According to FLS global product line manager for vertical regrind mills Peter Wulff, growing pressure to reduce energy consumption in mining operations is increasing the focus on technologies such as vertical grinding mills.

Although vertical mills, in which material is broken down through attrition rather than impact, have long been part of full-flowsheet provider FLS’s comminution portfolio, the company says it continues to advance this technology to enhance metal recovery and support sustainability objectives.

“As miners seek ways to maintain or improve recoveries from deposits whose ore grades are in decline, vertical grinding mills offer the advantages of internal classification and energy savings in one compact footprint,” says Wulff.

“The vertical orientation of the grinding chamber means that the basic laws of physics work in our favour to minimise overgrinding as finer particles can be discharged from the mill quickly, while coarser particles are held inside the grinding media charge until further reduced in size. This allows finer grinding while consuming less energy than traditional horizontal ball mills for the same duty,” explains Wulff.

Vertical mills are said to achieve as much as 25% to 30% energy saving, compared to horizontal mills. With certain deposits, such as copper, iron, and lead-zinc bearing ores, this increases the profitability of recovery in the downstream flotation process.

The FTM tower mill from FLS features a central agitator screw, which is the only moving component in contact with the slurry and steel media. This helps reduce energy and media consumption in hard ore applications while also minimising water use in secondary and tertiary grinding as a result of the high concentration of solids in the feed. The robust design of components and wear materials are designed to provide higher operational availability, supported by intelligent operations management software to maximise circuit performance.

The company’s VXPmill vertical grinding technology uses ceramic media rotated by a variable speed disc assembly allowing it to be customised to specific grinding duties. This vertical ceramic media stirred mill is used for finer grinding applications and can achieve product sizes below 20 micron. The system uses a modular impeller with removable discs and spacers to adjust the number of discs in operation to suit the target product size while avoiding excess energy consumption.

The reduced footprint of vertical grinding mills in comparison to horizontal mills, is an additional advantage in a process plant, helping to support space optimisation, while also requiring less costly civil engineering infrastructure for its base. “This lends the technology to easier retrofitting into an existing plant, especially where there are space constraints,” says Wulff.

Capital expenditure is also lowered as a result of components being factory tested and pre-assembled for rapid on-site erection – which translates to shorter lead times for installation and commissioning. Wulff highlights how these factors, combined with energy efficiency and high uptime, contribute to the lowest total cost of ownership.

The company says that a recent indication of the popularity of this technology was an order from a customer in India for 18 of FLS’s FTM-5000 vertical tower mills – reported to be the largest order yet for FLS and the wider industry. The mills will serve what is set to become one of the world’s most efficient iron-ore beneficiation plants.