IFAC MMM 2013 International Symposium Control, Optimization and Automation in Mining, Minerals and Metal Processing San Diego, California, USA, August 25-28, 2013 Edited by Florian Kongoli, FLOGEN
Development and Testing of Environmentally Friendly Hydro-Electrochemical Technology for Processing Copper Sulfide Concentrates of Armenian Deposits K.E. Hakobyan*, A.K. Hakobyan*, A.A. Melkomyan*, G.G. Karamyan*, V.S. Hayrapetyan*, D.M. Paramazyan*, V.A. Bryukvin**, V.G. Leontiev**, O.I. Tsybine** *
Kapan Laboratory of Metallurgy and Enrichment at Institute of Chemical Physics after A.B. Nalbandyan, NAS RA, Yerevan, 0014, 5/2 P. Sevak St., Armenia (e-mail:
[email protected]) ** A.A. Baykov Metallurgy and Materials Science Institute of RAS, 49, Leninskiy prospect, Moscow, 119991, Russia (e-mail:
[email protected]) Abstract: A new hydro-electrochemical technology is designed for processing concentrates of copper sulfides of Kajaran and Kapan (Armenia) deposits in a special mode (know-how). New technology provides a high degree of extraction of copper, iron, sulfur and precious metals, an economic efficiency and satisfies modern ecological requirements. The essence of technology lies in the fact that the copper concentrate, without drying, is immediately subjected to electrochemical dissolution. As a result the copper in the form of powder is deposited on the cathode, and then gradually deposited on the bottom of the electrolytic bath, while the iron goes into solution and subsequently can be removed by crystallization. Part of the sulfur is separated in the form of elemental sulfur from the decomposition of chalcopyrite and remains in the undissolved mass. The process is environmentally friendly because no gaseous or liquid waste is produced: electrolyte is circulated in closed cycle. Thermodynamic and kinetic parameters of the process are presented. Keywords: Copper sulfide, processing, desulfurization, pilot plant, optimal regimes, control. 1. INTRODUCTION
Electrochemical technologies are considered as very efficient methods for processing different metal concentrates providing high degree of all useful metal extraction. The Kapan laboratory has many years experience in this field and has developed different technologies for processing copper sulfide concentrates. Such work has been performed starting from seventies of former century in cooperation with Russian Academy of Science, (Zviadadze,1979, Subbotina, 1983, Subbotina, 1987). Our first hydro-electrochemical method was based on the direct electrolysis of sulfide copper-iron anodes (Fig.1). In turn anodes have been obtained by electrosmelting of sulfide materials (concentrate, cinder, matte) of Alaverdi Mining Combine (Armenia) (Hakobyan, 1987) in special regimes. In the result the row materials were fully processed with production of copper powder, iron and sulfur. In 1990 the Academy of Sciences of Armenia has approved and signed technological schedule for creation of corresponding pilot plant in the ARMCVETMET test factory (Bryukvin, 1986). 2. METHOD DESCRIPTION To investigate the conditions of electrochemical processes the concentrate of Kajaran deposit is used which contains (in %): copper – 27.0, iron – 26.0, sulfur – 33.0, silicon dioxide – 7.0, Mo – 0.09, arsenic – 0.025 , aluminum oxide – 2.0, zinc – 0.35, calcium oxide – 1.1, carbon – 0.6, magnesium oxide – 0.46, gold – 4 g/t and silver – 65.5 g/t.
In another set of experiments the copper concentrate of Kapan deposit was used. The essence of technology lies in the fact that the copper concentrate, without electrosmelting, was immediately subjected to electrochemical dissolution (Fig. 2.). As a result the copper in the form of powder is deposited on the cathode, and then gradually precipitated on the bottom of the electrolytic bath, and the iron goes into solution and subsequently can be removed by crystallization. Part of the sulfur is separated in the form of elemental sulfur from the decomposition of chalcopyrite and remains in the amount of undissolved mass. Another part of the sulfur goes into solution in the form of sulfuric acid. Gold and silver also remain in the undissolved part. From this the sulfur may be removed by flotation. At the end of electrolysis, the hard part was filtered, washed, dried and subjected to chemical analysis. Also chemical composition of the solution has been analyzed. The output of the solids and dissolved elements was calculated. It has been selected and modified the design of the new hardware of enlarged laboratory setup for processing of copper sulfide concentrates (anodes, cathodes, the size of a galvanic cell, etc.) in order to improve the performance and cost efficiency. Preliminary data show that the developed technology, in comparison with the known ones, has the following advantages: • Full use of raw materials and waste-free production ensuring the preservation of the environment, • Directly obtaining of high quality copper powder, providing high (97 – 97.5%) degree of extraction (with the possibility of further cathode copper obtaining)
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Copper concentrate was placed into diaphragm bag from porous polyvinyl chloride acid resistant cloth after which it was immersed into electrolyte. DC current was supplied through graphite rods with the overall surface of 0.012m2. Copper cathodes were positioned on a distance of 2 cm from the bag. The pulp in the bag was periodically stirred by glass rod. Electrolysis cell was immersed into thermostatic liquid. Electrolysis was carried out at the anode current density of 700 A/m2 (calculated on electrodes working area), and cathodes current density of 1000 A/m2. Electrolyte temperature was kept at 60 0C. The mass of the concentrate sample was 50 g and process time was 3.5 hours. The precipitated copper is in the form of powder having dendrite structure with particle size less than 0.05 mm. It is periodically removed from the electrolysis bath. After process completion the remainder of concentrate was filtered, washed, dried, weighted and subjected to chemical analysis on copper, iron and sulfur. It is composed mainly of elemental sulfur which is extracted by hot filtration. The solvent has been analyzed, too, on copper, iron, chlorine ion and sulfuric acid. The process is environmentally friendly because no gaseous or liquid waste is produced: electrolyte is circulated in closed cycle. The chemical composition and output of solid products are presented in the Tables 1 and 2. The balance of metals and sulfur shows that copper extraction from concentrate amounts 97% from which 93% is as cathode sediment and 4% is in solution. Also 90% of iron is transferred into solution and can be separated in the form of iron sulfate (vitriol) by low temperature crystallization; 69% of sulfur is in remainder from which 58% is in the elemental form, 11% as copper and iron sulfate, 46% is oxidized to 6valence state and transformed into sulfuric acid. The solid metallic remainder in which precious metals are collected is directed on future extraction. Distribution of electrolysis products is presented in the Table 3. Table 1. Chemical content of concentrate and remainder after electrolysis Content, % Product
Initial concentrate Remainder
Mass, g
Sulphur Cu
Fe
50
19
12
2
Selem
Ssulfate
Stotal
32
_
_
31
11
58
11
69
Table 2. Chemical content of solutions
Table 3. Distribution of metals and sulfur in electrolysis products Cathode sediment Cu
93
Volume, l
Cu
Fe
[Cl -]
H2SO4
Initial electrolyte Spent electrolyte
1.0
3.0
0.0
80
50
1.0
0.4
14.3
80
24
0
S Cu
0 2.4
Fe
8
Solution
Sulphur Sel
Ssulf
Stot
Cu
44
8
52
4
Fe
S as H2SO4
90
46
Thus our experiments have shown that the developed easy electrochemical technology allows to extract copper and iron with high efficiency and exclude sulfur dioxide release into atmosphere, and instead to obtain useful product, elemental sulfur. The last can be then converted into sulfuric acid or sodium sulfide. As for other useful metals containing in the remainder or in solutions, including precious metals, the future work is required for obtaining necessary regimes for these extraction. We plan that after optimizing all working parameters of our laboratory plant we will present its characteristics and will start to fabricate the industrial plant. ACKNOWLEDGMENTS This work has been performed in close cooperation with the Metallurgy and Material Sciences Research Institute after A.A. Baykov of the Russian Academy of Sciences. We also thank Alaverdi Copper-Molybdenum Combine for the support in implementation of this work. REFERENCES Zviadadze G.N., Subbotina E.A., Gozalashvili E.I., Khomenko L.E., Hakobyan K.E., Sarkisyan N. C. and V.K. Karapetyan, (1979), Electrochemical method of producing copper powder, USSR Patent No. 876759. Subbotina E.A., Hakobyan K.E. et all (1983). Development of theory, technology and equipment for processes in production of metallic powders, and alloys. Research report (in Russian). Subbotina E.A., Sabauri G.N., Ioffe L.A., Bryukvin V. A., Tsibin O.I., Abramov N.A., Hakobyan K.E., (1987), Electrochemical methods of treatment of sulfide copper concentrates, USSR Patent No. 1477787. Bryukvin V.A., Riznichenko V.A., Hakobyan K.Y et all, (1986), Technological schedule for designing of technical project of organization of pilot plant for production of copper powder by electrochemical method. MoscowYerevan-Alaverdi, Report, 54 pages, (in Russian).
Content, g/l Product
Fe
Undissolved remainder after electrolysis
327
