Modern Mining July 2020

IRON ORE

optimised liner profile helped to increase the reduc- tion ratio in the second stage of crushing, ensuring a better distribution of reduction across all three crushing stages. The 28 mm diamond mesh on the top deck of the ST4.8 was replaced with a 30 mm square mesh which marginally improved throughput on this deck. The bottom deck also had a 5 mm piano wire replaced with a more conventional 10 mm square mesh which helped to control the final product and made sure there were no large pieces of flaky mate- rial finding its way into the product stockpiles. And finally, a controversial decision was made. They would “split the train”. This essentially meant that most of the material would be subject to dou- ble handling, an issue not taken lightly by anyone involved in crushing and screening due to the high costs involved. A safety stockpile was created by the first half of the train which consisted of the mobile jaw, scalper and cone crusher (LT106, ST2.8, and LT200HP), which meant that the second train of an additional cone crusher and triple deck sizing screen (LT200HP Short Head and ST4.8) always had material to crush, even when the first mobile train was not available. When the second section of the mobile train would have to be stopped, the first sec- tion could carry on crushing material to be stockpiled and then fed into the second section of the train. Operational benefits Many operators want to link as many mobile units as possible to try to optimise production but often, by separating the crushing stages, there are many operational benefits in terms of maintenance time and continuing crushing when unplanned downtime occurs. Separating the process also meant that the

exposed by one of the site operators. They noticed that the natural fines being scalped out from the rest of the material looked to have a slightly more ‘reddish’ tint. This pointed to the possibility that the natural fines in the ROM were richer in iron than the rest of the ROM stockpiles. If there was some way to blend the richer material with the less rich, crushed ore, each 170 t stockpile could be brought to a level of concentration that would be accepted by the client. With its industry- unique two-way split, the Metso ST2.8 could be used to provide a consistent supply of iron-rich natural fines which could be blended into stockpiles wher- ever needed. Suddenly a few thousand tonnes of useless material was available for sale at full contract price once again. More gains Averting two disasters may have been enough for some, but the determined people at FLRM felt there was more progress to be made. Production figures were good, an average total of 150 t per hour of -8 mm product meant that only the most advanced fine-tuning would yield improvements. They turned to the experts yet again for some assistance and ideas. Pilot Crushtec International’s 30 years of experience, with the help of Metso’s well trusted process simulation software, Bruno, led FLRM towards further 10-15% gains in production. Average hourly production increased up to 205 t per hour at peak with the plant averaging about 175 tph throughout the day. How did they do it? The following tweaks were made to the process. The standard course liner in the secondary cone crusher, the Metso LT200HP, was changed out for a standard medium liner. The

Average hourly production increased up to 205 t per hour at peak with the plant averaging about 175 tph throughout the day.

18  MODERN MINING  July 2020