The use of sensor-based sorting (SBS) technology is allowing Companhia de Ferro Ligas da Bahia (Ferbasa) to avoid unnecessary processing by separating a fraction of the high-grade material from the metallurgical process feed in advance, a recent case study from STEINERT has revealed.
Ferbasa is in Ipueira, a municipality in the state of Bahia in the northeast of Brazil. It operates one of the largest chromite mines in Brazil and is considered a pioneer in the use of SBS technology, STEINERT says. The company processes chromite obtained from an underground mine, with the extracted material pre-concentrated using sorting technology that employs sensors, and is later used in the production of specialised steel alloys.
With a processing capacity of 12 Mt/y, the company has been using sensor-based sorting for 10 years, in a completely dry process that separates waste from high-grade chromite.
Eriberto Nascimento Leite, Mining Director at Ferbasa, says the ability to avoid unnecessary processing by separating a fraction of the high-grade material from the metallurgical process feed in advance through the use of SBS removes the requirement for any additional processing. In that way, particles which are not economically viable are eliminated from the process beforehand with only valuable material undergoing the follow-on concentration steps.
At Ferbasa, the use of SBS technology has enabled an increase in production, in addition to reducing costs in the subsequent processes, such as comminution and the use of inputs, such as reagents.
“Today, at Ferbasa, sensor-based sorting technology helps us adopt ESG practices, reducing waste, maximising production efficiency and contributing to the conservation of natural resources,” Nascimento says.
Nowadays, it is not only the mined ore that is processed, but also the stockpiles, which contain considerable amounts of chromium. The treatment of these stockpiles is only possible thanks to process automation and its high-capacity levels, which reach up to 180 t/h. Stockpile treatment has the potential to increase productivity in the mine. In terms of resource use, there is potential to reduce the consumption of water, energy and chemical reagents primarily because SBS is a dry separation process, unlike other pre-concentration processes such as dense media separation.
Ferbasa has always used a pre-concentration process with the aim of separating lump ore, which has a high chromite content, from the low-grade ore that goes to the concentration plant. However, this used to be a manual separation process. Bartolomeu Fonseca, the former Processing Manager at Ferbasa, discovered an article about sensor-based sorting technology from STEINERT. In 2012, he prepared material to be sent for tests at STEINERT’s Test and Development centre in Germany, and these were deemed successful.
Ten years ago, when the first equipment was being installed, Ferbasa’s employees were sceptical about its capacity to support the adverse conditions in the mine. This is why STEINERT Latinoamericana, a subsidiary of STEINERT GmbH in Germany, offered a “try and buy agreement”. Over the years, the equipment’s high level of durability has been verified, resulting in the first unit still being in operation today, with a total of 34,000 hours of runtime.
“Looking back, it was not easy to apply the technology, but I decided to move forward because I believed that the technology could be effective,” Fonseca says. “Now, already retired, I am very proud of the legacy that I have left to the company. I had the full support from the mining director at that time, Wanderley Lins, but it was my responsibility to make it work.”
In 2014, during the commissioning of the first sorting system, a STEINERT XSS-T, STEINERT Latinoamericana started a partnership with Ferbasa.
Alonside this, STEINERT currently has a team of 30 collaborators who serve several mining clients in Latin America, in addition to having a test centre near the office in Brazil, enabling tests to be carried out with more convenience and efficiency for local clients.
Ferbasa started operating its first equipment in 2014. By 2019, it already had six units installed for the processing of run of mine and low-grade stockpiles.
The production benefits from flexibility of the sorting systems, which generate waste material, pre-enriched material and high-grade material. The processing capacities are up to 120 t/h for particles of 1- 3 in (25-76 mm), reaching up to 180 t/h for particles from 2-5 in. In terms of the sizes processed, the combination of sensors facilitates the separation of particles up to 5 in; a feature that, STEINERT says, reinforces the robustness and efficiency of the equipment for the detection and ejection of extremely coarse particles. In total, recoveries reach values of up to 90%, with upgrades of up to 1.5-3 times the feed levels.
Currently, Ferbasa applies SBS technology to process 100% of their run of mine, using two units from STEINERT, the STEINERT XSS T and STEINERT KSS | XT L, in a two-step process. In the first step, waste material is rejected, and, in the second, pre-enriched and high-grade materials are generated. The high grade-material meets the content specifications to be sent to the metallurgic plant, while the pre-enriched material is sent to another plant to follow other concentration procedures. Furthermore, the technology is applied in the processing of low-grade stockpiles, using two STEINERT KSS | XT L units – which combines the X-ray transmission sensor with three other additional sensor options (Induction, 3D laser, and Colour) – in two steps to separate waste, pre-enriched material and high-grade material. As a result, the low-grade stockpiles are processed in an economically viable way and with high sustainability gains.