 Callahan
Mining Corporation
Gold Ore Processing Facility
Humboldt, Michigan
Roberts & Schaefer provided complete engineering, procurement,
and construction management services for Callahan Mining Corporation,
to convert an existing hematite flotation concentrator to a 2,000
TPD gold ore processing facility. In converting the existing mill
to process gold ore, the project stressed the evaluation of existing
equipment, and emphasized its reconditioning and reuse wherever
possible.
The project included adding a new two-stage crushing plant with
a jaw crusher, a cone crusher, and associated screening and conveying
equipment. Existing fine ore storage bins were re-used to store
crushed ore, to serve two grinding circuits, consisting of 900
HP ball mills in closed circuit with 20-inch cyclones.
Other mill equipment included rougher and cleaner flotation,
a cyanide leach circuit, static thickeners, and drum, and disk
vacuum filters. Leachate is clarified in a pressure leaf filter
prior to de-aeration ahead of zinc dust precipitation.
R&S provided all design engineering services for both the
crushing plant and the mill, including determining suitable environmental
mitigation measures, developing process flowsheets, P&ID,
and specifying and selecting equipment. R&S also provided
all electrical power and control design. Reuse of existing equipment
required detailed evaluation of the facility design, to match
available equipment to that required by the process, and to provide
a system that would operate efficiently at the lowest possible
capital cost.
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