US3257199A

US3257199A - Thermal reduction

Info

Publication number: US3257199A
Application number: US296282A
Authority: US
Inventors: Schmidt Walther
Original assignee: Reynolds Metals Co
Current assignee: Reynolds Metals Co
Priority date: 1963-07-19
Filing date: 1963-07-19
Publication date: 1966-06-21
Anticipated expiration: 1983-06-21
Also published as: GB1073025A

Description

June 21, 1966 w. SCHMIDT THERMAL REDUCTION 3 Sheets-Sheet 1 Filed July 19, 1963 TUE o u om ow 8 9 om 8: oam o m 534E995 Qmm o im 002 QS MVI 0503 009 0503 mt m okm mu 2828.00

| ooow 0503 o .mo- INVENTOR WALTHER SCHMIDT BY %m,2/M;m

ATTORNEYS June 21, 1966 w; SCHMIDT THERMAL REDUCTION 5 Sheets-Sheet 2 Filed July 19, 1963 wODmEkZwU m0 mwPJE OwJOOU 5 12 3% I llll I I Eqw I WmXw EEOU o 6 MON? m wmzzu NOE June 21, 1966 w CH T 3,257,199

THERMAL REDUCTION Filed July 19, 1963 5 Sheets-Sheet 5 CHARGE: AI2O3 Si 0 CARBON I INTERMETALLIc COMPLEXES I I H EAT l I RAw ALLOY MERCURY ExTRAcTIoN I I RAw ALLOY I AND I I MERCURY I I SEPARATION I I I ALUMINUM I MS INTERMETALLIc coMPLExEs I MERCURY SILICON DISTILLATION I E GRINDAND sIEvE I l MELTING I I I MERcURv ALUMINUM INTERMETALLIc ALUMINUM COMPLEXE I I I SINK FLOAT I FLOTATION I INTERMETALLIC SILICON COMPLEXES FIG. 3

INVENTOR WALTHER SC HMI DT BY wwfm ATTORNEYS relationship to cost, has served no useful purpose.

3,257,199 THERMAL REDUCTION Walther Schmidt, Henrico County, Va., assignor to Reynoltls Metals Company, Richmond, Va., a corporation of Delaware Filed July 19, 1963, Ser. No. 296,282 14 Claims. (Cl. 75-68) This invention relates to the direct thermal reduction of alumina-bearing materials to form aluminum alloys and more particularly, to the thermal smelting of raw aluminum-silicon alloys for the specific purpose of further purifying them so as to obtain either partially purified alloys or aluminum of commercial purity.

The thermal reduction of alumina-bearing materials to form aluminum alloys is well known in the art and usually involves treatment of oxidic ores such as bauxite, clay, kaolin, kyanite, mixtures of alumina and silica, etc. with suflicient carbon, at elevated temperatures, in order to reduce the charge to the metallic state. However, the many problems attending such a reduction reaction are also well known in the art and have, in fact, seriously hindered the heretofore practiced thermal reduction processes from becoming economically optimized. As is well known, it takes a certain amount of energy, usually in the form of electrical energy, to reduce aluminabearing materials to the corresponding liquid metal. If, in fact, the liquid metal cannot be fully recovered, a significant economic defect in the reduction process is developed in that expended energy, which has a direct In this regard, it is known, for example, that the aluminum metal resulting from the reduction of the alumina-bearing ores has a tendency to be vaporized out of the reaction zone and into the atmosphere, thereby detracting from the overall yield of aluminum. Additionally, and perhaps more significantly, the reduced aluminum metal easily reacts with the carbon present as the reducing agent or the carbon monoxide inherently formed in. the reaction system to yield aluminum carbide. The presence of aluminum carbide is extremely undesirable mainly due to the fact that aluminum carbide can form a fused ternary system with aluminum and aluminum oxide. The fused ternary system is extremely viscous and creates many practical operatingproblems since it accumulates at the cooler parts of the furnace building up gummy masses which ultimately must be removed by shutting down the furnace and cleaning it.

There have been many proposals made in the prior art in an attempt to solve the problems hereinabove referred to but, for the most part, the prior art solutions have not been completely satisfactory. For example,

it has been proposed to add heavy metals such as iron, copper and lead to the feed in order to dissolve the aluminum produced, thereby lowering its vapor pressure, so that the loss of aluminum by vaporization will be minimized. In addition, these heavy metals contribute gravity and bulk to aluminum, thereby enhancing the tendency of the liquid metals to rapidly settle down from the hot zone of the furnace to minimize the loss of aluminum due to vaporization. However, most heavy metals react with considerably more than their own weight of aluminum andsilicon upon solidification to form intermetallic compounds which have little or no commercial significance. In this regard, the gains made by decreasing the amount of aluminum lost by evaporation were more than offset by the losses of aluminum and silicon due' to their combination with the heavy metals added so that the overall effect of the process was to make it even more inefficient.

In addition, most of the heavy metals jcannot counteract the formation of aluminum carbide because the latter is more stable than the carbides of the metals added.

United States Patent Another proposal heretofore suggested involved counteracting the formation of aluminum carbide by the simultaneous reduction of silica to form silicon. It has long been recognized that 2 moles of aluminum carbide will react with 3 moles of silica to give 8 moles of aluminum plus 6 moles of silicon. The addition of silica to the feed was for the purpose of destroying the aluminum carbide formed by the reaction of the aluminum and the carbon present in the system. However, a very practical problem encountered in the use of silica is the fact that severe losses of aluminum from vaporization will result unless an excess of silica is employed in order to lower the vapor pressure of the aluminum. Thus, for commercial operations, a ratio of about 60% aluminum to about 40% silicon is a well established compromise between counteracting the formation of aluminum carbide and minimizing the loss of aluminum and silicon through vaporization.

However, when a relatively large amount of silica is employed as a furnace feed, the feedtends to form fused masses before silica will be substantially reduced. Reference to the phase diagram of. alumina and silica which appears in FIGURE 1 will show that a ratio of 57% A1 0 and 43% SiO has a melting point of about 1810 C. It can be seen that operating with a relatively high portion of silica can lead to the formation of gummy viscous products containing oxides, carbides and reduced metals which tend to accumulate to the cooler parts of the furnace, thereby causing shutdown of the furnace and expensive cleaning operations, Moreover, it is conventional practice to charge the furnace feed in the form of briquets in which the carbonaceous reducing agent is finely divided throughout the briquet, and if fusion of the oxides occurs, the carbonaceous material has a tendency to segregate from the liquid, thereby leaving the oxide unreduced. Another problem encountered with the use of high amounts of silica is the fact that the fused masses which can form, crust over and hinder the escape of carbon monoxide, which is inherently formed in the reaction system. The rapid removal of carbon monoxide is necessary in order to prevent the formation of aluminum carbide and aluminum oxide by its reaction with the reduced aluminum. It is therefore essential to provide a furnace feed which does not readily fuse but tends to keep in shape until it is reduced to metal. Therefore, again with reference to FIGURE 1, it would be more preferred to operate to the right of the l810 point, but at this point in the diagram insufficient silica would be present to counteract the formation of aluminum carbide as well as to sufficiently lower the vapor pressure of aluminum to minimize losses due to vaporization from the hot zone.

Therefore, it is the primary object of this invention to provide a novel process for the direct thermal reduction of alumina-bearing materials to form aluminum alloys.

It is another object of this invention to provide a novel process for the production of aluminum-silicon alloys wher'ein losses of aluminum due to vaporization from the reaction zone will be minimized.

It is a further object of this invention to provide a novel process for the production of aluminum-silicon alloys wherein considerably less silica is employed in the feed material thereby minimizing the danger of forming fused masses in the reduction furnace.

It is still another object of this invention to provide a novel process for the direct thermal reduction of alumina-bearing materials wherein materials of relatively high specific gravity are added to the furnace zone in order to aid in the rapid withdrawal of the formed aluminum from the reaction system.

It is still another object of this invention to provide a novel process for the direct thermal reduction of aluminabearing materials wherein the formation of aluminum carbide is minimized but not at the expense of losing more aluminum due to the formation of intermetallic compounds by the reaction of the formed aluminum and the heavy metals added.

It has now been found that the above objects can be attained by carrying out the direct thermal reduction of alumina-bearing materials in the presence of intermetallic complexes of iron and/ or titanium which have aluminum and silicon chemically bonded thereto. The intermetallic complexes, which are added to the feed in accordance with the novel teachings of this invention, form a liquid solution within the smelting furnace with the aluminum and silicon formed by reduction of the corresponding oxides. They are substantially saturated with both aluminum and silicon so that no further reaction with these elements will be possible when the raw alloy-solidifies.

While not wishing to be bound by any specific theory of operation, it nevertheless appears that the use of the novel intermetallics of this invention will accomplish all of the objectives attempted to be solved by the heretofore proposed processes without the disadvantages which inherently accompanied them. Thus, the intermetallics which are added will provide the-necessary bulk and gravity so that the liquid metal can be discharged from the hot zone at a very rapid rate thereby minimizing aluminum losses due to vaporization without the inherent disadvantages of having the added compounds react with both aluminum and silicon.

In addition, the intermetallics of this process will counteract the formation of aluminum carbide without the inherent danger of forming fused oxidic masses. Another advantage of the instant invention is the fact that the materials added will substantially lower the vaporization losses of aluminum since it will be dissolved by the intermetallics. However, of primary importance is the fact that the novel process of this invention will permit decreasing the silica to alumina ratio of the furnace feed thereby minimizing the danger of formingfused oxidic masses within the smelting furnace. As has heretofore been pointed out, the approximate ratio of alumina to silica in the heretofore practiced commercial smelting processes was usually 60:40 for the reasons hereinabove stated. The process of this invention will permit the use of furnace feeds having alumina to silica ratios of 7587:2513, and preferably 82-85 :18-15.

The intermetallic complexes of this invention consist substantially of complexes of iron and/ or titanium chemically combined with aluminum and silicon. The term intermetallic complex as used herein is intended to include both compositions having exact formulas as well as those which cannot be defined by a precise stoichiometrical formula. As is well known, ternary compounds, i.e., compounds of either iron or titanium with both aluminum and silicon, can be defined by known phase diagrams provided equilibrium conditions are assumed. However, in compositions containing both iron and titanium, simultaneously chemically bonded with aluminum and silicon, a wide variety of complexes are possible whether it be by solid solution of one compound in another or by isomorphic substitution of atoms of one metal in the intermetallic compound formed primarily with the other metal. Nevertheless, the intermetallic complexes which are added to the furnace feed in accordance with the instant invention are characterized by the fact that they have a relatively high density and densities between 3.4 and 4.3 grams per cubic centimeters are particularly preferred in order to achieve fast removal of the liquid metal from the hot zone of the furnace. Another characteristic of the intermetallic compounds of this invention is the fact that the iron and/or titanium complex is substantially fully satisfied with aluminum and silicon so that when the complexes are added to the furnace feed they will not react, upon solidification of the raw alloy, with additional aluminum and silicon, thereby detracting from the overall economy of the operation. Thus, these materials provide heavier bulk, have the property of lowering the vapor pressure of aluminum and counteract aluminum carbide formation without the inherent defects of the prior art compounds in that they are so inert to aluminum and silicon that they will no longer react to remove these desired products to any substantial degree.

As has heretofore been stated, the intermetallic complexes which can be employed in the novel process of this invention are complexes of iron and/or titanium with aluminum and silicon. If the intermetallic complex is based on iron, its content of iron can range from 25 30% by weight of the complex. If it is based on titanium, its content if titanium can range from 25-45% by weight of the complex. If the complex contains both iron and titanium, then the combined amounts of iron and titanium should not exceed 55 weight percent of the total complex. The balance of the complex is composed of aluminum and silicon and the relative proportions of these two materials must be chosen to effect chemical saturation, which commonly will be achieved by selecting from a weight ratio of 005-2 aluminum:14 silicon. The particularly preferred intenmetallic complexes are those wherein the aluminum is present in the higher end of the range in order to insure that the complex will be substantially saturated by chemical combination with the aluminum in order to minimize any possible reaction between the complex added and the aluminum inherently reduced in the furnace during solidification of the raw alloy.

' The intermetallic complexes which are employed in accordance with the instant process can be prepared simply by melting an alloy containing the desired components, i.e., an alloy containing aluminum and silicon and either or both of titanium or iron. The relative amounts of the individual components in the alloy are generally determined by the weight ratios desired in the intermetallic complex. However, the weight ratio of the individual components in the alloy need not be exactly the same as the weight ratios desired in the intermetallic complex since the formation of the intermetallic complex is a rather complicated reaction and allowances can be made for additional side reactions which must inherently take place. However, it has been found that the novel intermetallic compounds of this invention can be prepared by melting an alloy which contains the following weight ratios:

For 1 part of iron, 0.5-1 part silicon, 1.52 parts of aluminum For 1 part of titanium, 1 part of silicon, 0.05O.5 part of aluminum .ganese and/or chromium, especially in those cases where it is desired to obtain a casting alloy as a product of the reduction furnace. The intermetallic complexes containing manganese and/or chromium are prepared by including manganese and/ or chromium in the alloy which is to be melted. The amount of manganese and/ or chromium which can be present in the intermetallic complexes is not narrowly critical and advisably should not exceed 10% by weight of the total composition.

As has heretofore been pointed out, the intermetallic complexes which are used in the process of this invention are substantially saturated with both aluminum and silicon so that reaction with these elements during the solidification of the raw alloy will be minimized. It is an absolute requirement in the instant process that the intermetallic complexes employed be at least 75% chemically saturated with aluminum and/or silicon in order to minimize reaction with these compounds. It is to be understood, however, that the preferred embodiment of this invention would reside in those complexes wherein the chemical saturation with aluminum and silicon approaches 100% num. It is to be understood that the novel process of this invention is applicable in either of the two instances.

FIGURE 2 represents a typical flow sheet including process variations for the manufacture of a partially purifall within the scope of the instant invention and they are intended to be included herein. The variations in the basic process are governed by the desire to subject the raw alloys to steps of purification which produce either an aluminum-silicon alloy or commercially pure alumi- Specific examples of intermetallic complexes which can 5 fied aluminum-silicon alloy in accordance with the process be employed in the novel process 'of this invention are of this invention. As can be seen by reference to said shown inTable I below. In each case, the percentages figure, intermetallic complexes are added to the charge are expressed as weight percents. in a reduction furnace and heat is applied until the ores TABLEI Density Example Percent Percent Percent Percent Percent Percent in Grams Iron Manganese Chromium Titanium Aluminum Silicon per Cubic Centimeter 2s 44 28 3.46 28 3s 34 25 3 40 32 4.08 10 29 3s 4. 03 16 19 4. 05

The novel process of this invention is carried out sim- 25 are reduced to the liquid metal and then the liquid metal ply by adding the intermetallic complexes to a furnace is tapped and cooled to a preselected temperature rangfeed in a conventional reduction furnace. The furnace ing from about 580 to 680 C. It is to be understood feed is composed of three components, one being a carthat the composition of the liquid aluminum-silicon alloy bonaceous reductant, preferably in the form of coke or varies with the temperature to which the raw alloy is charcoal; the second being a mixture of alumina and silica 30 COOled and the specific compositions obtained at a particor alumina and silica-bearing ores, such as bauxite, clay, ular temperature are extremely well known in the art koalin, kyanite, or mixtures thereof; and the third comand are a matter of preference, depending upon the inponent being the'interrnetallic compounds hereinabove retended use for the finished alloy. However, in the vast ferred to. The amount of intermetallics which are added majority of commercial operations, it is customary to cool to the furnace feed should represent between 15 to 50 35 the liquid raw alloy to a temperature of approximately percent by Weight of the total amount of silica and alumina 600 C. wherein a eutectic composition of aluminum, present in the feed. The variation in the weight ratio of Silicon, iron and titanium exist containing approximately intermetallics added is obviously dependent on the specific 12% by weight of silicon, 1% iron and 0.1% titanium. nature of the furnace feed. For example, if relatively At this temperature the aluminum-silicon alloy exists in pure components are employed, such as Bayer-alumina 40 the liquid phase and the solid phases contain the interand quartz, it is then preferred to operate in the higher metallic complexes, elementary silicon, if an excess is end of the range; whereas if impure feed materials are empresent, and various intermetallic compounds resulting ployed, it is then preferred to operate in the lower end from impurities contained inthe feed material. The liquid of the range because these materials will inherently form alloy is then separated from the solid phases by convensome intermetallic compounds due to the impurities contional techniques including filtration, decantation or, more tained therein. preferably, centrifuging. The liquid phase thus contains As has heretofore been pointed out, the ratio of aluthe desired product whereas the solid phase contains free mina to silica in the feed is one'which is considerably silicon, various intermetallic complexes and a portion of high in alumina, so as to minimize the danger of forming the aluminum-silicon alloy due to the fact that the separafused masses of unreduced oxides. Therefore, the charge tion of liquid and solid phases can never be carried out in the novel process of this invention will comprise aluat 100% efficiency and the portion of the alloy usually mina and silica having a weight ratio of 75-87 parts of trapped in the solid phases is about 1015%. At this alumina and 25-13 parts of silica; 15-50 weight percent point, the solid phases can be discarded if it'is desired. of the total weight of both silica and alumina of inter- A more preferred embodiment of this invention would metallic complexes; and sufficient carbon as a reductant, reside in treatment of the solid phases in order to recover in order to reduce the metal-bearing ores to the liquid the aluminum-silicon alloy remaining therein. This sepmetal. The feed materials are usually heated in an elecaration can be accomplished merely by comminuting the trio furnace at a temperature of about 2000 C. until the solid phases in a ball mill and then passing the reduced oxides are reduced to the metallic state and the liquid particle sizes through a screen ranging from 30 to 300 alloys are tapped. The liquid alloys are then allowed to mesh Tyler and more preferably 140 to 200 mesh. It cool and the intermetallics plus elementary silicon, if has been found that the fraction which does not pass present in amounts above the eutectic aluminum-silicon through the screen will contain an extremely high percomposition, begin to crystallize out of the charge at about centage of the eutectic or quasi-eutectic aluminum-silicon 1000 C. thereby enriching the liquid in aluminum. alloy. This aluminum-silicon alloy can either be added When cooling approaches the eutectic point which 00- to the aluminum-silicon alloy previously recovered in the curs at about 578 C., an aluminum-silicon alloy exists liquid phase or, even more desirably, can be recycled -in the liquid phase which contains about 12 percent silicon back to the molten raw alloy and again reprocessed in and this liquid phase is then separated from the solid the manner above-described. phasesin accordance with conventional techniques. A mor particularly preferred embodiment of the in- It is to be understood that there are many variations vention would reside in further treating the solid phase of the basic'reduction process hereinabove described which remaining after removal of the partially purified aluminum-silicon alloy, that is, the solid phas containing silicon and intermetallic complexes, in order to recover the silicon especially if there is a substantial excess of elementary silicon present. The recovery of silicon from the intermetallic complexes can be accomplished by a tinuous.

wide variety of ways including gravity separation or sink float techniques with a high density liquid such as carbon tetrachloride 'mixed with bromoform wherein a siliconrich fraction can be recovered. The density of the liquid is adjusted to allow the silicon to float while the heavier intermetallics sink. Alternatively, the silicon can be separated from the intermetallic complexes by treatment with a flotation medium consisting of a fluorine-containing acid and a fluoride salt. The recovered silicon can then either be sold or used to-blend with aluminum to produce other aluminum-silicon alloys. The intermetallic complexes obtained are then recycled back to the charge in the reduction furnace so as to make the process con- It is to be understood that if an impure feed material is employed which, as has heretofore been set forth, will inherently produce a certain amount of intermetallic complexes, then a like quantity of intermetallic complexes should be discarded from the intermetallic complexes recovered-in order to prevent an undesirable build-up of these complexes in the furnace.

FIGURE 3 represents a variation of the reduction process wherein it is desired to produce commercially pure aluminum rather than an aluminum-silicon alloy. In this process, the steps are identical as those in FIG- URE 2 until the raw alloy is produced whereupon the raw alloy is treated with a metallic solvent such as zinc, lead, mercury, etc., as is well known in the art, in order to leach out the aluminum followed by separating the liquid and solid phases. The aluminum is then recovered from the liquid solvent by a number of conventional techniques including distillation and melting in order to obtain commercially pure aluminum. At this point, the solid phases can be discarded if such is desired or the solid phases can be reprocessed as hereinabove described and that part of the aluminum which had been trapped when the solids were separated can be reclaimed and recycled back to the raw alloy and the intermetallic complexes recycled back to the furnace feed. In like man- 'ner, the intermetallic complexes which have been introof recycling various intermediate products, thereby enhancing the overall economy of the operation.

Another preferred embodiment of this invention resides in having the feed materials charged to the reduction furnace in intimate contact with one another so as to be better able to dissolve the aluminum and silicon as soon as they are reduced from their corresponding ores. This can be accomplished by grinding all feed components to a size passing a screen below at least about 140 and preferably 200 US. standard mesh, mixing the finely divided particles thoroughly and forming them into briquets. Additionally, it is advisable to provide a certain amount of the feed in the form of a clay of sufficient plasticity in order to act'as a binder for the briquets. The clay, which is also a portion of the feed, can be present in amounts ranging from 5 to 20 percent. It has been found that by grinding and blending the feed materials in this manner the otherwise prevailing difficulties in continuous furnace operations are very much alleviated.

The following examples will now illustrate the best mode contemplated for carrying out this invention but it is to be understood that it is not intended to be limited thereto.

Example 1 Kilograms Bayer alumina 359 Ball clay Quartz 10 Charcoal 235 Intermetallic complex 200 The composition of the charged oxides is as follows:

TABLE 11 Bayer Clay, Ashes of Quartz, Total, Oxides Alumina, kg. Charcoal, kg. kg.

kg. kg.

Total 359 100 1. 4 10 470. 4

The 200 kilograms of intermetallic complexes which are charged in the furnace correspond mainly to the formula FeAl Si having a weight ratio of approximately 1 Fe:1. 5 A121 Silicon. The intermetallic complex contains about 7 kilograms of aluminum and 5 kilograms of silicon in an uncombined form, and the total composition is as follows:

The charge is then reduced in a conventional manner and tapped to yield a raw alloy of the following composition:

TABLE IV Kg. Aluminum 275 Silicon 87.3

Titanium 1.1

Iron 57.0

Total 420.4

The raw allow is cooled to approximately 610 C. and is then subjected to separation by a centrifuge to yield a liquid phase and solid phases having the following composition:

TABLE V Liquid Phase, kg. Solid Phase, kg.

minum: 12 silicon. The remaining solid phases are then 9 comminuted in a ball mill and sieved through a 100 mesh screen with the following results:

The plus 100 mesh fraction can then either be added to the aluminum-silicon alloy previously obtained or can be recycled back to the raw alloy and reprocessed. The minus 100 fraction can either be further. processed in order to remove the free silicon or can be recycled directly back to the furnace feed. From this example, it can be seen that a makeup 7.8 kilograms of intermetallics would have to be added.

Example 2 This example will also illustrate the preparation of aluminum silicon alloy but it dilfers from Example 1- in that an impure feed material is employed rather than the pure Bayer alumina.

A conventional electrical submerged arc furnace is charged with the following feed:

Kilograms Guiana bauxite 400 Bauxitic clay 100 Ball clay 100 Quartz 10 Charcoal 250 Intermetallic complex 100 The composition of the charge oxides is as follows:

Quartz Guiana Bauxitie Ball Total Oxides kg. Bauxite Clay Clay kg.

kg. kg. kg.

The 1.00 kilograms of intermetallic complexes which are charged in the furnace correspond to that of Example in Table I of the specification. The interlmetallic com- The charge is then reduced in a conventional man.- ner and tapped to yield a raw alloy of the following composition:

Aluminum 236.0 Silicon 93.3 Titanium 32.7 Iron 27.1

Total 389.1

The raw alloy is cooled to approximately 630 C. and

is then subjected to separation by centrifuging to yield 10 a liquid phase and solid phases having the following composition:

Metal Liquid Phase, kg. Solid Phase, kg.

The 197.7 kilograms of the liquid phase is an aluminum-.

Metal mesh (kg.) 100 mesh (kg) Aluminum 26. 4 44. 6 7. 8 56. 0 i 2. 8 29. 7 1. 8 22. 3

The plus 100 mesh fraction can either be added to the aluminum-silicon alloy previously obtained or can be recycled back to the raw alloy and reprocessed.

As can be seen, the minus 100 mesh fraction contains 152.6 kilograms of intermetallic complex and it can either be further processed in order to recover the free silicon or can berecycled directly back to the furnace feed. If this fraction is to be recycled directly back to the furnace feed without removal of silicon, then it can be seen that 52.6 kilograms must be discarded since this is approximately the amount of intermetallics which are produced by the impure feed materials of this example.

Example 3 This example will illustrate the novel process of this invention when it is desired to produce commercially pure aluminum rather than aluminum silicon alloy.

In this example, the process of Example 1 is repeated up until the 420.4 kilograms of the raw alloy is tapped. At this point, the raw alloy is subjected to conventional mercury extraction and the liquid amalgamated aluminum and the solid phases are separated. The aluminum amalgam is then purified by techniques involving distillation and melting to yield purified aluminum of the following composition:

Metal: Aluminum (kg) Aluminum 177.00 Silicon 0.20 Titanium 0.05 Iron 0.30

Total 177.55

The solid phases have the following composition:

Metal: Solids (kg) Aluminum 98.00 Silicon 87.10 Titanium 1.05 Iron 56.70

Total 242.85

1 1' The solid phases are then comminuted in a ball mill and sieved through a 100 mesh screen with the following results:

Metal Float, kg. Sink, kg.

Aluminum- 1. 5 81. 5 Silicon. 29. 5 53. 85 Titaniu.m l 57 Iron 15 54. 95

Total a1. 25 190.87

As can be seen, the float fraction is silicon having a relatively high degree of purity and this material can either be sold or used in the formation of other. types of aluminum-silicon alloys. The sink portion can be recycled back to the furnace feed in order to make the process continuous. It can be seen that on the next charge of the furnace a makeup of 9.13 kilograms of intermetallic complexes will be necessary.

Another modification of this invention involves further processing the partially purified aluminum-silicon alloy, obtained as the liquid phase in Examples 1 and 2, by leaching out aluminum by means of a metallic solvent such as zinc, mercury and lead.

Many other modifications and variations of the above process will be obvious to those skilled in the art and it is not intended that this process be limited except as necessitated by the appended claims.

What is claimed is:

1. In the process for the production of a raw aluminumsilicon alloy wherein oxidic ores comprising substantially alumina and silica are charged into a reduction furnace with sufficient carbon as a reductant,'heated until the ores are reduced to the metallic state, followed by tapping the raw alloy, the improvement Which comprises adding to the furnace feed a substantially fully satisfied intermetallic complex of aluminum and silicon with at least one metal selected from the group consisting of iron and titanium in an amount ranging from 1515 percent by weight of the total amount of alumina and silica charged.

2. The process of claim 1 wherein the intermetallic added is a complex of both titanium and iron with aluminum and silicon wherein the total amount of both iron and titanium ranges from 25-55 percent by Weight of the total composition.

3. The process of claim 1 wherein the intermetallic added is a complex of iron, aluminum and silicon wherein the iron is present in an amount ranging from 2530 percent by weight of the total composition.

4. A process for the production of a partially purified aluminum-silicon alloy from oxidicores which comprises subjecting a furnace feed comprising alumina, silica, and an intermetallic complex to reduction in the presence of a suflicient amount of a carbonaceous reducing agent until the oxides are reduced to the metallic state and a raw alloy is formed, tapping the resulting raw liquid alloy, cooling the rawalloy to a temperature sufficient to obtain a liquid phase and solid phases and separating the resulting liquid phase consisting of partially purified aluminum-silicon alloy from the solid phases, said intermetallic complex consisting of substantially fully satisfied complexes of aluminum, silicon and at least one metal selected from the class consisting of iron and titanium, wherein the amount of fully satisfied intermetallic complexes in the furnace feed ranges from 15 to 50 percent by weight of the total amount of alumina and silica charged and the weight ratios of said alumina and silica are as follows:

Al O :SiO =75-87:25-13 5. The process of claim 4 wherein the complex is one of iron, aluminum and silicon, wherein the iron represents 25-30 percent by weight of the total complex.

6. The process of claim 4 wherein the complex is one of titanium, iron, aluminum and silicon, wherein the total amount of iron and titanium ranges from 25-55 percent by weight of the total complex.

7. The process of claim 4 wherein the solid phases are substantially recycled back to the furnace feed.

8. The process of claim 4 wherein the solid phases are subjected to a further separation by comminution and sieving through a 30-300 mesh screen and the finer fraction is recycled back to the furnace feed.

9. The process of claim 4 wherein the solid phases are further separated by comminution and sieving through a 30-300 mesh screen, the coarser fraction being recycled to the raw alloy, and the finer fraction being recycled to the furnace feed.

10. The process of claim 4 wherein the partially purified aluminum-silicon alloy is further purified by treating it With a metallic solvent selected from the group consisting of zinc, mercury and lead, separating the aluminummetallic solvent liquid phase from the resulting solid phases and recovering aluminum.

11. The process for the production of aluminum which comprises subjecting a furnace feed comprising alumina, silica and intermetallic complexes to reduction in the presence of a suificient amount of a carbonaceous reducing agent until the oxides are reduced to the metallic state and a raw liquid alloy is formed, tapping the resulting raw liquid alloy, treating the raw alloy with a metallic solvent for aluminum, separating the aluminum-metallic solvent liquid phase from the resulting solid phases and recovering the aluminum, said intermetallic complex consisting of substantially fully satisfied complexes of aluminum, silicon and at least one metal selected from the class consisting of iron, and titanium, wherein the amount of said fully satisfied intermetallic complexes added to the furnace feed ranges from 15-50 percent by weight of the total amount of alumina and silica charged and the weight ratios of said alumina and silica are as follows:

12. The process of claim 11 wherein the metallic solvent for aluminum is selected from the the class consisting of zinc, mercury and lead.

13. The process of claim 11 wherein the metallic sol vent is mercury.

14. A process for the production of aluminum from oxidic ores which comprises subjecting a furnace feed comprising alumina, silica, and an intermetallic complex to reduction in the presence of a sufficient amount of a carbonaceous reducing agent until the oxides are reduced solvent liquid phase from the resulting solid phases and 13 14 fecovering the aluminum, said intermetallic complex con- 1,644,000 10/ 1927 Shumaker 7568 sisting of substantially fully satisfied complexes of alumi- 1,873,939 9/1932 L t 7568 num, silicon. and at least one metal selected from the Class 2,439,216 4 /1943 McLenan 5 consisting 01 iron, and titanium, wherein the amount of 3 102 805 9/1963 Messner 'said fully satisfied intermetallic complexes added to the 5 3116997 1/1964 Kohlmey; n 75 68 furnace feed; ranges from 15-50 percent by weight of the total amount of alumina and silica charged and the weight ratios of said alumina and silica are as follows: 156 854 mfg gf f If Al O :SiO =75-87:25- 13 10 DAVID L. RECK, Primary Examiner.

WINSTON A. DOUGLAS, Examiner.

H. W. CUMMINGS, Assistant Examiner.

References Cited by the Examiner UNITED STATES PATENTS 324,659 8/1885 Cowles 7568 1,534,316 4/1925 Hoopes 7568 15

Claims

14. A PROCESS FOR THE PRODUCTION OF ALUMINUM FROM OXIDIC ORES WHICH COMPRISES SUBJECTING A FURNACE FEED COMPRISING ALUMINA, SILICA, AND AN INTERMETALLIC COMPLEX TO REDUCTION IN THE PRESENCE OF A SUFFICIENT AMOUNT OF A CARBONACEOUS REDUCING AGENT UNTIL THE OXIDES ARE REDUCED TO THE METALLIC STATE AND A RAW ALLOY IS FORMED, TAPPING THE RESULTING RAW LIQUID ALLOY, COOLING THE RAW ALLOY TO A TEMPERATURE SUFFICIENT TO OBTAIN A LIQUID PHASE AND SOLID PHASES, SEPARATING THE RESULTING LIQUID PHASE CONSISTING OF PARTIALLY PURIFIED ALUMINUM-SILICON ALLOY FROM THE SOLID PHASES, TREATING THE PARTIALLY PURIFIED ALLOY WITH A METALLIC SOLVENT FOR ALUMINUM, SEPARATING THE ALUMINUM-METALLIC SOLVENT LIQUID PHASE FROM THE RESULTING SOLID PHASES AND RECOVERING THE ALUMINUM, SAID INTERMETALLIC COMPLEX CONSISTING OF SUBSTANTIALLY FULLY SATISFIED COMPLEXES OF ALUMINUM, SILCON AND AT LEAST ONE METAL SELECTED FROM THE CLASS CONSISTING OF IRON, AND TITANIUM, WHEREIN THE AMOUNT OF SAID FULLY SATISFIED INTERMETALLIC COMPLEXES ADDED TO THE FURNANCE FEED RANGES FROM 15-50 PERCENT BY WEIGHT OF THE TOTAL AMOUNT OF ALUMINA AND SILICA CHARGED AND THE WEIGHT RATIOS OF SAID ALUMINA AND SILICA ARE AS FOLLOWS: