Olympias Concentrator Plant Rehabilitation

Renewable | Kravvaritis & Partners | Engineers & Consultants, was appointed by Hellas Gold SA to undertake the auditing, permitting, engineering, design, construction supervision and commissioning of the Olympias concentrator plant rehabilitation. The fully refurbished plant was designed for a throughput of 800,000 tons per annum (tpa) for adjacent Olympias mine tailings re-processing. The concentrator site is located in the Halkidiki Peninsula in northern Greece.

The Olympias concentrator plant was commissioned in 1976 but had not been operated since production stopped in 1995.

The recovery of gold bearing pyrite / arsenopyrite concentrate was inefficient and a significant quantity reported to the tailings management facility (TMF) adjacent to the mine.

Approximately 2.4 Mt grading 3.4 g/t gold was accumulated and these tailings make up the initial feed to the rehabilitated concentrator. This feed material is mechanically reclaimed and re-pulped so as to feed the grinding circuit. The grinding circuit comprises of a ball mill. The slurry from the grinding circuit is classified via the mill cyclones and the cyclone overflow undergoes flotation to produce high grade gold bearing concentrate. The concentrate produced in flotation is thickened in high rate thickeners. The thickened concentrate is pumped to dedicated concentrate storage tanks prior to filtration via disk filters. The high grade gold bearing concentrate after filtration is ready for dispatch to market. The tailings from the concentrator are separated into coarse and fine fractions. The fine fraction, which is about 20% of the total, is filtered and then transported as filter cake to Stratoni for disposal on the existing TMF. The coarse fraction of the residue from the tailings phase was used by local contractors as aggregate.

Capital costs for the concentrator refurbishment at Olympias have been calculated at 20.000.000€.

The construction works commenced in mid 2010 and completed on schedule by Q2 2012. The concentrator plant got its operating permit in December 2012.