the benefits of better classification in grinding circuits
TRANSCRIPT
© 2016 Derrick Corporation
The Benefits of
Better Classification
in Grinding Circuits
Eng. David Perkins – Derrick Corp
Global Average Concentrator
Energy Consumption
0,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1995 2000 2005 2006 2007 2008 2009 2010 2011 2012
Energy/Ton Milled
Energy/Ton Conc
• Grades Decreasing
• Finer Grains
• Harder Ore
• Complex Minerology
• HSE Compliance
Why?
0,5
0,6
0,7
0,8
0,9
1
1,1
1,2
1995 2000 2005 2006 2007 2008 2009 2010 2011 2012
Energy/Ton Milled
Energy/Ton Conc
Mill – Cyclone Grinding CircuitThe Most Energy Intensive Unit Operation in Mining Today
Mill
Cyclone
Cyclone is easy to operate and can accommodate flowrate variations
It is inefficient
30-45% of product size returns back to mill
• Material overground
• Decrease flotation Recovery
• Increases power consumption
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Mill – Cyclone (100 tph)
Every 100 tons of product generates
Remilling 90 tons of material that is already product size
80t of -75um
80%-75um100t
400t
90t of -75um30%-75um 300t
100t
Classification efficiency is only 50%
Circulating load = 300%
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Mill – Screen (100 tph)
Circulating load = 100%
Classification efficiency 85-95%
Remilling 10 tons of material that is already product size
Every 100 tons of product generates
10t of -75um 100t
100t
10%-75um
200t
80t of -75um
80%-75um
100t
Separation Comparison
P80=70um
Hydrocyclone Derrick ® Stack-Sizer®
P80
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Under and Overgrinding
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Overgrinding Effects
Rougher flotation feed
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Undergrinding Effects%
Ch
alc
op
yri
teRougher flotation tailings
CS MiningCopper Mine in USA
• Supplemented Cyclones with Derrick ® Stack
Sizers® and 100 micron panels
• Recovery Increase by 40% (50% to 70%)
• Maintained Concentrate Grade.
Sociedad Minera El BrocalPb/Zn Mine/Mill in Peru
• Primary Classification with Cyclones
• Circulating Load 350%
• Capacity 145 tph
• Pb Recovery 63%
• Zn Recovery 73%
Sociedad Minera El BrocalPb/Zn Mine/Mill in Peru
Sociedad Minera El BrocalPb/Zn Mine/Mill in Peru
• Cyclones Replaced by Derrick ® Stack Sizer ®
and 230 micron panels
• Circulating Load 60%
• Idled 1 of 3 Ball Mills
• Capacity 245 tph
• Pb Recovery 71%
• Zn Recovery 78%
Sociedad Minera El BrocalPb/Zn Mine/Mill in Peru
OJSC ApatitPhosphate Mine/Mill in Russia
• Cyclones used as Primary Classifiers
• P80 = 190 microns
• Circulating Load 400%
OJSC ApatitPhosphate Mine/Mill in Russia
• Replaced Cyclones using Derrick ® Stack Sizer ®
with 390 micron panels
• Capacity increase by 30% - 60,000 tpd (total)
• P80 = 240 microns
• Circulating Load 135%
• Cost per Ton Down by 20%
KMArudaIron Mine/Mill in Russia
• Replaced Cyclones with Derrick ® Stack Sizers®
and 100 micron panels
• Increased Capacity by 20%
• Reduced Circulating Load from 215 to 130%
• Idled 1 of 2 Ball Mills
• Recovery Increased from 82.2 to 84.6%
• Maintained Concentrate Grade
KMArudaIron Mine/Mill in Russia
KMArudaIron Mine/Mill in Russia
Plant examples
• Nexa Resources – Vazante
• Hydro – Paragominas
• Taboca – Pitinga
• Nexa Resources – Cerro Lindo
• Esan – Balya
• South India Iron Ore
• Glencore – Iscaycruz
• Penoles – Saucito I & II
• Many many more
A few comments about classification…
• 300 to 400% circulating loads are common with
cyclone classification to minimize overgrinding.
• Even so, overgrinding is a common
characteristic of cyclone circuits.
• Circulating loads of around 100% are common
with screen circuits and overgrinding is
minimized, thus driving efficiencies.
• Today limitations for screens have centered
around capacity.
© 2016 Derrick Corporation
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Field trial
completed at
American Silica in
USA
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Current 5-deck
Stack Sizer
(1.22 m wide)
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New 8-deck
SuperStack
(1.42 m wide)
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SuperStack
compared to
Stack Sizer
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© 2016 Derrick Corporation. All rights reserved. Derrick and all its products indicated by trademark symbols are trademarks and/or registered trademarks of Derrick Corporation.
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