A Case Study on the Operation of a Flottweg Tricanter® Centrifuge for Solvent-Extraction Crud Treatment at Bwana Mkubwa, Ndola, Zambia

Bwana Mkubwa is a copper cathode producer located in Ndola, Zambia, operating at a capacity of 50,000 tons per annum and owned by First Quantum Minerals. The solvent-extraction circuit of Bwana Mkubwa was initiated in 1997, with operations expanded in 2002 to include ore treatment from the Lonshi mine in the Democratic Republic of Congo. This adaptation resulted in an increase of solids in the feed solution which presented significant challenges, particularly the formation of crud, an emulsion that complicates solvent-extraction processes. Initial attempts to filter crud using a press were unsuccessful due to rapid clogging and production of suboptimal outcomes. Consequently, in December 2003, the decision was made to install a Flottweg Z4E-3/441 Tricanter® centrifuge, which was operational by June 2004. The installation has since enabled substantial improvements in plant operability, significantly reduced organic losses by an estimated US$50,000 monthly, enhanced the efficiency of the solvent-extraction operations, and facilitated the rapid return of organic material to the circuit. These enhancements not only optimized plant functionality but also yielded considerable financial benefits.