Master's work

The Purpose of my research work is the analysis of an opportunity of manufacture ferroaluminium in the DC-arc furnace with use nepheline ores.

Aluminium is a strong deoxidant and is applied in quantity 0,3 - 1 kg/t for almost all of steel. Necessity of work on manufacture of complex aluminium ferroalloys is caused by the following reasons: 1) limitation of stocks of high-quality bauxites for manufacture of aluminium, presence of greater stocks of complex raw material and aluminium waste; 2) high cost of primary aluminium; 3) high efficiency of use of complex alloys.

On fig. 1 the technological scheme of complex use caolins, poor bauxites and others aliminium ores.

the Standard scheme of reception ferroaluminium.

Raw material for reception of alumina are the bauxites representing rock, consisting of many minerals: hydrates and oxides of iron. The chemical compound electrothermal ferroaluminium should be the following: the maintenance of aluminium depending on mark from 8 up to 24 %, the maintenance of impurity for all marks (no more): 4 % Si, 4 % C, 0,06 % S, P. The melt ferroaluminium is expedient for conducting in the typical closed electric furnaces of the big capacity. The technology of melt of an alloy consists in restoration of aluminium of the electrocorundum received from agglomerate of bauxites of any structure, stavrolite concentrate or another aluminium raw material. Thus receive also ferroalloys marks ФС20 and ФС25. The second stage represents continuous process with periodic release of metal and very much a small amount of slag. At reception of all aluminium ferroalloys aluminium is reducted from raw material at a heat with the advent of a liquid phase, and also dissolution of the reduction aluminium in a metal component. Technologies of reception and other alloys are based on this principle with aluminium.

Physical and chemical bases of process of manufacture of alloys of aluminium

In the nature aluminium meets in the form of Al ₂ O ₃ melt it at 2326К. Reduction aluminium is connected by carbon with formation complex oxycarbids of the aluminium, having high stability at presence of some other oxydes and metals. Absence of reliable thermodynamic data on оксикарбидам aluminium complicates the authentic thermodynamic analysis of all steps of consecutive restoration Al ₂ O ₃ the carbon, proceeding under the scheme: Al₂O₃>Al₄O₄C>Al₂OC>Al₄C₃>Al

Nephelines - minerals of complex structure. They have greater distribution to an earth's crust, than bauxites.

Provisional structure of ore: 30 % Al ₂ O ₃ , 45 % SiO ₂ , 4 % Fe ₂ O ₃ , 15 % Na ₂ O, 5,3 % K ₂ O, 0,7 % MgO.

It is visible, that with rise in temperature, restoration of aluminium is preceded with restoration of all others oxydes ofores, thus, the received alloy will not satisfy on ferroaluminium under the maintenance of silicon. One of possible schemes of manufacture ferroaluminium from nepheline ores is two-phasic process when at the first stage in reduction furnaces silicon from SiO ₂ and oxydes Na ₂ O and K ₂ O is restored, thus receive slag with aluminium and ФС23. Received slag with maintenance Al ₂ O ₃ up to 90 % then, at the second stage, in DC furnaces restore up to farroaluminium. Thus, it is possible to draw a conclusion that reception farroaluminium from nepheline ores is posible, provisional technological scheme of this process consists of two stages - at the first stage slag with the high maintenance of aluminium and the low maintenance of silicon, and at the second stage melt of directly aluminium in the DC-arc furnace is sucelted. The schemeof process is brought in figure 2.