PERTH (miningweekly.com) – A number of disruptive events at the Kipoi copper project, in the Democratic Republic of Congo, have resulted in ASX-listed Tiger Resources warning of a "material negative impact" on cash flows, as well as reduced revenues from lower copper production.
The miner in October 2016 reported that heap leach production was adversely affected by a reported seepage of process solution from the intermediate leach solution (ILS) pond.
As the ILS pond is integral to the production of copper from the heap leach circuit, Tiger will undertake full remedial work at the end of the wet season to bring the ILS pond back to full production.
In the interim, a decant pond was converted for use as an ILS pond.
However, Tiger on Wednesday said a leak within the decant pond resulted in the full contents of the pond discharging into the process water pond.
Repairs to the decant pond were completed on February 20, and the pond was returned to operations as an interim ILS pond, with no damage reported to the environment.
While the decant pond was off line, the grade of the pregnant leach solution feed to electrowinning was further reduced.
Further, a lightning strike on February 19 caused damage to electrical cables feeding one of the grasshopper conveyors and interrupted heap leach staking operations, with some 32 hours of time lost.
Operations resumed on February 20.
Additionally, the continued wet season is further reducing the heap performance, by diluting the grade of the pregnant leach solution, which is negatively affecting copper production from heaps.
Meanwhile, Tiger noted that its debottlenecking programme at Kipoi, designed to expand the nameplate copper production capacity from 25 000 t/y to 32 500 t/y of copper cathode, has failed to deliver on its targets.
Capital work completed as part of the debottlenecking included the addition of 14 new electrowinning cells, the completion of a coffer dam within the footprint of the new tailings storage facility (TSF), and the installation of a tank leach circuit with a design feed rate of 50 t/h.
While the additional electrowinning cells were now operating according to design parameters, a number of issues have arisen from the commissioning programme of the tank leach facility, and while actions were taken during commissioning to address these issues, they were not delivering a performance improvement.
Over the six-week commissioning period and, to date, the tank leach has achieved average throughput rates of only 19 t/h, compared with the 50 t/h design parameter.
Tiger noted that the tank leach performance is being impaired by two issues, including difficulty in recovering, screening and feeding the tailings material into the front-end of the circuit, which is resulting in higher material handling costs and reduced throughput rates and is causing damage to pumps and other components at the front-end of the circuit.
Additionally, the tank leach performance is also suffering from an inability to maintain the coarser size fraction of particles in suspension, which is further reducing throughput capacity and causing frequent stoppages to clean up settled material from the tanks and hoppers, and is causing damage to the tank leach circuit components.
Tiger told shareholders that it is unlikely that the design throughput rate at the tank leach can be achieved without modification to the existing flow sheet, adding that the company is currently exploring remedial actions.
Tiger said on Wednesday that it wis currently in discussions with its major shareholders and a senior lending group in order to address short-term and medium-term cash flow issues.