Smelting Jarosite and Sulphur Residue
in a Plasma Furnace
Justin Salminen, Jens Nyberg, Matej Imris and Bror Magnus Heegaard
Abstract Jarosite and sulphur residues are formed during electrolytic recovery of
zinc at Boliden Kokkola. In order to minimize the waste generation as well as promote
better recovery of metals, pyrometallurgical options have been studied to treat this
material. In addition to recovering more metals, another goal was to obtain clean
stable slag that could be used in construction. Pilot test work was carried out using
an ArcFume plasma process for directly smelting and fuming several combined
residues, i.e. jarosite plus sulphur residue from Boliden Kokkola zinc plant. The
tests were carried out in two stages, including a smelting stage and a reduction stage.
The obtained slag compositions after smelting were typically 1–2 wt% of Zn and
0.1–0.3 wt% of Pb. The smelting stage was followed by a shorter reducing stage
to further decrease volatile metals in the slag. Very low compositions of Zn < 1
and Pb < 0.03 wt% were reached. In the smelting stage, no coke was added. In the
reducing stage however, coke was added to ensure sufficient reductive conditions for
fuming volatile metals such as Zn, Pb, Ag, In, and Ge and obtain good recovery.
Heavy metals and elements such as As, Sb, Cd, and Cl reports into fume oxide as
well. Consequently, the overall direct CO 2 emissions were lower than expected due
to avoiding coke use in the smelting stage. The allowed contents of heavy metals in
the slag are determined by legislation and the targeted use of the slag.
Keywords Jarosite · Sulphur · Smelting · Plasma · Fume · Slag
J. Salminen (B) · J. Nyberg
Boliden Kokkola, Sinkkiaukio 1, 67101 Kokkola, Finland
e-mail: justin.salminen@boliden.com
J. Nyberg
e-mail: jens.nyberg@boliden.com
M. Imris · B. M. Heegaard
ScanArc, PO Box 41 SE 81321 Hofors, Sweden
e-mail: Matej@scanarc.se
B. M. Heegaard
e-mail: Bror.Magnus.Heegaard@scanarc.se
© The Minerals, Metals & Materials Society 2020
A. Siegmund et al. (eds.), PbZn 2020: 9th International Symposium
on Lead and Zinc Processing, The Minerals, Metals & Materials Series,
https://doi.org/10.1007/978-3-030-37070-1_34
391
in a Plasma Furnace
Justin Salminen, Jens Nyberg, Matej Imris and Bror Magnus Heegaard
Abstract Jarosite and sulphur residues are formed during electrolytic recovery of
zinc at Boliden Kokkola. In order to minimize the waste generation as well as promote
better recovery of metals, pyrometallurgical options have been studied to treat this
material. In addition to recovering more metals, another goal was to obtain clean
stable slag that could be used in construction. Pilot test work was carried out using
an ArcFume plasma process for directly smelting and fuming several combined
residues, i.e. jarosite plus sulphur residue from Boliden Kokkola zinc plant. The
tests were carried out in two stages, including a smelting stage and a reduction stage.
The obtained slag compositions after smelting were typically 1–2 wt% of Zn and
0.1–0.3 wt% of Pb. The smelting stage was followed by a shorter reducing stage
to further decrease volatile metals in the slag. Very low compositions of Zn < 1
and Pb < 0.03 wt% were reached. In the smelting stage, no coke was added. In the
reducing stage however, coke was added to ensure sufficient reductive conditions for
fuming volatile metals such as Zn, Pb, Ag, In, and Ge and obtain good recovery.
Heavy metals and elements such as As, Sb, Cd, and Cl reports into fume oxide as
well. Consequently, the overall direct CO 2 emissions were lower than expected due
to avoiding coke use in the smelting stage. The allowed contents of heavy metals in
the slag are determined by legislation and the targeted use of the slag.
Keywords Jarosite · Sulphur · Smelting · Plasma · Fume · Slag
J. Salminen (B) · J. Nyberg
Boliden Kokkola, Sinkkiaukio 1, 67101 Kokkola, Finland
e-mail: justin.salminen@boliden.com
J. Nyberg
e-mail: jens.nyberg@boliden.com
M. Imris · B. M. Heegaard
ScanArc, PO Box 41 SE 81321 Hofors, Sweden
e-mail: Matej@scanarc.se
B. M. Heegaard
e-mail: Bror.Magnus.Heegaard@scanarc.se
© The Minerals, Metals & Materials Society 2020
A. Siegmund et al. (eds.), PbZn 2020: 9th International Symposium
on Lead and Zinc Processing, The Minerals, Metals & Materials Series,
https://doi.org/10.1007/978-3-030-37070-1_34
391