The article examines results of studies on the effect of temperature, amount of carbon and pressure on the possibility of obtaining iron silicides and gaseous magnesium by carbon-thermal reduction of silicon and magnesium oxides containing in chrysotile-asbestos waste products. The studies were carried out using the HSC-6.0 software package (Outokumpy) and the second-order rotatable designs (Box-Hunter plans). It has been established that technology allows us to increase αSi(al), for example, at 1400 °C from 89.6 to 96.75%, reduce undesirable losses of silicon with gaseous SiO from 8.97 to 2.08% and slightly increase αMg(gas) from 97.41 to 97.54%. The alloy formed at 1300 °C contains 28.7% of silicon and corresponds to FS25 grade ferrosilicon.
The article presents the results of the experimental studies of the kinetics of electric smelting of the basalt from the Daubaba deposit, the main components of which are 50.5% SiO 2 , 19.9% Al 2 O 3 , 9.3% CaO, 9.6% Fe 2 O 3 with the extraction of the silicon and aluminum into the ferroalloy, calcium into the calcium carbide. The effect of electric smelting time (from 10 to 60 minutes) and the amount of lime (from 0 to 30% from weight of basalt) on the degree of extraction of Si and Al into the alloy and Ca into CaC 2 was determined. The studies were carried out by the method of planning the experiments with the usage of roto-standard plans of second order (Box-Hunter plan) with exploring graphic optimization of technological parameters. The electric smelting was carried out in a graphite crucible. The mass of the furnace-charge in each experiment was 400 g. It was found that: extraction of Si, Al into the alloy, and Ca into the calcium carbide becomes noticeable in the first 10 minutes of the process; in the absence of lime, the maximum degree of extraction of the silicon, aluminum in the alloy and the calcium, respectively, contain 80.8%, 72.2% and 69% in 45 minutes; the presence of lime in the furnace-charge allows you to increase the degree of extraction of the calcium in the calcium carbide to 79.8%, however, at this time, the extraction of the silicon and aluminum decreases. To extract 77.1-86.8% of the silicon, 75-82% of the aluminum in the alloy and 75-79% of the calcium in the calcium carbide, the duration of the electric smelting should be 46-50 minutes and the amount of lime to 6.1% from weight of basalt.
The article covers the results of researches on thermodynamic modeling of ferroalloy and calcium carbide obtaining from basalts of deposit Dubersay. The software package HSC-5.1, based on the principle of Gibbs energy minimum uses in the study. The influence of temperature (from 500 to 2500 °C) and the amount of carbon (from 40 to 60 % of the basalt mass) in the basalt–Fe–nC system was determined. It has been established that iron silicides are formed at T ≥ 1300 °C, Si at T ≥ 1400 °C, CaSi and Al at T> 1700 °C and CaC2 – at T ≥ 1800 °C. An increase of the amount of carbon from 40 to 60 % allows rise the degree of distribution of Si in the alloy up to 94 %, calcium in CaCl2 – up to 62.3 %, aluminum – to alloy up to 93.9 %. An increase of the amount of carbon allows increase the silicon concentration in alloy up to 55 % (at 1800 °C), aluminum – up to 17 % (at 2000 °C) and calcium carbide capacity – up to 350 dm3/kg. The method of rototable planning of the second order allows find equations of regressions of the influence of temperature and amount of carbon on the equilibrium distribution of silicon, aluminum, and calcium between the ferroalloy and calcium carbide. On the basis of this equations were determined, that within the temperature range 1956-1996 °C from the Dubersay deposit basalt, the ferroalloy with a content of ΣSi and Al 60.8-65.4 % (including 12- 15 % Si) and calcium carbide with a capacity of 250-300 dm3/kg are formed. Wherein degree of recovery into the alloy for silicon is 91-91.4 % and for aluminum is 63-75.1 % and calcium – into CaC2 is 60-60.7 %. The resulting ferroalloy by the content of silicon and aluminum can be attributed to the complex ferroalloy – ferrosilicoaluminium, calcium carbide – to the industrial product of grade from 3 and up to the highest.
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