Difference between revisions of "Benchmarking: Bond - Cadia East"
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The mill load, ball charge and pulp density was tweaked to mimic these power draws, corresponding to: |
The mill load, ball charge and pulp density was tweaked to mimic these power draws, corresponding to: |
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* SAG operating 9% v/v balls, 25.5% v/v total filling and 78% of critical speed (Austin model has fixed %solids) |
* SAG operating 9% v/v balls, 25.5% v/v total filling and 78% of critical speed (Austin model has fixed %solids) |
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| − | * ball mills operating 37% v/v total filling and 70% w/w solids (fixed speed mills, 72% speed) |
+ | * ball mills operating 37% v/v total filling and 70% w/w solids (fixed speed mills, 72% of critical speed) |
| − | The ball load required to match the reported power draw is very high, and could only be achieved with a significant reduction in the trunnion diameter (using ball retaining rings). Moreover, the motors are predicted to be operating at 100.5% of their rated output power to |
+ | The ball load required to match the reported power draw is very high, and could only be achieved with a significant reduction in the trunnion diameter (using ball retaining rings). Moreover, the motors are predicted to be operating at 100.5% of their rated output power to achieve the indicated power draw. |
===Model results=== |
===Model results=== |
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| Line 43: | Line 43: | ||
! E<sub>ball</sub> |
! E<sub>ball</sub> |
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! E<sub>total</sub> |
! E<sub>total</sub> |
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| + | ! Throughput |
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|- |
|- |
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| Model |
| Model |
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| − | | 12. |
+ | | 12.31 kWh/t |
| − | | |
+ | | 14.94 kWh/t |
| 27.7 kWh/t |
| 27.7 kWh/t |
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| − | | |
+ | | 1243 t/h |
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|- |
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| Measured |
| Measured |
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| Line 57: | Line 58: | ||
|- |
|- |
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| Difference |
| Difference |
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| − | | 1. |
+ | | 1.71 kWh/t |
| − | | 1. |
+ | | 1.74 kWh/t |
| 3.9 kWh/t |
| 3.9 kWh/t |
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| − | | - |
+ | | -239 t/h |
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|- |
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| Difference |
| Difference |
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| − | | |
+ | | 16.13% |
| − | | |
+ | | 13.18% |
| − | | 16% |
+ | | 16.39% |
| − | | -13% |
+ | | -16.13% |
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|} |
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| + | |||
| + | <gallery> |
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| + | File:CadiaEast.png|thumb|Cadia East circuit |
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| + | File:CadiaEast-SAG.png|thumb|Cadia East SAG mill |
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| + | File:CadiaEast-BM.png|thumb|Cadia East Ball mill |
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| + | File:Cadia-Pebble.png|thumb|Cadia East Pebble crusher |
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| + | </gallery> |
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| + | |||
| + | The predicted transfer size needed to balance the power draw between primary & second mills is very coarse, 5 mm. |
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| + | |||
| + | ===Discussion=== |
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| + | There is a substantial difference between the survey and the predictions. Some observations: |
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| + | * The rod mill work index was determined on an apparatus with smooth liners. This can cause a difference of 2-3 kWh/t versus the wave-liner apparatus specified by Bond. Using a rod mill work index of 24.0 kWh/t gives E<sub>total</sub> = 26.8 kWh/t; still 13% high. |
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| + | * The E<sub>ssbm</sub> predicts the energy required for a "standard" secondary crushing & ball milling plant that is believed to be one of the most energy efficient types of grinding circuits. This ore has E<sub>ssbm</sub> = 24.3 kWh/t which is still less than the survey E<sub>total</sub>. Very odd result that a SABC circuit is more efficient than an SSBM (ergo, HPGR) circuit on such a hard ore. |
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Latest revision as of 00:55, 22 May 2020
Contents
Benchmarking: Bond/Barratt - Cadia
Engelhardt, D., Robertson, J., Lane, G., Powwel, M.S. and Griffin, P., Cadia Expansion - From open pit to block cave and beyond. Proceedings of MetSoc 2012.
Design criteria and plant trial of underground Cadia East ore
Ore characterization
- blased underground ore, secondary crushed to 80 mm.
- WiC = 30 (metric)
- WiRM = 26.5 (metric)
- WiBM = 21.4 (metric)
- DWI = 9.9
- density = 2.7 t/m³
The ore was reported blasted undergrond (block caving had not yet started). Particle size distribution given as two points which confirm a Bond-compatible "root-2" PSD.
- 80% passing 80 mm
- 20% passing 5 mm
Modelling
Details of the mill operating conditions are not given, but the power draw at the shell is given.
- 15.737 MW SAG mill power draw
- 19.509 MW ball mill power draw
Circuit operating conditions:
- F80 = 80 mm
- P80 = 140 µm
- instantaneous throughput = 1482 t/h
The mill load, ball charge and pulp density was tweaked to mimic these power draws, corresponding to:
- SAG operating 9% v/v balls, 25.5% v/v total filling and 78% of critical speed (Austin model has fixed %solids)
- ball mills operating 37% v/v total filling and 70% w/w solids (fixed speed mills, 72% of critical speed)
The ball load required to match the reported power draw is very high, and could only be achieved with a significant reduction in the trunnion diameter (using ball retaining rings). Moreover, the motors are predicted to be operating at 100.5% of their rated output power to achieve the indicated power draw.
Model results
| ESAG | Eball | Etotal | Throughput | |
|---|---|---|---|---|
| Model | 12.31 kWh/t | 14.94 kWh/t | 27.7 kWh/t | 1243 t/h |
| Measured | 10.6 kWh/t | 13.2 kWh/t | 23.8 kWh/t | 1482 t/h |
| Difference | 1.71 kWh/t | 1.74 kWh/t | 3.9 kWh/t | -239 t/h |
| Difference | 16.13% | 13.18% | 16.39% | -16.13% |
Cadia East circuit
Cadia East SAG mill
Cadia East Ball mill
Cadia East Pebble crusher
The predicted transfer size needed to balance the power draw between primary & second mills is very coarse, 5 mm.
Discussion
There is a substantial difference between the survey and the predictions. Some observations:
- The rod mill work index was determined on an apparatus with smooth liners. This can cause a difference of 2-3 kWh/t versus the wave-liner apparatus specified by Bond. Using a rod mill work index of 24.0 kWh/t gives Etotal = 26.8 kWh/t; still 13% high.
- The Essbm predicts the energy required for a "standard" secondary crushing & ball milling plant that is believed to be one of the most energy efficient types of grinding circuits. This ore has Essbm = 24.3 kWh/t which is still less than the survey Etotal. Very odd result that a SABC circuit is more efficient than an SSBM (ergo, HPGR) circuit on such a hard ore.
