Lead Metal Production at Paroo Station Mine Using …
159
Cathode Starter Sheet Fabrication
Cathode starter sheets are fabricated form lead from the melting furnace. Hot metal
is pumped to a lead starter sheets casting drum. The drum produces lead sheet which
is cut to size then has the hanger bar (removed on the way to the furnace) inserted
and riveted to make the cathode starter sheet. Finished cathode starter sheets are
stored on a storage rack and automatically transported back to the electrowinning
plant and reinstated into the cells by the overhead crane in the electrowinning plant.
The capacity of the storage rack is 1200 starter cathodes.
Lead Melting/Cathode Handling Ventilation
An extraction system is provided for collecting off-gas from the furnace melting
operation. The system comprises of a spark arrestor/cyclone and baghouse for fume
extraction and dust collection. It is expected that only small quantities of dust will
be collected and this will be manually disposed of back into the leaching system for
recovery of any contained lead.
Bleed Treatment
A bleed stream of spent electrolyte (MSA rich) is treated for reagent and lead recovery. The bleed stream treatment removes impurities that build up in the circuit and
regenerates MSA for reuse in the process. The major impurities are Mn, Mg, Ca, and
Sr. A small “Chloride Bleed Stream” is also treated to remove other trace elements
such as sodium, potassium, and chloride ions.
In the first step, lead is recovered from the bleed stream by utilizing 10 electrowinning cells to strip lead over a 16 h cycle. The produced cathodes are harvested
and handled in similar manner to the production cells. During this process, the lead
concentration in the spent electrolyte solution is reduced to 3 g/L (spent electrolyte
Solution). The cells are the same design as the production cells and are provided
with hoods and connected to the same ventilation system as the production cells.
An Acid Purification Unit (APU) is used to de-acidify the spent electrolyte in
order to recover MSA for reuse in the leach areas. The spent solution is filtered
through a media filter and passed through the APU; which absorbs approximately
80% of the MSA. The MSA is stripped with demineralized water and returned to the
leach process.
The liquor discharge from the APU containing metallic salts and a small amount
of MSA is reacted with lime in agitated reactors to precipitate metal hydroxides
and solubilize the calcium methane sulphonates. The solution from the reactors is
thickened with the U/F being pumped to the precipitation residue filter, where the
precipitate is washed and discarded to tailings.
159
Cathode Starter Sheet Fabrication
Cathode starter sheets are fabricated form lead from the melting furnace. Hot metal
is pumped to a lead starter sheets casting drum. The drum produces lead sheet which
is cut to size then has the hanger bar (removed on the way to the furnace) inserted
and riveted to make the cathode starter sheet. Finished cathode starter sheets are
stored on a storage rack and automatically transported back to the electrowinning
plant and reinstated into the cells by the overhead crane in the electrowinning plant.
The capacity of the storage rack is 1200 starter cathodes.
Lead Melting/Cathode Handling Ventilation
An extraction system is provided for collecting off-gas from the furnace melting
operation. The system comprises of a spark arrestor/cyclone and baghouse for fume
extraction and dust collection. It is expected that only small quantities of dust will
be collected and this will be manually disposed of back into the leaching system for
recovery of any contained lead.
Bleed Treatment
A bleed stream of spent electrolyte (MSA rich) is treated for reagent and lead recovery. The bleed stream treatment removes impurities that build up in the circuit and
regenerates MSA for reuse in the process. The major impurities are Mn, Mg, Ca, and
Sr. A small “Chloride Bleed Stream” is also treated to remove other trace elements
such as sodium, potassium, and chloride ions.
In the first step, lead is recovered from the bleed stream by utilizing 10 electrowinning cells to strip lead over a 16 h cycle. The produced cathodes are harvested
and handled in similar manner to the production cells. During this process, the lead
concentration in the spent electrolyte solution is reduced to 3 g/L (spent electrolyte
Solution). The cells are the same design as the production cells and are provided
with hoods and connected to the same ventilation system as the production cells.
An Acid Purification Unit (APU) is used to de-acidify the spent electrolyte in
order to recover MSA for reuse in the leach areas. The spent solution is filtered
through a media filter and passed through the APU; which absorbs approximately
80% of the MSA. The MSA is stripped with demineralized water and returned to the
leach process.
The liquor discharge from the APU containing metallic salts and a small amount
of MSA is reacted with lime in agitated reactors to precipitate metal hydroxides
and solubilize the calcium methane sulphonates. The solution from the reactors is
thickened with the U/F being pumped to the precipitation residue filter, where the
precipitate is washed and discarded to tailings.