US1097156A - Process of reducing ores. - Google Patents

Description

H. C. ALFORD.

PROCESS OF REDUCING ORBS.

APPLICATION FILED SEPT. 1, 1911. RENEWED 00T.6,1913.

1,097,1 56, Patented May 19, 1914.

2 SHEETS-SHEET 1.

W1 TNESSES: IN VENTOR.

E E ill FM KI TTOItNE Y.

H. C. ALFORD.

PROCESS OF REDUCING ORBS.

APPLICATION EILED SEPT.1,1911. RENEWED 0OT.6.1913.

1,097,156, Patented May 19, 1914.

2 SHEETS-SHEET 2.

WI TNESSES [.V VENTOR.

5/ a I W M 272cm) flyord- W MWL ATTORNEY.

UNITED STATES Pg ENT OFFICE.

HARVEY CARROLL ALFORD, OF ST. LOUIS, MISSQUBI.

PROCESS OF REDUCJ ING ORES.

Specification of Letters Patent.

Patented May 19, 1914.

Application filed September 1, 1911, Serial No. 647,209. Renewed October 6, 1913. Serial No. 793,737.

act description, reference being had to the accompanying drawings, forming a part hereof.

My invention has relation to improvements in process of reducing ores (and metallic oXids generally) and it consists in the novel features fully set forth in the specification and pointed out in the claims.

In the drawings, Figure 1 is a combined vertical middle longitudinal section and elevation of the furnace; Fig. 2 is a vertical cross-section on the line 22 of Fig. 1; Fig. 3 is a vertical cross-section on the line 3-3 of Fig. 1; and Fig. 4 is a vertical cross-section on the line 44 of Fig. 1.

The present invention is an extension of, and improvement on, the subject-matter of my pending application for Letters-Patent, Serial Number 592,011, and while having the same objects in view and possessing the same advantages as the invention of said pending application, the present improvement is distinguished therefrom in that it contemplates the use of solid (or liquid) reducing reagents for the ores, in lieu of the gaseous reagent employed in my pending application.

The improvement herein not only provides for the reduction of the ores without resorting to smelting, but produces as a by product. a reducing gas such as used in the process of my pending application, such byproducts being available for any commercial or industrial purpose. Where solid (or liquid)-reducing reagents are employed, the ten'iperature of reduction must be not only higher than is the case with gaseous reagents (as in my pending application), but an excess of carbon must be employed in order to prevent the formation of carbon dioxid ((10,) the presence of which would produce a reversible reaction resulting in the reoxidation of the metal reduced from the ore, an example of such reversible reac tion where iron ore is treated being as fol- In other words, a reversible reaction is I one which reoxidizes (partially at least) the metal of the ore which has been reduced. Since carbon dioxid (CO however, is-reduced by iron at a temperature not below 1000 degrees Fahrenheit, and since with the use of solid (or liquid) reducing agents no reduction of iron can take place under 1000 degrees (more accurately 947 degrees Fahrenheit) it follows that in order to avoid the possible production of carbon dioXid (CO we muststart with an excess of carbon, or that amount which will insure the production of carbon monoxid (CO) in the immediate reaction of the reducing process, thus The reaction however; must take place at a temperature not less than 1000 degrees Fahrenheit, and Without access of oxygen or atmospheric air to the charge operated on. lVhere the reducing agent contains hydrogen (a certain percentage being always present in coals and oils) the reducing reaction should be such as not to produce vapor of water (H O) since water will reoxidize the iron reduced by the hydrogen, thus:-

It follows therefore, that a reaction resulting in the by-products CO and H,() is not only incomplete but reversible and should be avoided; but where the byproducts of the reducing action are CO and H the reaction is complete and there is no danger of a reversible reaction, or of reoxidation of the reduced metal. An example of a complete and non-reversible reaction where resort is had to reducing rea ents such as powdered coal, lignite, wood, or liquid hydrocarbons of variable composition all of which are contemplated by my process) and which as a rule carry a small percentage of moisture, may be illustrated by the following:

3Fe O,+14C+10H +3H O= in which C and Fe are solids, and CO and H are gases. Such a reaction is not reversible, and is complete because the excess of carbon 1S sumcient to reduce any metallic iron oxidized by the water vapor present in the charge, the gases (CO and H) being permanent in thepresence of free metallic iron and free carbgn. These gases are the same as are availed of in the process of my pendingapplication aforesaid, so that it becomes one of the objects of the present invention not only to reduce metallic ores (without fusion) by means of solid (or liquid) reagents or fuels such as above referred to,but to produce (as a byproduct) a gas'which may be employed as a reducing agent-for an ore charge in accordance with the process forming the subject matter of said pending application. The present process and the apparatus by which it may be best carried out may in detail be described as follows: Referring to the drawings, F represents the furnace proper, the chamber whereof is divided into two superposed chambers or compartments 1, 2, by a horizontal partition wall or deflector 3 extending rearward and terminating a suitable distance from the rear end wall of the furnace. The compartment 1 leads directly from the bottom chamoer 4 of the fire-box, the bottom of the chamber 4 being continuous with that of the chamber 1 so that the gases from the firebox may sweep into the reducing'furnace without material resistance. The fire-box comprises in addition to the bottom-chamber 4, an upper chamber 5 with which it communicates through a constricted passage or neck 6 on the order of thefire-box forming the subject-matter of my pendingapplication for smoke-consuming furnace, filed April 5, 1911, Serial Number 619,123. In the present case (as in the last mentioned pending application) the fuel is fed into the fire-box through the roof thereof by means of a tube 7 having slits or openings at the bottom' and positioned over the flaring feed-mouth 8 in the roof of the fire-box, the fuel being advanced through the tube from any suitable source (not shown) by a screw-feed 9 or its equivalent). The air which mingles with the fuel is supplied through the roof of the fire-box'by means of air-pipes or conduits 10 which enter into the general construction of the heating stove H forming an upper extension of the fur nace directly over the fire-box. The chamber of the heating stove receives the gases from the upper compartment 2 of the furnace, the said gases circulating around the air-pipesv 10 and being caused to zig-zag back and forth by the deflecting walls 11,

the gases (after parting with their heat) finally escaping from the stove through the exit pipe or flue 12. The upper ends of the air-pipes terminate in a box or distributer 13 to which air is admitted through a pi e 14.

y the construction aforesaid, the air for supporting combustion in the fire-box is pro heated, whereas the waste gases leaving thr stove are cooled, having their available heat units abstracted'before being allowed to discharge into the atmosphere. It follows therefore that a high degree of economy is practiced by the foregoing construction. Disposed longitudinally in the lower furnace compartment 1 is a rotatable reduction tube 15, and parallel thereto and superposed thereover in the upper compartment 2 is a rotatable ore-heating tube 16, each of said tubes being provided with Archiinedean screws 0. for advancing their respective contents in proper direction as presentl to be described. The respective tubes are provided with collars a resting on anti-friction rollers 1' to reduce friction, a construction well understood in the art andrequiring no detailed description here. parted to the tubes from a shaft 17 leading from any source of power (not shown), the shaft terminating in a pinion 18 which meshes with a gear 19 on the tube 15, the gear 19 in turn meshing with a gear 20 on the tube 16. Obviously the tubes will rotate in opposite directions, and for obvious purposes. Discharging into the intake end of the ore-heating tube 16, is an ore-hopper or chute 21 which delivers the crushed raw ore into the tube, said ore being advanced through the tube until it is discharged in a properly heated condition into a chute 22 which in turn discharges the ore (mixed Rotation is iinwith carbon) into the intakeend of the reduction' tube 15. The discharge end of the tube 15 leads into a Y, the lower leg m of which discharges the reduced ore to any convenient point, the upper leg m discharg. ing the gases resulting from the action of reduction, which gases may be used for any industrial or commercial purpose. Discharging into the chute 22 at a point below the tube 16 is a tube 23 leading downwardly at an incline from the coal bin 24, a screwconveyer 25 operated from a belt-pulley B (or other manner) serving to advance the powdere or crushed coal through the tube. This tube' is likewise kept hot by the spent gases traversing the heating stove, the tube passing across the stove between the airpi es 10. I

t follows from the foregoing that the heated ore and reduction carbon are jointly fed into the reduction tube 15 where they are intimately mixed by the screw a. In the present illustration I show a battery of two will of course be a separate feed-tube 23 for each furnace.

These details nowever,

are unimportant and may be varied to suit the conditions. Such a battery too will have a single fire-box extending across the series of furnaces, and a common heating stove. In the present connection a furnace will be understood to mean one reduction tube and ore-heating tube, with its heating stove and firebox.

The operation of the invention may be described as follows: Fire being started in the fire-box, and rotation being imparted to the tubes 15, 10, from the shaft 17 as described, ore is admitted into the tube 16 from the chut 21, and, as the contents of this tube is advanced forward it discharges into the chute 22, into which coal (or carbon) is likewise discharged from the tube 23 by the means already described. The mixture of carbon and heated ore is then advanced through the reduction tube 15 rearwardly when finally the reduced metal or sponge is precipitated down the leg m, the gases from the reduction escaping through the leg m, the operation being continuous. Obviously the gases from the fire-box traverse the chambers 1 and 2 heating the walls of the tubes 15, 16, thence escaping through the heating-stove chamber. In tie stove they heat the iucolning currents of air which furnish the oxygen for supporting the. combustion of the fuel delivered to the fire-box.

It was stated at the outset that a reversible reaction must not be allowed to take place in the reduction reaction (a reaction which herein takes place in the tube 15), and since the control ofthe reaction depends on the control of the temperature, the fire-box plays an important r6le in the present invention. I am able with my improved fire-box to accurately control the intensity of combustion and hence the tem-,

perature of the gases which leave the firebox and which circulate around the tubes 15, 16. The, heating gases (the gases from the fire-box) should enter the chamber 1 of the furnace at approximately 1600 degrees Fahrenheit, the same dropping to about 1350 degrees as they enter the chamber 2. There they serve to heat the walls of the heating tube and drop as they enter the stove H down to about 1300 degrees, whence they fina'lly escape at a temperature of about 300 degrees. The temperature of the contents of the tube 15 (the mixture of ore and coal) will approximate 1100 degrees (it should be not less than 1000 degrees to avoid reversible reaction), that of the tube 16 being about 1300 degrees, whereas the temperature of the reduction carbon in the tube 23 will be about 800 degrees. The inflowing air passing through the pipes 10 will be raised to approximately 1000 degrees. The temperature of the spent gases after leavmg the flue 12 will be about 300 degrees, so. that 1300 degrees of the heating gases have been availed of to brin about the results under my process. 1n 0 er Words (assuming the original temperature of the heating gases to be 1600 degrees), three-sixteenths efficiency has been utilized in the furnace, and ten-slxteenths in the stove, making a total i of thirteen-sixteenths, only three-slxteenths escaping into the atmosphere. The reduction within the tube 15.(by reason of the perfect control possible with my fire-box) will be on the order of the non-reversible kind given above the metallic oxid or ore in the tube being reduced to a metallic sponge and'discharged through the leg m,

and the gases of reduction being in the main a mixture of CO and H which is a valuable by-product. The carbon (or coal) delivered from the tube 23 must for reasons stated be in excess to avoid any reversible reaction, the necessityfor such excess arising from the high temperature at which reduction takes place with solid (or liquid) fuel as against a gaseous reducing reagent. The reducing rea nt (coal) is of course not pure carbon but a ydrocarbon, with usually some moisture, but the use of carbon (pure or impure) is'contemplated by the present invention. Since the reaction taking place Within the tube 15 is of the non-reversible kind, some solid carbon will be left in the tube with the metal. This carbon as well as the associated gangue may of course be removed or separated from the metal in any way known to the art. The rotation of the tubes 15, 16, obviously brings about the agitation to which the charges must necessarily be subjected to bring about perfect results.

The ore in the heating tube 16 need be raised to at least 1000 degrees Fahrenheit or approximately thereto (in the present case to about 1800 degrees) but mustnever reach the temperature of fusion. The mixture of ore and reducinghydrocarbon or fuel must then be maintained at least at that same temperature or a little over (.1100 degrees) for reasons already specified. ,In the claims, the expression approximately 1000 degrees Fahrenheit is to be construed as meaning a temperature below fusion of the ore, and a temperature sufficiently high to bring about a non-reversible reaction with a reagent,containing carbon in excess to avoid reoxidation of the metal. In lieu of tubes such as 15, 16, any equivalent holder or container is contemplated by my invention.

Having described my invention, what I claim is 1. In the reduction of metallic oxids, the process of externally heating a charge of the crushed material within a suitable container to a temperature approximately 1000 degrees Fahrenheit, then mixing therewith without access of air a hydro-carbon with an excess of carbon sufiicient to prevent reoxidation of the metal of the reduced oxid externally heating the mixture, thereby extracting the metal in the presence of such carbon excess.

'2. In the reduction of oxid ores, the process of externally heating a charge of the crushed ore within a suitable container to a proper working temperature and without fusion, then adding thereto without access of air a hydrocarbon with carbon in sufiicient excess to prevent a reversible reaction with the metal of the ore, thoroughly'mixing the charge with said hydrocarbon and externally heating the mixture whereby the metal is extracted in the presence of such carbon excess. and a gas comprising a mixture of hydrogen and carbon monoxid is generated.

3. In the reduction of iron oxid ores, the process of externally heating a charge of the ore in a suitable container within a furnace to a point below the temperature of fusion, pro ecting into the charge a proper complement of powdered coal without access of air and agitating the charge with said coal and externally heating the mixture, maintaining in the course of said agitation an excess of carbon to prevent reoxidation of the metal reduced from the oxid, and at the same time generating a mixture of carbon monoxid and hydrogen, conducting said gas to a suitable point of consumption, and removing the metal and gangue from the furnace.

4. In the reduction of iron oxid ores, the process of externally heating a charge of the ore in a finely divided state in a rotating tube or holder within a furnace, to a temerature below the point of fusion, then proecting thereinto powdered fuel with carbon in excess without access of air, and allowing the same to mix with the charge and react on the same externally heating the mixture, the carbon of such fuel being in excess to avoid reoxidation of the metal of the-reduced oxid, and atthe same time disengaging mixed gas.

5. In the reduction of iron oxid ores, the process of externally heating a charge of crushed ore to a temperature below fusion in a suitable container within a furnace and subjecting the same to agitation, delivering said charge into a separate container and adding carbon in excess thereto without access of air, agitating said mixture and maintaining the temperature thereof at approximately 1000 degrees Fahrenheit by external heat whereby the oxid is reduced and reoxidation avoided by the excess of carbon present in the charge.

6. In the reduction of oxid ores, the process of externally heating a charge of ore in a finely divided state while under agitation in a container, to a temperature below the point of fusion, conducting said heated ore to a container in conjunction with a proper complement of powdered hydrocarbon fuel without access of air to furnish carbon in excess of that necessary to effect reduction, agitating and externally heating the mixed charge in said container and maintaining the same at a temperature approximating 1000 degrees Fahrenheit. whereby the oxid is reduced to the metallic state with production of mixed gas in the presence of such carbon excess as a result of the reaction.

In testimony whereof I affix my signature, in presence of two witnesses.

HARVEY CARROLL ALFORD.

\Vitnesses EMIL STAREK,

Jos. A. MICHEL.

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