BATEMAN personnel made presentations on copper processing at the
recent Randol Copper Hydrometallury Workshop held in September 2000
in Tucson, Arizona, USA.
Application of microwaves to base-metal sulphide treatment
Microwave energy selectively targets sulphide particles, converting
them to oxides (in the presence of oxygen) which can be processed hydrometallurgically
to recover the base metal. The presentation covered testwork by BATEMAN
and EMR Microwave at the EMR pilot-plant facilities in Canada on the
treatment of halcopyrite concentrates.
The process was easy to control by varying the feed rate and airflow
and microwave processing was considered to offer the possibility of
commercial treatment of concentrates below 6 to 9 % sulphur. On average
over 96 % of the copper in the reactor-discharge product was converted
to a soluble form, as much as 60 % being present as water-soluble sulphate
and the remainder being soluble in dilute sulphuric acid. Subsequent
leaching was extremely fast with complete dissolution taking no more
than 30 minutes. The processing temperature had, however, to be kept
below 650 °C to avoid the formation of cupro spinel, which is insoluble
in weak sulphuric acid. Data on the energy requirements, operating temperatures,
copper extractions, sulphur dioxide production, residual oxygenlevels
and capacities were collected for sein a conceptual design of a 5 ton/day
copper-cathode production demonstration facility.
Future opportunities in copper hydrometallurgy
The presentation reviewed current copper solvent extraction /electrowinning
technology and focused on the recent adaptation of technologies from
other industries.
Electrowinning. The use of stainless-steel blanks as cathodes
has now largely eliminated sulphur contamination, while lead anodes
are still a basic part of these circuits, despite causing lead contamination,
which can be controlled by cobalt addition or dimensionally stable anodes
(DSA). Carbon seems a likely anode material of the future and could
reduce power consumption and operate at a voltage, which produces no
oxygen and consequently no acid mist in the tank house.
Solvent extraction. Improved mixing of the immiscible solvents
has resulted from the recent introduction of turbine-pump mixers from
the phosphate industry and vortex-ring and reciprocating mixers from
the paint industry. Settlers too have gone through many different arrangements
and modern units are enclosed to minimise evaporation and oxidation
of the solvent. Deep bed settlers will become the preferred design of
the future.
Mobile plants. Off-the-shelf modular plants for solvent extraction
and electrowinning are becoming feasible and should enable mine owners
to dismantle and move plants as the locality of mining changes, as has
been done for many years by operators of dense-media separation plants.
Further details are available from Mark F Vancas,
BATEMAN Manager, Process Engineering, on +1-520-624-7810 or email basemetals@batemanengineering.com
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