What is bauxite in simple words?

Abstract of a scientific article on materials technology, author of the scientific work – Dubovikov O.A., Yaskeläinen E.E.

Modern aluminum production, which has taken first place in the production of non-ferrous metals in the world, consists of three main stages: the extraction of ore, its processing into alumina and, finally, the production of primary aluminum. The production of alumina from bauxite, the main raw material of the alumina industry, is based on two main methods: the Bayer method and the sintering method developed in Russia under the leadership of Academician Nikolai Semenovich Kurnakov. Producing alumina using the Bayer method is more economically profitable, but it is also more demanding on the quality of bauxite raw materials. In relation to low-quality bauxites, a large number of research works have been carried out, aimed, firstly, at finding methods for enriching raw materials, secondly, at improving the combined sequential Bayer-sintering method, and thirdly, at developing new hydrometallurgical methods for their processing. Mechanical methods for bauxite enrichment have not yet yielded positive results, and during the development of a new hydrometallurgical high-alkaline autoclave process, significant instrumental difficulties were encountered that have not yet been resolved. To effectively process such low-quality bauxite raw materials, it is proposed to use the universal thermochemistry-Bayer method developed at the St. Petersburg Mining University under the leadership of Nikolai Ivanovich Eremin, which allows the processing of various substandard bauxite raw materials and is characterized by a competitive cost in relation to the sintering method and combined methods. The main stages of the thermochemistry-Bayer method: thermal activation of the raw material, its subsequent desiliconization with an alkaline solution and leaching of the resulting bauxite product using the Bayer method. Despite the high energy consumption at the firing stage, it makes it possible to condition low-quality bauxite raw materials for a number of technologically harmful impurities: such as organics, sulfide sulfur, carbonates, while crystalline hydrate and free water are removed. Subsequent desiliconization of thermally activated bauxite with an alkaline solution makes it possible to transfer it from the category of low-quality bauxite to raw materials suitable for processing using the Bayer method. i Nadoeli bannery? Vy vsegda mojete otklyuchit advertisement.

Similar topics of scientific work on materials technology, author of the scientific work – Dubovikov O.A., Yaskeläinen E.E.

The role of thermal activation in the production of alumina from low-quality bauxite The influence of the peculiarities of the mineralogical composition on the process of thermochemical enrichment of bauxite in Northern Onega Behavior of bauxite concentrates at the leaching stage using the Bayer method
Timan bauxites: mineralogical and technological features
The role of calcium oxide in the process of thermochemical conditioning of bauxite
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Text of the scientific work on the topic “Processing of low-quality bauxite raw materials using the Thermochemistry-Bayer method”

Processing of low-quality bauxite raw materials. PROCESSING OF LOW-QUALITY BOXITE RAW MATERIALS BY THE TERMOCHEMIYA-BAYER METHOD 1 St. Petersburg Mining University, Russia 2 Norilsk Nickel, Harjavalta, Finland Modern aluminum production, which has taken first place in the production of non-ferrous metals in the world, consists of three main stages: the extraction of ore, its processing into alumina and, finally, the production of primary aluminum. The production of alumina from bauxite, the main raw material of the alumina industry, is based on two main methods: the Bayer method and the sintering method developed in Russia under the leadership of Academician Nikolai Semenovich Kurnakov. Producing alumina using the Bayer method is more economically profitable, but it is also more demanding on the quality of bauxite raw materials. In relation to low-quality bauxites, a large number of research works have been carried out, aimed, firstly, at finding methods for enriching raw materials, secondly, at improving the combined sequential Bayer-sintering method, and thirdly, at developing new hydrometallurgical methods for their processing. Mechanical methods for bauxite enrichment have not yet yielded positive results, and during the development of a new hydrometallurgical high-alkaline autoclave process, significant instrumental difficulties were encountered that have not yet been resolved. To effectively process such low-quality bauxite raw materials, it is proposed to use the universal thermochemistry-Bayer method developed at the St. Petersburg Mining University under the leadership of Nikolai Ivanovich Eremin, which allows the processing of various substandard bauxite raw materials and is characterized by a competitive cost in relation to the sintering method and combined methods. The main stages of the thermochemistry-Bayer method: thermal activation of the raw material, its subsequent desiliconization with an alkaline solution and leaching of the resulting bauxite product using the Bayer method. Despite the high energy consumption at the firing stage, it makes it possible to condition low-quality bauxite raw materials for a number of technologically harmful impurities: such as organics, sulfide sulfur, carbonates, while removing crystalline hydrate and free water. Subsequent desiliconization of thermally activated bauxite with an alkaline solution makes it possible to transfer it from the category of low-quality bauxite to raw materials suitable for processing using the Bayer method. Key words: N.S. Kurnakov, N.I. Eremin, kaolinite, chamosite, bauxite deposits, bauxite, silicon module, thermal activation, desiliconization of calcined bauxite, bauxite concentrate, Bayer method. How to cite this article: Dubovikov O.A. Processing of low-quality bauxite raw materials using the thermochemistry-Bayer method / O.A. Dubovikov, E.E. Yaskeläinen // Notes of the Mining Institute. 2016. T.221. P.668-674. DOI 10.18454/РМ1.2016.5.668. Introduction. The quality of bauxite is assessed by a combination of factors that determine the cost of alumina production. The specific consumption of bauxite and caustic alkali is determined by the content of aluminum and silicon oxides, therefore, abroad, the quality of bauxite is assessed by the base number B = , where A1203(act) and SiO2(act) are the percentage of soluble aluminum oxide and silicon dioxide. Since this formula does not reflect the loss of alkali with red mud, Hungarian researchers proposed to evaluate the quality of bauxite using the formula <(C - C^0) /^b>, where C is a constant; C^0 is the cost of alkali lost with red mud; Qb is the amount of dry bauxite consumed per 1 ton of alumina [15]. N.N. Tikhonov proposed a comprehensive criterion for assessing the quality of bauxite [4], according to which the bauxite equivalent is equal to QbkQsh. The correction factor k takes into account the difference in the cost of alkali and bauxite, and the specific costs of bauxite Qb and alkali Qsh per 1 ton of alumina are respectively equal: Qb = 99/(AbPf) and Qsh = 990($^ + 1,45 $ bp + 0,14 Sb ) / (Апф), where the percentage of aluminum oxide in bauxite is Ab; sulfur – $b; silicon dioxides – and carbon – Sat, actual percentage extraction of alumina from bauxite – Pf; silicon dioxide – h and sulfur – p^. The main indicator of the quality of bauxite remains the silicon module or the weight ratio of aluminum oxide to silicon dioxide of bauxite raw materials, however, the mineral resource base tends not only to reduce the quality of bauxite raw materials, but also to increase the costs of their extraction. In the last century in Russia, research aimed at developing technologies for extracting alumina from low-quality bauxite was carried out at the Mining Institute and at the Russian Institute of Applied Chemistry under the general leadership of academician and professor of the Mining Institute Nikolai Semenovich Kurnakov. When determining the final scale of aluminum production, the USSR Government on September 14, 1929 adopted N.S. Kurnakov’s recommendation to process bauxite at Processing of low-quality bauxite raw materials. Volkhov aluminum smelter using the sintering method by the Muller-Yakovkin-Lileev method, and at the Dneprovsky aluminum smelter using the Kuznetsov-Zhukovsky method, proposed by Professor A.N. Kuznetsov, a professor at the Mining Institute, and his collaborator E.I. Zhukovsky. Currently, within the framework of one of the leading scientific schools of the Mining University, research is ongoing, carried out at one time under the leadership of the head of the department of metallurgy of light and rare metals of the Mining Institute Nikolai Ivanovich Eremin on the enrichment of low-quality bauxite raw materials, the idea of ​​which is to use the processes of thermal exposure and subsequent selective leaching, providing a targeted change in the chemical and mineralogical composition of bauxite and the possibility of processing the resulting concentrates within the framework of traditional alkaline methods. The quality of Bayer bauxite is, to a first approximation, determined by the silicon module μ^, according to which the theoretical extraction of alumina by the Bayer method is equal to [(μ^ – 1) / M«]100%, provided that all bauxite silicon dioxide is bound into hydrosodium aluminosilicate (HASN) of composition No. 20A1203 ^ 1,78nH2. With an increased content of silicon dioxide in bauxite, it will “transition” into production waste – red mud in the form of GASN, thereby causing large losses of alumina and alkali. After desiliconization of low-quality bauxites, it is possible to process them using the Bayer method, releasing not only alumina, but also obtaining a whole range of technogenic products based on silicon dioxide. The use of mechanical enrichment methods to increase the silicon modulus depends on the chemical and mineralogical properties of the processed raw materials. In some cases, a Bayer concentrate was obtained with an A1203 extraction of 50+70% and a concentrate yield of 60+70%. In this case, a high-silica product is inevitably obtained, the quality of which is low: = 1,5+2,5, and the amount of alumina entrained with them reaches 30+50%. Microbiological methods make it possible to somewhat improve the quality of bauxite, but their industrial use is very problematic at the present stage due to the length of the process [5]. Bauxite deposits. The main areas of bauxite concentration in Russia: North Ural bauxite region, Timan bauxite zone, North Onezh bauxite region, Belgorod region, Krasnoyarsk region (Fig. 1) [3]. Rice. 1. Main bauxite deposits, distribution of reserves and predicted bauxite resources (million tons) by constituent entities of the Russian Federation Processing of low-quality bauxite raw materials. Fig.2. Bauxites of the Vezhayu-Vorykvinskoe deposit at different magnifications W – boehmite/diaspore, Shm – chamosite, KL – kaolinite, Rt – rutile, Gt – goethite, Gb – gibbsite, Gm – hematite Approximately 26% of Russian bauxite reserves are located in the Timan bauxite zone (Komi Republic). These are the large Vezhayu-Vorykvinskoye field and the Verkhne-Shchugorskoye and Vostochnoye fields [12]. Bauxites are characterized by a high iron content and have a silicon modulus of 3 to 6. The presence of sulfur in the form of pyrite causes certain difficulties during processing. Bauxite occurs near the surface, which allows it to be mined by open-pit mining. The predicted resources of the Timan bauxite zone are about 40 million tons. The Vezhayu-Vorykvinskoye field is located in the area of ​​the Vorykva and Vezhayu rivers. The thickness of the ore deposits within the deposit varies from 1,0+1,5 to 30+32 m. The depth of the ore layer varies from 0,2+0,5 to 132 m. The material composition of bauxite is as follows, % by weight: 8102 8,8-19; M2O3 41-48; Fe2O21,9 29,8-3,5; FeO 7,4-2; TI2,4 3,2-0,07; CaO 0,9-11,6; PPP 12,5+205. An increased content of rare metals No. 0,005 (0,009-205%) and Ta0,0003 (2%) was also established. The main minerals are boehmite, kaolinite, chamosite and hematite (Fig. XNUMX). The bauxites of the deposit are of the industrial boehmite type. The Eastern field is located east of Vezhayu-Vorykvinskoye and is practically its continuation. Bauxites of the Vostochny deposit lie at depths from 78 to 400 m, their thickness ranges from 1,5 to 46 m. ​​The average composition of bauxites is as follows, % by weight: A1203 -50,26; 8102 – 7,39; Fe203 – 27,8; TYu2 – 2,6. An increased content of rare metal and rare earth elements is also noted: No. 205 (up to 0,0093%), Ta205 (0,0002%); Ga (up to 100 g/t); 8c (up to 120 g/t); V (up to 630 g/t). Minerals include boehmite, diaspore, kaolinite, chamosite, and hematite. Bauxites are classified as boehmite and diaspore-boehmite. The Verkhne-Shchugorskoye field is located northwest of Vezhayu-Vorykvinskoye, in the upper reaches of the Shchugor River. The thickness of the deposits ranges from 0,4 to 50 m. The content of A1203 is 49,76%, 8102 – 6,61%, Fe203 – 28,03%. Main minerals: boehmite, diaspore, kaolinite, hematite. Industrial type – monohydrate boehmite bauxite. The main silicon-containing minerals of the Timan bauxite zone are kaolinite and chamosite. Behavior of kaolinite during bauxite processing using the Thermochemistry-Bayer method. The thermochemical desiliconization of kaolinite raw materials is based on the property of kaolinite to decompose at temperatures above 900 °C into aluminosilicate with a lower content of silicon dioxide than in kaolinite and amorphous, highly soluble in alkaline solutions, free silicon dioxide [1, 2, 6, 8-10 ]. Along with X-ray diffraction and crystal optical methods of analysis, to reveal the mechanism of thermal activation of kaolinite N.I. Eremin used a simple and reliable chemical method. It was shown that the products of kaolinite firing at 925+1000 °C are amorphous 8102, y-A1203 and mullite with approximately equal quantitative distribution of aluminum oxide between them according to the reaction and graphical interpretation (Fig. 3): 6(Al03-28Al2) = 10(8102 amorphous) + 3(y – Al12O3) + (3A203O2-2vAlXNUMX). Processing of low-quality bauxite raw materials. Thus, the theoretically possible extraction of silicon dioxide during desiliconization of calcined kaolinite is more than 80%. Behavior of chamosite during bauxite processing using the Thermochemistry-Bayer method. While the behavior of kaolinite during heat treatment was completely clear, the issue of thermal transformations of chamosite remained unclear. Chamosite behavior ^e^+MA^sOyuKON x x <^e^)z(0,0H)b>in the thermochemistry-Bayer method largely determines the technological indicators of the entire process [7, 11, 13, 14]. The study involved samples of chamosites from the Belgorod site of the Kursk magnetic anomaly with varying degrees of oxidation and with different ratios of orthogonal to monoclinic modification (Table 1). Material composition of chamosites Sample number Content, % Degree of oxidation Modification ratio (O/M)** PPP A203 8102 Fe20з Fe0 R20 ТУ2 1 8,08 18,26 15,30 54,56 29,61 0,16 1,19 0,46 2,1 2 15,58 31,75 26,00 21,40 8,43 0,25 1,96 0,61 2,0 3 10,52 23,72 22,40 39,10 23,30 0,20 0,61 0,40 9,0 * Degree of oxidation ^e203^e0) / Fe203; ** (O/M) – orthogonal/monoclinic. According to the data obtained as a result of X-ray phase analysis, the studied chamosite samples belong to the kaolinite type, since there is no diffraction peak corresponding to the interplanar distance d = 1,4 nm, characteristic of chlorites. The radiographs of all initial samples show the main chamosite reflections: d = 0,7; 0,35; 0,25; 0,24 nm. Hematite is also found in the samples (d = 0,369 nm), in samples No. 2 and 3 there is kaolinite (d = 0,712; 0,443; 0,356 nm), in samples No. 1 and 3 there is a small amount of siderite (d = 0,279 nm), in the sample No. 2 – gibbsite (th = 0,483 nm) and quartz (th = 0,334 nm). The difference in the ratio of reflection intensities, especially in the region of reflections corresponding to interplanar distances d = 0,251 nm and d = 0,240 nm, is associated with a different ratio of the orthogonal and monoclinic forms of this mineral in chamosite samples. The orthogonal shape is characterized by reflection х = 0,251 nm, while the monoclinic form is characterized by х = 0,240 nm. To compare the reflection intensities d = 0,251 nm and d = 0,240 nm, the results of X-ray phase analysis were presented in the form of bar diagrams, the bars of which were obtained by measuring the peak height in the diffraction pattern from the background level of the spectrum. The ratio of the intensities of these reflections is proportional to the ratio of the content of forms in the sample. At 1st=0,240 > 1st=0,251 the monoclinic form predominates, at 1st=0,240 < 1st=0,251 the orthogonal form predominates. Typically, the orthogonal shape predominates in chamosite. Diffraction peaks 0,7; 0,35 nm belongs to both structural forms. Thus, comparing the reflection intensity ratio 1th = 0,251 / 1st = 0,240 for samples No. 1; 2; 3, accordingly, we have the following ratios of reflection intensities: 2,1; 2,0; 9. Chamosite samples were crushed to a particle size of -0,147 mm. Then some of them were burned. Diffractograms of the original and fired chamosite are presented in Fig. 4. Amorphous silica Gamma modification of aluminum oxide O 0H A1 0 Fig. 3. Graphic interpretation of the thermal decomposition of kaolinite Processing of low-quality bauxite raw materials. Bauxite is a rock, the most important source of aluminum. The material received its name in honor of the area where it was discovered and first described in 1821 by geologist Pierre Berthier – the commune of Les Baux in the south of France. Bauxite is an aluminum ore in the form of a stony or clay-like rock, homogeneous or layered. The main chemical component is alumina (Al2O3). In addition to it, the composition includes iron oxide (Fe2O3) and silica (SiO2), and the latter deteriorates the properties of the ore. Also, as impurities, the rock may contain iron hydroxides and silicates, oxides of titanium, calcium, magnesium, manganese and others. The mineral was formed as a result of lateritic weathering of alkaline, acidic, and sometimes basic rocks or the deposition in sea and lake basins of significant quantities of alumina contained in transported molecular solutions and sols.

Place of Birth

• Indonesia,
• India,
• Vietnam,
• Brazil,
• Australia,
• Guinea.

Almost 6/2 of the world’s bauxite reserves are concentrated in these 3 countries. At the same time, the leaders in rock production are India, China and Australia.

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In Russia, bauxite deposits were discovered in the Urals, Leningrad region, Komi Republic, Kemerovo region and on the Kola Peninsula.

The physical properties of bauxite can vary significantly. Thus, the structure can be either dense, with an earthy fracture, or porous, with a rough cellular fracture. Often the ground mass contains rounded bodies, creating an oolitic structure.

The color of the rock is equally diverse: from white to dark red, although brown and brick are the most common.

Due to this heterogeneity, bauxite is difficult to identify visually, which complicates the search for deposits.

Classification

By origin, bauxites are divided into residual (lateritic), sedimentary (redeposited) and mixed (when both processes participated in the formation of the rock).