Alex Doll: Created page with "==Benchmarking: Ball Mill Power Draw - Collahuasi== ''Villouta, R.M.'', '''Collahuasi: After years of operation''', Proceedings of the International Autogenous and Semiautogen..."

2014-05-31T15:57:46Z

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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==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/m<sup>3</sup>
* liner thickness 6 inches
* slurry 70% solids
* motor efficiency (efficiency to DCS value) 0.942 (author's notes from a site visit)

{| class="wikitable" border="1"
|-
!
! 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.

Benchmarking: Collahuasi ball mill model - Revision history

Alex Doll: Created page with "==Benchmarking: Ball Mill Power Draw - Collahuasi== ''Villouta, R.M.'', '''Collahuasi: After years of operation''', Proceedings of the International Autogenous and Semiautogen..."