Features of aluminum mining. Aluminum ores Types of aluminum ores

Aluminum is a metal coated with a matte silver oxide film, the properties of which determine its popularity: softness, lightness, ductility, high strength, corrosion resistance, electrical conductivity and lack of toxicity. In modern high technology The use of aluminum is given a leading place as a structural, multifunctional material.

The greatest value for industry as a source of aluminum is natural raw materials - bauxite, a rock component in the form of bauxite, alunite and nepheline.

Varieties of alumina-containing ores

More than 200 minerals are known that contain aluminum.

Only rock that can meet the following requirements is considered a raw material source:

• Natural raw materials must have a high content of aluminum oxides;
• The deposit must correspond to the economic feasibility of its industrial development.
• The rock must contain aluminum raw materials in a form that can be extracted in its pure form by known methods.

Feature of the natural rock bauxite

Natural deposits of bauxite, nepheline, alunite, clay, and kaolin can serve as a source of raw materials. Bauxite is the most saturated with aluminum compounds. Clays and kaolins are the most common rocks with a significant alumina content. Deposits of these minerals are found on the surface of the earth.

Bauxite in nature exists only in the form of a binary compound of metal with oxygen. This compound is extracted from natural mountain ore in the form of bauxite, consisting of oxides of several chemical elements: aluminum, potassium, sodium, magnesium, iron, titanium, silicon, phosphorus.

Depending on the deposit, bauxite contains from 28 to 80% alumina. This is the main raw material for obtaining a unique metal. The quality of bauxite as an aluminum raw material depends on its alumina content. This determines the physical properties bauxite:

• The mineral has a hidden crystalline structure or is in an amorphous state. Many minerals have hardened forms of hydrogels of simple or complex composition.
• Bauxite color various points prey ranges from almost white to dark red colors. There are deposits with a black color of the mineral.
• The density of aluminum containing minerals depends on their chemical composition and is about 3,500 kg/m3.
• The chemical composition and structure of bauxite determines solid properties mineral. The strongest minerals have a hardness of 6 units on the scale accepted in mineralogy.
• As a natural mineral, bauxite has a number of impurities, most often these are oxides of iron, calcium, magnesium, manganese, and impurities of titanium and phosphorus compounds.

Bauxites, kaolins, and clays contain impurities of other compounds, which are separated into separate industries during the processing of raw materials.

Only in Russia do they use deposits with rock deposits that contain lower concentrations of alumina.

Recently, alumina began to be obtained from nephelines, which, in addition to alumina, contain oxides of metals such as potassium, sodium, silicon and, no less valuable, alum stone, alunite.

Methods for processing aluminum containing minerals

The technology for producing pure alumina from aluminum ore has not changed since the discovery of this metal. Its production equipment is being improved, allowing it to produce pure aluminum. The main production stages of obtaining pure metal:

• Extraction of ore from developed deposits.
• Primary processing of waste rocks in order to increase the concentration of alumina is an enrichment process.
• Preparation of pure alumina, electrolytic reduction of aluminum from its oxides.

The production process ends with metal with a concentration of 99.99%.

Alumina mining and beneficiation

Alumina or aluminum oxides do not exist in nature in their pure form. It is extracted from aluminum ores using hydrochemical methods.

Aluminum ore deposits in deposits usually explode, providing a site for its extraction at a depth of approximately 20 meters, from where it is selected and launched into the process of further processing;

• Using special equipment (screens, classifiers), the ore is crushed and sorted, discarding waste rock (tailings). At this stage of alumina enrichment, washing and screening methods are used as the most economically advantageous.
• The purified ore settled at the bottom of the concentration plant is mixed with a heated mass of caustic soda in an autoclave.
• The mixture is passed through a system of high-strength steel vessels. The vessels are equipped with a steam jacket that maintains the required temperature. The steam pressure is maintained at 1.5-3.5 MPa until the aluminum compounds are completely transferred from the enriched rock to sodium aluminate in a superheated sodium hydroxide solution.
• After cooling, the liquid undergoes a filtration stage, as a result of which solid sediment is separated and a supersaturated pure aluminate solution is obtained. By adding aluminum hydroxide residues from the previous cycle to the resulting solution, decomposition is accelerated.
• For final drying of aluminum oxide hydrate, a calcination procedure is used.

Electrolytic production of pure aluminum

Pure aluminum is produced using a continuous process that produces calcined aluminum enters the electrolytic reduction stage.

Modern electrolysers are a device consisting of the following parts:

• Made of steel casing lined with coal blocks and slabs. During operation, a dense film of frozen electrolyte is formed on the surface of the bath body, protecting the lining from destruction by the electrolyte melt.
• A layer of molten aluminum at the bottom of the bath, 10–20 cm thick, serves as the cathode in this installation.
• Current is supplied to the aluminum melt through carbon blocks and embedded steel rods.
• The anodes, suspended on an iron frame using steel pins, are provided with rods connected to a lifting mechanism. As combustion proceeds, the anode moves down, and the rods are used as an element for supplying current.
• In workshops, electrolyzers are installed sequentially in several rows (two or four rows).

Additional purification of aluminum by refining

If the aluminum extracted from the electrolysers does not meet the final requirements, it is subjected to additional purification by refining.

In industry, this process is carried out in a special electrolyzer, which contains three liquid layers:

• Bottom – refined aluminum with the addition of approximately 35% copper, serves as an anode. Copper is present to make the aluminum layer heavier; copper does not dissolve in the anode alloy; its density must exceed 3000 kg/m3.
• The middle layer is a mixture of fluorides and chlorides of barium, calcium, and aluminum with a melting point of about 730 ° C.
• Upper layer - pure refined aluminum a melt that dissolves in the anode layer and rises upward. It serves as the cathode in this circuit. The current is supplied by a graphite electrode.

During the electrolysis process, impurities remain in the anode layer and electrolyte. The yield of pure aluminum is 95–98%. The development of aluminum-containing deposits has a leading place in national economy, thanks to the properties of aluminum, which currently ranks second after iron in modern industry.

In modern industry, aluminum ore is the most popular raw material. The rapid development of science and technology has made it possible to expand the scope of its application. What aluminum ore is and where it is mined is described in this article.

Industrial importance of aluminum

Aluminum is considered the most common metal. By the number of deposits in earth's crust he ranks third. Aluminum is also known to everyone as an element in the periodic table, which belongs to light metals.

Aluminum ore is the natural raw material from which this metal is obtained. It is mainly mined from bauxite, which contains aluminum oxides (alumina) in the largest quantities - from 28 to 80%. Other rocks - alunite, nepheline and nepheline-apatite are also used as raw materials for the production of aluminum, but they are of poorer quality and contain significantly less alumina.

Aluminum ranks first in non-ferrous metallurgy. The fact is that due to its characteristics it is used in many industries. Thus, this metal is used in transport engineering, packaging production, construction, and for the manufacture of various consumer goods. Aluminum is also widely used in electrical engineering.

To understand the importance of aluminum for humanity, it is enough to take a closer look at the household things that we use every day. Many household items are made of aluminum: these are parts for electrical appliances (refrigerator, washing machine etc.), dishes, sports equipment, souvenirs, interior elements. Aluminum is often used for production different types containers and packaging. For example, cans or disposable foil containers.

Types of aluminum ores

Aluminum is found in more than 250 minerals. Of these, the most valuable for industry are bauxite, nepheline and alunite. Let's look at them in more detail.

Bauxite ore

Aluminum does not occur in nature in its pure form. It is mainly obtained from aluminum ore - bauxite. It is a mineral that mostly consists of aluminum hydroxides, as well as iron and silicon oxides. Due to the high alumina content (40 to 60%), bauxite is used as a raw material for the production of aluminum.

Physical properties of aluminum ore:

• opaque mineral of red and gray colors of various shades;
• the hardness of the strongest samples is 6 on the mineralogical scale;
• The density of bauxite, depending on the chemical composition, ranges from 2900-3500 kg/m³.

Bauxite ore deposits are concentrated in the equatorial and tropical zone land. More ancient deposits are located in Russia.

How is bauxite aluminum ore formed?

Bauxite is formed from alumina monohydrate, boehmite and diaspore, trihydrate hydrargillite and associated minerals hydroxide and iron oxide.

Depending on the composition of nature-forming elements, three groups of bauxite ores are distinguished:

1. Monohydrate bauxite – contains alumina in monohydrate form.
2. Trihydrate - such minerals consist of alumina in trihydrate form.
3. Mixed - this group includes the previous aluminum ores in combination.

Deposits of raw materials are formed due to the weathering of acidic, alkaline, and sometimes basic rocks or as a result of the gradual deposition of large quantities of alumina on the sea and lake beds.

Alunite ores

This type of deposit contains up to 40% aluminum oxide. Alunite ore is formed in water pool and coastal zones under conditions of intense hydrothermal and volcanic activity. An example of such deposits is Lake Zaglinskoye in the Lesser Caucasus.

The rock is porous. Mainly consists of kaolinites and hydromicas. Ore with an alunite content of more than 50% is of industrial interest.

Nepheline

This is an aluminum ore of igneous origin. It is a fully crystalline alkaline rock. Depending on the composition and technological features of processing, several grades of nepheline ore are distinguished:

• first grade – 60–90% nepheline; it contains more than 25% alumina; processing is carried out by sintering;
• second grade – 40–60% nepheline, the amount of alumina is slightly lower – 22–25%; enrichment is required during processing;
• the third grade is nepheline minerals, which are of no industrial value.

World production of aluminum ores

Aluminum ore was first mined in the first half of the 19th century in the southeast of France, near the town of Box. This is where the name bauxite comes from. At first, this industry developed at a slow pace. But when humanity appreciated which aluminum ore was useful for production, the scope of aluminum application expanded significantly. Many countries have begun searching for deposits on their territories. Thus, the world production of aluminum ores began to gradually increase. The numbers confirm this fact. Thus, if in 1913 the global volume of ore mined was 540 thousand tons, then in 2014 it was more than 180 million tons.

The number of countries mining aluminum ore also gradually increased. Today there are about 30 of them. But over the past 100 years, leading countries and regions have constantly changed. Thus, at the beginning of the 20th century, the world leaders in the extraction of aluminum ore and its production were North America And Western Europe. These two regions accounted for about 98% of global production. After several decades, the countries became leaders in terms of quantitative indicators of the aluminum industry. of Eastern Europe, Latin America And Soviet Union. And already in the 1950s–1960s, Latin America became the leader in terms of production. And in the 1980–1990s. There was a rapid breakthrough in the aluminum industry in Australia and Africa. In the current global trend, the main leading countries in aluminum production are Australia, Brazil, China, Guinea, Jamaica, India, Russia, Suriname, Venezuela and Greece.

Ore deposits in Russia

In terms of aluminum ore production, Russia ranks seventh in the world ranking. Although aluminum ore deposits in Russia provide the country with metal in large quantities, it is not enough to fully supply the industry. Therefore, the state is forced to buy bauxite from other countries.

In total, there are 50 ore deposits in Russia. This number includes both places where the mineral is being mined and deposits that have not yet been developed.

Most of the ore reserves are located in the European part of the country. Here they are located in the Sverdlovsk, Arkhangelsk, Belgorod regions, in the Komi Republic. All these regions contain 70% of the country's total proven ore reserves.

Aluminum ores in Russia are still mined from old bauxite deposits. Such areas include the Radynskoye field in the Leningrad region. Also, due to a shortage of raw materials, Russia uses other aluminum ores, the deposits of which differ worst quality mineral deposits. But they are still suitable for industrial purposes. Thus, in Russia, nepheline ores are mined in large quantities, which also make it possible to obtain aluminum.

The French city of Les Baux de Provence, located in the south of the country, became famous for giving its name to the mineral bauxite. It was there in 1821 that mining engineer Pierre Berthier discovered deposits of unknown ore. It took another 40 years of research and testing to discover the possibilities of the new breed and recognize it as promising for industrial production aluminum, which in those years was more expensive than gold.

Characteristics and origin

Bauxite is the primary aluminum ore. Almost all the aluminum that has ever been produced in the world is converted from them. This rock is a composite raw material, characterized by a complex and heterogeneous structure.

It includes aluminum oxides and hydroxides as its main components. Iron oxides also serve as ore-forming minerals. And among the most common impurities:

• silicon (represented by quartz, kaolinite and opal);
• titanium (in the form of rutile);
• calcium and magnesium compounds;
• rare earth elements;
• mica;
• in small quantities gallium, chromium, vanadium, zirconium, niobium, phosphorus, potassium, sodium and pyrite.

By origin, bauxites are lateritic and karst (sedimentary). The first, high-quality ones, were formed in the climate humid tropics as a result of deep chemical transformation of silicate rocks (so-called laterization). The latter are of lower quality; they are a product of weathering, transfer and deposition of clay layers in new places.

Bauxites vary in:

1. Physical condition (rocky, earthy, porous, loose, clay-like).
2. Structure (in the form of fragments and peas).
3. Textural features (with a homogeneous or layered composition).
4. Density (varies from 1800 to 3200 kg/m³).

Chemical and physical properties

The chemical properties of bauxite have a wide range associated with the variable composition of the material. However, the quality of the mined minerals is determined primarily by the ratio of alumina and silica content. The greater the quantity of the first and the smaller the quantity of the second, the greater the industrial value. Important chemical feature mining engineers consider the so-called “breakability”, that is, how easily aluminum oxides can be extracted from the ore material.

Despite the fact that bauxite does not have a constant composition, its physical properties boil down to the following indicators:

Interestingly, physical status has nothing to do with the usefulness and value of bauxite. This is explained by the fact that they are processed into another material, the properties of which differ significantly from the original rock.

World reserves and production

Despite the fact that the demand for aluminum is constantly increasing, reserves of its primary ore are sufficient to satisfy this need for several more centuries, but not less than 100 years of production.

The US Geological Survey has released data according to which the world's bauxite resources amount to 55-75 billion tons. Moreover, most of them are concentrated in Africa (32%). Oceania accounts for 23% Caribbean And South America 21%, Asian continent 18%, other regions 6%.

The introduction of an aluminum recycling process also inspires optimism, which will slow down the depletion of natural reserves of primary aluminum ore (and at the same time save energy consumption).

The top ten countries in bauxite mining, represented by the same US Geological Survey, looked like this in 2016.

Vietnam is showing itself to be very promising, finishing 2016 with an indicator of 1,500 thousand metric tons. But Malaysia, which was third in 2015, has sharply reduced bauxite development due to expectations of strict environmental laws and today ranks 15th in the world ranking.

Bauxite is usually mined in open pits. To obtain a working platform, a layer of ore is blasted at a depth of 20 centimeters and then removed. Pieces of the mineral are crushed and sorted: waste rock (the so-called “tailings”) is washed away with a stream of washing water, and fragments of dense ore remain at the bottom of the processing plant.

The most ancient bauxite deposits in Russia date back to the Precambrian era. They are located in the Eastern Sayan Mountains (Boksonskoye field). Younger aluminum ore, dating back to the Middle and Upper Devonian, is found in the Northern and Southern Urals, in the Arkhangelsk, Leningrad and Belgorod regions.

Industrial Application

Mined bauxites are divided according to their subsequent commercial use into metallurgical, abrasive, chemical, cement, refractory, etc.

Their main use, which accounts for 85% of world production, is to serve as a raw material for the production of alumina (aluminum oxide).

The technological chain looks like this: bauxite is heated with caustic soda, then filtered, the solid residue is precipitated and calcined. This product- anhydrous alumina, the penultimate transformation in the aluminum production cycle.

Then all that remains is to immerse it in a bath of molten natural or synthetic cryolite and, through electrolytic reduction, isolate the metal itself.

The first to discover this technology in 1860 was the French chemist Henri Saint-Clair Deville. It replaced an expensive process in which aluminum was produced in a vacuum from potassium and sodium.

The next important area of ​​bauxite use is as abrasives.

When alumina is calcined, the result is synthetic corundum, a very hard material with a rating of 9 on the Mohs scale. It is crushed, separated and then added to sandpaper and various polishing powders and suspensions.

Sintered, powdered and fused into round granules, bauxite is also an excellent sandblasting abrasive. It is ideal for surface treatment, and due to its spherical shape it reduces wear on sandblasting equipment.

Another important purpose of bauxite is to participate as a proppant (a material that prevents specially created faults from closing) in the process of oil production using hydraulic fracturing. In this case, the treated bauxite rock particles resist hydraulic pressure and allow the cracks to remain open for as long as necessary for oil to escape.

Bauxite is also indispensable for creating fire-resistant products. Burnt alumina can withstand temperatures up to 1780 C. This property is used both for the production of bricks and concrete, and for the creation of equipment for the metallurgical industry, special glass and even fire-resistant clothing.

Conclusion

Chemists and technologists are constantly looking for adequate substitutes for bauxite that would not be inferior in their properties. Research has revealed that clay materials, power plant ash and oil shale can be used to produce alumina.

However, the cost of the entire technological chain is many times higher. Silicon carbide has performed well as an abrasive and synthetic mullite as a refractory. Scientists hope that before the time of complete exhaustion natural resources bauxite an equivalent replacement will be found.

Aluminum ore has gained the most popularity in modern industry. Aluminum is the most common metal of all metals existing on earth today. In addition, it holds third place in the ranking in terms of the number of deposits in the bowels of the Earth. Also, aluminum is the lightest metal. Aluminum ore is a rock that serves as the material from which the metal is obtained. Aluminum has certain chemical and physical properties that make it possible to adapt its application to completely various areas human activity. Thus, aluminum has found its wide application in such industries as mechanical engineering, automotive, construction, in the production of various containers and packaging, electrical equipment, and other consumer goods. Almost every household appliance used by humans every day contains aluminum in one quantity or another.

There are a huge number of minerals in which the presence of this metal was once discovered. Scientists have concluded that this metal can be extracted from more than 250 minerals. However, it is not profitable to extract metal from absolutely all ores, therefore, among all the existing variety, there are the most valuable aluminum ores, from which the metal is obtained. These are: bauxite, nepheline, and alunite. Of all aluminum ores, the maximum aluminum content is found in bauxite. They contain about 50% of aluminum oxides. As a rule, bauxite deposits are located directly on earth's surface in sufficient quantities.

Bauxite is an opaque rock that has a red or grey colour. The strongest bauxite samples on the mineralogical scale are rated at 6 points. They come in different densities from 2900 to 3500 kg/m3, which directly depends on the chemical composition.

Bauxite ores are distinguished by their complex chemical composition, which includes aluminum hydroxides, iron and silicon oxides, as well as from 40% to 60% of alumina, which is the main raw material for the production of aluminum. It is worth saying that equatorial and tropical earth belts are the main area famous for its bauxite ore deposits.

For the nucleation of bauxite, the participation of several components is necessary, including monohydrate alumina hydrate, boehmite, diaspore, as well as various iron hydroxide minerals along with iron oxide. The weathering of acidic, alkaline, and in some cases basic rocks, as well as the slow settling of alumina at the bottom of reservoirs, leads to the formation of bauxite ore.

From two tons of alumina, aluminum turns out to be half as much - 1 ton. And for two tons of alumina it is necessary to extract about 4.5 tons of bauxite. Aluminum can also be obtained from nephelines and alunites.

The former, depending on their grade, can contain from 22% to 25% alumina. While alunites are slightly inferior to bauxites, and consist of 40% aluminum oxide.

Aluminum ores of Russia

The Russian Federation is ranked 7th among all countries in the world in terms of the amount of aluminum ore mined. It is worth noting that this raw material is mined in colossal quantities on the territory of the Russian state. However, the country is experiencing a significant shortage of this metal, and is not able to provide it in the volume necessary to absolutely supply the industry. This is the priority reason why Russia has to purchase aluminum ores from other countries, as well as develop deposits with low quality mineral ores.

There are about 50 deposits in the state, the largest number of which are located in the European part of the state. However, Radynkskoye is the oldest deposit of aluminum ores in Russia. Its location is Leningrad region. It consists of bauxite, which since ancient times has been the main and irreplaceable material from which aluminum is subsequently produced.

Aluminum production in Russia

At the beginning of the twentieth century, the emergence of the aluminum industry took place in Russia. It was in 1932 that the first aluminum production plant appeared in Volkhov. And already on May 14 of the same year, the company managed to receive a batch of metal for the first time. Every year, new aluminum ore deposits were developed on the territory of the state and new capacities were put into operation, which were significantly expanded during the Second World War. The post-war period for the country was marked by the opening of new enterprises, the main activity of which was the production of manufactured goods, the main material for which was aluminum alloys. At the same time, the Pikalevsky alumina plant was put into operation.

Russia is famous for its variety of factories, thanks to which the country produces aluminum. Of these, UC Rusal is considered the largest, not only within the Russian state, but throughout the world. He managed to produce about 3.603 million tons of aluminum in 2015, and in 2012 the company reached 4.173 million tons of metal.

Aluminum- one of the most important structural materials. Due to its lightness, mechanical strength, high electrical conductivity, and high corrosion resistance, it has found wide application in the aviation, automotive, electrical industries, other branches of modern technology, and in everyday life. In terms of production and consumption in the world, it ranks second among metals after iron.

The raw material for aluminum production is alumina, which is obtained from bauxite, nepheline ores and other high-alumina rocks. Main bauxite, providing 98% of the world's alumina production, is bauxite. Russia is the only country in the world where such low-quality aluminum raw materials as nepheline ores are used.

The total reserves of bauxite in 29 countries of the world exceed 40 billion tons, 95% of them are concentrated in the tropical zone, including more than 50% in Guinea, 40% in Australia, Venezuela, Brazil, India, Vietnam and Jamaica. Bauxite is mined in 24 countries in the amount of 140 million tons per year, 80% of production occurs in Australia, Guinea, Jamaica, Brazil, China and India. Annual alumina production in bauxite-mining countries exceeded 52 million tons, and primary aluminum smelting exceeded 24.5 million tons. last years Aluminum production increased more than 10 times.

Are considered unique Place of Birth bauxite with reserves of more than 500 million tons, large and medium - 500 - 50, small - less than 50 million tons.

Bauxite is a residual or sedimentary rock consisting of aluminum hydroxides, iron oxides and hydroxides, clay minerals and quartz. By mineral composition There are gibbsite, boehmite, and diaspore bauxites. It was noted that in young, untransformed deposits, gibbsite ores predominate, while in older and transformed deposits they are replaced by boehmite and diasporic ores.

All industrial types of bauxite deposits are exogenous formations. They are divided into weathering and sedimentary deposits. Weathering deposits are divided into residual lateritic and residual redeposited, and sedimentary deposits are divided into those occurring in terrigenous formations of platform areas and associated with carbonate formations of geosynclinal areas. The characteristics are given in table 1.2.1.

Table 1.2.1 The main geological and industrial types of aluminum deposits

Laterite deposits are of major industrial importance (90% of world reserves).

In Russia, bauxite deposits are being developed in the North Ural (SUBR) and South Ural (YUBR) bauxite-bearing regions (84% of production) and the Tikhvin region (16%). Due to the lack of raw materials to meet the needs of the domestic metallurgy, Russia annually imports about 50% (3.7 million tons) of alumina from Ukraine, Kazakhstan and non-CIS countries.

Bauxite is the main ore for aluminum production. The formation of deposits is associated with the process of weathering and transfer of material, in which, in addition to aluminum hydroxides, there are also other chemical elements. Metal extraction technology provides a cost-effective industrial production process without generating waste.

Characteristics of ore mineral

Name mineral raw materials for aluminum mining comes from the name of the area in France where deposits were first discovered. Bauxite consists of aluminum hydroxides and contains as impurities clay minerals, oxides and hydroxides of iron.

By appearance Bauxite is a stony, and less commonly clay-like, rock that is uniform or layered in texture. Depending on the form of occurrence in the earth's crust, it can be dense or porous. Minerals are classified according to their structure:

• clastic - conglomerate, gravel, sandstone, pelitic;
• concretionary - legumes, oolitic.

The bulk of the rock in the form of inclusions contains oolitic formations of iron or alumina oxides. Bauxite ore is usually brown or brick in color, but there are deposits of white, red, gray, and yellow shades.

The main minerals for ore formation are:

• diaspora;
• hydrogoethite;
• goethite;
• boehmite;
• gibbsite;
• kaolinite;
• ilmenite;
• aluminohematite;
• calcite;
• siderite;
• mica.

There are bauxites of platform, geosynclinal and oceanic islands. Aluminum ore deposits were formed as a result of the transport of weathering products of rocks, followed by their deposition and the formation of sediment.

Industrial bauxite contains 28-60% alumina. When using ore, the ratio of the latter to silicon should not be lower than 2-2.5.

Deposits and extraction of raw materials

The main raw materials for industrial aluminum production in the Russian Federation are bauxite, nepheline ores and their concentrates, concentrated in Kola Peninsula.

Bauxite deposits in Russia are characterized by low quality raw materials and difficult mining and geological mining conditions. There are 44 explored deposits within the state, of which only a quarter are exploited.

The main production of bauxite is carried out by JSC Sevuralboxytruda. Despite the reserves of ore raw materials, the security processing enterprises uneven. For 15 years, there has been a shortage of nephelines and bauxites, which leads to the import of alumina.

World reserves of bauxite are concentrated in 18 countries located in tropical and subtropical zones. The location of the highest quality bauxite is confined to areas of weathering of aluminosilicate rocks in humid conditions. It is in these areas that the bulk of the global supply of raw materials is located.

The largest reserves are concentrated in Guinea. Australia leads the world in the extraction of ore raw materials. Brazil has 6 billion tons of reserves, Vietnam - 3 billion tons, India's high-quality bauxite reserves amount to 2.5 billion tons, Indonesia - 2 billion tons. The bulk of the ore is concentrated in the depths of these countries.

Bauxite is mined by open and underground methods. Technological process processing of raw materials depends on its chemical composition and involves phased implementation of work.

At the first stage, alumina is formed under the influence of chemical reagents, and at the second, the metal component is extracted from it by electrolysis from a molten fluoride salt.

Several methods are used to form alumina:

• sintering;
• hydrochemical;
• combined.

The application of methods depends on the concentration of aluminum in the ore. Low quality bauxite is processed in a complex manner. The mixture of soda, limestone and bauxite obtained as a result of sintering is leached with a solution. Formed as a result chemical treatment The metal hydroxide is separated and filtered.

Application of mineral resource

The use of bauxite in various branches of industrial production is due to the versatility of the raw material in its mineral composition and physical properties. Bauxite is an ore from which aluminum and alumina are extracted.

The use of bauxite in ferrous metallurgy as a flux when smelting open-hearth steel improves specifications products.

In the production of electrocorundum, the properties of bauxite are used to form a super-resistant, fire-resistant material (synthetic corundum) as a result of smelting in electric furnaces with the participation of anthracite as a reducing agent and iron filings.

The mineral bauxite with a low iron content is used in the manufacture of fire-resistant, quick-hardening cements. In addition to aluminum, iron, titanium, gallium, zirconium, chromium, niobium and TR (rare earth elements) are extracted from ore raw materials.

Bauxite is used for the production of paints, abrasives, and sorbents. Ore with a low iron content is used in the manufacture of refractory compounds.

BRIEF HISTORICAL INFORMATION. About 1900 years ago, Pliny the Elder first named alum, which was used as a mordant for dyeing fabrics, “alumene.” 1500 years later, the Swiss naturalist Paracelsus discovered that alum contains aluminum oxide. Pure aluminum was first extracted from bauxite by the Danish scientist G. Ørsted in 1825. In 1865, the Russian chemist N. Beketov obtained aluminum by displacing it with magnesium from molten cryolite (Na 3 AlF 6). This method found industrial application in Germany and France at the end of the 19th century. In the middle of the 19th century. aluminum was considered a rare and even precious metal. Currently, aluminum is second only to iron in terms of global production.

GEOCHEMISTRY. Aluminum is one of the elements most abundant in the earth's crust. Its clarke is 8.05%. Under natural conditions, it is represented by only one isotope, 27 Al.

Under endogenous conditions, aluminum is concentrated predominantly in alkaline nepheline- and leucite-containing rocks, as well as in some varieties of basic rocks (anorthosites, etc.). Significant masses of aluminum accumulate due to alunitization processes associated with hydrothermal processing of acidic volcanogenic formations. The largest accumulations of aluminum are observed in residual and redeposited weathering crusts of acidic, alkaline and basic rocks.

In the sedimentary process, alumina dissolves and is transported only in acidic (pH< 4) или сильно щелочных (pH >9.5) solutions. Precipitation of aluminum hydroxides begins at pH = 4.1. In the presence of SiO 2, the solubility of Al 2 O 3 increases, and in the presence of CO 2 it decreases. Colloidal Al 2 O 3 compared to colloidal SiO 2 is less stable and coagulates faster. Therefore, in the process of their joint migration, the separation of these elements occurs. Due to the different geochemical mobility of aluminum, iron and manganese compounds, their differentiation occurs in the coastal zone of sedimentation basins. Bauxite accumulates closer to the shore, in the upper part of the shelf - iron ores, and at the bottom of the shelf - manganese ores. Aluminum hydroxides have significant adsorption capacity. The minerals that make up bauxites constantly contain Fe, V, Cr, Zn, Mn, Cu, Sn, Ti, B, Mg, Zr, P, etc. in variable quantities.

MINERALOGY. Aluminum is a component of about 250 minerals. However, only a few of them are of industrial importance: diaspore and boehmite, gibbsite (hydrargillite), nepheline, leucite, alunite, andalusite, kyanite, sillimanite, etc.

Diaspora HAlO 2 (Al 2 O 3 content 85%) crystallizes in the orthorhombic system, the habit of the crystals is lamellar, tabular, needle-shaped, the aggregates are leafy, cryptocrystalline, stalactite-like. The color of the mineral is white, grayish, with an admixture of Mn or Fe - gray, pink, brown, glassy to diamond luster, hardness 6.5–7, specific gravity 3.36 g/cm 3 .

Boehmit AlOOH – polymorphic modification of diaspore (by the surname Boehm), lamellar crystals, cryptocrystalline aggregates, bean-shaped, white color, hardness 3.5–4, specific gravity ~ 3 g/cm 3 . Formed during hydrothermal alteration of nepheline.

Gibbsite (hydrargillite) Al(OH) 3 (Al 2 O 3 64.7%) crystallizes in a monoclinal, less often in a triclinic system, pseudohexagonal crystals, lamellar and columnar, porcelain-like aggregates, earthy, sintered, worm-shaped, spheroidal nodules, hardness 2.5–3, specific gravity 2.4 g/cm3.

Nepheline Na (Al 2 O 3 34%) crystallizes in the hexagonal system, the crystals are prismatic, short-columnar, thick-tabular, colorless, gray, meat-red, luster from glassy to greasy, hardness 5.5–6, specific gravity 2.6 g/cm 3.

Leucite K (Al 2 O 3 23.5%) – framework silicate, isostructural with analcime; crystals - tetragontrioctahedrons, dodecahedrons. The color of the mineral is white, gray, hardness 5.5–6, specific gravity 2.5 g/cm 3 .

Alunite KAl 3 (OH) 6 2 (Al 2 O 3 37%) crystallizes in the trigonal system, the crystals are tabular, rhombohedral or lenticular, the aggregates are dense and granular. The color of the mineral is white, grayish, yellowish, brown, glassy to pearlescent luster, hardness 3.5–4, specific gravity 2.9 g/cm 3 . It is found in the weathering crust, where H 2 SO 4 is abundant.

Andalusite Al 2 O (in the province of Andalusia, Spain) is one of three polymorphic modifications of aluminum silicate (andalusite, kyanite and sillimanite), formed at the lowest pressure and temperature. Aluminum is slightly replaced by Fe and Mn. Crystallizes in the rhombic system, the crystals are columnar, fibrous, granular and radiant-columnar aggregates, pink color, glassy luster, hardness 6.5–7, specific gravity 3.1 g/cm 3 .

The most important ores of aluminum are bauxite - a rock consisting of aluminum hydroxides, oxides and hydroxides of iron and manganese, quartz, opal, aluminosilicates, etc. Based on the mineral composition, bauxites are distinguished as diaspore, boehmite, gibbsite, as well as complex bauxites, consisting of two or three of the above minerals. Amorphous alumina, which is part of industrial aluminum minerals, ages over time, as a result of which it is transformed into boehmite, and the latter turns into gibbsite.

INDUSTRIAL APPLICATION. Aluminum, due to its lightness (density 2.7 g/cm3), high electrical conductivity, high corrosion resistance and sufficient mechanical strength (especially in alloys with Cu, Mg, Si, Mn, Ni, Zn, etc.), has found wide use in various industries. The main areas of application of aluminum and its alloys are: automobile, ship, aircraft and mechanical engineering; construction (load-bearing structures); production of packaging materials (containers, foil); electrical engineering (wires, cable); production of household items; defense industry.

RESOURCES AND RESERVES. The main raw material of the global aluminum industry is bauxite. Bauxite proper includes aluminous rocks containing at least 28% Al 2 O 3. Aluminum is also obtained from nepheline and alunite ores. An electrical engineering method has been developed for producing aluminum from sillimanite, andalusite, kyanite crystalline schists and gneisses and other non-bauxite alumina sources. Bauxites, as a rule, form areal deposits that reach the surface or are only slightly covered, as a result of which their discovery and establishment of the industrial characteristics of deposits is a relatively simple task.

World bauxite resources are estimated at 55–75 billion tons. About 33% of them are concentrated in South and Central America, 27% in Africa, 17% in Asia, 13% in Australia and Oceania, and only 10% in Europe and Northern Europe. America.

The total reserves of bauxite in the world are 62.2 billion tons, and proven reserves are 31.4 billion tons. The top six countries with the largest reserves are Guinea, Australia, Brazil, Jamaica, India and Indonesia (Table 8). These countries are the main suppliers of gibbsite bauxite to the world market. Other bauxite-mining countries, such as China and Greece, use boehmite-diaspore bauxite. Russia does not have sufficient reserves of bauxite for domestic consumption, and its share in the world balance of this raw material is less than 1%.

Unique deposits include deposits with bauxite reserves of more than 500 million tons, large – 500–50 million tons, medium – 50–15 million tons and small – less than 15 million tons.

MINING AND PRODUCTION. World bauxite production 1995–2000 amounted to 110–120 million tons. The main producers of bauxite were Australia, Guinea, Jamaica, Brazil and China. The volume of production of this type of mineral raw material in Russia was about 4–5 million tons, while in Australia it was 43 million tons. In Australia, the largest mining company is « Alcan Aluminum».

In Russia, the development and extraction of bauxite is carried out at the deposits of the Urals OJSC "Sevuralboxytruda" (SUBR) and OJSC "South Ural Bauxite Mines" (YBR), where proven reserves can ensure the operation of mines for 25–40 years. Bauxite is mined using the mining method from great depths.

Alumina production in the world from various mineral sources in 1995–2000. amounted to 43–45 million tons. In Australia, which is the undoubted world leader, the main producers of alumina are companies « Alcoa» , « Reynolds Metals» And « Comalco» .

METALLOGENY AND AGES OF ORE FORMATION. The most favorable conditions for the formation of bauxite deposits arose at the early stage of the geosynclinal stage, when geosynclinal deposits of alumina mineral raw materials were formed, as well as at the platform stage, when laterite and sedimentary deposits appeared.