Snowden is currently working on a project with Sierra Rutile Limited (SRL), which operates the Sierra Rutile heavy mineral sand mining operation in Sierra Leone. The scope of the project is to prepare an optimised strategic life of mine plan for SRL’s world class rutile project near the Imperri Hills, located about six hours drive southeast of the capital, Freetown. The objective of the strategic plan is to consider the best way to tackle the many discrete resources identified at the mine. Mining methods, concentration methods and dry mineral separation methods are all options under consideration. Optimised expansion opportunities will be identified and built into the strategy where possible.
The Sierra Rutile mine has had an interesting and colourful history. Mining started in the late 1960s, during the 1980s and 1990s the mine became a world class supplier of high quality rutile to the international TiO2 pigment and industrial applications industries. Production peaked in 1991 at 155,000 t of rutile. During the 1990s and early 2000s, Sierra Leone suffered political and social instability under an unstable government, due to a civil war which waged between 1991 and 2002. The mine did not operate from 1995 to 2005.
Since mining resumed during 2006, the mine operated at modest rates and SRL has prepared a number of studies looking at ways to extract maximum value from the 17 deposits with reported resources. More recently in January 2011, SRL reported Measured and Indicated Resources of 441 Mt containing 1.29% recoverable rutile.
SRL mines with a large bucket line dredge from the Lanti deposit at 1,000 t/h) to produce 60,000 to 70,000 t of rutile per year. SRL aims to produce 200,000 t of rutile per year.
Snowden is joined on this project by Downer stable mates CPG-MT and CPG Australia. CPG-MT has experience in undertaking consulting studies, designing and constructing mineral processing plants and manufacturing processing equipment for mineral sands, coal and iron ore projects. CPG Australia specialises in analysing logistical requirements and designing systems for bulk materials movement.
The Snowden project team recently visited the SRL site and has since developed a number of strategic options for evaluation. Alternatives being reviewed include different throughput rates, different extraction sequences, and different approaches for each operational unit which include: mining methods (dredging and dry mining), concentrators (floating and land based), mineral separation plant (expansion, recovery improvement and product suite) and logistics (haulage by road, pumping or conveyor and product handling, storage and shipping).
Snowden’s unique strategic optimisation process uses the Mixed Integer Linear Program optimising platform, Evaluator, (developed in house) to identify the optimum combination of unit strategies to allow SRL to extract the maximum value from its project.
When the project is completed at the end of September, SRL will have an optimal direction forward which has considered a number of possible alternatives to capacity, sequence and method, knowing that the future work of adding detail to produce the life-of-mine plan will be based on a sound starting point – the optimum strategy delivering the most value.