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High intensity grinding mills by Outotec

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The High Intensity Grinding (HIG) mill from Outotec has been designed specifically to manage complex, fine-grained ore bodies that are rapidly becoming more economically viable.

Complex ore bodies require a finer grind size for maximum mineral recovery and grade, setting new challenges particularly for grinding technology. Utilised and proven for more than 30 years, the technology has been further developed, resulting in the HIGmill now being available in the minerals processing industry.

The HIGmill is highly adaptable, making it suitable for a wide variety of processes while also meeting energy efficiency challenges with minimised energy usage of up to 40-50% compared with traditional ball mills. Over 260 HIGmills have been commissioned and proven in the marketplace.

The mill finds application in the regrinding of concentrates. The flows from these types of upstream processes can vary considerably due to fluctuations in ore grade and quality, as can the target fineness due to variations in the ore mineralogy. Flow fluctuations in the mill can be dampened by maintaining the net energy constant via control of the mill shaft speed. Product fineness is also controlled by adjusting the shaft speed and power input.

Operational range can be optimised by changing volumetric media filling, bead size and/or bead material.

Grinding efficiency

In a typical application, the HIG process begins with the circuit feed being pumped to a scalping cyclone upstream of the mill, which ensures a tighter product specification and defines the pulp density. The defined underflow is then mixed with water to optimal grinding density and pumped into the mill at base level. The slurry enters a grinding chamber containing grinding media and rotating discs, which provide momentum to stir the charge against a series of static discs.

As the flow transfers upwards, the ore slurry passes through the rotating discs and the free space between the static counter discs lining the wall. Due to the vertical arrangement of the mill, classification is conducted simultaneously throughout the grinding process with larger particles remaining longer at the peripheral, while smaller particles move upwards. The process is typically a single pass with no external classification necessary. With the grinding media evenly distributed, the ore particles remain in constant contact, significantly increasing grinding efficiency.

Energy efficiency

Gravity keeps the media compact during operation, ensuring high intensity, inter-bead contact and efficient, even-energy transfer throughout the volume. The disc configuration and the whole chamber geometry have been optimised for efficient energy transfer to the bead mass, internal circulation and classification.

Key features of Outotec High Intensity Grinding mill:

  • Installed power up to 5,000kW makes it one of the largest fine grinding units in the marketplace
  • Mill heights can be varied to optimise the media load and power input for specific applications
  • Chamber volumes range from 400 to 27,500 litres with corresponding drives from 132 to 5,000kW
  • Capability to use small size high density grinding media in mill sizes above 3,000kW
  • Optimises product fineness on-line
  • Compact design with very small footprint allows easy installation and simplifies maintenance
  • Addresses a wide range of grinding applications due to adaptability to fluctuating process conditions
  • Drum segments and wear components specifically designed to make maintenance simple and quick
The mills are available with or without a mounting frame depending on the project needs. Mills in brown field projects are typically supplied with a frame, while mills in green field projects are integrated into the concentrator building.

Components of the High Intensity Grinding (HIG) mill:

  • Scalping cyclone with feed pump
  • Feed, mixing and storage tanks
  • Feed pump
  • Media addition systems for grinding media
  • Motor and drive components
  • Gearbox and oil supply system
  • All instrumentation, controls and motor control centre
  • PLC control with human machine interface (HMI)
  • Vertical process package engineering and plant model

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