Sillimanite group minerals: a new promising raw material for the Russian aluminum industry

Russian Geology and Geophysics 51 (2010) 1247–1256 www.elsevier.com/locate/rgg

Sillimanite group minerals: a new promising raw material for the Russian aluminum industry G.G. Lepezin *, S.A. Kargopolov, V.Yu. Zhirakovskii V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akademika Koptyuga 3, Novosibirsk, 630090, Russia Received 20 November 2009; received in revised form 26 April 2010; accepted 12 May 2010

Abstract The raw-material base of the Russian aluminum industry is considered. The raw materials include common (bauxites, nepheline syenites) and uncommon (nepheline ores, synnyrites, anorthosites, power-and-heating plant ashes, kaolines) types of ores. With regard to many criteria (reserves and quality of ores, technology of their processing, etc.), the problem of alumina deficit can be solved by mining sillimanite group minerals Al2SiO5 (wt.%: Al2O3 = 62.9, SiO2 = 37.1), namely, andalusite, sillimanite, and kyanite. Their proved reserves converted to the final product (aluminum) exceed 400 mln tons. This will be enough for more than a hundred years provided that aluminum is produced in the present-day output (4 mln tons in 2008). Almost all deposits can be explored by strip mining, with application of the gravitation, flotation, and electromagnetic separation methods for ore dressing. The alumina content in concentrates reaches 60–62 wt.%. Only high-grade bauxites and the above concentration methods can ensure such a high yield of Al2O3. Sillimanite group minerals can be processed together with nepheline ores by sintering or be used for the direct electrothermal production of silumin and aluminum, excluding the alumina production stage. The latter method is the most promising in Russia. © 2010, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. Keywords: bauxites; nepheline ores; synnyrites; anorthosites; ashes; kaolines; sillimanite group minerals; electrothermics; alumina; silumin; aluminum

Introduction Aluminum is most highly consumed among nonferrous metals. Light weight, plasticity, high heat conductivity and electroconductivity, resistance to corrosion, and other properties permit it to be used in aircraft and motor-car industries, electrotechnical machine building, house building, and production of consumer goods, package, and other materials. According to the U.S. Geological Survey data, the world production of aluminum in 2008 was 39.7 mln tons (mainly in China (13.1 mln tons) and in Russia (4.2 mln tons)). The leading producing companies are Rio Tinto Alcan (Australia– England), Alcoa, Reynolds, and Kaiser Aluminum & Chemical Corp. (USA), Camalco (Australia), Norsk Hydro (Norway), Pechiney (France), Alusuisse (Switzerland), and OK RUSAL (Russia). There are twelve operating aluminum plants in Russia, six of them are in Siberia (BRAZ (Bratsk), IRKAZ (Irkutsk), KRAZ (Krasnoyarsk), SAZ (Sayansk), KhAZ (Khakassiya),

* Corresponding author. E-mail address: [email protected] (G.G. Lepezin)

NKAZ (Novokuznetsk)), two, in the Uralian region (BAZ (Bogoslovsky), UAZ (Uralian), and four are in the west and northwest of Russia (KAZ (Kandalaksha), VAZ (Volkhov), NAZ (Nadvoitsk), VOLAZ (Volgograd). In 2008, these plants produced more than 4 mln tons of aluminum (Table 1). The building of a new aluminum plant, Alyukom–Taishet (output of 750,000 tons), in the Irkutsk Region is close to the completion. It is planned to build the Boguchany aluminum plant (output of 600,000 tons) in the lower-Angara region. Thus, the tendency for aluminum production growth in Russia is obvious. The deficit of Russian raw-material alumina for aluminum plants is now 50% and will continue to grow. In this paper we consider the strategy of solution of this problem, disregarding the present-day economic crisis. Experts believe that the Russian aluminum industry can be competitive only if the total energy consumption does not exceed 15–17% and the transport costs, 6–8% (Kal’chenko, 2001). The actual situation is as follows: The energy consumption reaches 20–30%, and the transport costs, 17–18% (for comparison, in Canada they are as low as 2–3%). How can, e.g., Siberian aluminum plants be competitive with foreign

1068-7971/$ - see front matter D 2010, V . S. Sabolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.rgg.2010.11.004

1248

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

Table 1. Dynamics of aluminum production in Russia and in the world Plant

Operation since

Annual production (ths tons) 2001

2002

2003

2004

2005

2006

2007

2008

VAZ

1932

21.5

22.0

23.0

23.0

22.9

23.4

24

24

UAZ

1939

85.0

92.0

103.3

125.2

128.7

132.6

128

133.6

BAZ

1943

175.0

178.0

180.0

183.1

182.7

183.6

189

185.6

NKAZ

1943

282.0

288.0

295.9

305.0

310.8

323.2

350

318

KAZ

1951

70.0

76.0

78.0

71.7

72.2

74.3

80

75.7

NAZ

1954

72.3

74.0

76.0

76.7

78.0

80.2

84

81.5

VOLAZ

1959

145.2

150.0

151.0

156.3

155.4

158.4

168

170

IRKAZ

1962

272.0

275.0

278.0

287.8

293.5

294.7

294

358

BRAZ

1966

919.1

918.3

932.5

960.0

973.6

983.7

1045

1000

KRAZ

1966

852.5

867.0

903.5

921.4

925.3

948.0

989

1000

SAZ

1986

406.8

409.0

459.0

483.6

504.0

531.0

555

537

KhAZ

2007

–

–

–

–

–

–

160

300*

Total

–

3301.4

3349.3

3480.2

3593.8

3647.1

3733.1

4066

4200

World production

–

23922

25520

27962

29281

31269

33218

37410

38759

* Design output.

ones, lacking their own raw-material alumina and thus buying it in Australia and supplying first by sea and then by rail transport for 4000–4500 km? The alumina production and transportation costs are 30–40% higher for Russian plants than those for American ones. To increase the profitability of aluminum production and reduce its cost, it is recommended (Bronevoi and Lankin, 2001; Kuleshov, 1997; Prokopov, 2002; Purdenko, 1997; Sizyakov, 1999, and others): (1) to create vertically and horizontally integrated structures from raw-material mining to production of aluminum goods; (2) to conclude long-term agreements with alumina suppliers; (3) to introduce energyand resource-saving technologies; and (4) to build energy-generating plants in large companies. These recommendations are certainly useful but general. Their realization can at best help the organization and technology of aluminum production in Russia to approach those in leading foreign countries. In the future it is possible to increase the domestic consumption of aluminum, but there is a problem where to get a raw material and what to do with high transportation costs. Alumina is supplied from the former Soviet republics (Ukraine, Kazakhstan) and foreign countries (Australia, Brazil, Guinea, etc.). The exhausted alumina resources, low technological level of aluminum output, low consumption of final products, and high energy and transport costs are just a minor part of problems calling for operative decision. The situation will be still more complicated if tolling and off-shore production are abolished. When Russia enters the WTO and accepts the condition of energy market liberation, cheep electric energy will disappear. Thus, the cheep labor force will be the only advantage of Russian aluminum producers over foreign rivals.

Alumina production According to the data of the International Aluminum Institute (IAI), the aluminum production in 2007 amounted to 78.346 mln tons. In Russia, aluminum is produced by the Bogoslovsky and Uralian Plants, Pikalevo Glinozem Enterprise, and Boksitogorsk and Achinsk alumina integrated plant (Table 2). Production of one ton of aluminum requires more than two tons of alumina (calculated requirement is 1.92 tons). Production of aluminum in Russia increases, but the production of alumina does not change. Today its deficit exceeds 5 mln tons. If the projects of building of new aluminum plants are realized, this deficit will increase to 9–15 mln tons. Almost all world commercial alumina is produced from bauxites. The hydrochemical method for their processing elaborated by Bayer in 1899 is leading in the world alumina industry. It is efficient and simple but applicable only to high-grade bauxites. To process low-grade bauxites, nephelines, alunites, kaolines, and other types of alumina raw-material, the sintering technology is used. The Bayer method is cheap and widespread, whereas the sintering technology is more expensive but the most universal. Foreign alumina industry works using high-grade bauxites. The world resources of bauxites, the main raw material for alumina production, are evaluated by the U.S. Geological Survey at 55–75 bln tons, with the Russian resources amounting to ~1%. Theoretically, alumina and aluminum can be extracted from many natural and technogenic products. The problem is the scales of their resources, their accessibility and exploration costs (prime cost, profitability, and payback), the appropriate

1249

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256 Table 2. Dynamics of alumina production in Russia Plant or integrated plant

Put into operation in

Annual production (ths tons) 2001

2002

2003

2004

2005

2006

2007

2008

Boksitogorsk alumina integrated plant (Boksitogorsk) 1938

165

121

131

132

133

138.3

143.0

156.4

Uralian aluminum plant (Kamensk-Ural’skii)

1939

651

675

714.5

721.3

725.7

725.8

760.0

730.3

Bogoslovsky aluminum plant (Krasnotur’insk)

1944

1049

1075

1100

1095.2

1098

1078

1100

1084

Pikalevo alumina plant (Pikalevo)

1959

220

239

274

251

195.1

197.5

205.0

?

Achinsk alumina integrated plant (Achinsk)

1970

965

1035

1050

1040

1060

1038

1 082

1069.4

3050

3145

3245.6

3268

3229.2

3232

3339.0

3040

Total

technology of their mining, concentration, and extraction, and the ecologic consequences of building corresponding enterprises. All this will be taken into account on our following examination of bauxites, nepheline ores, synnyrites, anorthosites, kaolines, commercial ashes, and sillimanite group minerals (SGM). The above raw materials are either already used in alumina production (bauxites, nepheline ores) or are promising sources of aluminum (all the rest). Bauxites are a conventional raw material in Russia. Their main resources (91%) are localized in the European part of the country. The developed bauxite deposits in the North Uralian, North Onezhskoe, and Central Timan regions and the nondeveloped Vislovskoe deposit in the Belgorod Region bear ~70% of the proved reserves. Bauxite mining annually increases by several percent, whereas the proved reserves become reduced (Fig. 1). Bauxites in the North Uralian bauxite-bearing region (Kal’inskoe and Krasnaya Shapochka deposits) are of first grade (wt.%): Al2O3 = 53.4, SiO2 = 4.8. They are mined by the underground method from a depth of 900–1000 m. The prime cost of mining is high, which poses the question of closing the mines. Bauxites in the North Onezhskoe bauxite-bearing region are of low grade (wt.%): Al2O3 = 53.4, SiO2 = 17.3.

The Belgorod bauxite-bearing region (Iksinskoe deposit) has large resources of high-grade bauxites (wt.%): Al2O3 = 49.5, SiO2 = 8.3. But they occur at a depth of 500 m, which makes their mining unprofitable. The main expectancies for bauxite production growth are set upon the Central Timan bauxite-bearing region with proved ore reserves of 250 mln tons. The bauxites there are of medium grade (wt.%): Al2O3 = 50.3, SiO2 = 7.7. The planned production capacity of the Boksit Timana Joint Stock-Company was evaluated at 2.5 mln tons of produced ores (in 2006, 2.39 mln tons were mined, and for seven months of 2008, 1.175 mln tons). There are also bauxites in Siberia (Chadobetskoe, Barzasskoe, Tatarskoe, Boksonskoe, and other deposits), but they are of complex mineralogical composition (much Fe2O3 (30–40 wt.%), Ti (up to 10%), and phosphorus compounds (0.3–1.3%). The alumina content in them is 36–40%; the silica module is 3.7–6.2. Bauxites of the Chadobetskoe deposit are suitable for commercial exploitation but permit building at best a medium-power alumina plant. Nepheline ores are another conventional alumina raw material in Russia. At present, the Khibinskie nepheline concentrate deposits (29% Al2O3 and ~19% alkalies) and Kiya-Shaltyrskoe urtite deposit (25–26% Al2O3, ~10% alka-

Fig. 1. Dynamics of bauxite mining and increment in bauxite reserves in 1991–2007 (A) and reduction in proved bauxite reserves (A + B + C) (B). Compiled after (The State..., 2007), with our supplements. 1, bauxite mining; 2, increment in bauxite reserves (A + B + C1).

1250

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

Fig. 2. Correlation between the amount of mined ore and the alumina output at the Achinsk alumina integrated plant (from the OK RUSAL data).

lies) are exploited. Other aluminum-promising deposits are Mukhal’skoe (Al2O3 = 27–28%, K2O + Na2O = 10–15%) and Bayankol’skoe (Al2O3 = 27–24%). Nepheline ores are processed at three enterprises. The Volkhov and Pikalevo plants work on nepheline concentrates from the Apatit Joint-Stock Company, and the Achinsk integrated plant, on urtites from the Kiya-Shaltyrskoe deposit. This is a complex raw material. Alumina is extracted using the sintering technology; other products of the ores are soda, potash, and cement. In 2009, the Pikalevo plant had to pass to cement production because of the price conflict with the Apatit Joint-Stock Company. The Achinsk integrated plant also encounters difficulties. The ore impoverishment at the KiyaShaltyrskoe deposit provokes an increase in the amount of mined rocks and waste products (slimes) and, correspondingly, in the prime cost of produced alumina. Since 2000–2002, the volume of ore mining has increased with a high rate (Fig. 2) because of the ore degradation. There are also about 100 nepheline deposits and ore occurrences in the Kemerovo Region and Krasnoyarsk Territory (Goryachegorskoe, Belogorskoe, Medvedka, Andryushkina Rechka, Uzhurskoe, Tatarskoe, etc.). The first two are considered a reserve basis of the Achinsk integrated plant. There are about 20 ore massifs in eastern Transbaikalia. The alumina content in ores varies from 22 to 27% (K2O + Na2O = 12–20%); the urtites of the Bayankol’skoe deposit are the alumina-richest (Al2O3 = 26.5%). This deposit is localized within the Sangilen upland (Tuva Republic). The balance ore (types A + B + C) reserves are estimated at 350 mln tons. Other promising raw materials for alumina and aluminum production are synnyrites, anorthosites, kaolines, ashes, and SGM. The largest accumulations of synnyrites occur in the Synnyr, South Sakun, and Malyi Murun massifs in Siberia. They are poor in Al2O3 (20–22 wt.%); therefore, large-scale production of aluminum from this raw material is impossible. Synnyrites are of interest mainly as a source for the production of Cl-free potassic fertilizers, since they contain up to 19–20% K2O. Alumina will be extracted from them, if ever, only as a coproduct.

Anorthosites, which are widespread in Russia (their reserves are tens to hundreds of billions of tons), are also considered as a raw material for Al2O3 and aluminum production. They occur in the Kola, Anabar, Aldan, and Okhotsk provinces. One of the largest anorthosite belts extends from eastern Transbaikalia to the coast of the Sea of Okhotsk. There are many patented technologies of alumina and aluminum production from anorthosites; most of them are based on acid (H2SO4, HNO3, HCl) leaching. A method for their semicommercial processing is also known. In the 1970s, the Toth Company produced aluminum using carbothermal chlorine technology. The Alcoa company produced aluminum (up to 15,000 tons/year) by chloride electrolysis. In Norway rich in anorthosite resources, technological research was carried out at the level of national programs (e.g., Anortal project). Unfortunately, all these technologies are ineffective mainly because of the equipment corrosion and high output of coproducts. The Amur Research Center is also involved in the elaboration of technologies of anorthosite processing for the aluminum production excluding the stage of aluminum production. By now, only laboratory research has been carried out. At present, anorthosites should be considered a feldspathic raw material, which can be used to produce ceramics for everyday and technical use, building materials, abradants, plastic and rubber fillers, special dyes, etc. Alumina can also be extracted from power-and-heating plant ashes. Their Al2O3 content sometimes reaches 30–40%. Utilization of ash heaps is urgent from different aspects. For this purpose, acid (H2SO4, HBO3, HCl) technologies of their processing into aluminum sulfate, alumina, blinding and building materials, nitrate fertilizers, cement, cast iron, and titanium were developed. Though the technologies of processing of coal wastes are known and have been approved, their practical application is difficult, first of all, because acid-resistant equipment and acids used are expensive. Moreover, the composition of ash can significantly change depending on the composition of coal and the way of its burning. Therefore, the large-scale production of alumina and aluminum from ashes is unreal. Another promising raw-material for alumina and aluminum production is kaolines. They are used to produce silumin by the electrothermal method. Kaoline deposits are localized in the Chelyabinsk, Sverdlovsk, Orenburg, Tomsk, and Amur Regions and in the Krasnoyarsk Territory. Because of the low quality of kaolines (Al2O3 = 21–22% or up to 34% in concentrates) and their small reserves, large-scale production of alumina, silumin, and aluminum from them has no potential. Today kaolines are used to produce heat-resistant materials, ceramics, porcelain, faience, plastics, rubber fillers, different kinds of paper, dyes, etc. Sillimanite group minerals (andalusite, sillimanite, kyanite) have the same chemical formula, Al2SiO5. Theoretical composition (wt.%): Al2O3 = 62.9; SiO2 = 37.1. The proved SGM reserves of the western countries are 450 mln tons. The ore deposits with 10% SGM are developed

1251

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

by strip mining, with different concentration techniques: gravitation, flotation, and magnetic and electric separation. The concentrate-processing power of plants is 5000– 50,000 tons/year. Ore mining and concentrate production are performed in the South African Republic (SAR), USA, India, France, Brazil, and Sweden. Andalusite is mined in the SAR and France; kyanite and sillimanite, in the USA, India, and Ukraine; kyanite is also mined in Brazil, Sweden, and Spain. These countries produce a total of 700,000–750,000 tons of concentrates a year. The SGM prices increased for the last 50 years from 20 to 160–260 dollars for ton. The Siberian Branch of the Russian Academy of Sciences has been studying SGM for many years (Lepezin, 1997a,b, 2003, 2004, 2005; Lepezin et al., 1979, 1989, 1996, 1997, 2003; Lepezin and Goryunov, 1988; Lepezin and Semin, 1989; Semin et al., 1980, 1982, 1983). The fields of their application and particular deposits are described in literature. Also, the chemical and mineralogical compositions of ores were determined, ore dressing technologies were developed, high- and first-grade concentrates were prepared, heat resistance characteristics of materials made of them were determined, and production recommendations were given. In Russia, large SGM deposits and ore occurrences are localized on the Kola Peninsula (Keivy group of deposits), in Karelia (Khizovara deposit), in the Uralian region (Abramovskoe, Karabashskoe, Borisovskoe, Mikhailovskoe, etc.), and in Siberia (Tymbinskoe, in the Chita Region; Kyakhtinskoe, in the Buryatian Republic; Kitoiskoe, in the Irkutsk Region; ore occurrences on the Vitim–Patom upland; Bazybaiskoe, in the Krasnoyarsk Territory; deposits in the transAngara region of the Yenisei Ridge; Tarlashkinkhemskoe, Mugurskoe, Morenskoe, and Ulorskoe, in the Tuva Republic; Kuraiskoe, Chaustinskoe, Buguzunskoe, and Nizhneberezovskoe, in Gorny Altai and Rudny Altai). Almost all deposits can be developed by the open method. The concentration technology includes gravitation, flotation, and electromagnetic and electric separation. Combined methods are the most effective. At present, SGM are widely used for the production of heat-resistant materials, ceramics, porcelain, etc. (Lepezin and

Goryunov, 1988). These minerals can also be processed into alumina by sintering both separately (Lainer and Ekimov, 1972) and in the mixture with nepheline ores (Semin et al., 1980, 1982). They can be used for the electrothermal production of silumin and aluminum.

Comparative analysis With the existing aluminum output, the problem of alumina deficit in Russia cannot be solved at the expense of domestic bauxites, nepheline ores, and, the more so, synnyrites, anorthosites, ashes, and kaolines because of their low quality and low reserves and the absence of effective and ecologically safe processing technologies. Operation of aluminum plants on foreign alumina is also unpromising. Its purchase and transportation costs can be compensated only partly at the expense of cheap labor and still cheap electric power. Sillimanite group minerals are the most promising for alumina and aluminum production in Russia (Lepezin, 2003, 2004, 2005), since they have obvious advantage over other kinds of raw material. The SGM-bearing ores are of simple composition (Khizovara deposit in Karelia, Abramovskoe, Karabashskoe, and Borisovskoe deposits in the Uralian region, Kyakhtinskoe deposit in Siberia, etc.) and can serve as a basis for the wasteless production of concentrates, which, in turn, can be used for the production of SGM commodity products, quartz, rutile, and micas. Alumina in SGM concentrates amounts to 60–62 wt.% (Tables 3 and 4). No other kind of raw material but high-grade bauxites can yield such high Al2O3 concentrations, whatever method of ore dressing is used. These minerals are next in alumina content after corundum, diaspore (boehmite), hydrargillite (gibbsite), and mullite (Table 5). Taking into account that corundum and mullite do not form large accumulations and high-grade bauxites are nearly lacking in Russia, SGM can be considered the most important for Russian alumina and aluminum industry, the more so that their proved reserves exceed those of bauxites and nepheline ores (Fig. 3). The SGM deposits are evenly distributed over the Russian area and are localized in economically developed regions (Kola Peninsula, Karelia, Urals, Krasnoyarsk Terri-

Table 3. Chemical analyses of SGM concentrates from Russian deposits (wt.%) Component

Theoretical composition of SGM–Al2SiO5

Average statistical composition of SGM (n = 186)

Selective chemical analyses of SGM concentrates

SiO2

37.1

37.01

40.06

39.01

TiO2

–

–

0.55

0.25

0.067

0.35

0.23

0.66

Al2O3

62.9

62.72

57.07

59.47

60.45

62.64

60.20

60.40

FeO

–

0.29

0.61

0.10

0.37

0.00

0.26

0.49

MnO

–

0.01

0.10

0.00

0.10

0.10

0.10

0.10

MgO

–

0.03

0.01

0.03

0.00

0.00

0.09

0.05

CaO

–

0.01

0.06

0.03

0.03

0.03

0.54

0.06

Na2O

–

0.00

0.40

0.22

0.09

0.00

0.00

0.00

K2O

–

0.00

0.06

0.10

0.05

0.06

0.53

0.30

37.47

36.78

37.21

37.57

1252

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

Table 4. Average statistical compositions of SGM from the largest Russian deposits and ore occurrences (wt.%) No.

SiO2

Al2O3

Fe2O3

Cr2O3

MnO

MgO

n

Deposits and ore occurrences

1

37.1

62.9

–

–

–

–

–

Theoretical composition of Al2SiO5

2

36.44

62.12

0.22

0.02

–

–

4

Keivy group

3

36.62

62.73

0.06

0.02

0.01

0.01

8

Khizovara

4

37.05

63.02

0.15

0.01

0.01

–

6

Malobrusyanskoe

5

37.06

63.15

0.07

0.01

0.00

–

8

Abramovskoe

6

36.60

62.42

0.32

0.00

0.01

0.01

27

Karabashskoe

7

36.63

62.30

0.30

0.03

–

–

2

Borisovskoe

8

36.85

62.51

0.41

–

0.01

0.01

8

Gold-bearing sands of the Andree-Yul’evskii mine

9

36.87

62.38

0.47

0.01

0.01

0.01

4

Sangilen ore occurrences

10

37.02

61.93

0.54

0.02

–

–

10

Kyakhtinskoe

11

35.91

61.98

0.19

–

0.01

0.01

3

Kitoiskoe

12

36.44

62.72

0.20

0.01

0.01

0.01

4

Bazybaiskoe

13

36.77

62.03

0.87

0.01

0.01

–

9

Sangilen ore occurrences

14

36.71

62.47

0.40

0.01

0.01

0.01

17

Sangilen ore occurrences

15

36.59

62.88

0.24

0.01

0.01

0.03

11

Trans-Angarian ore occurrences

Note. 2–9, kyanites; 10–13, sillimanites; 14–15, andalusites; n, number of samples. Table 5. Theoretical compositions of high-alumina minerals (wt.%) Mineral

A12O3

SiO2

FeO

H2O

A1

Si

Formula

Corundum

100.0

0.0

0.0

0.0

52.9

0.0

A12O3

Boehmite, diaspore

85.0

0.0

0.0

15.0

45.0

0.0

A12O3 ⋅ H2O

Mullite

71.8

28.2

0.0

0.0

38.0

13.2

3Al2O3 ⋅ 2SiO2

Hydroargillite (gibbsite)

65.3

0.0

0.0

34.7

34.6

0.0

Al(OH)3

And., sil., ky.

62.9

37.1

0.0

0.0

33.3

17.3

A12O3 ⋅ SiO2

Staurolite

53.4

28.5

17.0

1.1

28.8

13.3

Fe2A19Si4O23(OH)

Chloritoid

40.5

23.9

28.5

7.1

21.4

11.2

FeA12 ⋅ SiO5(OH)2

Kaolinite

39.5

46.6

0.0

13.9

20.9

21.8

Al2O3 ⋅ 2SiO2 ⋅ 2H2O

Pyrophyllite

28.3

66.7

0.0

5.0

15.0

31.2

Al2O3 ⋅ 2SiO2 ⋅ 2H2O

Note. And., andalusine; sil., sillimanite; ky., kyanite.

tory, Tuva Republic, etc.). Almost all of them can be developed by strip mining.

The possibilities of alumina output increase at the expense of coprocessing of nepheline ores and SGM concentrates

Fig. 3. Proportion of the reserves of bauxites, nepheline ores, and SGM (A + B + C1 + C2) (data for 1 January 2007). 1, 2, reserves of the above ores of types P1 + P2; 3, portion of high-grade ores in the reserves. High-grade ores are bauxites with a silicon module of 10, nepheline ores with Al2O3 > 26 wt.% (llike those produced at the Achinsk alumina integrated plant), and SGM corresponding in composition to the international criteria for exploited deposits.

The problem of alumina deficit in Russia has been discussed for many years. Only the aluminum plants of the SUAL company are provided with aluminum, as they have an own raw-material base. The RUSAL enterprises are in difficult situation. Siberian bauxites are unpromising for them because of low quality and relatively small reserves. To provide alumina plants with aluminum at the expense of nepheline syenites, it is necessary to build at least six or seven integrated plants commensurate in power with the Achinsk one. The ores from other deposits must be not poorer in quality than the Kiya-Shaltyrskoe ores, and the coproducts must be marketed, but this is unreal. Wasteless production of one ton of alumina

1253

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

will theoretically yield more than one ton of coproducts and eleven tons of cement. The actual situation is as follows: Earlier, the Achinsk alumina integrated plant produced ~4 tons of cement (now much lesser), and 7 tons of slimes went to waste. Optimal alumina production is estimated at 200,000– 250,000 tons a year. In this case, slimes can be completely utilized and cement can be marketed; thus, the alumina production will be profitable. The main drawbacks of the commercial use of nephelines are huge material and fuel-and-power costs and investments, which will strongly increase when low-alumina ores (like those from the Goryachegorskoe deposits, with Al2O3 22%) come into use. According to technical conditions (MRTU 6-12-54-80), nepheline concentrate must contain (on conversion to anhydrous substance) no less than 28.5% Al2O3 and 17.5% Na2O + K2O. Therefore, these oxides must be concentrated, which can be made by different methods: 1. Dressing of nepheline ores. This concentration method is ineffective; it permits obtaining concentrates suitable for processing by sintering but provides a low yield of alumina and a high yield of tailings (Table 6). 2. Addition of bauxites instead of nepheline ore dressing. This will improve the quality of alumina in the ore mixture and reduce the costs of raw material, fuel, and main and secondary materials. But the high content of iron oxides in most of Russian bauxites and the necessity of their transportation to Siberia from remote regions of the country make this method economically and technologically unprofitable. 3. Addition of SGM into undressed nepheline ores. This method is the most promising, as exemplified in Table 7. Addition of 30% SGM concentrate (Al2O3 = 57 wt.%) to nepheline rock like that from the Goryachegorskoe deposit (Al2O3 = 22%) increases the alumina content in the mixture to 32.5%. Remind that the highest-grade Kola nepheline concentrates contain 28–29% Al2O3 and the Kiya-Shaltyrskoe ores, 27%; the best ore dressing methods yield 27–30% Al2O3 (the theoretical content of alumina in nepheline is 35.9%). If the mixture consists of 60% SGM concentrate and 40%

nepheline ore, the content of Al2O3 will reach 43% and thus be close to that in bauxites. Additives of SGM concentrates increase the amount of alumina in the mixture and at the same time decrease the specific cost of nepheline ore, which is used for the production of soda, limestone, and other materials. The laboratory studies (Semin et al., 1980, 1982) showed that the technological quality of produced mixtures thus improves: The chemical interaction shifts to the low-temperature region, the area of sintering becomes larger, the porosity of sintered material increases, etc. Practical realization of this approach will permit the producers: (1) to increase the alumina production rate and output by 1.2–1.6 times with the existing production power and technologies at the expense of using an ore mixture with 30–60% SGM concentrate; (2) to reduce specific capital outlays for the expansion of coexisting and construction of new alumina plants; (3) to reduce the slime yield, operating costs of the production of a ton of alumina, power and material costs, and man efforts; (4) to increase the alumina production rate; and (5) to use undressed low-grade nepheline ores. Processing of mixtures can be realized by the well-developed sintering method and on an acting setup, without construction and development of its new types. The idea of coprocessing of SGM and nepheline ores on the alumina production was supported by USSR’s Gosplan (protocol from 30 January 1987), VAMI (technical-meeting protocol from 14 November 1986; protocol 8 of the Section on Alumina and Chemicals Production from 18 March 1987), and the Achinsk alumina integrated plant (protocol of the meeting from 13 November 1990). The idea was reported in detail by Lepezin and Semin (1989). Since the technology was developed in laboratory conditions (Semin et al., 1980, 1982, 1983), pilot tests are necessary. Ore mining at the Kiya-Shaltyrskoe deposit is performed selectively, i.e., high-grade ores are extracted, and low-grade ones go to wastes. Added SGM concentrates will keep the alumina content at the required level and prolong the provision of the Achinsk alumina integrated plant with raw material.

Table 6. Results of dressing of different types of Siberian alumina ores (Lepezin and Semin, 1989), wt.% Type of ore

Initial rock

Concentrate

Tailings

Product yield, %

SiO2

Al2O3

Fe2O3

SiO2

Al2O3

Fe2O3

SiO2

Al2O3

Fe2O3

–

21.30

12.78

–

29.70

2.10

–

19.30

15.20

19.58

–

23.50

9.40

–

29.71

2.79

–

20.82

12.15

29.49

–

22.13

11.14

–

28.73

3.27

–

18.78

15.58

35.74

–

23.80

9.43

–

32.21

2.19

–

21.20

11.68

23.94

–

20.09

11.10

–

24.66

4.73

–

16.03

16.80

46.36

–

23.39

9.80

–

27.29

4.62

–

19.52

14.94

49.85

Sillimanite ores from Kyakhtinskoe deposit

61.02

35.51

1.30

36.68

59.56

1.27

78.14

14.72

0.71

41.0

Sillimanite ores from Bazybaiskoe deposit

74.33

18.08

2.88

42.10

53.08

1.52

93.84

3.06

–

7.78

–

–

–

40.32

55.76

0.47

92.58

3.03

0.51

21.08

Uzhur nepheline ores

1254

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

Table 7. Chemical composition of nepheline ores, SGM concentrates, and ore mixtures (wt.%) Ore or ore mixture

Chemical composition of ore or ore mixture SiO2

Al2O3

Fe2O3

CaO

Na2O + K2O

Kiya-Shaltyrskoe nepheline ore (Kn)

40.30

27.00

4.40

7.90

14.00

Goryachegorskoe nepheline ore (Gn)

43.00

22.00

9.30

7.00

10.00

SGM concentrate (SGMC)

40.06

57.07

0.61

0.06

0.46

Kiya-Shaltyrskoe nepheline ore + SGM concentrate 0.7Kn + 0.3SGMC

40.23

36.02

3.26

5.55

9.94

0.4Kn + 0.6SGMC

40.16

45.04

2.13

3.20

5.88

Goryachegorskoe nepheline ore + SGM concentrate 0.7Gn + 0.3SGMC

42.12

32.52

6.69

4.92

7.14

0.4Gn + 0.6SGMC

41.24

43.04

4.09

2.84

4.28

Electrothermal SGM-based commercial silumin and aluminum production Silumin is an alloy of silicon with aluminum, which has a low density (2.4–2.7 g/cm3), a high specific strength at normal temperature, and fine casting properties. More than a half of all casting nonferrous alloys widely used in defense industry, aircraft building, transport machine building, and other industries are prepared from silumin. At present, silumin is produced by alloying crystalline silicon with aluminum in electric or flame furnaces. This method requires electrolythic production of aluminum and is characterized by high costs of the production of alumina, anodic mass, cryolite, and electric energy and the capital construction of large workshops with electrolyzers and converter substations. Electrothermics is an alternative technology. It was realized on industrial scale by the Metalhazelshaft Company in Germany in 1926. The ore-thermal method was actively developed in Switzerland and France in the 1920s– 1930s (Belyaev, 1970; Gasik et al., 1971; Gudima and Shein, 1975). Application of this method included construction of half-way units and pilot-production plants. A detailed review of the foundation and development of electrothermics in Russia and in the world was made by Saltykov and Baimakov (2003). Investigations in this field were also carried out in Russia. The VAMI research center developed a two-stage scheme of processing of silicon-aluminum raw material in laboratory and large-scale experimental conditions. At the first stage, electrothermal ore-reducing smelting of raw material is performed, and at the second, the obtained alloy is processed to either aluminum hardeners or technically pure aluminum. In 1934, the Dneprovsk aluminum plant began to produce silicoaluminum through the reduction of kaoline by charcoal. In 1939, the plant produced an Al-rich (up to 70%) alloy. The production technology was introduced in industry in 1964. In 1948, the Central Laboratory of the Uralian aluminum plant obtained Si-Al alloys from the Abramovskoe deposit (Sverdlovsk Region) kyanite concentrates. In the early 1960s, the Irkutsk aluminum plant carried on pilot tests on the production

of electrothermal silumin, with sillimanite concentrates from the Kyakhtinskoe deposit (Buryatia Republic) used as a raw material. Aluminum-silicon alloy is obtained through the reducing smelting of briquettes composed of SGM concentrate, kaoline, alumina, and reducing agents, with an alloy containing 32–35% Si as an intermediate product. Mixtures of charcoal, petroleum coke, coal, and charcoal ash are used as reducing agents. According to numerous expert estimates, electrothermal production of silumin and aluminum has the following advantages (Belyaev, 1970; Brusakov et al., 1965, 1978, 1981, 1987; Gasik et al., 1971; Gudima and Shein, 1975; Kaluzhskii et al., 1980; Verigin, 1958): (1) the production cycle excludes complex and expensive alumina production; (2) the power of ore-thermal furnace is much higher than the power of electrolyzer (a furnace with a production rate of 10,000 tons Al a year can serve instead of 30 electrolyzers); (3) there is no need to transform alternating current into constant one, which reduces electric-energy losses; (4) there is no need to use fluorine compounds; (5) the consumption of electric energy per unit product decreases by 20%, and the product cost, by 30%; and (6) the capital outlays for the building of a workshop with an ore-thermal furnace are 30–40% lower than the capital outlays for the building of alumina and electrolytic workshops. Production of silumin even with the use of electrolytic aluminum for dilution yields a great economic effect (Table 8). Note that since the raw material is of local occurrence, there is no dependence on its suppliers, and the transport costs are the minimum. The electrothermal technology favors lower specific and capital outlays. The degree of their reduction depends directly on the unit power of ore-thermal furnace. It can be increased by using plasma heating, which ensures (Kaluzhskii et al., 1978, 1980): (1) high temperatures with a high concentration of energy in the reaction space; (2) stabilization of the electric regime of furnace and its independence on the electric properties of the burden; (3) high voltage on the plasma arc, which permits application of more powerful plasma generators with low current; and (4) work over a broad temperature

1255

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

Table 8. Technical-and-economic indices of electrothermal production of aluminum and its alloys in comparison with their electrolytic production (Kostyukov et al., 1974) Index per ton of product, %

Casting aluminum alloys

Deformed alloys and aluminum

Silumin produced through dilution

Investment decrease

30–40

30–35

10–12

Cost decrease

25–35

15–25

8–10

Electricity consumption decrease

10–15

10–15

5–7

Labor productivity increase

20–40

–

10

Table 9. Proved reserves and predicted resources of ores, SGM (Al2SiO5), alumina, and aluminum (ths tons) in Russia (Lepezin, 2003, 2004, 2005) Region

Ore

Al2SiO5

Al2O3

Al

3,400,000

1,186,879

676,518

358,556

Karelia

116,820

25,000

14,250

7553

Urals

66,684

11,710

6675

3537

Siberia

51,1750

13,109

74,732

39,608

Total

4,095,254

1,236,698

772,175

409,254

Proved reserves (types C2, C1, B, A) Kola Peninsula

Predicted resources (types P2 and P3) Kola Peninsula

11,000,000

3,840,000

2,188,230

1,159,762

Urals

109,890

30,000

17,100

9063

Siberia

8,138,400

2,588,517

1,475,455

781,991

Total

19,248,290

6,458,517

3,680,785

1,950,816

region in any medium. Argon, hydrogen, air, natural gas, and their mixtures can be used for plasma formation. According to literature data, the electric-energy consumption in a smelting aggregate with a plasma generator is 10,000–12,000 kW/h per ton of Si-Al raw material. For comparison, the electric-energy consumption during the electrolytic production of a ton of aluminum is 16,000 kW/h. If the technology of electrothermal production of silumin and aluminum from SGM is well-developed and effective, has proved itself, and has been tested on the industrial scale, why is such production not developed in our country? Do we lack such a raw material? On the contrary, its resources in Russia amount to billions of tons. Their largest accumulations occur in four provinces (Keivy (Kola Peninsula), Karelia, Urals, and Siberia). The proved SGM reserves converted to the final product, aluminum, exceed 400 mln tons (Table 9). In the case of the annual production of 4 mln tons of aluminum, as today, the ore reserves will last more than 100 years.

Conclusions Having compared the aluminum and alumina outputs (4.4 mln tons and ~3.0 mln tons in 2008, respectively), we see that the Al2O3 deficit is ~5 mln tons, with most of it being at the Siberian aluminum plants. With the existing aluminum production from Russian bauxites, nepheline ores (main sources of alumina in our country), synnyrites, anorthosites, ash heaps, and kaolines, it is impossible to solve the deficit problem. Provision of aluminum plants with alumina imported

from foreign countries and former Soviet republics also shows no promise. There is only one solution—to use new kinds of raw material and apply new technologies. Sillimanite group minerals are an appropriate raw material. They can be processed together with low-grade nepheline ores or be used as a source for the direct electrothermal production of silumin and aluminum, excluding the alumina production stage. Certainly, it is impossible to organize large-scale electrothermal production of silumin and aluminum in short time. Therefore, the following sequence of operations for the gradual passing from one raw material to another and changing the production technology is proposed: 1. To exploit an SGM deposit with an annual concentrate output of 10,000–30,000 tons. The deposit must be localized in a region with a well-developed infrastructure and not far from the railway. Such deposits exist in Russia; their exploitation will take one to two years and require relatively low capital outlays. 2. To organize the commercial production of SGM concentrates. This is sure business, because the above concentrates are in demand of the plants producing heat-resistant, ceramic, and other materials. 3. To carry out pilot tests on the electrothermal production of Si-Al alloys and aluminum from SGM concentrates. 4. To exploit large SGM deposits, based on the results obtained, and organize the commercial production of silumin and aluminum. This work was supported by Integration Project 139 from the Siberian Branch of the Russian Academy of Sciences, State contract AB-11-03/31 dated at 21 April 2008, and

1256

G.G. Lepezin et al. / Russian Geology and Geophysics 51 (2010) 1247–1256

program 23 from the Presidium of the Russian Academy of Sciences.

References Belyaev, A.I., 1970. Light Metallurgy [in Russian]. Metallurgiya, Moscow. Bronevoi, V.A., Lankin, V.P., 2001. The state and possible lines of development of the raw-material base of the Russian aluminum industry. Tsvetnye Metally, No. 3, 19–54. Brusakov, Yu.I., Verigin, V.M., Varyushenkov, A.I., Chel’tsov, V.M., 1965. Pilot tests and large laboratory studies on the electrothermal production of Al-Si alloys and their processing into silumin. Trudy VAMI, Nos. 54– 55, 242–256. Brusakov, Yu.I., Rzhavin, S.A., Chesnokov, V.A., 1978. Comparative efficiency of using silica-alumina raw material for the electrothermal production of Al-Si alloys. Trudy VAMI. Lit’e i Obrabotka Alyuminiya, No. 102, 64–70. Brusakov, Yu.I., Varyushenkov, A.I., Volodatskii, V.F., 1981. The improvement of the technology of silicon production in the form of Al-Si alloys in high-power furnaces. Trudy VAMI. Nauchnye Issledovaniya i Opyt Proektirovaniya v Metallurgii Legkikh Splavov, 110–116. Brusakov, Yu.I., Gpazatov, A.N., Zapshchinskii, I.S., 1987. Study of the conditions of slime formation on the electrothermal production of Al-Si alloys. Trudy VAMI. Intensifikatsiya Proizvodstva Produktsii iz Alyuminiya, Kremniya i Ikh Splavov, 67–77. Gasik, M.I., Emlin, B.I., Klimkovich, N.S., Khitrik, S.I., 1971. Electric Melting of Aluminosilicates [in Russian]. Metallurgiya, Moscow. Gudima, N.V., Shein, Ya.P., 1975. Brief Reference-Book on Nonferrous Metallurgy [in Russian]. Metallurgiya, Moscow. Kaluzhskii, N.A., Kozlov, V.M., Ostanin, Yu.D., Chernyakhovskii, L.V., 1978. Using plasma heating for the restoration of alumina-containing materials on the production of aluminum alloys. Trudy VAMI. Lit’e i Obrabotka Alyuminiya, No. 102, 59–63. Kaluzhskii, N.A., Dobatkin, V.I., Gopienko, V.G., 1980. The prospects for electrothermal production of aluminum alloys. Tsvetnye Metally, No. 1, 40–50. Kal’chenko, V.S., 2001. The electricity and railway transportation tariffs and their influence on the competitiveness of Russian metal production. Tsvetnye Metally, No. 12, 60–62. Kostyukov, A.A., Kil’, I.G., Nikiforov, V.P., 1974. Metallurgist’s ReferenceBook on Nonferrous Metals. Aluminum Production [in Russian]. Metallurgiya, Moscow. Kuleshov, V.V. (Ed.), 1997. Russian Aluminum Industry in the Market Conditions [in Russian]. IEiOP SO RAN, Novosibirsk. Lainer, A.I., Ekimov, S.V., 1972. Decomposition of kyanite through its sintering with limestone. Izvestiya Vuzov. Tsvetnaya Metallurgiya, No. 4, 30–37. Lepezin, G.G., 1997a. Russian deposits and ore occurrences of sillimanite group minerals and the prospects of commercial concentrate production on their basis. Ogneupory i Tekhnicheskaya Keramika, No. 8, 27–32. Lepezin, G.G., 1997b. Kyanite, a material of the 21st century. Chelyabinskii Rabochii (newspaper), 6 September. Lepezin, G.G., 2003. Does Russian aluminum have the future? EKO, No. 5, 144–159.

Lepezin, G.G., 2004. The strategy of development of a raw-material base for the Russian aluminum industry. Khimiya v Interesakh Ustoichivogo Razvitiya, No. 12, 501–516. Lepezin, G.G., 2005. The state of the raw-material base of the Russian aluminum industry and the strategy of its development. Marksheideriya i Nedropol’zovanie, No. 2, 19–24. Lepezin, G.G., Goryunov, V.A., 1988. Areas of application of minerals of the sillimanite group. Geologiya i Geofizika (Soviet Geology and Geophysics) 29 (5), 80–87 (68–74). Lepezin, G.G., Semin, V.D., 1989. Prospects for development of raw material base of the aluminum industry of Siberia. Geologiya i Geofizika (Soviet Geology and Geophysics) 30 (2), 85–95 (77–85). Lepezin, G.G., Sherman, M.L., Semin, V.D., Kravtsov, I.S., 1979. Prospects for the use of metamorphic rocks of the Altai-Sayan folded region and Yenisei range as a source of highly aluminiferous raw material. Geologiya i Geofizika (Soviet Geology and Geophysics) 20 (11), 35–43 (26–32). Lepezin, G.G., Semin, V.D., Stepanov, S.A., Medvedev, G.P., Semina, Z.F., 1989. Bazybai field of quartz-sillimanite ores (geology, petrochemistry, and industrial importance). Geologiya i Geofizika (Soviet Geology and Geophysics) 30 (6), 80–87 (70–76). Lepezin, G.G., Perepelitsin, V.A., Pokusaev, V.I., 1996. The prospects for the organization of commercial production of kyanite concentrates in the Uralian region. Ogneupory i Tekhnicheskaya Keramika, No. 8, 17–19. Lepezin, G.G., Sokol, E.V., Zhirakovskii, V.Yu., Frenkel’, A.E., Osipov, V.A., 1997. Kyanite deposits and ore occurrences in the Central and South Urals. Ogneupory i Tekhnicheskaya Keramika, No. 2, 29–33. Lepezin, G.G., Semin, V.D., Stepanov, S.A., 2003. The RUSAL enterprises are close to a raw-material crisis. Kontinent Sibir’ (newspaper), No. 25. Prokopov, I.V., 2002. The Russian and world aluminum industry at the boundary of the 20th and 21st centuries: predictions for growth and product consumptions. Tsvetnye Metally, No. 2, 70–77. Purdenko, Yu.A., 1997. The Russian Aluminum Industry: State of the Art, Problems, and Development Prospects [in Russian]. Vost.-Sib. Knizhnoe Izd., Irkutsk. Saltykov, A.M., Baimakov, A.Yu., 2003. Organization and development of electrothermal production of Al-Si alloys. Tsvetnye Metally, No. 7, 101–105. Semin, V.D., Medvedev, G.P., Semina, Z.F., 1980. Author’s Certificate 734952 (USSR). A Method for Processing Low-Grade Alkaline Aluminosilicate Raw Material. Bulletin of Inventions, No. 18. Semin, V.D., Medvedev, G.P., Semina, Z.F., Urvantsev, V.V., 1982. Search for an effective technology for the complex processing of low-grade aluminosilicate rocks, in: The Scientific Fundamentals of the Complex Use of Ores and Concentrates [in Russian]. TsMET AN SSSR, Moscow, Part 1, pp. 54–60. Semin, V.D., Medvedev, G.P., Semina, Z.F., 1983. The ways of involvement of low-grade aluminosilicate ores in industrial production. Izv. Vuzov. Tsvetnaya Metallurgiya, No. 4, 43–45. Sizyakov, V.M., 1999. The state of the art of the Russian aluminum industry: problems and development prospects (analytical review). Zapiski Gornogo Instituta, 123–144. The State of Use of the Russian Federation Mineral and Raw-Material Resources in 2006. State Report [in Russian], 2007. MPR, Moscow. Verigin, V.N., 1958. Electrothemal production of aluminum and its alloys. Trudy Vost.-Sib. Filiala AN SSSR 2 (13), 72–86.

Editorial responsibility: N.P. Pokhilenko