in accordance with the cycle illustrated in Fig. 1; or (B) by cold separation in accordance with the cycle illustrated in Fig. 2. In either case, the iron produced is eventually separated from the other products and is the principal product of the entire process.

Turning now to the Fig. 1 form of the invention in: cluding hot separation, the products resulting from the reaction in the reducer or reducing zone may be conducted through a passage shown at 69 to a separator generally indicated at 70. This separator may take any desired form, the details of which are per se no part of the present invention.

The metallic iron produced is collected in the conical lower portion 71 of the separator 70 and may be removed therefrom through a passage 72 having spaced valves 73 therein. As the separation is effected while the gases are hot, any ferrous chloride, which has not been reduced in the reducing zone,'will pass therefrom and through the separator as gas, mixed with unrea cted hydrogen and with the HCl produced by the reaction in the reducing zone. ln addition to this, there will be more or less inert gases, such as nitrogen, which may be used as aforesaid as the carrier gas by introducing it into the vaporizer. These gases may pass through a passage 74 to the last stage or portion of the chloridizing zone, here shown as the chloridizer 17. In the preferred form of the present invention, the chloridizing gases are those derived from the separation of the solid material following the reducing action in the reducing zone. Means (not shown) are preferablyprovided for retaining these gases hot, so that-heat loss is minimized and so that condensation of ferrous chloride in the lines is effectively prevented. This also serves as a method of introducing a substantial amount of heat into the chloridizing zone. In the chloridizing zone, due to the lower temperatures therein in respect to those in the reducing zone, any ferrous chloride present will be condensed, so as to pass out of the chloridizing zone as a solid along with ferrous chloride produced in that zone. The remaining gases will supply the gases required to be present in the chloridizing zone as aforesaid. In the event that it is necessary to supply additional HCl to the cycle, this gas may be supplied from any suitable source thereof to the gases passing between the separator 70 and the chloridizing zone, ,i. e., to the passage 74. Such make-up HCl may be introduced through a pipe 75 connected to the pipe 74 and provided with a suitable valve (as shown).

In completing the cycle, the only portion thereof which hasnot been fully explained is the disposition of gases leaving the chloridizing zone. These gases will contain some hydrogen, which has not been used in reducing iron oxide and which it is desired to recirculate, water vapor produced in the chloridizing zone by the reaction between hydrogen and iron oxide and between HCl and iron oxide, and also any water vapor introduced as moisture in the raw material, and any unreacted HCl. There may also be present more or less inert gas. These mixed gases are then preferably cooled and scrubbed in a suitable scrubbing device generally indicated at 76. For this purpose, these gases may be passed through a spray chamber through which cold water is supplied through a passage 77. The function of this scrubber is to condense out a large portion of the water vapor, and also to remove from the gas substantially all the HCl, which will pass out of the scrubber in the waste water as an HCl solution. This waste water including the dissolved HCl passes out, as shown, through a pipe 78. If the concentration of HCl in this waste water were sufficiently high, it could be recovered therefrom by means known to the art and which per se form no part of the present invention. The gases leaving the scrubber 76 pass through a pipe 79 enroute to the reducing zone.

In the event that some inert gas, as nitrogen, is being supplied to the vaporizer as aforesaid as a sweep gas or carrier gas, it may be necessary to bleed out and waste some of the gases leaving the chloridizer 11, so as to prevent the building up of the concentration of inert gas in the recirculating gases to an undesired high value. For this reason, a branch pipe 80 is provided, flow through which is controlled by a valve 81, the gases being discharged to the atmosphere or disposed of in any desired manner.

Suitable pumping means indicated at 82 are also interposed in the pipe 79 to insure the desired circulation of the gases as shown.

Due to the fact that hydrogen is used up in reducing ferrous chloride in the reducing zone and may also be used up to some extent in reducing iron oxide in the chloridizing zone, it is always necessary to supply to the recirculating gases in the system some make-up hydrogen.

. This may be done through a branch pipe 83 leading from some source of hydrogen (not shown) to the pipe 79 and provided with a suitable valve 84 by which the hydrogen being supplied to the system may be controlled. In order to determine and control the flow of gas and particularly the rate of supply of hydrogen to the reducing zone, a flow meter generally indicated at 85 is preferably interposed in the pipe 79 between the make-up hydrogen branch pipe 83 and the reducer 54. Gas flow through the pipe 79 into the pipe 58 and thence into the reducer may also be controlled by a valve 86 in one of these pipes as shown.

Turning now to the Fig. 2 form of the invention in which cold separation is employed, effective on the productsleaving the reducing zone, such products are shown passing from the reducer 54 through a pipe 87 to a cold separator 88, in which these gases are cooled at least to a temperature such that ferrous chloride will be condensed to solid form. Thus, both the iron and the ferrous chloride will be solid in the separator 88 and may be separated therein from the remaining gases. The separator 88 will include suitable cooling means in a manner not particularly illustrated in the accompanying drawings. The remaining gases may then pass through the pipe 74 to the chloridizing zone as described in connection with the Fig. 1 form of the invention, being augmented as may be necessary by make-up HCl through the branch pipe 75 under control of the valve therein.

Solid materials from the separator 88, which-consist essentially of metallic iron and unreduced ferrous chloride, may then be passed from the separator under suitable control (not shown) to a recovery system by which the iron may be separated from the ferrous chloride, so that both may be used as desired. One such system is indicated diagrammatically in Fig. 2 as including a leaching bath 89, in which the ferrous chloride may be dissolved in a suitable solvent. This solvent may include water, with suitable provisions being made to prevent undesired rusting of the iron. The undissolved iron may then be separated from the solution of ferrous chloride in asuitable separating means, such as a filter 90, and the iron passed to a suitable point where it maybe used. The solution may then be evaporated to leave the ferrous chloride, which may be used for any desired purpose, including admixing it with the raw material introduced into the chloridizing zone, so that it maythus be returned to the process. Alternatively, this ferrous chloride may be used for any other purpose for which it is adapted. In the event that some relatively expensive solvent is used, such as one or more of, the organic solvents, it may be desired to save the solvent and recycle it to the leaching bath through a passage 91 in which a pump 92 1S interposed. The details of this leaching, solvent extraction process form per se no part of the present invention and may be replaced by equivalent apparatus of any desired type. With this exception, the cycle illustrated in Fig. 2 may be essentially the same as in Fig. 1, so that the various common elements are indicated by the same reference characters.

The cycle as to some of the materials employed, which has been explained in considerable detail as to the several apparatus elements used in the process, must be coordinated together in practice, so that there will be a balance effected throughout all the operations. The primary control of the cycle is carried on by controlling the rate of feed of solid material to the vaporizer, for example, by controlling the speed of the motor 38. Then when the vaporizer is in operation, the flash type of vaporization effects a control of the rate of supply of ferrous chloride vapor to the reducing zone. If then, the rate of supply of hydrogen to the reducing zone is carefully controlled by controlling the amount of make-up hydrogen admitted through the pipe 83 by the valve 84, with the rate of supply of the gases indicated by the reading of the flow meter 85, the reaction within the reducing zone may be carefully and properly controlled. This in turn will control the amount of HCl produced in the reducing zone. This amount of H01, coupled with the amount of make-up 7 HQ introduced into the system by pipe 75 under control of the valve therein, will control the amount of HCl introduced into the chloridizing zone. This amount of HCl can then be balanced by the amount of raw material supplied to the chloridizing zone under control of the variable speed. motor 14. Thus, there is required in the entire system to assure a balance throughout, only one intermediate storage point, namely, the hopper 33, for the chloridized solid material. With this one storage point, it is possible to effect accurate control of every element in the system and all the recirculations therein.

Another interlocking arrangement in the process, which is necessary to be provided in order that the process as a whole shall be effective, is in connection with the hot separation cycle disclosed in Fig. 1. If the gases passing from the separator through the pipe 74 to the chloridizing zone are at a temperature higher than about 1250 F., ferrous chloride contained as a vapor in these gases may tend to condense as a liquid in the chloridizing zone, rather than as a solid; and also these highly heated gases will tend to melt the ferrous chloride produced in the agromet llll chloridizing zone upon their initial cbntact therewith. Any molten ferrous chloride in the chloridizing zone will tend to agglomerate with the rest of the solid materials in this zone and will prevent a desired, substantially free flow of these materials through the chloridizing zone. This will also result in hindering chloridization by mechanically masking the unchloridized material and preventing contact between it and the chloridizing gases. As a result and in order to avoid all these difiiculties, it is practically necessary that the gases being supplied to the chloridizing zone be at a temperature below about 1250" F., and preferably, in order to conserve heat, be almost up to this temperature, such as about 1200 F. Under these circumstances, due to ,the partial pressures of the other gases present, ferrous chloride will not condense out in the pipe 74, but will condense out in the chloridizer as a solid, rather than as a liquid.

hydrogen and FeCls vapor, introduced in these proportions into the reducing zone and maintained at a temperature of about 1250' R, react in such a manner that 94.3% of the FeCl: is reduced to metallic iron. After separation from the metallic iron, the exhaustgases, having the composition set forth above, are recycledto the chloridizing zone.

There follows examples illustrative of the various conditions under which the process of the invention may be practiced and of the interrelation of the several steps of the process. In these examples, the quantities given throughout are based on the production of one ton of iron powder in order that there may be a uniform basis for comparison of the various conditions as set forth.

Example I This example illustrates the conditions under which the process is practiced when the reduction step is carried out in such a manner as to produce an exhaust gas, used directly and as such for chloridizing and containing a relatively low HCl content, i. e., about 5% by volume:

For each ton of iron powder produced, 7240 pounds of Tobin Formation ore is fed into the chloridizing zone. This ore has the following average analysis:

Per cent Ignition loss 4.1 Gangue 49. F620: 46.6

' The ore is fed into the cold end of the chloridizing zone at a temperature of about 300 F. to prevent condensation of water vapor and HCl in the feeder. The ore moves through the chloridizing zone countercurrent to the stream of chloridizing gas and is gradually raised in temperature to about 1000 F. Because of the relatively high percentage of hydrogen in the chloridizing gas, it is necessary to keep the temperature of the solid material in the chloridizer below about 1050 F. in order to prevent the reduction of the FeClz formed to metallic iron at this oint.

p The chloridizing gas, which is recycled directly from the reducing zone, has a composition of about 0.15% FeClz vapor, 5.0% HCl, 92.55% Hz and 2.3% H all by volume. For each ton of iron produced, the weights of gas entering the chloridizing zone are: 270 pounds of FeClz, 2642 pounds of HCl, 2700 pounds of hydrogen and 600 pounds of water vapor. This includes 52 pounds of HCl added as make-up.

During its passage through the chloridizing zone, the

FeaOa in the ore is chloridized to the extent of about 85%, thus producing 8640 pounds of chloridized ore per ton of iron produced. This chloridized ore, together with 270 pounds of FeCl-z, which has condensed from the chloridizing gas in the chloridizing zone, is passed to a vaporizing zone, where its temperature is raised to about 1900 F. driving off 4830 pounds of FeClz vapor and leaving behind 4080 pounds of gangue to be discharged.

In the chloridizing zone, the gas stream loses practically all of its HCl content and some of its hydrogen content, while picking up water vapor from the moisture content of the ore and from the products of the reduction and chloridizing reactions. The resulting exhaust gases from the chloridizing zone contain about 94.3% Hz, 5.6% H20 and 0.1% HCl, all by volume and contain, per ton of iron produced, 52 pounds of HCl, 1720 pounds of water vapor and 2680 pounds of hydrogen. This gas is then passed through a scrubbing zone, wherein substantially all the HCl and 1320 pounds of water vapor are removed. The resulting gas contains 97.7% hydrogen and 2.3% water vapor by volume. To this is added 102 po unds of make-up hydrogen, so that the gas entering the reducing zone contains about 97.9% hydrogen and 2.1% water vapor by volume. Thus, the gases entering the reducing zone, per ton of iron produced, contain 2782 pounds of hydrogen and 400 pounds of water vapor. The

Example II This example illustrates the operation of the process when the reduction of FeClz is carried out so as to produce an exhaust gas from the reducing zone containing about 10% l-lCl by volume:

For each ton of metallic iron produced, 7240 pounds of Tobin ore of the composition given in Example I is introduced into the chloridizing zone in the same manner as described above in Example 1. However, because of the lower hydrogen content of the chloridizing gas, it is possible, in this instance, to raise the temperature of the ore to about 1100 F. at the hot end of the chloridizing zone, without the liability of reduction of FeClz, which is undesired at this stage of the process. As a result of this higher temperature limit, it is possible to chloridize somewhat more rapidly than under the conditions described in Example I.

The chloridizing gases recycled directly from the reducing zone, contain about 0.45% FeClz vapor, 10% HCl, 87.55% hydrogen and 2% water vapor, all by volume. For each ton of metallic iron produced, there is fed into the chloridizing zone about 410 pounds of FeClz vapor, 2540 pounds of HCl (including 24.5 pounds of make-up I-ICl), 1270 pounds of hydrogen and 260 pounds of water vapor. The gases leaving the chloridizing zone contain about 0.1% HCI, 10.3% water vapor and 89.6% hydrogen; or, expressed in terms of weight, 24.5 pounds of HCl, 1580 pounds of water vapor and 1228 pounds of hydrogen. These gases are subsequently passed to a scrubbing zone, wherein 24.5 pounds of l-ICl and 1320 pounds of water vapor are removed. Subsequently, 114 pounds of make-up hydrogen are added to the scrubbed gases, so that the gases entering the reducing zone contain about 2.1% water vapor and 97.9% hydrogen by volume. These gases as introduced into the reducing zone contain about 1342 pounds of hydrogen and 260 pounds of water vapor per ton of metallic iron produced.

The ore is chloridized in the same manner described in Example I above; and the chloridized ore is then passed to a vaporizing zone wherein the ferrous chloride is vaporized and separated from the gangue. Because of the somewhat larger recycled load of ferrous chloride vapor, there are 410 pounds of FeClz introduced into the chloridizing zone by condensation, as compared with 270 pounds introduced in the same way by the operation of the process in accordance with Example I. Thus, the total amount of ferrous chloride vapor passed to the reducing zone per ton of metallic iron produced is 4970 pounds. This reacts with the 1342 pounds of hydrogen,

which is introduced into the reducing zone as aforesaid.

Example 'III This example illustrates the operation of the process when the reduction of ferrous chloride vapor is carried out in such a manner as to produce an exhaust gas from the reducing zone containing about 15% HCl by volume.

As in the two previous examples, 7240 pounds of Tobin ore, of the composition given in Example I, is introduced into the chloridizing zone for each ton of metallic iron produced. Because of the lower hydrogen concentration in the chloridizing gas, it is now possible to raise the temperature in the hot'end of the chloridizing zone to about 1200 F. without the formation of metallic iron from the reduction of solid FeClz. However, at this temperature, certain mechanical difficulties begin to be encountered due to the agglomeration of solid material. Thus, 1200 F. appears to be about the maximum practical temperature at which the hot end of the chloridizing zone can be maintained. As a result of this higher temperature limit, it is possible to chloridize still more rapidly than under the conditions described in either of the two preceding examples.

The chloridizing gases, recycled directly, from the reducing zone, contain about 0.8% FeCla vapor, 15.0% HCl, 82.35% hydrogen and 1.85% water vapor, all by volume. Thus, for each ton of metallic iron produced, there is fed into the chloridizing zone about 490 pounds of ferrous chloride vapor, 2620 pounds of HCl (including 15.8 pounds of make-u HCl), 160' pounds of water vapor and 795 pounds of ydrogen. The gases leaving the chloridizing. zone contain about 0.1% H01, 17.2% water vapor and 82.7% hydrogen, all by volume; or expressed in terms of weight, about 15.8 pounds of HCl, 1480 pounds of water vapor, and 750 pounds of hydrogen. These gases are subsequently passed to a scrubbing zone, wherein about 15.8 pounds of HCl and 1320 pounds of water vapor are removed. Subsequently about 114 pounds of .make-up hydrogen are added to the scrubbed gas, so that the gas entering the reducing zone contains about 98% hydrogen and 2% water vapor by volume, These gases as introduced into the reducing zone contain about 864 pounds of hydrogen and 160 pounds of water vapor per ton of metallic iron produced.

The iron ore is chloridized in the same manner de-- scribed in the previous examples; and the chloridized ore is passed to the vaporizing zone. Under these cond tions, the gases leaving the reducing zone contain a slightly higher amount of condensed ferrous chloride, namely, about 490 pounds per ton of iron produced. Thus, per ton of iron produced, about 5050 pounds of FeClz vapor are introduced into the reducing zone along with the hydrogen-containing gas.

With the several ingredients present in these proportions, it becomes necessary to maintain the reducing and separating zones at a temperature of about 1300 F., as the increased concentration of ferrous chloride with respect to the hydrogen, as compared to the other two methods of operation (Examples I and II) would cause the condensation of ferrous chloride with the iron at lower temperatures, i. e., at about 1240 F. Thus, it is essential for this purpose that the reducing and separating steps be carried out at the higher temperature, i. e., about 1300 F.

Reduction in the reducing zone under these conditions is about 91% efiicient as to the percentage of FeClz vapor reduced to metallic iron.

After separation from the metallic iron, the exhaust gases having the composition set forth above, are recycled to the chloridizing zone.

It will be noted that there are certain apparent advantages in the method of operation described in this example as compared withthose described in the previous two examples. For instance, even though the reduction efiiciency is somewhat decreased, the amount of hydrogen which must be circulated in the system is very much decreased. Because of the relatively high concentration of FeCla vapor in the gases in the reduction zone, itis necessary, as explained above, to maintain this zone at somewhat higher temperatures, which results in a slight decrease in reduction elficiency.

Example IV This example illustrates the method of operating the process when the reduction of ferrous chloride vapor is carried out in such a manner as to produce an exhaust gas for chloridizing, containing about 25% E01 by volume:

When operating in this manner, 7240 pounds of Tobin ore of the composition given in Example I are introduced into the chloridizing zone for each ton of metallic iron produced. The temperature at the hot end of the chloridizing zone under these conditions, is limited to 1200 F., because of the mechanical difficulties due to the agglomeration encountered above these temperatures, as explained in connection with Example III above. The chloridizing gases entering this zone contain about 5.25% FeClz vapor, 25% HCl, 68.3% hydrogen and 1.45% water vapor, all by volume. Thus, there is introduced into the chloridizing zone about 1930 pounds of FeCl: vapor, 2607 pounds of HCl (including 8.5 pounds of make-up HCl), 398 pounds of hydrogen and 75 pounds of water vapor. The gases leaving the chloridizing zone contain about 0.1% HCl, 71.5% hydrogen and 28.4% water vapor, all by volume. These gases are then passed to a scrubbing zone, in which all the HCl, i. e., about 8.5 pounds, and 1320 pounds of water vapor are removed.

' 1.7% water vapor by volume. These gases as thus introduced into the reducing zone contain about 463 pounds of hydrogen and 75 pounds of water vapor.

Because of the relatively high FeCl: content of the chlorrdizmg gas, a correspondingly larger amount of ferrous chloride is now passed from the .reducing zone and condensed in the chloridizing zone, so that for each tone of iron produced, about 6490 pounds of ferrous chloride vapor. are now passed to the reducing zone from the vaporizing zone. Because of the relatively high concentratron of FeCl: with respect to hydrogen in the reducing zone, it is now necessary to maintainthe temperature in this zone at about 1450 F. to prevent the condensation of ferrous chloride during the reduction and separation steps. tion efliciency in the reducing zone is about 78%.

After separation from the metallic iron, the exhaust gases from the reducing zone, having the composition set forth above, are recycled to the chloridizing zone.

It will be noted that because of the high temperatures required to prevent the condensation of ferrous chloride in the reducing and separating zones, the efficiency of the reducing step of the process is somewhat lowered. It will also be noted, however, that a decrease in the amount of hydrogen to be circulated in the system is also obtained.

From the above, it is expected that a concentration of about 25% HCl by volume in the chloridizing gas is about the maximum practical concentration for most commercial operations of the process. This is so even though somewhat higher concentrations are operative, and may in some instances be desired for special purposes.

Example V This example illustrates the method of operating the process when the reduction of ferrous chloride vapor is carried out in such a manner as to produce an exhaust gas for chloridizing, containing about 35% HQ by volume.

When operating in this manner, 7240 pounds of Tobin ore of the composition given in Example I are introduced into the chloridizing zone for each ton of metallic iron produced. The chloridizing gases entering this zone contain about 29.5% FBCI: vapor, 35% HCl, 35% hydrogen and 0.5% water vapor, all by volume. Thus, there is introduced into the chloridizing zone about 7700 pounds of FeClz vapor, 2590 pounds of HCl (including about 5.3 pounds of make-up HCl), pounds of hydrogen and 20 pounds of water vapor. The gases leaving the chloridizing zone contain about 0.1% HCl, 62% water vapor and 37.9% hydrogen, all by volume. These gases are then passed to a scrubbing zone, in which all the HCl and about 1500 pounds of water vapor are removed. After leaving the scrubbing zone, about 102 pounds of make-up hydrogen are added, so that the gases entering the reducing zone contain about 98.5% hydrogen and 1.5% water vapor by volume. These gases, as introduced into the reducing zone, contain about 217 pounds of hydrogen and about 20 pounds of water vapor.

Because of the high FeCls content of the chloridizing gas, a large amount of ferrous chloride is now condensed in the chloridizing zone, so that for each ton of iron produced about 12,260 pounds of ferrous chloride vapor are now passed to the reducing zone from the vaporizing zone. Because of the relatively high concentration of FeClz with respect to hydrogen in the reducing zone, it is now necessary to maintain the temperature in this zone at about 1650 F. to prevent the condensation of ferrous chloride during the reduction and separation steps. Under these conditions, the reduction efficiency in the reducing zone is about 36%.

After separation from the metallic iron, the exhaust gases from the reducing zone, having the composition set forth above, are recycled to the chloridizing zone.

Example VI This example is set forth to illustrate the variations in operating the process encountered when a considerable quantity of inert gas is present in the recirculated gas stream:

For heat-saving purposes, it is sometimes desirable to Under these conditions, the reducintroduce an inert gas, as nitrogen, into the system, especially in the vaporizing zone thereof. The presence ofnitrogen enables the solid FeClz to be vaporized at a substantially lower temperature than otherwise. To this end, a sufficient amount of nitrogen may be introduced into the system to make up about 50% by volume of the recirculated gases. Thus, when operating n one of the preferred manners, i. e., where the chloridlzmg gas, exclusive of nitrogen, contains about 15% HCl by volume, the method of operation 18 similar to that described' in Example 111 above with the exceptions herein noted. The chloridizing gases recycled from the reducing zone contain about 0.40% FeCh vapor, 7.25% HCl, 40.50% hydrogen, 1.85% water vapor and 50% nitrogen, all by volume. The we1ght quant1t1es of the material fed into the chloridizing zone in this gas stream are about the same per ton of metallic iron produced as described in Example III, except that a higher amount of make-up HCl, i. e., 33.7 pounds, must be added before the gas enters the chloridizing zone. In order to produce one ton of metallic iron, 7240 pounds of Tobin ore of the composition given in Example I, 15 introduced into the chloridizing zone. The gases leaving the chloridizing zone contain about 0.1% I-ICl, 39.9% hydrogen, 7.95% water vapor and 52.05% nitrogen by volume. In order to prevent nitrogen from building up to too high a percentage in the system, it is necessary to bleed out a certain amount of gas from the system. As shown in Fig. 1, these gases are exhausted from the system beyond the scrubber 76, but it is contemplated that they could be withdrawn between the chloridizing and scrubbing steps. It is found convenient to bleed about 8% by volume of the exhaust gases from the chloridizing zone from the system in this manner. The remalmng gases are then passed through the scrubbing zone, as described in the previous examples, where substantially all the HCl content and some of the water vapor are removed by condensation. The gases leaving the scrubbing zone then have added thereto about 176 pounds of make-up hydrogen per ton of metallic iron produced, so that the gases entering the reducing zone have a composition of about 50% nitrogen, 2% water vapor and 48% hydrogen by volume. These gases as supplied to the reducing zone, contain per ton of iron produced,-about 325 pounds of water vapor, 870 pounds of hydrogen and 12,650 pounds of nitrogen.

The chloridized ore and condensed ferrous chloride are supplied from the chloridizing zone into the vaporizing zone at the rate of about 9130 pounds of chloridized material per ton of metallic iron produced and about 1120 pounds of nitrogen are passed through the vaporizing zone. This quantity of nitrogen permits the vaporization of FeClz at about 1750 F. as compared with the 1900 F. temperature that would be required were vaporization carried out without this carrier gas and at atmospheric pressure. The above-mentioned quantity of nitrogen, together with 5050 pounds of FeClz vapor, are supplied to the reducing zone and are there reacted at a temperature of about 1300 F. with the hydrogen-containing gases. Under these conditions, about 90.3% of the FeClz vapor is reduced to metallic iron. After separation from the metallic iron, the exhaust gases having the composition set forth above, are recycled to the chloridizing zone.

In addition to saving heat in the vaporizing step by the introduction of nitrogen, it is also possible to carry out the separation of metallic iron from the exhaust gases at a temperature as low as 1175 F., without condensation of FeClz, because of the large percentage of nitrogen present. However, in bleeding the system of the nitrogen, which is necessary to prevent undesired buildup of that gas, there is a certain hydrogen loss, amounting to about 61.5 pounds of hydrogen per ton of metallic iron produced.

Example VII volume of I-ICl for recycling to the chloridizing zone, and where a separate step of recovery of FeCl: in solid form is included in the process, the method of operation is substantially the same as that described in Example III above, as to the quantities and proportions of reactants circulated throughout the system with the exceptions hereinafter given. If the exhaust gases from the reducer are treated, as by cooling, to separate metallic iron and unreacted FeClz vapor from them, the remaining recycled gases will not contain any FeCln vapor. These gases, under these circumstances, will contain about 15% HCl, 83.15% hydrogen and 1.85% water vapor. For each ton of metallic iron produced, about 490 pounds of FeClz vapor will be condensed to solid form. This may be separated from the metallic iron by, for example, treatment with a suitable solvent as described above. When the solid ferrous chloride produced is recycled to the vaporizing zone and mixed with chloridized ore which is introduced from the chloridizing zone, there will be a total of 490 pounds of FeCl: and 8640 pounds of chloridized ore, totalling 9130 pounds of material leaving the chloridizing zone per ton of metallic iron produced. The FeCl from both these sources is then vaporized by raising the temperature in the vaporizing zone to 1900 F., and the vapor is passed to the reducing zone, where the reduction reaction takes place under the same conditions with regard to temperature, proportions of reactants, reduction efiiciency, etc. as described in Example III, above.

Example VIII A usual method of practicing the process of the invention is to provide iron oxide-containing material and HCl in the chloridizing zone in such proportions that preferably around of the iron oxide will be converted to FeClz. However, in some cases it may be desired to obtain a higher conversion of the iron oxide to ferrous chloride in the chloridizing zone. This example illustrates a method of practicing the invention to secure this result:

For each ton of metallic iron produced, 6160 pounds of Tobin ore of the composition given in Example I, is introduced into the chloridizing zone. This ore is reacted with the exhaust gas from the reducing zone, which is of the same composition.as the exhaust gas described in Example III above, containing about 0.8% FeCla vapor, 15% HCl, 82.35% hydrogen and 1.85% water vapor. To these gases, about 79 pounds of make-up HCl are added per ton of metallic iron produced, in order to insure that the amount of HCl introduced into the chloridizing zone will be in excess of that required to convert substantially all of the iron oxide in the ore to FeClz. The gases leaving the chloridizing zone contain about 0.5% HCl, 17.2% water vapor and 83.3% hydrogen, all by volume. These gases are then passed through a scrubber, wherein about 79 pounds of HCl and 1320 pounds of water vapor are removed per ton of metallic iron produced. The gases from the scrubbing zone will be of the same composition and contain the same amounts of material as the gases leaving the scrubber described in Example III a ove.

The solid material leaving the chloridizing zone after treatment in the manner described, includes about 7610 pounds of chloridized ore and 490 pounds of condensed FeClz per ton of metallic iron produced. After the 5050 pounds of FeClz contained in this material have been vaporized, 3050 pounds of gangue and non-volatiles per ton of metallic iron produced must be disposed of. This is' compared with 4080 pounds of gangue and nonvolatiles per ton of metallic iron produced when greater quantities of ore are introduced initially as in Examples I through VII above. It will be noted that the same amount of FeClz vapor may thus be produced from a smaller quantity of ore. This is due to the substantially complete chloridization illustrated by this example. The ferrous chloride vapor is then introduced into the reduction zone and there reacted with hydrogen, producing the same results as described in Example III above. The iron is then separated from the exhaust gases, which are recycled to the chloridizing zone.

It will be noted that while 1080 less pounds of ore 'are used when operating according to this phase of the process, to produce a ton of metallic iron than by the 'several methods described in Examples I through VII, a

correspondingly greater HCl loss occurs. Thus, in this example, 79 pounds of HCl are lostfrom the system per ton of metallic iron produced; while in Example III, which is comparable in other respects except as to completeness of the chloridizing, only about 14.8 pounds of HCl are lost from the system on a corresponding basis.

Example IX Although for some purposes it may be desired to operate the process under conditions of complete chloridizing, as discussed in Example VIII above, the converse result may, in certain cases, be desired, i. e., a substantially complete conservation of HCl at the possible expense of the degree of chloridizing of the ore. As an example of such a type of operation, 8800 pounds of Tobin ore of the composrtionset forth in Example I, is introduced into the chloridizing zone per ton of metallic iron produced. This ore is reacted with the same quantities of chloridizing gases containing 15% HCl, as described in Example III, above. of ore introduced into the chloridizing zone is sufficient to extract all of the HCl from the chloridizing gas, it is usually unnecessary to add any make-up HCl between the reducing and chloridizing zones, as in the other examples. The gases leaving the chloridizing zone are substantially free of HCl and contain about 18.3% water vapor and 81.7% hydrogen by volume. These gases are then passed through a scrubber or condenser, where 1350 pounds of water vapor are removed per ton of metallic iron produced. The gases leaving the scrubber or condenser are then of the same composition as the gases leaving the scrubber in Example III, above. After 1070 pounds of make-up hydrogen are added per ton of metallic iron produced, the gases are introduced into the-reducing zone.

The solid material from the ChlOlldlZll'lg zone now contains about 10,140 pounds of chloridized ore .and 490 pounds of condensed FeClz. Upon vaporization there is produced about 5050 pounds of lfeClz vapor and 5580 pounds of gangue and non-volat le material. The FeClz vapor is then passed to the reducing zone for reaction with hydrogen.

It will be noted that HCl is substantlally completely conserved by this method of operation, since a considerable excess of iron oxide-containing material is used. However, only incomplete chloridization of the ore is obtained so that only about 70% of the iron oxide is converted to FeClz. In addition to this 1500 pounds of additional non-volatile material must be handled per ton of metallic iron produced, as compared with the process operated to obtain about 85% chlorrdlzation, as in Examples I through VH, above.

Example X Per cent Ignition loss 12.28 Pesos 71.80 Gangue 15.95

Where the process is operated under the same conditions of reducing and chloridizing as in Example III above, i. e., with a chloridizing gas containing about 15% HCl by volume and by operating the reducing zone at a temperature of 1300 F., it is found that it is necessary to introduce only about 4700 pounds of ore per ton of metallic iron to be produced. This is compared with 7240 pounds of Tobin ore necessary to produce the same amount of iron under the similar conditions of operation. When this high grade ore is used, a greater amount of moisture is generated in the chloridizing gas per ton of metallic iron produced, i. e., about 1750 pounds of water vapor per ton of metallic iron. Thus, it is necessary to remove more water vapor in the scrubber. However, the amount of gangue and'non-volatiles to be disposed of is considerably less, i. e., 1260 pounds per ton of metallic iron produced as compared with 4080 pounds for Tobin ore.

While several embodiments of the invention have been disclosed In the specification and drawings and have been illustrated in the examples given, it will be understood that the process may be further varied as will occur to Because the amount those skilled in the art from the foregoing disclosure. The appended claims are to be considered as embracing such equivalents wherever this is not precluded by expressed limitations therein.

What is claimed is:

1. The process of preparing metallic iron from a solid iron oxide-containing material, comprising the steps of chloridizing a substantial proportion of the iron oxide of said material to form ferrous chloride by contacting said solid material in a chloridizing zone and at a temperature of at least 500 F. but below the melting point of said ferrous chloride with a gaseous mixture containing, as essential ingredients, HCl and hydrogen and wherein the HCl-concentration is from about 5% to about 25% by volume based upon the total of hydrogen plus HCl in said gaseous mixture; passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone and there raising the temperature thereof sufiiciently to vaporize the ferrous chloride content of this material; separating the vaporized ferrous chloride produced in said vaporizing zone from the nonvolatile material and passing the vaporized ferrous chloride into a reducing zone; separately introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for reaction with the ferrous chloride vaportherein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in said reducing zone between a temperature at which said ferrous chloride is retained in vapor form and the melting point of said metallic iron; separating the products resulting from the reaction in said reducing zone between said gaseous medium including hydrogen and said ferrous chloride vapor into (a) solid material including the metallic iron and (b) gaseous materials; including make-up HCl in said gaseous materials in amount required to provide the aforesaid relativeproportions of HCl and hydrogen in said chloridizing step and passing the resulting gaseous materials to said chloridizing zone as said gaseous mixture which is supplied to said chloridizing zone for use as aforesaid; removing the gaseous products of the reaction in said chloridizing zone from such zone and separating therefrom a substantial amount of the water vapor content thereof, and passing the remaining gases, from which water vapor has been removed and to which make-up hydrogen is added, into said reducing zone as said gaseous medium which is separately introduced into said reducing zone.

2. The process in accordance with claim 1, wherein said gaseous materials resulting from said reaction between hydrogen and ferrous chloride vapor in said reducrng zone and which are passed to said chloridizing zone contain from about 10% to about 15% 'of HCl by volume based upon the total of hydrogen and HCl with the balance being inert gas.

3. The process of preparing metallic iron from a solid 11011 oxide-containing material, comprising the steps of chloridizing a substantial proportion of the iron oxide of said material to form ferrous chloride by contacting said solid material in a chloridizing zone and at a temperature of at least 500 F. but below the melting point of said ferrous chloride with a gaseous mixture containing, as essential ingredients, HCl and hydrogen and wherein the HCl concentration is from about 5% to about 25% by volume based upon the total of hydrogen plus HCl in said gaseous mixture; passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone at a controlled rate and there raising the temperature thereof sufiiciently to vaporize substantially all the ferrous chloride content of this material at a rate substantially equal to the rate of introduction of said solid ferrous chloride into said vaporizing zone; separating the vaporized ferrous chloride produced in said vaporizing zone from the non-volatile material and passing the vaporized ferrous chloride into a reducing zone; separately introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for reaction with the ferrous chloride vapor therein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in said reducing zone between a temperature at which said ferrous chloride is retained in vapor form and the melting point of said metallic iron; separating the products resulting from the reaction in said reducing zone between said gaseous medium including hydrogen and ferrous chloride vapor into (a) solid material including the metallic tron and (b) gaseous materials; including make-up HCl m said gaseous materials in amountrequired to provide the aforesaid relative proportions of HCl and hydrogen in said chloridizing step and passing the resulting gaseous materials to said chloridizin zone as said gaseous mixture which is supplied to said chloridizing zone for use as aforesaid; removing the gaseous products of the reaction in said chloridizing zone from such zone and separating therefrom a substantial amopnt of the water vapor content thereof, passing the remaining gases from which water vapor has been removed and to which make-up hydrogen is added into said reducing zone as said gaseous medium which is separately introduced into said reducing zone; and controlling and balancing the operations of the several steps of the process aforesaid by controlling the rate of supply of ferrous chloride to said vaporizing zone, the rate of supply of hydrogen to said reducing zone and the amount of make-up HCl included in said gaseous materials passing to said chloridizing zone.

4. The process of preparing metallic iron from a solid iron oxide-containing material, comprising the steps of continuously chloridizing a substantial proportion of the iron oxide of said material to form ferrous-chloride by continuously contacting said solid material in a chloridizing zoneand at a temperature of at least 500 F. but below the melting point of said ferrous chloride with a gaseous mixture containing, as essential ingredients, HCl and hydrogen and wherein the HCl concentration is from about to about 25% by volume based upon the total of hydrogen plus HCl in said gaseous mixture; continuously passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone at a controlled rate and there continuously raising the temperature thereof sufiiciently to vaporize the ferrous chloride content of this material; continuously separating the vaporized ferrous chloride produced in said vaporizing zone from the non-volatile material and continuously passlng vaporized ferrous chloride into a reducing zone; separately and continuously introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for continuous reaction with the ferrous chloride vapor therein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in said reducing zone between a temperature at which said ferrous chloride is retained in vapor form and the melting point of said metallic iron; continuously separating the products resulting from the reaction in said reducing zone between said gaseous medium including hydrogen and said ferrous chloride vapor into (a) solid material including the metallic iron and (b) gaseous materials; including make-up HCl in said gaseous materials in amount required to provide the aforesaid relative proportions of HCl and hydrogen in said chloridizing step and continuously passing the resulting gaseous materials to said chloridizing zone as said gaseous mixture which is continuously suppliedto said chloridizing zone for use as aforesaid; continuously removing the gaseous products of the reaction in said chloridizing zone from such zone and continuously separating therefrom a substantial amount of the water content thereof, continuously passing the remaining gases from which water vapor has been removed and to which make-up hydrogen is continuously added into said reducing zone as said gaseous medium which is separately introduced into said reducing zone, and controlling and balancing the operations of the several steps of the process aforesaid by controlling the rate of supply of ferrous chloride to said vaporizing zone, the rate of supply of hydrogen to said reducing zone and the amount of make-up HCl included in said gaseous materials passing to said chloridizing zone.

5. The process of preparing metallic iron from a solid iron oxide-containing material including some iron in a trivalent state, comprising thesteps of converting a substantial proportion of the iron oxide of said material to ferrous chloride by substantially simultaneous reduction and chloridization by contacting said material while passing it through a chloridizing zone with a gaseous mixture containing hydrogen and HCl and wherein the HCl concentration is from about 5% to about 25% by volume based upon the total of hydrogen plus HCl in said gaseous mixture, and progressively raising the temperature of said material as it passes through said ChlOlldlZlllg zone from an initial temperature in the range of about 500 to about 800 F. to a final temperature in the range of about 800 to about 1200" F.; passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone and there raising the tem-. perature thereof sufiiciently to vaporize the ferrous chloride content of this material; separating the vaporized ferrous chloride produced in .said vaporizing zone from the non-volatile material and passing the vaporized ferrous chloride into a reducing zone; separately introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for reaction with the ferrous chloride vapor therein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in said reducing zone between a temperature at which said ferrous chloride is retained in vapor form and the melting point of said metallic iron; separating the products resulting from the reaction in said reducing zone between said gaseous medium including hydrogen and said ferrous chloride vapor into (a) solid material including the metallic iron and (b) gaseous materials; including make-up HCl in said gaseous materials in amount required to provide the aforesaid relative proportions of HCl and hydrogen in said chloridizing step and passing the resulting gaseous materials to said chloridizing zone as said gaseous mixture which is supplied to said chloridizing zone for use as aforesaid; removing .the gaseous products of the reaction in said chloridizing zone from such zone and I separating therefrom a substantial amount of the water vapor content thereof and passing the remaining gases from which water vapor has been removed and to which make-up hydrogen is added into said reducing zone as said gaseous medium which is separately introduced into said reducing zone.

6. The process of preparing metallic iron from a solid iron oxide-containing material, comprising the steps of chloridizing a substantial proportion of the iron oxide of said material to form ferrous chloride by contacting said solid material in a chloridizing zone and ma temperature of at least 500 F. but below the-melting point of said ferrous chloride with a gaseous mixture containing, as essential ingredients, HCl and hydrogen and wherein the HCl concentration is from about 5% to about 25 by volume based upon the total of hydrogen plus HCl in said gaseous mixture; passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone and there raising the temperature thereof sufiiciently to vaporize the ferrous chloride content of this material; separating the vaporized ferrous chloride produced in said vaporizing zone from the nonvolatile material and passing the vaporized ferrous chloride into a reducing zone, separately introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for reaction with the ferrous chloride vapor therein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in said reducing zone between a temperature at which said ferrous chloride is retained in vapor form and the melting point of said metallic iron; separating the solid metallic iron from the gaseous materials resulting from the reaction in said reducing zone, including the H01 and ferrous chloride vapor; including make-up HCl in said gaseous materials in amount required to providelthe aforesaid relative proportions of H01 and hydrogen in said chloridizing step and passing the resulting gaseous materials to said chloridizing zone as said gaseous mixture which is supplied to said chloridizing zone for use as aforesaid; condensing ferrous chloride vapor contained in said resulting gaseous materials to solid form in said chloridizing zone; removing the gaseous products of the reaction in said chloridizing zone from such zone and separating therefrom a substantial amount of the of said material to form ferrous chloride by contacting said solid material in a chloridizing zone and at a temperature of at least 500 F. but below the melting point of said ferrous chloride with a gaseous mixture containing, as essential ingredients, HCl and hydrogen and wherein the HCl concentration is from about to about 25% by volume based upon the total of hydrogen plus HCl in said gaseous mixture; passing the remaining solid material as thus chloridized from said chloridizing zone to a vaporizing zone and there raising the temperature thereof sutficiently to vaporize the ferrous chloride content of this material; separating the vaporized ferrous chloride produced in said vaporizing zone from the nonvolatile material and passing the vaporized ferrous chloride into a reducing zone; separately introducing into said reducing zone a gaseous medium, the essential active reducing ingredient of which is hydrogen, for reaction with the ferrous chloride vapor therein to reduce at least a substantial portion of the ferrous chloride vapor to metallic iron, while maintaining the temperature in s id reducing zone between a temperature at which said fe rous chloride is retained in vapor form and the melting point of said metallic iron; cooling the products of the reaction in said reducing zone to form a solid mixture of metallic iron and ferrous chloride and remaining gaseous materials, separating said solid mixture from said gaseous materials and recovering the iron content thereof as a product of the process; including makeup HCl in said gaseous materials in amount required to provide the aforesaid relative proportions of HCl and hydrogen in said chloridizing step and passing the resulting gaseous materials to said chloridizing zone as said gaseous mixture which is supplied to said chloridizing zone for use ducing zone and which are passed to said chloridizing zone contain ferrous chloride vapor, and passing said gaseous materials with the make-up HCl included therein to said chloridizing zone at a temperature around 1200 F. but below 1250" F.

References Cited in the file of this patent UNITED STATES PATENTS 942,569 Koehler -2 Dec. 7, 1909 2,224,041 Ebner Dec. 3, 1940 2,290,843 Kinney July 21, 1942 2,663,633 Crowley et al Dec. 22, 1953 FOREIGN PATENTS 598,660 Great Britain Feb. 24, 1948 OTHER REFERENCES A Comprehensive Treatise on Inorganic and Theoretical Chemistry by Mellor, vol. 14, published by Long mans, Green and Co., 1935, page 11.

Claims (1)

1. THE PROCESS OF PREPARING METALLIC IRON FROM A SOLID IRON OXIDE-CONTAINING MATERIAL, CONPRISING THE STEPS OF CHLORIDIZING A SUBSTANTIAL PROPORTION OF THE IRON OXIDE OF SAID MATERIAL TO FORM FERROUS CHLORIDE BY CONTACTING SAID SOLID MATERIAL IN A CHLORIDIZING ZONE AND AT A TEMPERATURE OF AT LEAST 500* F. BUT BELOW THE MELTING POINT OF SAID FERROUS CHLORIDE WITH A GASEOUS MIXTURE CONTAINING, AS ESSENTIAL INGREDIENTS, HCI AND HYDROGEN AND WHEREIN THE HCI CONCENTRATION IS FROM ABOUT 5% TO ABOUT 25% BY VOLUME BASED UPON THE TOTAL OF HYDROGEN PLUS HCI IN SAID GASEOUS MIXTURE; PASSING THE REMAINING SOIL MATERIAL THUS CHLORIDIZED FROM SAID CHLORIDIZING ZONE TO A VAPORIZING ZONE AND THERE RAISING THE TEMPERATURE THEREOF SUFFICIENTLY TO VAPORIZE THE FERROUS CHLORIDE CONTENT OF THIS MATERIAL; SEPARATING THE VAPORIZED FERROUS CHLORIDE PRODUCTED IN SAID VAPORIZING ZONE FROM THE NONVOLATILE MATERIAL AND PASSING THE VAPORIZED FERROUS CHLORIDE INTO A REDUCING ZONE; SEPARATELY INTRODUCING INTO SAID REDUCING ZONE A GASEOUS MEDIUM, THE ESSENTIAL ACTIVE REDUCING INGREDIENT OF WHICH IS HYDROGEN, FOR REACTION WITH THE FERROUS CHLORIDE VAPOR THEREIN TO REDUCE AT LEAST A SUBSTANTIAL PORTION OF THE FERROUS CHLORIDE VAPOR TO METALLIC IRON, WHILE MAINTAINING THE TEMPERATURE IN SAID REDUCING ZONE BETWEEN A TEMPERATURE AT WHICH SAID FERROUS CHLORIDE IS RETAINED IN VAPOR FORM AND THE MELTING POINT OF SAID METALLIC IRON; SEPARATING THE PRODUCTS RESULTING FROM THE REACTION IN SAID REDUCING ZONE BEWTWEN SAID GASEOUS MEDIUM INCLUDING HYDROGEN AND SAID FERROUS CHLORIDE VAPOR INTO (A) SOLID MATERIAL INCLUDING THE MATALLIC IRON AND (B) GASEOUS MATERIALS; INCLUDING MAKE-UP HCI IN SAID GASCOUS MATERIALS IN AMOUNT REQUIRED TO PROVIDE THE AFORESAID RELATIVE PROPORTIONS OF HCI AND HYDROGEN IN SAID CHLORIDIZING STEP AND PASSING THE RESULTING GASEOUS MATERIALS TO SAID CHLORIDIZING ZONE AS SAID GASEOUS MIXTURE WHICH IS SUPPLIED TO SAID CHLORIDIZING ZONE FOR USE AS AFORESAID; REMOVING THE GASEOUS PRODUCTS OF THE REACTION IN SAID CHLORIDIZING ZONE FROM SUCH AND SEPARATING THEREFROM A SUBSTANTIAL AMOUNT OF THE WATER VAPOR CONTENT THEROF, AND PASSING THE RAMAINING GASES, FROM WHICH WATER VAPOR HAS BEEN REMOVED AND TO WHICH MAKE-UP HYDROGEN IS ADDED, INTO SAID REDUCING ZONE AS SAID GASEOUS MEDIUM WHICH IS SEPARATELY INTRODUCED INTO SAID REDUCING ZONE.

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