Swiss Tower Mills Minerals AG (STM) was founded in 2011 to introduce the well proven fine grinding technology of industrial minerals to the mining industry. Today more than 200 grinding mills are operating today to grind industrial minerals with truly minimized energy requirements; over 30 units are currently operating in the hard rock mineral processing industry. STM’s technology enables the mining industry to profit from more than 40 years of development and operational experience in fine and ultra-fine grinding.

In the meantime, the HIGmill™ has been accepted by the hard rock mineral processing market. Numerous tests have been successfully performed, both laboratory or on site. STM has received several orders from very small test and pilot mills, up to several large 6.5 MW HIGmills. A 700 kW HIGmill for a copper concentrate regrind application at the Kevitsa mine in Finland has been commissioned in February 2015 and is operating successfully; both the copper recovery and the copper grade in the final copper concentrate have been increased significantly, where at the same time the nickel grade in the final copper concentrate has been reduced. Other HIGmillsTM are in Operation now in a copper and in a platinum concentrator.

Declining ore grades and more complex ore bodies lead to a clear trend for fine grinding. Fine grinding technology has already been used for more than half a century in the ceramics, pigment, paint, paper and pharmaceutical industries. The unique grinding technology, which Swiss Tower Mills Minerals AG offers for the mineral processing industries, has been well proven over more than 40 years in the industrial mineral segment: over 200 fine and ultra-fine grinding mills are in operation, with a total installed power of over 300 MW. The largest units in operation have each an installed motor power of 5 MW. Swiss Tower Mills Minerals AG has made this exceptional grinding technology available to the mineral processing industry.

The ceramic grinding beads in the mill shell are put in motion by the grinding rotors which are mounted on the mill shaft. The mill shaft is powered by a motor and gearbox arrangement. The high packing density of the grinding media produces strong friction, which causes efficient grinding of the product. The variable speed of the milling shaft allows for an energy efficient grinding process to reach the required product particle size.

The feed material is supplied as a slurry from below by a feed pump. The mineral particles, which become smaller during the grinding process, rise up in the mill cylinder and leave the mill via a natural overflow on top. Gravity supports to retain the grinding beads, which have a higher density than the slurry, in the milling chamber.

The fineness of the final product (slurry) is adjustable through the following factors:

• Feed rate
• Slurry concentration
• Amount of grinding beads
• Speed of the mill shaft

The HIGmill™ provided the following process related advantages:

• Steep particle distribution curve (PSD) without external classification
• Single pass grinding (no re-circulating loads)
• Flexibility to handle conveniently process variables as:
  • Fluctuation of slurry feed rate
  • Fluctuation of particle feed sizes
  • Feed slurry consistency / ore characteristics
  • Required product size
• Simple flow sheet leads to cost reduction
• Relative small pumps (no re-circulating loads)

Both CAPEX and OPEX are significantly minimized with this regrind mill technology.

The HIGmill™ cover a wide range of applications for fine and ultra-fine grinding, such as:

• Concentrate regrinding (gold, copper, moly, platinum, lead, zinc, ...)
• Iron ore fine grinding
• Tailings regrinding
• Slag & fly ash grinding for recovery of recyclable metals