Complex Processing tailings of the Balkhash Concentrating Factory

At flotation concentration of copper ores the tailings are formed, which contain both nonferrous metals and a significant amount of silicon and iron. The nonferrous metals from the tailings can be taken by flotation or leaching; but the silicon and iron is used irrationally as a backfilling material in mined-out space. The work purpose was the development of a complex technology of processing the Balkhash concentrating factory’s tailings (Kazakhstan) with production of a collective polymetallic concentrate and ferroalloys. The research has been fulfilled by a method of thermodynamic modelling using the software package HSC-5.1 (Outokumpy), a method of rototable experiment planning with regard to the chloride sublimation roasting of the Balkhash concentrating factory’s (BCF) tailings (0.27-0.39 % of Cu; 0,54-2.03 % of Zn; 0.13-0.5 % of Pb; 12.35-22.73 % of Fe; 7.04-13.09 % of ÑàÎ; 0.3-1.48 % of MgÎ; 6.2-11.71 % of Al2O3; 0.02-0.011 % of Mo; 0.04-0.07 % of As; 38.49-57.99 % of SiO2; 0.41-0.58 % of Na; 0.61-0.74 % of K; 0.8-1.3 % of S) and electrosmelting cinders after the roasting. It is found, that copper is extracted from the flotation tails by chloride sublimation worse, than zinc and lead. For limitation of iron chloridosublimation it is necessary to carry out the process at 7-fold oxygen excess and 3-fold CaCl2 one. High degree of nonferrous metals’ chloridosublimation (8089 % of Cu, 95-99 % of Zn, > 99 % of Pb) and low degree of iron chloridosublimation (11.23 % of Fe) is observed at 1140-1200°C during 39-60 min and the surplus of CaCl2 in 3,2 times. Electrosmelting the cinders of the chloride sublimation roasting of the Balkhash concentrating factory’s (BCF) flotation tailings in a mix with coke and quartzite allows to produce a ferroalloy with silicon content of 28-63 % (at extraction in the ferroalloy of 8087.3 % of silicon). Ferrosilicon of a grade of FS50 is formed at the electrosmelting a charge containing 11 % of steel cuttings, 20 % of quartzite from the ore mass and 126-133 % of coke from a theoretically required quantity for the silicon and iron reduction. Ferrosilicon of a grade of FS45 is produced at electrosmelting the cinders in the presence of 20 % of quartzite, 6-11 % of steel cuttings and 100-106 % of coke.

At flotation concentration of coppercontaining ores waste products are formed (to 98 % on 1 tonne of the ore (Samygin, Filipov, & Shehkirev ,2003;Morozov, Abdykirova, & Falei, 2015)).Now a quantity of flotation wastes only on the Balkhash and Dzhezkazgan concentrating factories makes nearly 1bn t.These wastes, occupying considerable ground areas (approximately 40 km 2 for the Balkhash factory), not only make worse environmental ecology, but also contain a significant amount of valuable metals.Kazakhstan produces 360-390 ths t of copper (Alshapov, 2004; State of Kazakhstan mineral raw material base (2015, February 18); World goods markets (2015, February 18)) and loses annually with the concentration tailings more 6-8 ths t of copper, 36-48 ths t of zinc, 4-5 ths t of lead, to 500 ths t of silicon and 150 ths t of iron.Therefore the concentration tailings are potential raw materials not only for nonferrous metallurgy, but also for manufacture of iron-silicon alloys.In world practice sufficiently rich tails are processed by secondary flotation and leaching; it allows reextracting no more than 50-60 % of nonferrous metals.In the process, as a rule, a nonmetallic component does not earmark for manufacture of the products in demand (Turkebaev, & Sadykov,1988;Glazunov, & Davydov, 1980;Snurnikov, 1986; Enne, Sycheva, Edakina, Bykov, etc., 1992; Rudnev,2004;Vorobyev, & Iskushina, 1997;Jagin, Davydov, Rudnov, etc., 2001;Golik, 2010).In our opinion a perspective method of processing the Balkhash concentrating factory's tails is a combined chloride electrothermal way allowing to recover not only nonferrous metals, but also to produce ferroalloys of various grades (Rybnikova,  The given article contains the research results of nonferrous metals' recovery from the Balkhash concentrating factory's flotation tails using chloride sublimation roasting and manufacture of ferroalloys from the roasting cinders.

Investigated raw material
For the research performance we have used the BCF's tailings.Chemical content of the tailings (in accordance with the data of the production association "Balkhashstvetmet"): 0.27-0.39% of Cu; 0.54-2.03% of Zn; 0.13-0.

Technique of carrying out the research
The thermodynamic modelling of nonferrous metals' chloridosublimation from the BCF's tailings has been performed with use of the software package ÍSC-5.1 (Outokumpy) based on a principle of the Gibb's energy minimum.For calculations we have used the subprogram "Equilibrium compositions", which allows on the basis of quantitative composition of substances to calculate equilibrium distribution degree of an element between all components of a system (Roine, 2002).
Determination of optimum technological parameters of the nonferrous metals' chloridosublimation from the flotation wastes has been carried out by a method of experiment planning using rototable plans of the second order with the subsequent construction of volume and plane images of independent variables' influence on optimization parameters (chloride sublimation degree of a metal -á chl Me ) (Ahnazarova, & Kafarov, 1978).Chloride sublimation of Cu, Pb, and Zn from the tails has been fulfilled in an air flow in a vertical furnace with carborundum heaters.Before the experiment carrying out the BCF's tailings have been pelletized in a bowl granulator (diameter -0.4 m, height of an edge -0.08 m).A calcium chloride solution is applied as a binder.The pellet granules in diameter 0.8-1.0cm were dried at 230-240°C during 30 minutes.After the drying the granules in where G charge and G cinder -a charge mass and a cinder mass accordingly, g; G Me(charge) and C Me(cinder) -a metal content in a charge and in a cinder, g.The metals' content in the tails and in the cinder was determined by means of a device AAS-1 (Germany).Electrosmelting the cinder has been carried out in an arc electric furnace with controlled output (from 0 to 10 of kilovolt-ampere).The cinder with coke and steel cuttings was melted during 55-60 minutes in a graphite crucible, which is 10 cm high and its internal diameter is 7 cm.Diameter of a graphite electrode is 3 cm.The charge weight is 250-280 g.Extraction degree of silicon and iron in an alloy is calculated according to the formula: where G cinder and G alloy -a cinder mass and an alloy mass accordingly, g; C Me (cinder) and C Me (alloy) -a metal content in a cinder and in an alloy accordingly, %.The silicon content in the alloy was determined by a bottle method using kerosene.

RESULTS AND DISCUSSION
The information about chloridosublimation of copper, zinc and lead from the BCF's tails in the presence of calcium chloride is represented in Figure 3.
It follows from the figure 3 that at the 3,2fold excess of CàCl 2 for the reactions: increase of the oxygen amount to 7-fold excess somewhat reduces α chl Cu (from 93 to 88 %), slightly influences on α chl Zn (90-92 %) and Pb (> 99 %), however in this process undesirable chloridosublimation of iron (as FeCl 2 and FeCl 3 ) decreases from 10.4 to 2.4 % at 1200°C.Table 1 contains the information about influence of independent factors (temperature, T, °C; duration of the process, τ, minute; CaCl 2 amount, XA, % from theoretically possible for the reactions 1-3).On the basis of these data using a program Microsoft Excel (Inkov, 2006) we have found adequate regression equations f (T, τ, XA).The regression equations' significance was defined in accordance with the Student's test, and adequacy of the equations -in accordance with the Fisher's test.The following equations were obtained: ...( 6) for the chloride sublimation of lead (in a temperature interval of 800-1000 0 C).A regression equation α chl Pb = f (T, τ, XA) looks like: On the basis of the received equations using the program Mathcad (Ochkov, 2007) a 3D image of a response surface of α chlMe and its horizontal sections has been constructed for XA = 32 % (smaller amount of CaCl 2 does not provide high α chl Me).It follows from the figure 4, that 85-90 % of α chl Cu can be reached in the area fnm (320 %, 1174-1200 0 C, 51.6-60 min), 95-99 % of α chl Znin the area zyx (320 %, 1160-1200 0 C, 39-60 min), 90-98 % of α chl Pb -in the area uko (320 %, 920-1000 0 C, 41-56 min).As α chl Cu < α chl Zn < α chl Pb, that the At the chloride sublimation roasting of the tails the chloride sublimation of iron is undesirable.At the development of iron chloridosublimation the nonferrous metals' sublimates are polluted by iron chlorides.Therefore it is necessary to define conditions at which α chl Me (for the present instance, copper) will has a maximum value, and α chl Fe -a minimum one.Figure 5 represents the joint information about α chl Cu and α chl Fe from which follows that high (80-89 %) α chl Cu and low (1-1.25 %) α chl Fe are observed at 1140-1200°C during 39-60 minutes at 320 % of CaCl 2 (the area ltz).For this case á chl Zn makes 95-99 % and α chl Pb is > 99.0 %.
The experiment matrix of electrosmelting the cinder formed after the tailings' roasting is represented in the table 2. Optimization parameters in this experiment series are: silicon extraction

Table 1 .
The experiment planning matrix and the results of Cu, Zn and Fe chloride sublimation from the tailings of the Balkhash concentrating factory

Table 2 .
The experiment planning matrix and the results of electrosmelting the cinder of chloride sublimation roasting the BCF's tailings At chloride sublimation roasting the granulated tails in air stream α chl Cu < α chl Zn < α chl Pb; α chl Cu is 80-89 %, α chl Zn is 95-99 %, á chl Pb is more than 99.0 % and α chl Fe makes 1-1.23 % at the following conditions: 1140-1200°C, duration of the process -39-60 min and 3.2-fold CaCl 2 excess.c)Electrosmelting the cinders formed after the chloride sublimation roasting of the Balkhash concentrating factory's tailings in a mixture with coke and quartzite allows to produce a ferroalloy containing 28-63 % of silicon; at the extraction of 80-87.3% of silicon in the alloy the ferrosilicon FS50 can be obtained at 11 % of steel cuttings, 20 % of quartzite (from the ore weight) and 126-133 % of coke (from the theoretical amount required for the silicon and iron reduction); the ferrosilicon FS45 is formed at the electrosmelting the cinder in the presence of 20 % of quartzite, 6-11 % of steel cuttings and 100-106 % of coke.