Education of the republic of uzbekistan tashkent state technical university named after islam karimov

MATERIAL AND METHODS.
For this purpose, we propose introducing quantities of 
such compounds (CaCO
3
) into the firing mixture that would have a greater chemical affinity for 
FeO and SiO
2
than zinc oxide [7]. 
This will make it possible, even at moderate temperatures and at a much higher rate, to 
bind iron and silicon oxide into vital compounds, and conditions will be created under which 
zinc oxide remains in a free state [7-11]. This will significantly increase the degree of transition 

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Geological Engineering
132 
of zinc into solution during leaching, reduce the zinc content in the cake, and expand the 
through-extraction of zinc into finished products. 
CaCO
3
as an additional additive to the firing charge is justified because, at firing 
temperatures, calcium carbonate decomposes with the formation of calcium oxide and carbon 
dioxide, which are directly involved in preventing the formation of ferrites and zinc silicates. To 
determine the optimal parameters of zinc batch firing with the addition of CaCO
3
as an 
additional component to it, we performed thermodynamic calculations to determine the change 
in the free energy of the reactions of the interaction of the main features of zinc concentrates and 
limestone at temperatures of 945-995 °C, covering the conditions of firing in the RL furnace
Limestone decomposition proceeds according to the following reaction: 
CaCO
3
= CaO + CO
2
(2) 
RESULTS.
The completeness of this reaction is directly dependent on temperature, 
which is confirmed by thermodynamic calculations of the change in the Gibbs free energy 
(Figure 1). 
According to the proposed mechanism of reactions of the interaction of the components 
of the charge during the roasting of sulfide zinc concentrate at oxidation temperatures, 
decomposition of complex sulfides (FeS
2
, etc.) occurs with the release of elemental sulfur 
according to the following reactions: 
FeS
2
= FeS + S
2
(3) 
In figure 2 shows the diagrams of the change in the value of the change in the free energy 
of reactions (3).