This project started up in 1967 and is still operating on the West Coast of Tasmania. The magnetite has been altered by volcanic activity and is not a banded iron – banded iron is typical for the other projects in Australia, the US and Russia.
This gives the project significant processing advantages in terms of weight recovery and liberation. The concentrate is transported to the Coast by pipeline – to a pellet plant and port owned by the project.
The plant was designed in the US based on 20 years of experience in taconite operations by Pickand Mather and the Coleraine Laboratories.
The long term success of the project is probably due to the long term emphasis on operational improvements and cost savings rather than consideration of expansion projects – the pipeline effectively limited the project to 2.5Mtpa.
The management style of the original owners – Pickand Mather and the Japanese – with tight capital controls also helped during the period of iron prices in the $US20 range.
• The weight recovery was 45 to 48% with some pit regions reaching 60% – this was the result of the volcanic origin
• The target grind was 85%-45micron (80%-40micron) set by the pipeline rather than grade control. This achieved 68 to 69%Fe.
• From a grade point of view the ore body was relatively uniform – though there were differences in grindability which had an impact on the Autogenous mill operation. Coarse blending using haulage fleet distribution was practiced and at one stage this was increased to fully blended trucks using 100% rehandle. The latter had significant benefits in terms of pelletising but was expensive to operate.
• The bulk of tailings was produced at 1mm – so a very coarse liberation curve. The project would have been suitable for dry magnetic separation (DMS) but the autogenous milling was cheaper than crushing to 10mm so there was no opportunity for DMS. Water supply was not an issue for the project – the Savage River, in the valley below, never ran dry.
• in the early years in Central and Northern pits the mine operated with and all material to concentrate ratio of 6:1 or 7:1. This has increased significantly has the pits have increased in depth. Discussions have been underway for some time on an underground expansion since the magnetite is known to reach to 300m below sea level (the river is 100m above sea level and the top of the mine 300m above sea level). High iron ore prices have allowed the mine to operate with higher strip ratios.
• The mine is 80km from the port – though the road distance is over 100kms. The road is not suitable for long distance haulage or access by rail – so the project is dependant on the pipeline. Since rail costs in good conditions are $0.05/tkm this is still significantly higher than the $0.006/tkm for the pipeline. Even after 56 years the pipeline is in reasonable condition with only one failure – and that caused by operator error rather the line failure.
• Water supply – easily available for the cost of pumping up 300m from the river over a distance of 3kms. Little or no water is returned from the tailings dam – the poorer quality does have an impact of the product grade when it is recycled.
• Power – the project was developed in the time of cheap hydro power at $0.02/kWh – this has increased significantly with the connection to the Victorian grid – but with a usage of 60kWh/t concentrate it is one of the lowest users of power/t of concentrate.
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