INDA 2017

Best of Germany 2014 - Mining Equipment and Mining Technology

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Page 34 of 51

VDMA 33 2017 • VDMA MINING SUPPLEMENT thickened underflow fed to the filter press can be increased by as much as 25%. One gold operation in Nevada recently replaced the centrifugal thickener underflow pumps with ABEL series EM 100 electromechan- ical diaphragm pumps. Cone water additions and gland seal water were no longer required. Also, the maintenance costs associated with the thickener underflow pumps were greatly reduced. This same plant's filter press used centrifugal slurry pumps for its feed pumps. The wear on the centrifugal pumps was consider- able with pump wet ends wearing out as often as every two weeks, and costing as much as $20,000 to replace each time. Downtime and lost production mounted with each repeated occurrence. To mitigate the problem, the centrifugal filter press feed pumps were supplemented by ABEL series HMD-G-80-1000 piston-dia- phragm pumps. The ABEL pumps employ a hydraulically balanced elastomeric diaphragm, ideal for moving abrasive slurry at higher pressures. By working in parallel, the centrifugal pump "fast-fills" the filter press at lower pressures, then hands over consolidation of the press cycle to the ABEL. The resulting pump maintenance costs and downtime were greatly reduced. Filter cake quality improved due to the positive displacement action of the ABEL pump. The plant has since added another thickener-filter press process train to increase gold production. ABEL EM 100 pumps were speci- fied for thickener underflow and ABEL HMD-G-80-1000 pumps were specified for filter press feed duty. The ABEL HM series pumps are hydraulically driven piston-di- aphragm pumps. Reciprocating the motion of the piston moves an elastomeric diaphragm by means of a hydraulic end. Ball checks and seats on the product end are available in various materials. This characteristic design allows the pump to transfer abrasive slurry or sludge at pressures up to 1,450 psi (10 MPa). Aspirational Flotation A lot of mineral processing professionals are classifying the flotation technologies into three groups: mechanical agitator flotation, pneu- matic flotation and column flotation. This is a mistake as column flotation is a form of pneumatic flotation, explained Lutz Markworth, head of product management flotation for MBE Coal & Minerals Technology. "A lot of different pneumatic flotation technologies are available on the world market," Markworth said. "The flow direction of the feed and the air is important. Some technologies use a con- current flow, while others rely on a counter-current flow. And the flow of aerated feed pulp is arranged as downstream, upstream or in a tangential direction into the separation vessel." Other important considerations for pneumatic flotation are the needs for a high efficient reagent conditioning process prior to the separation vessel, the creation of perfect air bubble size range and amount, as well as the high efficient attachment of the air bubbles to the mineral particles. The upstream pneumatic flotation principle, realized in MBE's PNEUFLOT cell, generates the air in a special designed Venturi-based aerator on top of the separation vessel, Markworth explained. To float fine and coarse particles simultaneously with improved efficiency, MBE Coal & Minerals Technology developed in 2015 and installed in 2016 a new designed froth channel discharge system for potash, reverse iron ore and coal flotation with excellent results in terms of recovery and yield. The PNEUFLOT technology, according to Markworth, is the only one using upstream flotation process in one machine. "After leaving the ceramic nozzles with an upward motion into the separation ves- sel, coarse particles that are not perfectly attached to air bubbles at that stage are 'shot' into the froth zone, making contact with bigger air bubbles and are discharged properly into the new designed froth channel system," Markworth said. The coarse particles are discharged into the froth channels be- fore any sedimentation can take place. Froth discharge velocity can be controlled and set to an optimal condition for all kinds of froth characteristics. Markworth believes the froth channel discharge system could improve recovery by 6%-8% in the same machine at the same flotation time for potash and silica flotation as well as 9% more yield in coal flotation. An ABEL EM 100 pump is being used as a thickener underflow pump. The new channel system discharges froth for reverse iron ore flotation in Brazil.

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