Experimental Phase Equilibria Studies of the Pb-Fe-O System in Air, in Equilibrium with Metallic Lead and at Intermediat
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I.
INTRODUCTION
MOST industrial lead smelting operations include a process step that involves the reduction of lead slag and the separation of metallic lead bullion. These of highPbO slags also contain iron oxide, SiO2, CaO, ZnO, and other components, such as ‘‘Cu2O.’’ Al2O3, and MgO. To optimize the conditions of these industrial processes, detailed information is required of: (a) slag–solid equilibria at various oxygen potentials; (b) the activities of lead species in the slag at corresponding conditions; and (c) the partitioning of elements between metal, slag, solids, and gas phases. The present study is a part of an overall integrated thermodynamic modeling and experimental research program to support the optimization and development of complex lead smelting, refining, and recycling processes. An essential part of the program is the experimental determination of gas–slag–metal–solid oxide equilibria in those Pb-containing systems where the appropriate information is lacking or controversial. This particularly applies to all iron-containing slag systems in equilibrium with metallic lead, since the previous
M. SHEVCHENKO and E. JAK are with the Pyrometallurgy Innovation Centre (PYROSEARCH), The University of Queensland, Brisbane, QLD 4072, Australia. Contact e-mail: [email protected] Manuscript submitted May 10, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
research[1,2] has not covered these conditions. The lead-containing slag systems studied previously[1–11] were focused on equilibria in air, with limited investigations[12] at most reducing conditions (equilibria with metallic iron), which have low PbO concentrations in the slag (1100°C) p(O )=0.21 isobar FactSage + new results: isotherms Univariants Compounds
A
10
Pb2Fe11O18
8
B
1272
hematite 6 I
4
D
1100
2
C
PbO
PF5+x
0 Hem 10 PbFe12O19
20
FeO1.5
E
40 PF1±x 50
30
60
mol.% PbO→
H G
PF5+x
70
F
PF1±x
80
PbO
PbO
90
(b’) 6
FactSage prediction: p(O )=0.21 isobar FactSage + new results: isotherms Univariants Experiment: slag + solid + Pb(liq) slag + 2 solids slag + solid + air
↑ mol.% FeO 5
950
Pb metal (liq)
4 900
spinel 3 850 900
800 795±5 D 790
2 850
P1+xF12-x
820 C
780
1
PF5+x 950
65
H
PF1±x
I
825
70
75
mol.% PbO→
790
810
PbO
F
800 G 850
855±5
60 ←FeO1.5
900
874±5
0
875
E 771±5
780
772±5
950
80 780
810
85
(c) Fig. 5—continued.
Most of the PbO-FeO1.5-FeO compositional triangle belongs to the Pb metal and spinel primary phase fields. Limited ranges at high temperatures are occupied by wustite and hematite primary phase fields. The reactions hematite + Liquid fi spinel + magnetoplumbite and Liquid fi wustite + spinel + Pb are METALLURGICAL AND MATERIALS TRANSACTIONS B
estimated to occur at 1545 K (1272 C, point B) and 1636 K (1363 C), respectively, according to the current FactSage database. The part of the diagram close to the PbO-‘‘FeO1.5’’ join at high temperatures is not shown, since it corresponds to high oxygen partial pressures, >1 atm.
sp+wustite+Pb sp+Pb
Spinel 30
liq
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