Difference between revisions of "Benchmarking: Collahuasi ball mill model"

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(Created page with "==Benchmarking: Ball Mill Power Draw - Collahuasi== ''Villouta, R.M.'', '''Collahuasi: After years of operation''', Proceedings of the International Autogenous and Semiautogen...")
 
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Latest revision as of 16:57, 31 May 2014

Benchmarking: Ball Mill Power Draw - Collahuasi

Villouta, R.M., Collahuasi: After years of operation, Proceedings of the International Autogenous and Semiautogenous Grinding Technology conference (SAG 2001), Vancouver, Canada, Pages I-31 – I-42

  • Ball mill dimensions 22 ft diameter by 36 ft (35.5 ft effective grinding length)
  • shell-supported, flat ended mills
  • twin-pinion drive
  • Synchronous fixed speed motor size 4850 kW (with pinion)
  • Mill speed originally 74% of critical, later changed to 78% of critical.
  • Ball charge 35% v/v (retaining ring)
  • DCS power draw originally 8900 kW, rose to 9200 kW

Assumptions:

  • ore density 2.6 t/m3
  • liner thickness 6 inches
  • slurry 70% solids
  • motor efficiency (efficiency to DCS value) 0.942 (author's notes from a site visit)
DCS Power, kW Speed, %

of critical

Mill filling Morrell Model, kW Nordberg model, kW

(no density correction)

Nordberg model, kW

(density correction)

original 8900 74% 35% v/v 9044 (+1.6%) [deduct 5%] 8183 (-8.8%) [deduct 5%] 8717 (-2.1%)
later 9200 78% 35% v/v 9655 (+4.9%) [deduct 5%] 8890 (-3.5%) [deduct 5%] 9471 (+2.9%)

All power values relative to DCS.

Discussion

The Nordberg models aren't really set up for flat-ended mills; the empirical basis of Nordberg models are cone-ended mills. Literature suggests a typical 5% factor be applied to convert a flat-ended mill (shell-supported) to a cone (trunnion-supported). The values in the table deduct 5% from the raw values shown in the Nordberg model.

As this is a somewhat atypical mill configuration, the Overflow ball mill using full Morrell C-model is recommended as the cone angle is a parameter of the equations. It is possible to get the Nordberg model to mimic the 5% reduction shown above (by modifying the mechanical efficiency factor), but not recommended.