Putting HPGR technology through its paces.

An FLSmidth HPGR pilot test machine was run between 2011 and 2012 at the Kennecott Utah Copper mine, USA. The plant was an open-circuit, single-pass HPGR with no direct edge recycle or fines screening. Screening was done at 25 mm and the product was transported to a stockpile by conveyor belt. The pilot circuit produced 72-109 t/h, depending on the roll speed set-point. Metal protection was installed on the belt feeder under the grizzly screen bin before the cone crusher and on the conveyor delivering feed to the HPGR feed bin. Variations in roll speed, grinding pressure, feed-gate position, and feed top size were tested. The HPGR product was tested for particle size distribution, Bond's work index, moisture content, and micro-fracturing. Evaluation was also carried out of: base material of the roller tyre; tungsten carbide stud grade, arrangement, size, and shape; means of stud attachment to the roller tyre; comparison of studded and smooth tyres; and roller tyre variations. There was found to be a direct linear relationship between the roll speed and machine throughput, and power draw had a direct linear relationship with the specific pressure. Optimum specific pressure was around 4 000 kN/m2, at which point a roll speed of 1.2 m/s achieved maximum throughput of 125 t/h with a power consumption of 1.8 kWh/t.
An FLSmidth HPGR pilot test machine was run between 2011 and 2012 at the Kennecott Utah Copper mine, USA. The plant was an open-circuit, single-pass HPGR with no direct edge recycle or fines screening. Screening was done at 25 mm and the product was transported to a stockpile by conveyor belt. The pilot circuit produced 72-109 t/h, depending on the roll speed set-point. Metal protection was installed on the belt feeder under the grizzly screen bin before the cone crusher and on the conveyor delivering feed to the HPGR feed bin. Variations in roll speed, grinding pressure, feed-gate position, and feed top size were tested. The HPGR product was tested for particle size distribution, Bond's work index, moisture content, and micro-fracturing. Evaluation was also carried out of: base material of the roller tyre; tungsten carbide stud grade, arrangement, size, and shape; means of stud attachment to the roller tyre; comparison of studded and smooth tyres; and roller tyre variations. There was found to be a direct linear relationship between the roll speed and machine throughput, and power draw had a direct linear relationship with the specific pressure. Optimum specific pressure was around 4 000 kN/m2, at which point a roll speed of 1.2 m/s achieved maximum throughput of 125 t/h with a power consumption of 1.8 kWh/t.