Method for obtaining metals, their compounds, and alloys from mineral raw materials

In this method for obtaining metals, their compounds, and alloys from mineral raw materials a burden is prepared by mixing a comminuted raw material with additions of chemical elements taken from the chemical composition of the starting raw material, oxidizing roasting is then carried out accompanied by evacuating and utilizing gaseous oxides, and a reduction process proceeds followed by separation of metals and their compounds. According to the invention, in the course of preparing the burden compounds of the above chemical elements containing oxygen are added to the mixture at a ratio of the compounds to the chemical elements ranging from 1:1 to 1:100 and at a total quantity of additions in the burden at least 5%. The oxidizing roasting process proceeds in an oxygen-containing atmosphere at a temperature from 1400.degree. to 1600.degree. C. followed by cooling and comminuting solid oxides obtained. Prior to metallothermy these oxides are mixed with a reducing metal being used at a ratio of the total of oxides of the metals obtained, alloys to the reducing metals ranging between 1:0.3 and 1:0.7. Reduction process proceeds at a temperature 2000.degree. to 2300.degree. C.

CROSS-REFERENCE TO RELATED APPLICATION 
This is a continuation of International Application PCT/RU93/00140 with an 
international filing date of Jun. 23, 1993, now abandoned. 
FIELD OF THE INVENTION 
This invention relates to metallurgy, and more particularly to a method for 
obtaining metals, their compounds and alloys from mineral raw materials, 
such as from sulfide ore concentrates. 
BACKGROUND OF THE INVENTION 
One problem, outstanding in the world metallurgical practice, is a 
comprehensive wastefree reprocessing of industrial iron-containing refuse, 
pyrite cinder of ore concentrates, and especially flotation and magnetic 
separation tailings of sulfur-bearing ores of iron and other metals. These 
tailings and concentrates contain compounds of manganese, cobalt, 
vanadium, titanium, chromium, nickel and some other metals in amounts 
below 4-1%, as well as rare-earth and trace elements. Until now tailings, 
although being a valuable complex raw material, were not reprocessed and 
went to waste in hundreds of millions of tons to occupy large surface 
areas and foul the environment. 
There is known a method of recovering a valuable metal from a lump material 
containing this metal and elementary sulfur. In the course of recovering 
the metal the lump material is heated to 140.degree.-170.degree. C., 
cooled to less than 90.degree. C., and subjected to extraction with 
tetrachloroethane. Then the solid fraction is separated from liquid. Used 
as a starting material is slime formed as a result of nickel electrolysis. 
Nickel matte is used here as the anode. 
However, this method is not suitable for reprocessing sulfur-bearing ores, 
because hydrometallurgical process are hazardous for the environment and 
require large quantities of water. 
There is also known a method for reprocessing sulfide ores containing up to 
60% iron, which invovles oxidizing roasting of the ores at a temperature 
below 750.degree. C. However, this method is not adaptable to roasting 
lean ores. In addition, because of high content of sulfur in the calcine, 
solid products of roasting (iron oxides) are of little use for further 
processing. Also widely used in metallurgy for obtaining metals and their 
compounds are thermal reduction methdos, for example, ones based on the 
reduction by aluminum. According to one such method, metal oxides are 
reduced by aluminum in an exothermic reaction at a temperature of 
2400.degree.-2500.degree. C. to elementary metals and aluminous slag. The 
aluminous slag can be melted and easily separated from the metal. It 
should be noted, however, that this method is not suitable for processing 
sulfur-bearing minerals due to the presence of sulfur therein. 
One more promising method involves aluminothermic reduction of oxides of 
reactive metals (Ti, Nb, Ta, Zr, Hf, Mo, Cr, V) by melting the meatl 
inside an induction furnace, and adding thoroughly mixed granules of 
reagents containing CaO oxide. Electric power applied to the melt is 
controlled so as to maintain a temperature exceeding the preset minimum. 
Reduction process per se proceeds in an inert atmosphere of argon (cf., 
GB, A 1,475,781). 
However, this method is not suitable for reprocessing sulfur-bearing 
minerals, becuase of the presence of sulfur which tends to form sulfides 
with the metal. Also, without an extra source of heat (induction heating) 
this method fails to separate metal and slag after the exothermic 
reduction reaction. 
A method which bears the closest resemblance to the one to be claimed 
herein in terms of its technical essence and results obtainable is 
disclosed in JP, A, 49-42,761. This prior art method teaches a direct and 
dry processing of enriched sulfide ore by directly charging a sulfide 
concentrate mixed with copper, lead, zinc and iron into a melt present in 
a furance. Then the concentrate is mixed with air, oxygen, or a mixture of 
air and oxygen, for the mixture to be oxidized and melted. Outgoing gases 
carrying sulfur dioxide are evacuated. The thus obtained melt is mixed 
with a reducing agent, such as coke and air, oxygen, or a mixture thereof. 
The outgoing gases carrying zinc and lead obtained during the reduction 
process are sulimated to separate the metals from the melt, and the 
sublimating agent, such as chloride, or air, or oxygen, or a mixture 
thereof, is mixed with the remaining melt. The process results in a melt 
containing iron and outgoing gases carrying copper and negligible 
quantities of lead and zinc. 
However, the products of reduction contain carbon monoxide generated when 
oxides are liberated from coke. In addition, the thus recovered iron has a 
poor quality because it is contaminated with copper, lead, and zinc. 
Another disadvantage of this prior art method is the impossibility to 
reprocess tailings which are poor in iron, but contain numerous inert 
oxides of silicon, magnesium, and calcium, because the process requires 
higher temperatures and higher rates of heat flow from an external heat 
sources, and necessitates the use of a reducing agent other than carbon. 
SUMMARY OF THE INVENTION 
The present invention aims at the provision of a method for obtaining 
metals, their compounds and alloys from a mineral raw material 
characterized by a complete, comprehensive and waste-free reprocessing of 
the raw material, reduced hazard to the environment, and minimized 
consumption of power thanks to utilizing the heat of exothermic reactions. 
The aim of the invention is attained in a method for obtaining metals, 
their compounds and alloys from a mineral raw material involving the 
preparation of a burden by mixing the comminuted raw material with 
additive including chemical elements selected from the chemical 
composition of the starting material, carrying out oxidizing roasting 
accompanied by evacuating and utilizing gaseous oxides, and carrying out a 
reduction process with subsequent separation of metals and their 
compounds, according to the invention, in the course of preparation of the 
burden the compounds of said chemical elements containing oxygen are added 
to the mixture at a ratio of these compounds to the chemical elements 
ranging from 1:1 to 1:100 and at a total proportion of additions in the 
burden at least 5%, whereas the oxidizing roasting is carried out in an 
oxygen-containing atmosphere at a temperature from 1400.degree. to 
1600.degree. C. followed by cooling and comminuting the resulting solid 
oxides; prior to the metallothermic process these oxides are mixed with 
the reducing metal being used at a ratio of the total of metal oxides, 
alloys to the reducing metal ranging from 1:0.3 to 1:0.7; the reduction 
process per se proceeding at a temperature between 2000.degree. and 
2300.degree. C., 
The herein proposed method allows to ensure a virtually complete and 
waste-free processing of any mineral iro-containing raw material. The 
method is ecologically friendly, and can save substantial amounts of power 
thanks to utilizing the heat of exothermal process liberated by chemical 
reactions. 
The essence of the invention resides in the following. The process can be 
viewed as two successively linked stages (viz, oxidation and reduction 
stages). The two stages are accompanied by liberation of substantial 
amounts of heat thanks to chemical interaction between the burden 
components. The start of the process coincide with the action of an 
external factor, such as a heating coil (thermal pulse) across the burden 
at a rate of 0.05 to 12 mm/sec, and proceeds in layers. The intermediate 
product of the first stage, viz, a combination of solid oxides, cannot be 
utilized because it has such "harmful" impurities present in the starting 
material or tailings as arsenic, zinc, tin, and lead. However, after the 
second stage, reduction, such as aluminothermy, which proceeds at a high 
temperature in the atmospheric air, the elements of the addition are 
sublimated, oxidized, and slagged off as the reducing metal, particularly 
corundum, with the properties thereof unaffected. An ingot of the metal, 
or its alloy, which is also formed in the second stage, more specifically, 
a ferroalloy, is refined whereby the residue contains only ferrosilicon 
alloyed with aluminum, manganese, nickel and chromium, and modifying 
additions including traces of rare-earth metals and trace elements. 
It has to be stated that the two said stages are associated by the 
chemistry of the process. More specifically, the quantity of additions 
used in the first stage determines not only the temperature and 
composition of products (oxides) in this stage, but also the temperature 
within the preset temperature range of 2000.degree.-2300.degree. C. in the 
second stage of the process with the aforedescribed relationship between 
the oxides obtained and reducing metal (aluminum) ranging from 1:0.3 to 
1:0.7, and, consequently, the optimized composition of the products of the 
second stage and their separation in the liquid state. 
Used as the additions in the stage of oxidizing roasting are the chemical 
elements taken from the chemical composition of the starting material. 
These elements can include iron, aluminum, magnesium, titanium, calcium, 
silicon, or their mixtures in various proportions. It is most practicable 
to use powdered iron, or powdered wastes of case iron and steel. 
The second component of the addition is generally a compound based on the 
elements included in the chemical composition of the raw material 
containing active oxygen which is liberated in response to heating. It is 
used to ensure 100% oxidation of all the components present in the 
starting material. 
Barium, sodium, calcium peroxides, and magnetites can be used as these 
compounds. The products of the first stage, viz, those resulting from the 
oxidizing roasting, are most preferable for use as the addition. These 
products include magnetite to promote the oxidation process, and to 
optimize composition of the burden for the second stage of the process. 
The range of parameters of the proposed method is determined by the 
following considerations. Reduction in the quantity of the addition to 
below 5% leads to termination of roasting in the oxidation stage of the 
process. 
An increase in the ratio between the chemical element and oxygen-containing 
compound to below 100:1 leads to imcomplete sulfur combustion. Conversely, 
a reduction in this ratio to less than 1:1 results in temperature increase 
over 1600.degree. C. and deteriorated quality of products due to "deadbum" 
sintering. The choice of temperature range in the first stage is 
determined by optimized composition of the products of roasting. A 
reduction in this temperature to below 1400.degree. C. leads to incomplete 
combustion, whereas a temperature higher than 1600.degree. C. results in 
excessive sintering of the products and incomplete combustion. 
In the second stage of the process variations in the ratio between the 
components to over and below the specified range lead to that the process 
of phase separation tends to die down, because the temperature of the 
process falls below the melting point of the components, or the melt 
becomes enriched in the light-fraction ingredient in case of an excess in 
the quantity of the reducing metal. Reduction in the process temperature 
below 2000.degree. C. causes the process to die down, whereas a 
temperature higher than 2300.degree. C. makes the process very vigorous, 
and can lead to completed ejection of the reaction mass from the 
autoclave. 
Research has shown that the method can utilize lean ores, industrial 
wastes, and the like, which allows to reduce the surface areas occupied by 
dumps, waste disposal areas, and slime ponds (the estimates show a 
reduction by 10,000-100,000 t/yr). The technology offered by the method 
also allows to reduce the amount of energy consumed for the end product to 
40 kWh per 1 ton. Experiments have demonstrated that waste materials can 
be successfully turned into products of industrial importance (corundum, 
ferrosilicon alloyed with additions of nonferrous metals). 
BEST MODE OF CARRYING OUT THE INVENTION 
The method of the invention is carried out in the following manner. 
Tailings of magnetic separation of iron ore are dried and comminuted. A 
burden is prepared from the thus obtained powder material by mixing it 
with additions. The additions are preselected from the elements included 
in the chemical composition of the starting raw material. It is preferable 
to use iron powder or powdered cast iron wastes. Another addition 
ingredient is a compound also taken from the chemical composition of the 
starting raw material and containing active oxygen (oxygen-containing 
compound). Normally, it is part of the product of the oxidation stage 
recyclable into the process and containing magnetite decomposable into a 
lower oxide and active oxygen in response to heating. The quantity of the 
addition in the burden should be at least 5% by mass. 
After mixing the burden containing tailings and additions is placed in an 
oxygen-containing atmosphere of an autoclave, and the heating coil is 
energized to initiate an exothermal reaction. Combustible components of 
the tailings, such as iron sulfides and material of the addition, 
particularly iron powder, take part in the reaction. Circulating oxygen 
and the second component of the addition act here as oxidizing agents. 
Combustion proceeds at a rate of about 0.05 mm/s and a temperature ranging 
from 1400.degree. to 1600.degree. C. 
The reaction is accompanied by the formation of solid oxides and gaseous 
sulfur oxide which is easily utilized. Termination of the oxidizing 
roasting is followed by comminution of the solid oxides, after which these 
oxides are mixed with the reducing metal viz., aluminum. The ratio between 
the oxides and reducing metal in the range 1:0.3-1:0.7 is determined by 
the quantity of exothermally reducible iron and silicon oxides present in 
the burden, and by the stoichiometric proportion of aluminum. The 
preferable combustion temperature during aluminothermy is 
2000.degree.-2300.degree. C. 
Subsequent to mixing, the aluminothermic burden is charged into a closed, 
but not airtight autoclave, and a short heat pulse is applied to initial 
combustion in the presence of atmospheric air. The rate of the combustion 
process here can be as high as 12 mm/s. After a wave of chemical reduction 
reaction the products of combustion, viz., ferrosilicon with additions and 
aluminum oxide (corundum), are in the liquid phase. Then they are 
separated due to a substantial difference in their density (.about.8 g/cm 
and .about.4 g/cm, respectively), and crystallized. 
The products obtained from the aforedescribed process can be utilized as 
abrasives (corundum), and as deoxidizing and modifying additions in 
metallurgy (ferrosilicon). 
Described hereinbelow are specific examples for carrying out the method 
according to the invention.

EXAMPLE 1 
Raw material in the form of wastes resulting from magnetic separation of 
sulfide ores composed of, in % by mass: FeS.sub.2 -14; Fe.sub.2 O.sub.3 
-19; SiO.sub.2 -30; Al.sub.2 O.sub.3 -20; CaO-11, MgO-5, and less than one 
per cent in the total of Ti, Cr, Mn, Co and Zn oxides are dried and 
commiunted to a grain size less than 100 .mu.m across. The percentage of 
additions as, Zn and Pb in the powder amounts to approximately 0.5%. 
Then one kg of the powdered raw material is mixed with 150 g iron powder 
and 50 g calcium sulfate. The mixture is loaded into an oxygen-circulating 
autoclave to be thermally treated in an atmosphere of oxygen. Combustion 
is irritated at the autoclave end to which oxygen is admitted. In a 
combustion wave the temperature grows to 1500.degree. C., and the wave 
propagates at a rate of 0.5 mm/8. Sulfur dioxide liberated during 
combustion is utilized for the production of sulfuric acid. Because the 
content of sulfur dioxide in gaseous products can be as high as 90-95%, 
this gas is utilized completely, and does not pose an environmental 
problem. Solid products resulting from the stage of oxidizing roasting, 
viz., oxides of iron, silicon, aluminum, calcium magnesium, and ingredient 
metals, have a composition suitable for the reduction stage, i.e., the 
"active ingredient" includes 552 grams of iron oxide and 300 grams of 
silicon oxide. At the second stage solid products are removed from the 
autoclave, comminuted to a grain size less than 100 m, and mixed with 300 
g of aluminum powder. Apart from the active ingredient, the solid products 
of the first stage contain an "inert ingredient" in the form of 200 g 
aluminum oxide, 110 g calcium oxide, 50 g magnesium oxide, and 10 g of 
other metal impurities. Then the burden is mixed with aluminum, placed in 
a closed autoclave, and ignited. In the course of combustion and reduction 
of iron and silicon oxides by aluminum in an exothermic reaction and 
magnesium oxide in an endothermic reaction ingredient metals are 
recovered. Combustion promotes a temperature increase to about 
2150.degree. C., whereby all the components of the mixture are melted and 
separed. Liquid iron, silicon, and ingredient metals form ferrosilicon 
alloyed with titanium, manganese, vanadium, and zirconium in an amount of 
525 g. The molten ferrosilicon is separated from molten slag of compound 
aluminum-calcium oxide thanks to its high density. Molten products of 
combustion have the form of an interfaced double-phase liquid. Slag 
overlies ferrosilicon. After cooling and crystallization the slag is 
easily separated from the ferrosilicon ingot. Magnesium recovered 
thermally by aluminum is evaporated and trapped in the condenser. 
In this manner, one kg of the starting raw material referred to at the 
beginning of the example yields 150 g sulfur dioxide, 525 g ferrosilicon, 
1010 g compound aluminum-calcium oxide in the form of refractory 
aluminuous clinker, and 30 g magnesium. 
Examples 2 to 8 are summarized in Table 1. 
All additions are given per one kg of the starting raw material. 
TABLE 1 
______________________________________ 
Ratio 
(oxygen- 
containing 
compound): 
Temperature 
Compo- (chemical 
of 
sition element); 
combustion 
of raw Type, total in the first 
material, quantity quantity 
stage of 
Ex- mass %; of additions 
of oxidizing 
ample particle in the burden; 
additions, 
roasting, 
No. size grain size mass % .degree.C. 
1 2 3 4 5 
______________________________________ 
2 FeS.sub.2 .about.8% 
Chem. 1:1 1450.degree. C. 
Fe.sub.2 O.sub.3 .about.8% 
element-iron 
SiO.sub.2 .about.55% 
in the form of 
80% 
Al.sub.2 O.sub.3 .about.10% 
powdered 
CaO .about.8% 
cast iron 
MgO .about.4% 
wastes - 40%; 
Ti, Cr, Ni -100 .mu.m 
Mn oxides, (oxygen- 
rare-earth containing 
metals, etc 
compound)- 
5%; in the form 
As, Zn, Pb of solid 
0.5% powdered 
-100 .mu.m oxides- 
products of 
combustion 
in first 
stage from 
previous 
experiments 
including: 
Fe O 40% 
SiO 25%; 
Al, Ca, Mg+ 
impurities 
40%; -100 .mu.m 
3 FeS.sub.2 .about.14% 
(chem. elem.) 
1:101 1000.degree. C. 
Fe.sub.2 O.sub.3 .about.19% 
iron powder 
SiO.sub.2 .about.30% 
198 g; 16.5%; 
16.7% 
Al.sub.2 O.sub.3 .about.20% 
-100 .mu.m 
CaO .about.11% 
(oxygen- 
MgO .about.5% 
containing 
Ti, Cr, Mn, 
compound)- 
Co, Zr in the form 
oxides, of powdered 
rare-earth calcium 
metals, peroxide- 
etc. &lt;1%; 1.9 g; 0.16% 
-100 .mu.m -100 .mu.m 
4 FeS.sub.2 .about.8% 
(chem. elem.) 
2:1 1800.degree. C. 
Fe.sub.2 O.sub.3 .about.8% 
iron powder 
SiO.sub.2 .about.55% 
200 g; 37.5% 
Al2O.sub.3 .about.10% 
-100 .mu.m 
CaO .about.8% 
Oxygen-con- 
MgO .about.4% 
taining 
Ti, Cr, Mn, 
chem. elem. 
Ni oxides, in the form 
rare-earth of powdered 
metals, etc. 
calcium 
&lt;1%; peroxide 
-100 .mu.m 400 g; 
-100 .mu.m 
5 FeS.sub. 2 .about.14% 
(chem. elem.) 
1:1 combustion 
Fe.sub.2 O.sub.3 .about.19% 
iron powder dies down 
SiO.sub.2 .about.30% 
20 g, 1.9% 3.8% after 
Al.sub.2 O.sub.3 .about.20% 
-100 .mu.m initiation 
CaO .about.11% 
(oxygen-con- 
MgO .about.5% 
taining 
Ti, Cr, Mn, 
chem. elem.) 
Zr oxides, calcium 
rare-earth peroxide 20 g, 
metals, etc. 
1.9% 
&lt;1%; -100 .mu.m 
-100 .mu.m 
6 FeS.sub.2 .about.14% 
(chem. elem.) 
1:10 1570.degree. C. 
Fe.sub.2 O.sub.3 .about.19% 
iron powder 
SiO.sub.2 .about.30% 
300 g; 22.5% 
24.8% 
Al.sub.2 O.sub.3 .about.20% 
-100 .mu.m 
CaO .about.11% 
(oxygen-con- 
MgO .about.5% 
taining chem. 
Ti, Cr, Mn, 
element 
Co, Zr powdered 
oxides, calcium 
rare-earth peroxide 
metals, etc. 
30 g; 2.3%; 
&lt;1%; -100 .mu.m 
-100 .mu.m 
7 FeS.sub.2 .about.14% 
(chem. elem.) 
1:1 1490.degree. C. 
Fe.sub.2 O.sub.3 .about.19% 
iron powder 
SiO.sub.2 .about.30% 
400 g; 100 .mu.m 
44% 
Al.sub.2 O.sub.3 
(oxygen-con- 
.about.20% taining chem. 
CaO .about.11% 
element) - 
MgO .about.5% 
powdered 
Ti, Cr, Mn, 
product as in 
Co, Zr Example 2, 
oxides, 400 g; 100 .mu.m 
rare-earth 
metals, etc. 
&lt;1%; 
-100 .mu.m 
8 Fe in the (chem. elem.) 
1:1 1410.degree. C. 
form of powdered 
oxide 14.8% 
cast iron 60% 
SiO.sub.2 .about.63.1% 
30%; 
Al.sub.2 O.sub.3 
-100 .mu.m 
.about.0.4% 
(oxygen-con- 
CaO .about.3.1% 
taining chem. 
Mg .about.3.1% 
compound) 
TiO.sub.2 .about.0.7% 
powdered 
Na2O solid oxides- 
.about.0.03% 
products of 
K2O .about.0.03% 
combustion 
S .about.0.06% 
in first stage 
CaO.sub.2 none; 
from previous 
-100 .mu.m experiments 
containing 
FeO .about.40% 
SiO .about.25% 
other oxides 
Al, Ca, Mg+ 
ingredient 
compounds 
30%; 
-100 .mu.m 
______________________________________ 
Ratio Tempera- 
oxides ture 
Character- (reducing of combus- 
Character- 
istics of metal) Al tion in istics 
combustion in second second of products in 
Ex- products stage of stage the second 
ample in first the (metallo- 
stage of the 
No. stage process thermy), C 
process 
1 6 7 8 9 
______________________________________ 
2 products 1:0.4 2280.degree. C. 
yield of 
obtained: product 95%; 
SO + composition: 
solid corundum 
oxides; and calcium 
analysis: oxide 
Fe gen. .congruent.37% ferroalloy; 
Si gen. .congruent.13% separation 
O gen. .congruent.37% slag/ferro- 
Mg gen. .about.0.7% alloy 94%; 
Ca gen. .about.3% ferroalloy 
Al gen. .about.2% yield 30%; 
residual composition 
sulfur &lt;0.5%; of ferroalloy: 
good quality Fe .about.75%. 
product, Al .about.3%, 
yield .about.90%; Si .about.15%; 
As, Zn, Pb Mn, Cr, Ni, 
.about.0.5% Ti .about.40%; 
traces of 
rare-earth 
metals; 
quality 
optimum; 
As, Zn, Pb 
&lt;0.1% 
3 incomplete sulfur combustion; product unfit for further 
processing 
4 "deadborn" sintering of product occurred in oxidizing 
roasting; product unfit for further processing 
5 -- -- -- -- 
6 products 1:0.28 1990.degree. C. 
combustion 
obtained: died down 
SO.sub.2 + solid product failed 
oxides; to separate 
analysis: 
Fe gen. 29% 
Si .about.12% 
Mg .about.0.8% 
Ca .about.8% 
Al .about.10% 
residual 
sulfur &lt;1% 
7 products 1:8 2500.degree. C. 
all burden 
obtained: was ejected 
SO.sub.2 +solid from the 
oxides; reaction 
analysis: volume 
Fe gen. .about.57% 
Si .about.13% 
Mg .about.0.7% 
Ca .about.3% 
Al .about.2% 
residual 
sulfur &lt;0.5% 
8 products 1:0.4 2280.degree. C. 
yield of 
obtained: products - 
SO.sub.2 + solid 95% compo- 
oxides sition: 
analysis: corundum 
Fe gen. .congruent.37% and calcium 
Si .congruent.13% oxide + 
O .congruent.37% ferroalloy; 
Mg .about.0.7% separation 
Ca .about.3% slag/ferro- 
Al .about.2% alloy .about.94%; 
residual ferroalloy 
sulfur &lt;0.5%; yield .about.30%; 
good quality composition 
product yield of ferroalloy; 
.about.90%; Fe .about.75%, 
As, Zn, Pb Al 3%, Si 
.about.0.5% .about.15% 
ingredients: 
Mn, Cr, Ni, 
Ti .about.40%, 
traces of 
rare-earth 
metals; 
optimum 
quality; 
As, Zn, Pb 
&lt;0.1% 
______________________________________ 
It can be seen from Table 1 showing characteristics of the products in the 
second stage of the process that optimized relationship between the 
distinctive features of the proposed method allow the maximum yield of 
ferroalloy and corundum having a grain strength 200/160 and 160/125 .mu.m, 
which is comparabel with the grain strength of artificial diamonds. 
INDUSTRIAL APPLICABILITY 
Products obtained by the proposed method can be industrially utilized for 
making sulfuric acid, alloying and deoxidizing additions, corundum and 
mullite corundum refractory materials, or high-alimina cements. 
The method is friendly to the environment in spite of 100% processing of 
the starting raw material. The method is energy-efficient, and can be 
implemented in standard production equipment and controlled.