Characterization of Phase Equilibria and Thermodynamics …
341
Phase Equilibria in High-PbO Slag Systems in Air, with Pb
Metal and with Pb–Cu Metal Alloys
There are major experimental difficulties in measuring phase equilibria in highPbO slag systems in oxidizing conditions and particularly in equilibrium with Pb
and Pb–Cu metal alloys. The slags and liquid metal alloys are chemically aggressive, dissolving conventional refractory and metal containment materials resulting
in contamination of the system with unwanted chemical components, difficulties
in retaining the original liquid phase as a uniform amorphous phase on quenching due to low viscosity, fast crystallization, and high vapor pressures leading to
selective vaporization of metal and metal oxide species. These difficulties have been
overcome in recent research [6], which has resulted in important advances in experimental technique. These improved techniques include the use of primary phase
substrates and closed system experiments in which samples are sealed in evacuated
silica ampoules. Using these approaches, many PbO-containing systems have been
characterized; some examples are listed below:
In air, the liquidus and phase equilibria for the systems, the PbO–“FeO 1.5 ”–CaO [6]
and PbO–“FeO 1.5 ”–SiO 2 [7].
In equilibrium with metallic Pb, the liquidus and phase equilibria for the system
PbO–“FeO”–SiO 2 [8].
In equilibrium with Cu–Pb metal alloys, new information on the liquidus surface for
the PbO–“Cu 2 O”–SiO 2 system in equilibrium with Pb–Cu metal and the distribution
of copper between slag and bullion [9]. Note that the Pb–Cu metal alloy present in
this system is in the solid state for a range of Pb/Cu ratios.
In summary, with the development of improved experimental techniques, many loworder oxide and oxide-metal sub-systems of high importance for Pb and Zn complex pyrometallurgy have been accurately characterized over the last decade. These
include many Pb- and Zn-containing oxide sub-systems. Using the same methodology and similar research techniques, a great deal of new fundamental data on
phase equilibria in Cu-containing oxide-metal sub-systems has also recently become
available.
Slag-Matte Equilibria
The distribution of elements between slag and matte is one of the key factors in
lead smelting and refining. No systematic studies were found in the open literature describing the equilibria between the lead slag, matte, and metal. The problems
associated with characterizing phase equilibria in lead matte systems are even more
challenging than those with metal due to the high vapor pressures of PbS gas species.
With the recent advances in experimental capability, it is now possible to obtain accurate measurements of metal distributions in multi-phase systems containing sulfur.
341
Phase Equilibria in High-PbO Slag Systems in Air, with Pb
Metal and with Pb–Cu Metal Alloys
There are major experimental difficulties in measuring phase equilibria in highPbO slag systems in oxidizing conditions and particularly in equilibrium with Pb
and Pb–Cu metal alloys. The slags and liquid metal alloys are chemically aggressive, dissolving conventional refractory and metal containment materials resulting
in contamination of the system with unwanted chemical components, difficulties
in retaining the original liquid phase as a uniform amorphous phase on quenching due to low viscosity, fast crystallization, and high vapor pressures leading to
selective vaporization of metal and metal oxide species. These difficulties have been
overcome in recent research [6], which has resulted in important advances in experimental technique. These improved techniques include the use of primary phase
substrates and closed system experiments in which samples are sealed in evacuated
silica ampoules. Using these approaches, many PbO-containing systems have been
characterized; some examples are listed below:
In air, the liquidus and phase equilibria for the systems, the PbO–“FeO 1.5 ”–CaO [6]
and PbO–“FeO 1.5 ”–SiO 2 [7].
In equilibrium with metallic Pb, the liquidus and phase equilibria for the system
PbO–“FeO”–SiO 2 [8].
In equilibrium with Cu–Pb metal alloys, new information on the liquidus surface for
the PbO–“Cu 2 O”–SiO 2 system in equilibrium with Pb–Cu metal and the distribution
of copper between slag and bullion [9]. Note that the Pb–Cu metal alloy present in
this system is in the solid state for a range of Pb/Cu ratios.
In summary, with the development of improved experimental techniques, many loworder oxide and oxide-metal sub-systems of high importance for Pb and Zn complex pyrometallurgy have been accurately characterized over the last decade. These
include many Pb- and Zn-containing oxide sub-systems. Using the same methodology and similar research techniques, a great deal of new fundamental data on
phase equilibria in Cu-containing oxide-metal sub-systems has also recently become
available.
Slag-Matte Equilibria
The distribution of elements between slag and matte is one of the key factors in
lead smelting and refining. No systematic studies were found in the open literature describing the equilibria between the lead slag, matte, and metal. The problems
associated with characterizing phase equilibria in lead matte systems are even more
challenging than those with metal due to the high vapor pressures of PbS gas species.
With the recent advances in experimental capability, it is now possible to obtain accurate measurements of metal distributions in multi-phase systems containing sulfur.