Difference between revisions of "Benchmarking: Collahuasi ball mill model"
(Created page with "==Benchmarking: Ball Mill Power Draw - Collahuasi== ''Villouta, R.M.'', '''Collahuasi: After years of operation''', Proceedings of the International Autogenous and Semiautogen...") |
(No difference)
|
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.