Production of SHG Zinc From 100% Recycled Materials
89
Table 3 First Zn produced
Bay 1
Bay 2
LME
Al (%)
0.0002
ND
0.001
Cd (%)
ND
ND
0.003
Cu (%)
0.001
0.0011
0.001
Fe (%)
0.0059
0.0014
0.002
Pb (%)
0.0146
0.0113
0.003
Sb (%)
ND
ND
0.001
Zn (%)
99.955
99.970
99.995
restart project. The values in the restart project are within specification and are
expected to improve as operation proceeds due to the completion of activated carbon
washing, which released Ni and Fe into the initial electrolyte inventory in the SX
stripping—EW loop.
The first metal from the Restart Project was stripped 30 h after the power was
switched on with excellent cathode morphology. Based on experience during the
Skorpion start-up, first Zn from the MZP was not expected to be SHG quality due
to the use of fresh non-passivated Pb-Ag anodes and the low initial concentration of
Mn in the electrolyte. The composition of the metal produced is shown in Table 3,
confirming that Pb was out of specification for SHG and Fe slightly over spec for the
Zn produced from Bay 1, while Zn from Bay 2 was within spec. The low levels of
the remaining classical impurities, often found in SHG Zn, is typical of the quality
produced by the MZP and confirms that the facility will produce SHG Zn once
passivation of the Pb-Ag anodes is achieved.
Manganese addition system fire and subsequent repair work
One of the upgrades completed during the project involved a first of its kind Mn
dissolution system, where high purity Mn metal flakes were dissolved in spent electrolyte to produce MnSO 4 which was then fed back to the electrolyte circulation tank.
Shortly after the first Zn stripping from the cells, a fire broke out in the Mn dissolution
tank, which spread to the cell house, ultimately destroying the cooling towers and
electrolyte circulation piping, and causing damage to some concrete components,
the electrode cranes, and electrowinning cells. Although the exact cause of the fire is
still under investigation, it is generally considered plausible that hydrogen had built
up to a level higher than the LEL in the tank and that an external source of ignition
had ignited the hydrogen.
Cell house rebuild and resumption of operations
At present the cell house and associated equipment are undergoing refurbishment,
while one of the electrode cranes, the cooling towers and associated electrolyte
circulation piping are being replaced. The refurbishment work is expected to be
completed early in 2020, with Zn production expected to resume before April 2020.
89
Table 3 First Zn produced
Bay 1
Bay 2
LME
Al (%)
0.0002
ND
0.001
Cd (%)
ND
ND
0.003
Cu (%)
0.001
0.0011
0.001
Fe (%)
0.0059
0.0014
0.002
Pb (%)
0.0146
0.0113
0.003
Sb (%)
ND
ND
0.001
Zn (%)
99.955
99.970
99.995
restart project. The values in the restart project are within specification and are
expected to improve as operation proceeds due to the completion of activated carbon
washing, which released Ni and Fe into the initial electrolyte inventory in the SX
stripping—EW loop.
The first metal from the Restart Project was stripped 30 h after the power was
switched on with excellent cathode morphology. Based on experience during the
Skorpion start-up, first Zn from the MZP was not expected to be SHG quality due
to the use of fresh non-passivated Pb-Ag anodes and the low initial concentration of
Mn in the electrolyte. The composition of the metal produced is shown in Table 3,
confirming that Pb was out of specification for SHG and Fe slightly over spec for the
Zn produced from Bay 1, while Zn from Bay 2 was within spec. The low levels of
the remaining classical impurities, often found in SHG Zn, is typical of the quality
produced by the MZP and confirms that the facility will produce SHG Zn once
passivation of the Pb-Ag anodes is achieved.
Manganese addition system fire and subsequent repair work
One of the upgrades completed during the project involved a first of its kind Mn
dissolution system, where high purity Mn metal flakes were dissolved in spent electrolyte to produce MnSO 4 which was then fed back to the electrolyte circulation tank.
Shortly after the first Zn stripping from the cells, a fire broke out in the Mn dissolution
tank, which spread to the cell house, ultimately destroying the cooling towers and
electrolyte circulation piping, and causing damage to some concrete components,
the electrode cranes, and electrowinning cells. Although the exact cause of the fire is
still under investigation, it is generally considered plausible that hydrogen had built
up to a level higher than the LEL in the tank and that an external source of ignition
had ignited the hydrogen.
Cell house rebuild and resumption of operations
At present the cell house and associated equipment are undergoing refurbishment,
while one of the electrode cranes, the cooling towers and associated electrolyte
circulation piping are being replaced. The refurbishment work is expected to be
completed early in 2020, with Zn production expected to resume before April 2020.