Pyrometallurgical Recovery of Valuable Metals …
541
company proposed to treat the flue dusts from the copper smelter by a combination
of hydro- and pyrometallurgy. Thermodynamic considerations and plant trial results
are presented in this paper.
Results and Discussion
Description and Results of the Plant Trials
The dusts from smelting and converting furnaces at Dongying Fangyuan were mixed
and treated by leaching and smelting reduction. The typical compositions of the
mixed dusts are given in Table 1. It can be seen that Pb and Cu concentrations varied
significantly due to the different sources of the copper concentrates and the furnaces
used. In addition to the Pb and Cu, valuable Ag and Bi are also present that need to
be recovered. Most of the Pb, Bi, Cu, and Zn were present in the dusts as sulphate
and oxide. Significant amount of arsenic present in the dust needs to be treated and
fixed in the stable form. The dust was mixed with water and H 2 SO 4 to control liquid:
solid = 3:1 and pH ≈ 1. The leaching was conducted at 50–60 °C heated by steam.
It was expected that most of the Cu, Zn, sulphur, and arsenic would be dissolved into
the solution. Cu and Zn will be recovered following the standard hydrometallurgical
process. The arsenic will be fixed as ferric arsenate precipitate which is a stable phase
acceptable environmentally. The residue was dried for pyrometallurgical processing.
The residue from the leaching process, after drying, was fed into a bottom-blown
furnace together with silica, lime, and coke according to the required ratios. Oxygenenriched air and natural gas were injected through three lances on the bottom of the
furnace to provide reductant and heat, and to stir the bath. The Pb-based alloy and
slag were tapped separately. The dust from the furnace was recycled to the furnace.
The alloy contains approximately 85 wt% Pb and 10 wt% Bi with small amounts
of Cu, Sb, As, and Ag. Matte containing Cu, Pb, Fe, and S was also observed from
time to time indicating that copper and arsenic were not completely removed in the
leaching process.
The quenched slag samples were mounted and polished for analyses. The
microstructures and compositions of the phases present in the slags were determined
by a JEOL JXA 8200 Electron Probe X-Ray Micro-analyser (EPMA) with wavelength dispersive detectors. (JEOL is a trademark of Japan Electron Optics Ltd.,
Tokyo). An accelerating voltage of 15 kV and a probe current of 15 Amps were
used. The Duncumb-Philibert ZAF correction procedure supplied with JXA-8200
was applied. The average accuracy of the EPMA measurements was estimated to be
within ±1 weight percent. Typical microstructures and phase compositions are given
in Fig. 1 and Table 2, respectively, for two slag samples FY183 and FY186. It can
be seen that liquid and melilite [2CaO.(Zn,Fe)O.2SiO 2 ] were present in both slag
samples. No significant alloy droplets were present in the slag indicating complete
separation of the alloy from the slag. 16.8 wt% PbO was present in the liquid of
541
company proposed to treat the flue dusts from the copper smelter by a combination
of hydro- and pyrometallurgy. Thermodynamic considerations and plant trial results
are presented in this paper.
Results and Discussion
Description and Results of the Plant Trials
The dusts from smelting and converting furnaces at Dongying Fangyuan were mixed
and treated by leaching and smelting reduction. The typical compositions of the
mixed dusts are given in Table 1. It can be seen that Pb and Cu concentrations varied
significantly due to the different sources of the copper concentrates and the furnaces
used. In addition to the Pb and Cu, valuable Ag and Bi are also present that need to
be recovered. Most of the Pb, Bi, Cu, and Zn were present in the dusts as sulphate
and oxide. Significant amount of arsenic present in the dust needs to be treated and
fixed in the stable form. The dust was mixed with water and H 2 SO 4 to control liquid:
solid = 3:1 and pH ≈ 1. The leaching was conducted at 50–60 °C heated by steam.
It was expected that most of the Cu, Zn, sulphur, and arsenic would be dissolved into
the solution. Cu and Zn will be recovered following the standard hydrometallurgical
process. The arsenic will be fixed as ferric arsenate precipitate which is a stable phase
acceptable environmentally. The residue was dried for pyrometallurgical processing.
The residue from the leaching process, after drying, was fed into a bottom-blown
furnace together with silica, lime, and coke according to the required ratios. Oxygenenriched air and natural gas were injected through three lances on the bottom of the
furnace to provide reductant and heat, and to stir the bath. The Pb-based alloy and
slag were tapped separately. The dust from the furnace was recycled to the furnace.
The alloy contains approximately 85 wt% Pb and 10 wt% Bi with small amounts
of Cu, Sb, As, and Ag. Matte containing Cu, Pb, Fe, and S was also observed from
time to time indicating that copper and arsenic were not completely removed in the
leaching process.
The quenched slag samples were mounted and polished for analyses. The
microstructures and compositions of the phases present in the slags were determined
by a JEOL JXA 8200 Electron Probe X-Ray Micro-analyser (EPMA) with wavelength dispersive detectors. (JEOL is a trademark of Japan Electron Optics Ltd.,
Tokyo). An accelerating voltage of 15 kV and a probe current of 15 Amps were
used. The Duncumb-Philibert ZAF correction procedure supplied with JXA-8200
was applied. The average accuracy of the EPMA measurements was estimated to be
within ±1 weight percent. Typical microstructures and phase compositions are given
in Fig. 1 and Table 2, respectively, for two slag samples FY183 and FY186. It can
be seen that liquid and melilite [2CaO.(Zn,Fe)O.2SiO 2 ] were present in both slag
samples. No significant alloy droplets were present in the slag indicating complete
separation of the alloy from the slag. 16.8 wt% PbO was present in the liquid of