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MEI Online: Plant Operation News: Africa: January 22nd 2008


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:: Gravity Circuit Upgrades Pays Dividends at Damang

In March 2002, Gold Fields acquired majority interest in the Damang Gold Mine in Ghana from Ranger Minerals Ltd. of Australia. The latter had brought Damang into production in 1998 and operated the mine until the Gold Fields acquisition in 2002.

Although the process plant at Damang had included a gravity circuit since it was originally commissioned, the centrifugal concentrators originally selected by the operator failed to meet recovery or availability expectations. Within 18 months of the take-over by Gold Fields a decision was made to initiate phase one of a three phase gravity improvement project. Phase one involved the immediate installation of a single Knelson XD48 concentrator to be operated in parallel with the two competitor units.

During the first full year of operation in this onfign, gravity recovery at Damang jumped by over 35% from 20.1% to 27.2%. Buoyed by these results, met staff began looking for ways to further increase gravity recovery and concluded that with the Knelson XD48 now on-line, the feed tonnage to the gravity circuit could be increased. This led to phase two of the circuit upgrade. This involved the installation of a dedicated gravity feed screen for the Knelson unit. By increasing the tonnage to the Knelson, the recovery by gravity at Damang was boosted to 34.5% of overall recovery; an increase in excess of 71%.

Phase three of the gravity circuit upgrade was implemented in August 2007, when the original two centrifugal units were de-commissioned/replaced by a second KC-XD48 and feed screen combination. After nearly 6 months of operation in this new configuration, gravity circuit recovery at Damang with 2 - KCXD48, has settled in at 36.3% of overall plant recovery an increase of over 80% from the original installation of the competitor’s two centrifugal concentrators. This has resulted in:

  • a total increase in overall plant recovery of in excess of 2%
  • improved circuit availability
  • reduction in monthly maintenance costs in excess of USD25,000/mo
  • a payback period of less than 30 days

“Results thus far have been extremely good. We’ve steadily increased our gravity recovery from 20.1% in 2002 to 36.3% at present, stated Charles Amoah, Metallurgical Manager at Damang. “Ore source has not changed significantly and we therefore attribute these step-changes in gravity recovery predominantly to the Knelsons."




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