The HIGmill comprises a mill body, shaft with grinding discs, shell mounted counter rings, gearbox, and drive. The grinding chamber is filled up to 70% with grinding beads. Rotating discs stir the charge and grinding takes place between beads by attrition. The number of discs (grinding stages) depends on the application and can be as high as 20. Feed slurry is pumped into the mill via the bottom connection. When the flow transfers upwards, it passes all consecutive grinding stages. The final product discharges into open atmosphere at the top of the machine.
Because of the tall and narrow vertical mill body arrangement, grinding media is evenly distributed and mineral particles remain in constant contact, significantly increasing grinding efficiency.
Energy efficiency
Gravity keeps the media compact during operation to ensure high intensity inter-bead contact, as well as efficient, even energy transfer throughout the volume. The disc configuration and the whole chamber geometry have been optimized for efficient energy transfer to the bead mass, internal circulation, and classification.
Largest industrial units in operation up to 5000 kW
The Outotec HIGmill comes in various drum diameters. The mill heights can be varied to optimize the media load and power input for specific applications. Chamber volumes range from 5 to 30,000 liters with corresponding drives from 5 to 5000 kW. The HIGmill is the only ultrafine grinding technology in commercial use that can use small-size high-density grinding media in mill sizes above 3000 kW.
On-line particle size optimization to maximize process efficiency
HIGmill offers a unique opportunity to optimize on-line product fineness. The control principle is to measure scalping cyclone feed quantity and adjust the mill shaft speed to reach target energy per total feed flow. Alternatively, particle size distribution is measured by the Outotec® PSI® on-line particle analyzer and the shaft speed adjusted to maintain constant product size.
A compact, simple installation and process
HIGmill has a less complex and more compact process layout and flow sheet than other stirred media mills. The process comprises just a scalping cyclone, feed tank and pump, and the mill itself. The benefit of high power intensity and vertical installation is a very small footprint. The head room over the mill is small and the flanged split-shell construction reduces the space needed for maintenance. The top-supported hanging arrangement keeps the floor and sides clear, simplifying maintenance and emptying the beads.
