Pilot Crushtec Iron Ore Case Study
Companies who thrive in the African Mining Industry are the ones that learn how to turn extremely difficult conditions into lucrative opportunities. This takes levels of insight, vast amounts of practical experience and perseverance that are not easy to achieve. We spoke to Franco Le Roux Mining (FLRM) who have managed to find success in an application which would intimidate most mining contractors to see what separates them from the rest.
The opportunity was a contract for remining of an old, untouched ROM stockpiles at a large Iron Ore Mine. The contract was initially drawn up based on a few assumptions regarding the material properties, which were later proven to be quite far from reality. This could easily have spelled disaster for the project as it so often does, but some inspired thinking, along with the adaptability of Metso Lokotracks, helped FLRM navigate these obstacles seamlessly.
The assumption made regarding the material properties were that amongst the ROM stockpiles meant for remining, there would be an average of 37% natural fines (below -8mm) that could be recovered and sent directly to the smelter. With this initial material description, the client specified a 3-tier approach to the project; phase 1 would involve recovery of just the natural fines through the use of a mobile scalper, phase 2 would incorporate a mobile jaw crusher to increase the fines generated for recovery by the mobile scalper and phase 3 would add two mobile cone crushers as well as a mobile sizing screen to ensure all material would pass -8mm.
Shortly after implementation of phase one, it became clear that the working assumptions from which the job was specified were just not the facts of the material properties. Instead of 37% natural fines on the product, the stockpiles were proving to contain between 17–22% of fines, about half of what was expected. Such a massive difference between the initial specification and reality would most often spell disaster for the viability of the contract due to the large tonnages which required crushing, but thanks to some foresight by the engineers who had already specified the process capabilities, a solution was already in the works, which meant that they would have to immediately skip to phase 3 — a fully mobile three-stage crushing and screening plant to achieve the required tonnages of end-product.
Fortunately, due to Pilot Crushtec’s high level of experience, planning and equipment stock holding, the full complement of machinery required — one mobile jaw crusher (Metso Lokotrack LT106), two mobile cone crushers (Metso Lokotrack LT200HP and LT200HP Short Head), and a triple deck mobile screen (Metso Lokotrack ST4.8) — were deployed to site within a few weeks of the problem being identified on-site. A crisis was swiftly averted, and Franco Le Roux Mining got back to doing what they had to do, putting -8mm crushed iron ore on the ground.
However, mining in Africa is never predictable nor simple and it did not take long for the ghost of the initial assumptions to come back and challenge FLRM Mining once again. Not only were there fewer natural fines in the ROM stockpiles than expected, but the concentration of iron within the ore was also proving lower than expected. This meant that many of the 170 ton stockpiles produced would not be accepted by the smelter, making all the crushing and screening being done on-site not produce sellable product.
After a few days of consultation, proposals, internal meetings and site visits, a unique idea was 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 ton stockpile could be brought to a level of concentration that would be accepted by the client.
With its industry-unique two-way split, it could be used to provide a consistent supply of iron-rich natural fines which could be blended into stockpiles wherever needed. Suddenly a few thousand tons of useless material was available for sale at full contract price once again.
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 tonnes per hour of -8mm 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 process simulation software, Bruno, led FLRM towards further 10–15% gains in production. Average hourly production increased up to 205 tonnes per hour at peak with the plant averaging about 175 tph throughout the day.
The standard coarse liner in the secondary cone crusher, the Metso LT200HP, was changed out for a standard medium liner. The optimised liner profile helped to increase the reduction ratio in the second stage of crushing.
The 28 mm diamond mesh on the top deck of the ST4.8 was replaced with a 30 mm square mesh. The bottom deck also had a 5 mm piano wire replaced with a 10 mm square mesh which helped to control the final product.
They also “split the train”, creating a safety stockpile between stages so the second train always had material to process. This reduced bottlenecks, improved uptime, and lowered fuel and wear costs.
Separating the process also meant that the first two stages of crushing could run at full capacity while the tertiary stage was not restricting output. This decreased the cost of production and increased residual value by reducing operating hours on primary equipment.
What FLRM Mining has experienced is that in a world of increasing uncertainty, plans can be turned on their heads at a moment’s notice when working with raw materials. Success depends on adapting quickly and being willing to innovate — even in the smallest details.
