|Publication number||US3661562 A|
|Publication date||May 9, 1972|
|Filing date||Dec 7, 1970|
|Priority date||Dec 7, 1970|
|Publication number||US 3661562 A, US 3661562A, US-A-3661562, US3661562 A, US3661562A|
|Inventors||Lanier Carroll W, Seth Kishan K|
|Original Assignee||Ethyl Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (8), Classifications (12)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1151 3,661 ,562
Seth et a1. May 9, 1972 54] REACTOR AND METHOD OF MAKING 2,598,735 6/1952 Webb ..75/41 X ALUMINUM-SILICON ALL Y 3,418,108 12/1968 Von Stroh ..75/43  Inventors: Kishan K. Seth; Carroll W. Lanier, both of Baton Rouge, La.
 Assignee: Ethyl Corporation, New York, NY.
 Filed: Dec. 7, 1970  Appl. No.: 95,766
 US. Cl ..75/68 R, 75/41, 75/68 A  Int. Cl. ..C22b 21/02, C22b 5/10  Field of Search ..75/68 R, 68 A  References Cited UNITED STATES PATENTS 88,480 3/1869 Hinde ..75/42 891,248 6/1908 Gronwall 75/42 X 938,634 11/1909 Betts 75/68 R 1,379,023 5/1921 Jones ..75/68 R 1,551,615 9/1925 Parsons et a1 ..75/68 A 1,836,005 12/1931 Berry 2,040,651 5/1936 Frankl Primary Examiner-Henry W. Tarring, ll Attorney-Donald L. Johnson, John F. Sieberth, Paul H. Leonard and Arthur G. Connolly ABSTRACT A reactor or blast furnace adapted for the production of an aluminum-silicon alloy, wherein two separate reaction zones are provided. Coke or other suitable carbonaceous material is fed into one reaction zone and a mixture of coke and aluminasilica ore is fed into the second reaction zone. Substantially pure oxygen, a supporter of combustion, is introduced into the reaction zone or section containing coke for combustion. Hot carbon monoxide gases produced by the coke combustion are introduced into the second reaction zone or section containing ore and coke for reducing the ore. A suitable opening is provided in the wall separating the two reaction zones for permitting the hot carbon monoxide to move from one reaction zone to the other. The reaction zone in which the ore is reduced includes a suitable tap-hole for drawing ofi of molten aluminum-silicon alloy.
17 Claims, 4 Drawing Figures COKE OR ORE COKE PATENTEUMAY 9 I972 SHEET 1 [1F 3 COKE OR ORE COKE FIG. I
PATENTEDMAY 9 I972 3,661,562
SHEET 3 [IF 3 DOUBLE DOUBLE BELL BELL HOPPER HOPPER .-I CO HEATING HEATING ZONE ZONE 0 OXIDATION REDUCTION 2 ZONE-\ /ZONE SOURCE p40 HEATED o I 92 :52
43 2 HEARTH EARTH HEATER H FIG. 4
REACTOR AND METHOD OF MAKING ALUMINUM- SILICON ALLOYS BACKGROUND OF THE INVENTION The present invention is in the field of metallurgy and relates broadly to a method of manufacturing aluminum-silicon alloys and an improved reactor for such method.
It has been known that high silicon aluminum alloys are useful for a number of purposes, particularly casting, and that ores such as clays are available in quantity which can be reduced to high silicon aluminum alloys by reaction with carbon in an electric arc furnace. Although there have been some processes for making aluminum from naturally occurring aluminum oxides or silicates as taught by U.S. Pat. Nos. 1,551,615 and 1,552,728, respectively, using fuel fed or other furnace, respectively, there has been no known commercial method of carbothermically reducing naturally occurring alu minum silicates or clays in a blast furnace for the production of an aluminum-silicon alloy. At the present time aluminumsilicon alloys are manufactured using substantially pure aluminum and substantially pure silicon. This is, of course, considerably expensive.
An article entitled Carbothermic Smelting of Aluminum by P. T. Stroup published in Transactions of the Metallurgical Society of AIME, Volume 230, pages 356-371 (1964), provides an excellent history of the work done in smelting aluminum carbothermically.
It has been previously discovered that the introduction of substantially pure oxygen directly into a blast furnace for carbothermically making aluminum-silicon alloys from natural alumina-silica clays considerably improves the production of such alloys. A process of this type is described in U.S. application Ser. No. 60,426, filed Aug. 3, 1970. It has also been discovered that the use of silicon carbide or other suitable carbide in the hearth of the furnace in lieu of carbonaceous material such as coke further enhances the production of aluminum-silicon alloys. This process is described in U.S. application Ser. No. 60,425, filed Aug. 3, 1970.
The present invention is an improvement over these prior art processes and provides a further means for effectively producing aluminum-silicon alloys from alumina-silica ores or clays.
The instant invention eliminates two major problems as sociated with these prior art processes. The combustion of coke with oxygen in a separate reactor avoids contact between oxygen and nascent aluminum-silicon alloy and thus prevents reoxidation of the nascent alloy. Moreover separating the coke required for burning and reduction into two separate reactors allows closer control of the carbon to ore ratio and prevents the formation of carbides of silicon and aluminum by reactions between the nascent alloy and excess carbon.
Also, the free flowing nature of the coke pellets and the absence of the condensibles in the products of combustion result in no hang-up conditions in the oxidation reactor.
SUMMARY OF THE INVENTION A blast furnace adapted for the production of aluminum-silicon alloys from alumina-silica ores, comprising two distinct reaction zones or reactors, an oxidation or combustion reactor and a reduction reactor. The furnace also includes a means for introducing oxygen into the oxidation reactor and in a preferred form of the invention an oxygen heater or other suitable means for heating the oxygen prior to introduction into the furnace.
The invention also relates to a method of carbothermically reducing alumina-silica ores to form an aluminum-silicon alloy utilizing a blast furnace comprising separate zones for oxidation or combustion and reduction. Carbon in the form of coke or other suitable carbonaceous material is introduced into the oxidation zone and burned in the presence of substantially pure oxygen, preferably preheated. 'Carbon monoxide gas formed from such combustion is transferred or introduced into the second zone through a suitable passageway or passageways connecting the two zones. Alumina-silica ore and suitable carbonaceous material such as coke, preferably in the form of pelletized or briquetted coke-ore particles, are introduced into the reduction zone. Aluminum-silicon alloy is formed in liquid phase in the reduction zone and collected in the base or hearth thereof. The alloy is drawn off peridically through a suitable tap hole in the bottom of the reduction zone or reduction zone reactor.
In the preferred form of the invention, lumps or particles of silicon carbide are placed into the bottom of the reduction zone reactor to form all or part of the reduction zone bed or hearth. Although preheated oxygen temperatures of from about 0 C. to about 2,000 C. are effective, optimum results are produced when the oxygen is preheated to about 1,000 C. The rate of feeding coke and the residence time of the oxygen in the oxidation section is such that the combustion gases entering the reduction section are essentially pure carbon monoxide. The combustion gases contain neither oxygen nor carbon dioxide.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section of a blast furnace of the present invention.
FIG. 2 is a section of the blast furnace of the present invention drawn along lines 2-2 of FIG. 1.
FIG. 3 is a partial vertical section of a blast furnace illustrating an alternate embodiment of the present invention.
FIG. 4 is a schematic presentation of the instant invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT In the preferred form of the invention, silicon carbide lumps or particles are placed in the bed or hearth of the reduction reactor of a two-section or double reactor blast furnace in a sufficient quantity to completely form the furnace bed. Alternatively, the reduction bed may comprise coke and silicon carbide lumps. The silicon carbide must be present in sufficient quantity, however, to avoid the problem of aluminum carbide or silicon carbide forming with the carbon from the coke in sufficient quantity to be a processing problem. Some coke or other suitable form of carbon may need to be added to the reduction zone bed to react out any residual oxygen picked up from blast.
In the preferred embodiment of the invention, one or more openings is placed in the oxidation reactor or combustion section or zone of a double or two-section blast furnace for receiving oxygen thereinto from an'external source. Pure oxygen is introduced into the furnace to burn with the carbon (coke, charcoal or other suitable carbon) in the oxidation reactor, thereby producing carbon monoxide gas at very high temperatures. The hot carbon monoxide gas fills the oxidation reactor and passes into the reduction reactor which has been filled with an ore and coke mixture required for the carbother' mic reduction of the ore to an aluminum-silicon alloy. Cooling of the hot carbon monoxide gas provides the necessary energy for the ore reduction reaction, although it does not enter into the reduction reaction. The carbon in the coke reacts with the ore to form metal and more carbon monoxide.
preferably, the oxygen is preheated prior to introduction into the oxidation reactor of the two-section blast furnace. The oxygen is preheated to a temperature of about l,O00 C. in any suitable oxygen heater before introduction into the reactor. Oxygen temperatures of from about 0 C. to about 2,000 C. are suitable, if desired. At the high temperatures of the blast furnace, the hot oxygen reacts with the carbon forming hot carbon monoxide gas, Such gas does not react with the aluminum or silicon metal products produced at the high temperatures required in the reduction zone.
In a typical ore reduction, a blast furnace similar to the type disclosed in said application Ser. Nos. 60,425 and 60,426, but having two distinct sections, one for oxidation and one for carbothermic reduction, is employed. The oxidations zone contains a means for introducing oxygen into the oxidation reactor and the reduction zone contains a means for the metal removal from the reduction reactor. The charge to the oxidation zone comprises coke or charcoal. The charge to the reduction zone comprises coke or charcoal and an ore comprising aluminum and silicon. Silicon carbide or other suitable carbide is added to the reduction zone charge as desired.
The coke and coke-ore mixture are charged into their respective zones by means of a "bell in the usual manner. The oxygen is introduced into the oxidation zone, and temperatures in excess of 2,100 C. are maintained in the oxidation zone of the furnace. Molten aluminum-silicon alloy is collected in the bottom of the reduction zone and is removed therefrom by means of the usual taphole.
Unlike an iron blast furnace, the aluminum-silicon furnace is essentially slag free. Some small amount of slag may occur as a result of a slight deficiency of carbon in the furnace. This unreacted molten ore collects at the bottom of the hearth area in the reduction zone and does not effect the aluminum-silicon product ,which collects in the hearth. The silicon carbide lumps which fill the reduction zone hearth area are prevented from contacting the hot oxygen from the tuyeres area. The use of two separate sections avoids re-oxidizing of the alloy.
Referring now to FIG. 1 of the drawings, a typical two-section blast furnace A is shown. The furnace comprises two distinct sections, an oxidation or combustion section B and a reduction section C. Each section is similarly constructed, narrowing somewhat toward both the top and bottom. The walls 1 of the furnace andthe dividing wall 2 are built of steel and lined with suitable refractory. The base 3 of the oxidation section is girdled with a pipe 4, called bustle pipe, through which oxygen is forced. Leading from the pipe 4 are smaller pipes 5, called tuyeres, which conduct the oxygen into the furnace.
The top of the oxidation section B is closed by a movable trap 6, called the bell, and coke 7 or other suitable carbonaceous material is introduced thereinto. The gases resulting from the combustion in the oxidation or combustion section B fill the void spaces 8 and flow into the reduction section or reactor C through the passageway-9. The passageway 9 comprises a plurality of openings 9a. for the gases to travel from the combustion section B to the reduction section C.
I The base 10 of section C is similar to the base 3 of section B but contains a taphole 11 for withdrawing the molten aluminum-silicon alloy formed in the reduction section C, The liquid metal can be drawn off from time to time by the conduit or liner 12 extending from the taphole ll. Lumps of silicon carbide or other suitable carbides 13 are placed in the bottom 14 of the reduction section C up to a height of just below the openings 9a in the passageway 9 between the sections B and C. Alternatively, lumps of coke and silicon carbide may be used, but the silicon carbide should be in sufficient quantity to substantially inhibit the formation of silicon carbide, and aluminum carbide from the aluminum and silicon in the alloy and the carbon in the bottom of the reduction section.
The top of the section C is also closed by a movable trap 15, and is a second bell, through which the raw materials 16, comprising coke and ore, are introduced into the reduction section C. The gases resulting from the combustion of the fuel in the oxidation section B and reduction of the ore in section C escape through the upper pipe 17. These gases have a temperature of about 250 C. and are essentially pure carbon monoxide which is a valuable by-product.
Charges of coke, preferably in pelletized form are introduced at suitable intervals into the oxidation section B through the bell 6 via the hopper 18. The upper bell 19 is opened at desired intervals to admit the coke 7 into the compartment or area 20 above the lower bell 6.
Charges of raw materials 16, comprising coke and ore which are preferably pelletized together, but may be mixed together in predetermined proportions are introduced at suitable intervals into the reduction section C through the bell via the hopper 21. The upper bell 22 is opened at desired intervals to admit the raw materials 16 into the compartment or area 23 above the lower bell 15. a
The coke 7 and raw materials 16 are conveyed to their respective sections B and C by means of a car 24 or by any other suitable method. Two cars or a plurality of cars may be used rather than the single car as illustrated. At the bottom of the furnace, the silicon carbide being less soluble in the nascent Al-Si alloy remains substantially stable. Any silicon carbide that is dissolved can be recovered from the alloy in subsequent processes and recycled to the furnace.
The temperature of the furnace at the point at which the oxygen enters is greater than 2,l00 C., and gradually decreases toward the top of the combustion section B, where it is only from about C. to about C. The temperature of the gases passing from the section B to the section C is also greater than 2,l00 C. Heating of the ore begins at the top of the section C through exchange of the sensible heat in the hot carbon monoxide. As the ore descends, reduction proceeds by the action of the coke or carbon, and the resulting aluminum and silicon collects as a liquid in the bottom l4 of the reduction section C.
The process is essentially slag-free, but a portion of the ore could remain partially reduced because of a slight deficiency of carbon in the furnace. This partially reduced ore remains molten at the hearth temperature of about 1,900" C. and collects in the bottom of the heart 14 of the section C.
After a desired quantity of aluminum-silicon alloy has collected, it is drawn off, and run out into suitable containers for further processing or use. A molten slag is drawn off with the alloy, separated therefrom and charged back to the furnace. The process is preferably a continuous one, and once the furnace is started, it is kept in operation for a desired length of time, usually several months without interruption.
lfthe carbonaceous material charged to section B of the furnace A is of a type which leaves an ash, a taphole and liner similar to that of the taphole ll and'liner 12 is desirable in the base 3.
In FIG. 2 of the drawings, the bustle pipe 4 and the tuyeres 5 can be readily seen. Oxygen introduced from an external source into the bustle pipe 4 passes therefrom into the tuyeres 5 and through the openings 5a into the combustion zone B of the furnace A. The number of openings for conducting oxygen into the combustion zone will vary depending upon the size of the furnace. There should be however at least a means for conducting oxygen into the combustion zone.
FIG. 3 represents an alternate embodiment of the present invention and illustrates a single hopper 31 with a divided double bell system-32. Each half of the double bell32a and 32b,
move independently of the other and permits the coke and raw materials to be introduced separately from each side thereof. Coke 33 or other suitable carbon is introduced into the hopper 31 by means of the car 34 or other suitable means. Ore-coke pellets 35 or a suitable mixture of coke (carbon) and ore are introduced into the hopper 31 from the car or other desired means.
In FIG. 4 of the drawings, the furnace A is illustrated schematically. Oxygen is supplied to the furnace from a suitable source 40. The oxygen is transferred to an oxygen heater 41 via a suitable conduit 42. After the oxygen is heated to the desired temperature, usually about l,000 C., it is introduced into the oxidation or combustion section B of the furnace A via a suitable conduit 43. The carbon introduced into the oxidation zone is converted into carbon monoxide gas by the oxygen and such gas is conducted into the reducing zone of the reduction section C wherein the ore introduced thereinto is converted into molten metal to be ultimately drawn off.
It can be appreciated that the disclosure and description herein are merely illustrative and explanatory thereof and that various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.
The opening and/or openings into the furnace for the introduction of oxygen thereinto are preferably so arranged as to be substantially in line with the combustion area in the furnace and so constructed as to be suited for oxygen introduction. Other suitable openings may be arranged as desired depending upon the size and construction of the articular type of furnace selected.
The ores which may be used in the instant invention are naturally occurring alumina-silica or aluminum silicate clays and/or minerals. Some examples of these raw materials are diaspore, kyanite, boehmite, sillimanite, andalusite, mullite, kaolinite clays and/or minerals. They may also contain quartz, crystobalite and the like. Impurities may also be present. Preferably, the ores should contain from 50 percent alumina to 70 percent or more alumina.
The ores may be physically or chemically treated or other wise beneficiated prior to introduction into the furnace. The type of treatment is varied with the type of ore used.
The present invention is also suitable for the production of ferro-silicon or silicon, with the raw materials being varied for such use.
The form of the carbon that is used is not critical. Some forms which may be used are metallurgical coke, coal, lamp black, graphite and petroleum coke. In iron blast furnace operations, metallurgical coke is preferred because of its low reactivity with carbon dioxide in the upper portion of the furnace. This lowers the so-called carbon volatility losses. The volatility problems does not occur in the aluminum blast furnace and the form of the carbon is therefore not critical in this respect.
In the preferred form of the invention, the coke charge and the coke-ore charge are pre-prepared in pellets or intimately mixed briquettes. The pellets preferably are from about inch to about 1 inch in diameter. Smaller or larger sizes may be used if desired for a particular operation. The pellets or briquettes are also preferably of a uniform particle size.
The coke and ore are finely ground prior to pelletizing or prior to introduction into the furnace. For optimum results the coke and ore are mixed at a ratio of about 1 part carbon to about l-3 parts ore. The pellets should have a satisfactory crush strength and sufficient abrasion resistance so that they do not disintegrate during the various handling stages and during travel through the reactor.
In general, the smaller the particles being processed, the less time required for processing. The particle size should be sufficiently large, however, to prevent fluidization of the ore passing down through the furnace by the hot carbon monoxide flowing up.
The temperature in the reduction zone of the furnace should be a minimum of about 2,050 C. up to a maximum of the temperature at which aluminum-silicon alloy boils, approximately 2,500 C. An optimum temperature is about 2,200 C., with a preferred temperature range being from about2,l50 C. to about 2,250C.
The pressure of the blast furnace is about p.s.i.g. and that of the oxygen being introduced thereinto is about p.s.i.g. The external pressure must be sufficiently greater than the internal pressure to permit the injection of oxygen into the furnace.
A small scale blast furnace operation is carried out with a furnace whose inside dimensions are one foot in diameter by ten feet in height for each section. About 90 pounds of coke and 80 pounds of coke-ore pellets are fed to the top of the furnace each hour. Coke pellets and coke-ore pellets are A to 1% inches in diameter with the coke-ore pellets comprising about 75 percent by weight kyanite ore and about 25 percent by weight of coke breeze. Essentially pure oxygen heated to about 950 C. is fed through a nozzle near the bottom of the oxidation zone of the furnace. The rate of oxygen flow is 120 pounds per hour.
After steady operation is achieved, the rate of carbon monoxide gas being drawn off from the top of the reduction section of the furnace is about 270 pounds per hour. The carbon monoxide is essentially pure and is at a temperature of about 250 C. Every two hours the metal is tapped from the hearth area of the reduction zone. The average tap size is about 60 pounds. The metal comprises by weight by about 60 percent aluminum and 40 percent silicon, with small amounts of iron, titanium, carbon and oxygen.
Silicon carbide sublimes about 2,200 C. so the temperature of the reduction zone hearth should be maintained below such temperature. In addition to silicon carbide, other forms of carbide may be used. Some examples are zirconium carbide, titanium carbide, tantalum carbide and hafnium carbide.
The silicon carbide should preferably be in lump or particulate formv with the lumps uniform in size, to provide a large void volume which can be filled with aluminum-silicon alloy. The lumps are preferably from about /4 inch to about 1% inches in diameter. The lumps are also preferably of a size close to the size of the feed pellets so that the voids between the silicon carbide lumps will not tend to become filled with unreacted feed pellets.
The hot carbon monoxide from the blast furnace may be recycled through the coke bed with the hot oxygen, if desired. The use of the recycled carbon monoxide in this manner will reduce the temperature obtained in the primary ore reduction region.
Silicon and ferro-silicon alloys may be produced in a manner similar to that described hereinfor aluminum-silicon alloys using appropriate ores and/0r raw materials to achieve the desired end results.
The foregoing disclosure of the invention is illustrative and descriptive thereof and various changes may be made within the scope of the claims without departing from the scope of the invention.
What is claimed is:
1. A process for producing aluminum-silicon alloys in a fuelfed furnace having two reaction zones, which comprises, providing a charge containing carbon and pure oxygen in the first reaction zone, igniting the charge in the first reaction zone to oxidize the carbon to carbon monoxide; providing a charge containing carbon, an alumina-silica ore and carbon monoxide in the second reaction zone; heating the charge in the second reaction zone to reduce the ore in the furnace; continuing the operation until an aluminum-silicon alloy is produced; and, recovering the aluminum-silicon alloy.
2. The process of claim 1, wherein the oxygen is preheated prior to being introduced into the first reaction zone of the furnace.
3. The process of claim 2, wherein the oxygen is preheated to a temperature of at least about 1,000 C.
4. The process of claim 2, wherein the oxygen is preheated to a temperature of about 0 C. to about 2,000" C.
5. The process of claim 2, wherein the oxygen is preheated to a temperature of from about 500 C. to about 1,500 C.
6. The process of claim 2, wherein the alumina-silica ore is a diaspore clay.
7. The process of claim 2, wherein the alumina-silica ore is a kyanite concentrate.
8. The process of claim 2, wherein the alumina-silica ore is kaolinite.
9. The process of claim 2, wherein carbon monoxide is removed from the second reaction zone and recycled into the first reaction zone.
10. The process of claim 2, wherein the reaction temperature in the first reaction zone is about 2,l00 C. to about 2,500 C.
11. The method of claim 1, wherein the burden in the second reaction zone is supported on a bed comprising particles of silicon carbide which are substituted for all or part of the carbon bed.
12. The method of claim 1, wherein the burden in the second reaction zone is supported on a bed comprising particles of carbide selected from the group consisting of silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, hafnium carbide and the like, which carbide particles are substituted for all or part of the carbon bed.
13. The method of claim 12, wherein said carbide is present in an amount sufficient to substantially prevent the formation of aluminum carbide and other carbides in harmful amounts.
16. The method of claim 1, wherein the reaction in the second reaction zone is carried out between about 1,800 C. and about 2,500 C.
17. The method of claim 1, wherein the reaction in the second section of the blast furnace is carried out at a temperature of above 2,050 C.
(5/69) OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 1,5 2 Dated y 9, 972
Inventor(s) Kishan K. Seth and Carroll W, Lanier It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 2, line 6, reads "peridically", should read periodically Column 2, line 60 reads "preferably", should. read Preferably Column 4, line 55, reads "car or" should read car 36 or Column 5, line 2, reads 'arcicular should read particular Column 5, line 75, reads y weight y" d" read, :1. P55. Weight about Column line #5, reads "1000'c." should read 1000 c.
Signed and sealed this 27th day of February 1973.
EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents
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|International Classification||C22B21/02, C22C1/02, C22B21/00, F27B1/00, F27B1/04|
|Cooperative Classification||C22B21/02, C22C1/026, F27B1/04|
|European Classification||C22C1/02C, C22B21/02, F27B1/04|