142
D. Dreisinger et al.
The milled flotation feed is conditioned with sodium hydrosulphide and a sodium
isobutyl xanthate collector (SIBX) and frother reagent scheme is used to recover a
lead concentrate. Test work has indicated that significant improvements can be made
fairly simply and cost effectively to the existing flotation plant. Rougher flotation
kinetics have shown that approximately 60% of the lead can be recovered at a grade
of 55–60% lead from rougher cell 1 in each rougher train, bypassing the first mechanical cleaning train directly to final cleaning. The remaining rougher and scavenger
concentrate is then pumped to the first cleaner train as per the current circuit, but
the first cleaner train is now only required to treat 40% of the lead in the combined
rougher scavenger concentrate.
In a similar manner concentrate from cell 1 or the 1st cleaner, train can be bypassed
directly to final cleaning and the remaining 1st cleaner concentrate is recycled to the
head of the 1st cleaner train and these cells are then run for recovery not grade. 1st
cleaner tailings pass directly to the tailing thickener. Concentrates from the 1st cell of
the rougher and 1st cleaner banks are then treated in a single stage of column flotation
essentially removing the majority of the gangue slimes entrained in the concentrates
using a positive bias on the wash water to wash the slimes from the concentrates.
Column concentrate gravitates to the concentrate thickener and column tailings are
recycled to the head of the 1st cleaner cells.
These changes to the flowsheet configuration plus an improved reagent conditioning regime have produced approximately a 10% improvement in metallurgical
recovery at a slightly higher concentrate grade from a lower head grade in comparison to historical data. The predicted life of mine lead flotation recovery is 83% based
on a head grade of 3.8% Pb. The flotation concentrates are filtered on an existing
plate and frame filter and the concentrate filtration rate has improved by an order of
magnitude through removal of the gangue slimes by the inclusion of column flotation in the circuit. The concentrate is dried after filtration in order to minimize water
ingress into the hydrometallurgical plant and to remove residual flotation chemicals
to minimize foaming issues in leaching.
Hydrometallurgy Process Development
The first stage MSA leach dissolved all of the cerussite in the flotation concentrate with leach extractions typically 100% of the cerussite in less than 10 min of
atmospheric leaching at 45 °C, and 84% on average of the lead in the concentrate.
Leaching time was typically dictated by the rate at which MSA could be added,
while controlling the frothing due to carbon dioxide evolution. A CCD circuit was
instituted to recover the lead. The washed MSA leach residue then moved to the
anglesite conversion stage.
Recovery of the anglesite in the concentrate was designed as a two-stage process. The washed MSA leach residue was treated with acid (H 2 SO 4 ) to convert all
minor lead minerals (e.g. Pyromorphite) to lead sulfate. The acidified residue was
D. Dreisinger et al.
The milled flotation feed is conditioned with sodium hydrosulphide and a sodium
isobutyl xanthate collector (SIBX) and frother reagent scheme is used to recover a
lead concentrate. Test work has indicated that significant improvements can be made
fairly simply and cost effectively to the existing flotation plant. Rougher flotation
kinetics have shown that approximately 60% of the lead can be recovered at a grade
of 55–60% lead from rougher cell 1 in each rougher train, bypassing the first mechanical cleaning train directly to final cleaning. The remaining rougher and scavenger
concentrate is then pumped to the first cleaner train as per the current circuit, but
the first cleaner train is now only required to treat 40% of the lead in the combined
rougher scavenger concentrate.
In a similar manner concentrate from cell 1 or the 1st cleaner, train can be bypassed
directly to final cleaning and the remaining 1st cleaner concentrate is recycled to the
head of the 1st cleaner train and these cells are then run for recovery not grade. 1st
cleaner tailings pass directly to the tailing thickener. Concentrates from the 1st cell of
the rougher and 1st cleaner banks are then treated in a single stage of column flotation
essentially removing the majority of the gangue slimes entrained in the concentrates
using a positive bias on the wash water to wash the slimes from the concentrates.
Column concentrate gravitates to the concentrate thickener and column tailings are
recycled to the head of the 1st cleaner cells.
These changes to the flowsheet configuration plus an improved reagent conditioning regime have produced approximately a 10% improvement in metallurgical
recovery at a slightly higher concentrate grade from a lower head grade in comparison to historical data. The predicted life of mine lead flotation recovery is 83% based
on a head grade of 3.8% Pb. The flotation concentrates are filtered on an existing
plate and frame filter and the concentrate filtration rate has improved by an order of
magnitude through removal of the gangue slimes by the inclusion of column flotation in the circuit. The concentrate is dried after filtration in order to minimize water
ingress into the hydrometallurgical plant and to remove residual flotation chemicals
to minimize foaming issues in leaching.
Hydrometallurgy Process Development
The first stage MSA leach dissolved all of the cerussite in the flotation concentrate with leach extractions typically 100% of the cerussite in less than 10 min of
atmospheric leaching at 45 °C, and 84% on average of the lead in the concentrate.
Leaching time was typically dictated by the rate at which MSA could be added,
while controlling the frothing due to carbon dioxide evolution. A CCD circuit was
instituted to recover the lead. The washed MSA leach residue then moved to the
anglesite conversion stage.
Recovery of the anglesite in the concentrate was designed as a two-stage process. The washed MSA leach residue was treated with acid (H 2 SO 4 ) to convert all
minor lead minerals (e.g. Pyromorphite) to lead sulfate. The acidified residue was