Sar Cheshmeh Mine, Sar Cheshmeh, Iran
National Iranian Copper Industries Corporation (NICICO)
2000 - ongoing
The Sar Cheshmeh Mine, operating since 1980, is the largest of the NICICO’s mines. The nominal throughput of the mine, which was 22 Mtpa prior to the commissioning of Phase 2 expansion in 2015, increased to 33 Mtpa.
The Phase 2 expansion involved diversion of the existing tailings stream, carried in a flume, into a 4.5 km long gravity pipeline carrying the tailings over undulating terrain to the site of the new Paste Thickeners.
At the time of construction, the Paste Thickeners, 12 in number, each 25 m in diameter, were the largest such installation in the world. The feed to the paste thickeners has a nominal solids concentration of 42% and the solids flow of almost 4,000 t/hr requiring a 1,050 mm diameter steel pipe for transport.
We were engaged, in conjunction with Slurry Systems, to complete the hydraulic design of the pipeline.
The gravity pipeline system commences from the diverted tailings flume some 3.5 km from the Concentrator. The diverted tailings enters a pipeline feed chamber through a safety screen. The pipeline profile includes two valleys separated in the middle by a high point. The pipeline route therefore differs from most gravity pipelines which typically flow continuously downhill.
The pipeline design was based on the tailings rheology test results. Corrosion tests were conducted to confirm the suitability of unlined steel pipe. The operating envelope of the 1,050 mm Internal Diameter (ID) gravity flow pipeline has a maximum solids throughput of 7,500 t/h at Cw of 52%, an estimated flow rate of 9,500 m3/h and a velocity of 3.1 m/s. The design minimum flow rate is estimated to be in the order of 4,000 m3/h with a velocity of 1.3 m/s.
There is approximately 39 m of head difference between the pipeline entrance and exit which is 27 m more than the typical hydraulic gradient for the average slurry flow. Slack (open channel) flow is therefore likely to occur over the first few hundred metres of the pipeline. The use of chokes to minimise slack flow was not incorporated in the design as an excess head difference is required during flushing of the pipeline. The initial 310 m of the pipeline was designed utilising a 1,042 mm reinforced rubber slurry mining hose that can be replaced as increased corrosion / abrasion is expected as a result of the predicted slack flow. The predicted slack flow velocities are in the order of 10 m/s to 11 m/s.
We, in conjunction with Hydro Tasmania, were involved in the completion of the detailed design, construction documentation and provision of construction technical assistance.
The Sar Cheshmeh gravity pipeline successfully commenced operation in 2012 and is currently transporting approximately 32 Mtpa of tailings to the paste thickeners site.