The 1600 kW vertical stirred HIGmill™ from STM was installed and commissioned in July 2019 at the brownfield Santa Elena plant in Mexico. In this case it’s not a typical regrind application, but a secondary grinding application, since the feed (ore) is coming from the ball mill cyclone overflow. The grinding duty is from 150 µm (F80) to 50 µm (P80).
To prevent overgrinding during the first months of operation, Santa Elena requested an enormously reduced power draw of the mill; which was indeed achieved and demonstrates one aspect of the immense operational flexibility of the STM vertical grinding mills.
Together with the installation of this 1600 kW vertical stirred mill, also anew variable speed drive was added to the existing 2200 kW ball mill. The combination of the variable speed ball mill and the new vertical stirred mill produced with the equal amount of energy if not less a P80 of 50 – 60 µm, compared to the previously achieved P80 of around 76 µm with only the ball mill circuit; this clearly demonstrates the energy efficiency of the unique selective grinding mechanism in STM’s vertical stirred mill in open circuit, compared to the conventional ball mill in closed circuit.