Konkola Concentrator - Zambian Copperbelt (sitios de interés)
Descripción del sitio
3.3.2 Process Plant
The plant dates from 1958 and, in August 2005, had a capacity of 2.4 Mtpa. No 1 shaft is close to the concentrator and the ore is delivered by conveyor belt. No 3 shaft is some 3 km distant and ore is delivered by 30 t and 50 t truck.
Ore grade was typically 3.5 to 3.8% from No 1 shaft and 2.5 to 2.8% from No 3 shaft. The ore has an average grade of circa 3% copper. The copper is broadly described as being either acid insoluble (predominantly highgrade sulphide minerals) or acid soluble (essentially oxide copper although small amounts of bornite and chalcocite are also soluble in acid). The flotation recovery of the acid insoluble minerals is high at above 90 %,whereas the recovery of the acid soluble fraction is at circa 40% range. Gangue material is predominantly silica with some dolomite.
The processing route entailed washing, two stages of crushing, milling, flotation of sulphide mineral and flotation of oxide mineral and finally dewatering.The first stage of processing was washing to remove fines from the minus 150 mm ore. There were two washing plants. The South washing plant took ore from No 1 shaft and the North washing plant took ore from No 3 shaft.
The milling circuit was designed to produce a feed to the flotation circuit with a size of 85% passing 74 micron. The milling circuit consisted of nine Hardinge ball mills and two Vecor ball mills.The main flotation circuit consisted of three banks of primary sulphide rougher cells, secondary sulphide rougher cells and oxide rougher cells. The slimes flotation circuit consisted of one bank of cells. The concentrate was cleaned in a column cell and then re-cleaned whilst the tailings were pumped to two banks of cells for scavenging.
Dewatering of concentrate was by thickening, filtration and thermal drying. There were four thickeners followed by four drum filters. Thermal drying was done in two coal fired rotary dryers.
The updated 2005 feasibility study envisages a new concentrator being built adjacent to the new No 4 shaft. The new plant would consist of a 3 Mtpa module comprising a mill feed silo, SAG and ball milling and large flotation cells. This was planned to allow the plant to treat a total of 6 Mtpa ore by 2008. Concentrate from both the new and the old expanded facilities would be thickened using the existing thickeners and then filtered in a new filter plant to be sited near the current concentrate shed. The filtered concentrate would be placed in covered storage prior to despatch by rail or road.