Aluminum ore: deposits, mining. Properties of aluminum ore The ore from which aluminum is squeezed

home Aluminum ore occupies a special place in modern industry. Thanks to certain physical and chemical properties

aluminum is used in many branches of human activity. Automotive manufacturing, mechanical engineering, construction, and the production of many consumer goods and household appliances are no longer possible without the use of this type of non-ferrous metal. Aluminum mining is a complex and labor-intensive process.

Features of aluminum ore An ore is a natural mineral formation that contains a specific metal or mineral. IN pure form There is practically no aluminum in nature, so it is mined from aluminum ore. IN earth's crust

• its content is about 9%. Today, there are about 250 varieties of mineral compounds that include aluminum, but not all of them are profitable to process. The following types of ore are considered the most valuable for the aluminum industry:
• bauxite;
• alunite;

nepheline Bauxite It is most often used as a raw material for metal mining, because it contains up to 60% aluminum oxides. The composition also includes silicon and iron oxides, quartz, magnesium, sodium and other chemical elements and compounds. Depending on their composition, bauxite has different densities. Color rock

predominantly red or grey. To produce 1 ton of aluminum, 4.5 tons of bauxite are needed. Alunite

the ore is not far behind bauxite, as it contains up to 40% alumina - the main supplier of aluminum. It has a porous structure and has many impurities. Aluminum mining is profitable only when the total amount of alunite is equal to the total amount of additives.

It is an alkaline rock of igneous origin. They rank third in terms of aluminum oxide content. From the first grade of nepheline ore, 25% or more alumina can be processed. From the second grade - up to 25%, but not less than 22%. All mineral compounds containing aluminum oxides less than this value have no industrial value.

Aluminum mining methods

The production of metal is possible only from alumina, for the formation of which the ore is crushed to a powder state and heated with steam. This way it is possible to get rid of most of the silicon and leave the optimal raw material for subsequent smelting.

Aluminum ore is being mined open method, if the depth is shallow. Bauxite and nepheline, due to their dense structure, are usually cut using a surface miner using a milling method. Alunites are a type of loose rock, which is why a quarry excavator is optimal for removing it. The latter immediately loads the rock onto dump trucks for further transportation.

After the extraction of primary raw materials, several mandatory stages of rock processing follow in order to obtain alumina:

1. Transportation to the preparatory workshop, where crushing equipment crushes the rock to a fraction of about 110 mm.
2. The prepared raw materials, along with additional components, are sent for further processing.
3. The rock is sintered in furnaces. If necessary, the aluminum ore is leached. This produces a liquid aluminate solution.
4. The next stage is decomposition. As a result, an aluminate pulp is formed, which is sent for separation and evaporation of the liquid.
5. Cleaning from excess alkalis and oven calcination.

The result is dry alumina, ready for aluminum production. The final stage is hydrolysis treatment. In addition to the method described above, aluminum is also mined using the mine method. This is how the rock is cut out from the layers of the earth.

Aluminum mining sites in Russia

In the world ranking in terms of aluminum ore production, Russia ranks seventh. About 50 deposits have been explored throughout the territory, among which there are still undeveloped deposits. The richest ore reserves are concentrated in Leningrad region and in the Urals, where one of the deepest “aluminum” mines operates. The depth of the latter reaches 1550 meters.

Despite the widely developed non-ferrous metallurgy, and Aluminum production, in particular, the resulting volume is not enough to supply the industry of the entire country. Therefore, Russia is forced to import alumina from other countries. This need is also due to the lower quality of ore. One of the most profitable deposits in the Urals produces bauxite with a 50% alumina content. In Italy, a rock is mined that contains 64% aluminum oxides.

About 80% of the total mass of aluminum ore in Russia is mined in closed mines. Quite a lot of deposits are located in Belgorod, Arkhangelsk, Sverdlovsk regions, as well as the Komi Republic. In addition to bauxite, nepheline ores are also mined. The profitability of this type of metal production is less, but still the result partly compensates for the country's shortage of raw materials.

A special place in the aluminum industry is occupied by the production of metal from recycled materials. This method significantly saves energy and ore resources, and reduces the level of damage caused environment. Here Russia lags somewhat behind other countries, but the performance of most domestic enterprises is improving noticeably every year.

World production of aluminum ores

Over the past hundred years, the level of aluminum ore production has increased to incredible levels. If in 1913 the global volume of the rock was approximately 550 thousand tons, today this figure exceeds 190 million tons. About 30 countries are currently mining aluminum ore. The leading position is occupied by Guinea (West Africa), where many deposits are concentrated with reserves equal to 28% of the world share.

In terms of direct ore production volumes, China should be ranked first. Thus, the country of the “setting sun” produces more than 80 million tons of raw materials per year. The top five are as follows:

• China- 86 million tons;
• Australia- 82 million tons;
• Brazil- 31 million tons;
• Guinea- 20 million tons;
• India- 15 million tons.

Next comes Jamaica with 9.7 million tons and, finally, Russia, whose total aluminum ore production is 6-7 million tons. Leaders in the aluminum industry have changed over the years.

The ore was first mined in France, in the town of Box, due to which the most common type of ore is called bauxite. Soon they could boast of better performance Western Europe And North America. Half a century later, the undisputed leader became Latin America. Now Africa, Australia, China and other developed countries have taken the lead.

Non-ferrous metals are an integral part of modern industry. Without them, the development of many industries would not be possible. Aluminum, as a lightweight, durable and functional metal, is considered a key structural material of the present time.

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 volcanic 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. mineral composition There are diaspore, boehmite, gibbsite, and complex bauxites, consisting of two or three of the listed 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. Production volume of this species mineral raw materials 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.

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.
• The color of bauxite at different mining locations ranges from almost white to dark red. 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. It ranks third in terms of the number of deposits in the earth's crust. 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 greatest number– 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 - these 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 areas in 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. This industry first 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 of the humid tropics as a result of deep chemical transformation of silicate rocks (the 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. How more quantity of the first and less 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%, the 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 is 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 isolate the metal itself by electrolytic reduction.

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 the composition sandpaper and a variety of 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 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.

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. It ranks third in terms of the number of deposits in the earth's crust. Aluminum is also known to everyone as an element in the periodic table, which belongs to light metals.

Aluminum ore is a natural raw material from which it is mainly mined from bauxite, which contains aluminum oxides (alumina) in the largest amount - 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 to produce various types of 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 zones of the earth. 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 basins 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 it 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. A few decades later, Latin America and the Soviet Union became the leaders in quantitative indicators of the aluminum industry. And already in the 1950-1960s, Latin America became the leader in terms of production. And in the 1980-1990s. there was a rapid breakthrough in aluminum 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 large quantities of metal, 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 are of poorer 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.

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 technologies, 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:

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:

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:

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:

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 the national economy, thanks to the properties of aluminum, which currently ranks second after iron in modern industry.