1993 Volume 33 Issue 1 Pages 79-87
Most metallurgical processes are consisting of two essential steps of chemical reaction followed by phase separation. When the process is in equilibrium, the both steps can be evaluated based upon thermodynamic data. To explain the principle of phase separation, systems related to practical smeltings such as slag-metal or slag-matte was reduced into ternary system and ternary phase equilibria were derived from binary data based upon the regular solution model. The special interest is focussed to the fact that ternary phase separation tendency is observed between a neutral component and a strong intermediate compound even though all the constituent binary systems have miscible trends.
The experimental results on the oxidic dissolution of valuable metals in the binary and ternary slags in FeOx-SiO2-CaO system are reasonably explained by taking into account the immiscible trend between MO and xBO·AO in a ternary MO-AO-BO (metal oxide-acidic oxide-basic oxide) system. The behavior of activity or activity coefficient of metal oxide derived by the regular solution model is compared with the experimental results obtained for SnO, CuO0.5 and PbO.
The experimentally determined ternary miscibility gaps for the systems Cu-Pb-As, Cu-Pb-Sb, Sn-Fe-Si and Sb-Fe-S are explained thermodynamically, and it is recognized that the basic principles of a few smelting processes for lead, tin and antimony are reasonably explained by these ternary miscibility gaps. Through these examples, it is suggested, in principle, that the process of metal extraction can be designed thermodynamically.
