From FAG …From FAG …(fully)(fully)
to SAG …to SAG …(semi)(semi)
to BAG !to BAG !(barely)(barely)
The Theoretical Rationale behindThe Theoretical Rationale behindCURRENT TRENDS IN OPERATING PRACTICECURRENT TRENDS IN OPERATING PRACTICE
OF SEMIAUTOGENOUS GRINDING OPERATIONSOF SEMIAUTOGENOUS GRINDING OPERATIONS
Dr. Jaime E. SepúlvedaDr. Jaime E. SepúlvedaMolyMoly--Cop Grinding SystemsCop Grinding Systems
� Feed the mill with large rocks (up to 10”-12”), so avoiding the traditional crushing, classification and multiple storage stages of intermediate size particles.
� Use these rocks as a ‘zero-cost’ grinding media: Autogenous Grinding.
� Add large diameter steel balls (up to 6”):
� The concept ofAUTOGENOUS GRINDING was born from the idea of avoiding the use and
Basic ConceptsSEMIAUTOGENOUS GRINDING
Basic ConceptsSEMIAUTOGENOUS GRINDING
� Add large diameter steel balls (up to 6”): Semiautogenous Grinding.
� Considering that rocks are lighter than balls, it was assumed (wrongly?) that such rocks should fall from the highest possible position and therefore, SAG mills adopted their typical “pancake” shape: D>L.
avoiding the use and consumption of steel grinding balls, by replacing them with the same rockscontained in the fresh feed ore.
Alternative Circuit ConfigurationsSINGLESTAGE GRINDING (FAG or SAG)
Alternative Circuit ConfigurationsSINGLESTAGE GRINDING (FAG or SAG)
ProductProduct
WaterWater
FeedFeed
Alternative Circuit ConfigurationsDOUBLESTAGE GRINDING (DSAG)Alternative Circuit Configurations
DOUBLESTAGE GRINDING (DSAG)
WaterWaterFeedFeed
ProductProduct
WaterFeedFeed
LargeLarge(> 4”)(> 4”)
Do they Do they Grind?Grind?
ROCKSROCKSDo theyDo theygrind grind
themselves?themselves?
Are they Are they ground by ground by media?media?
Yes, Yes, less thanless thanBallsBalls
YesYesNoNo
Semiautogenous GrindingSemiautogenous GrindingWHICH WOULD BE THE ACTUALWHICH WOULD BE THE ACTUAL
ROLE OF THE ‘ROCKS’?ROLE OF THE ‘ROCKS’?
Semiautogenous GrindingSemiautogenous GrindingWHICH WOULD BE THE ACTUALWHICH WOULD BE THE ACTUAL
ROLE OF THE ‘ROCKS’?ROLE OF THE ‘ROCKS’?� The mid size rocks, denominated Critical Sizes or Pebbles do not act as grinding media and they do notallow themselves to be ground.
� They use up space in the charge affecting the productivity of the mill.
� As a corrective measure, it has been
MediumMedium(2” to 4”)(2” to 4”)
SmallSmall(< 2”)(< 2”)
BallsBalls
VeryVerylittle !little !
NoNo
Very Very little !little !
Little ! Little ! requirerequire
large ballslarge balls
NoNoYesYes
measure, it has been arranged for such Pebbles to leave the charge through the mill grate, classifying and crushing them by conventional methods.
Alternative Circuit ConfigurationsAlternative Circuit ConfigurationsDOUBLESTAGE GRINDINGDOUBLESTAGE GRINDING
WITH PEBBLE CRUSHING (SABCWITH PEBBLE CRUSHING (SABC--1)1)
Alternative Circuit ConfigurationsAlternative Circuit ConfigurationsDOUBLESTAGE GRINDINGDOUBLESTAGE GRINDING
WITH PEBBLE CRUSHING (SABCWITH PEBBLE CRUSHING (SABC--1)1)
WaterWater
ProductProductPebblesPebbles
WaterWaterFeedFeed
WaterWater
ProductProductPebblesPebbles
Alternative Circuit ConfigurationsAlternative Circuit ConfigurationsDOUBLESTAGE GRINDINGDOUBLESTAGE GRINDING
WITH PEBBLE CRUSHING (SABCWITH PEBBLE CRUSHING (SABC--2)2)
Alternative Circuit ConfigurationsAlternative Circuit ConfigurationsDOUBLESTAGE GRINDINGDOUBLESTAGE GRINDING
WITH PEBBLE CRUSHING (SABCWITH PEBBLE CRUSHING (SABC--2)2)
WaterWaterFeedFeed
� Since Fully Autogenous Grinding (FAG) was first proposed, early last century, there has been a continuous evolution in operational practices with regard to:� The addition of increasing amounts of steel balls
as ancillary grinding media,� The sustained increment in diameter of such
balls,� The removal and crushing of the critical sizes
(pebbles) that otherwise would accumulate in the load and …The pre-crushing (elimination) of either the
� With time, the fully AUTOGENOUS option has been gradually diverting from its original conception to
load and …� The pre-crushing (elimination) of either the
larger rocks or the intermediate particle size fractions contained in the fresh feed ore.
� Consequently, little is left today of the original intention of using the larger rocks as autogenousgrinding media for the smaller particles.
� This presentation is aimed at illustrating the theoretical rationale behind the observed current trends in SAG operating practices, with the aid of Moly-Cop Tools 2.0.
diverting from its original conception to become nowadays just a simple case of a poorly operated CONVENTIONAL BALL MILL …
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Software for the Analysis of
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Mineral Grinding
Processes
Processes
Processes
Processes
Processes
Processes
Processes
Processes
2.0
My Grandpa made it!
MolyMoly--Cop ToolsCop ToolsMolyMoly--Cop ToolsCop Toolsis available is available free of chargefree of charge to to
all interested partiesall interested [email protected]@molycop.cl
0.100
1.000
SiE
Balls on Particles Rocks on Particles Self-Breakage Overall
Theoretical BackgroundSPECIFIC SELECTION FUNCTION,
ton/kWh
Theoretical BackgroundSPECIFIC SELECTION FUNCTION,
ton/kWh
� The model included in Moly-Cop Tools was first published at the SAG 2001 Conferenceby J. E. Sepúlveda, “A Phenomenological Model of Semi-Autogenous Grinding Processes in a Moly-Cop Tools Environment”, Vol. 4, pp. 301-315, Vancouver, Canada.
� After that, the model has been providing quite satisfactory
0.010
10 100 1000 10000 100000 1000000
Particle Size, microns
Squite satisfactory descriptions of actual SAG processes, in all cases where the proper plant and/or pilot scale data has been made available.
Simulation N° 0 Remarks Base Case Example
Ore Density, ton/m3 2.80
0.017 1000 ton/hr (all mills)0.9 40.00 % Solids
4 76.72 % - 100#167.0 P80
# of Cyclones 4.00 243 d50cDiameter 26.00 0.315 Bpf
Height 78.00 0.331 Bpw Mesh # Inlet 10.00 Opening Vortex 10.00 76.10 % Solids By-Pass Apex 5.00 D50/D Circ.
1000 ton/hr, Fresh FeedMesh # 1 131488 F80
Opening 304800 2.90 % Moisture By-Pass 0.000 D50/Ds 1.00 1
m 100.00 Upper 0 ton/hrSplit 0.00
Mesh # 1 1Opening 304800 Lower 0 ton/hrBy-Pass 0.000 0.00 % of Feed 369 ton/hr D50/Ds 1.00 2.90 % Moisture 36.91 % of Feed
m 100.00 2.90 % Moisture
61.50 % - 1/2" 61.50 % - 1/2"
2
F80 131488 % - 1.5" 58.97
Water, m3/hr 344
Diameter, ft 35.30 Grate ScreenLenght, ft 15.00 5 10
Speed, % Critical 78.00 76200 13335 Charge Level, % 26.00 0.070 0.017
Balls Filling, % 10.00 0.70 0.90
⊕⊕⊕⊕
⊕⊕⊕⊕
∅∅∅∅
1
2
Complex Circuit Simulation ... SABC-1Complex Circuit Simulation ... SABC-1
D50/D Circ. m % - 200# in psi 10.19 Load, %
Mill Discharge (Guess) 2.367 29.66 (Actual) 2.367
(Delta) 0.000
89 Water, m3/hr
475 2.00 # of Mills
Balls Filling, % 10.00 0.70 0.90 % Solids (slurry) 76.00 3.00 4.00
App. Density, ton/m3 3.331 % Solids 72.79 Gross kW 10093 % - 100# 21.26
kWh/ton 10.09 T80 6112 m3/hr 731
Mesh Opening Fresh Crushed CrushedFeed Pebbles 1 Pebbles 2
1 12" 304800 100.00 100.00 100.00 m3/hr, Water 2 8" 203200 97.60 100.00 100.00
Size Distributions
3 6" 152400 83.93 100.00 100.00 4 4.15" 101600 73.57 100.00 100.00 5 2.95" 76200 67.87 100.00 100.00 6 2.1" 50800 62.82 100.00 100.00 7 1.48" 38100 58.97 100.00 100.00 8 1.05" 26670 53.78 98.07 98.07 9 0.742" 18850 49.78 90.24 90.24
10 0.525" 13335 42.74 61.50 61.50 11 0.371" 9423 38.32 48.04 48.04 12 3 6680 34.00 31.84 31.84 13 4 4699 29.28 23.55 23.55 14 6 3327 25.65 18.08 18.08 15 8 2362 22.57 14.32 14.32 16 10 1651 20.19 11.53 11.53 17 14 1168 18.16 9.20 9.20 18 20 833 16.79 7.80 7.80 19 28 589 15.65 6.65 6.65 20 35 417 14.66 5.74 5.74 21 48 295 13.79 5.06 5.06 22 65 208 12.84 4.43 4.43 23 100 147 12.01 3.96 3.96 24 150 104 11.12 3.50 3.50 25 200 74 10.28 3.10 3.10
19.00 Diameter, ft 24.00 Lenght, ft 76.00 Speed, % Critical 38.00 Charge Level, % 38.00 Balls Filling, %
% Solids 60.01 72.00 % Solids (slurry) m3/hr 1723 5.395 App. Density, ton/m3
4631 Gross kW 9.26 kWh/ton
Current Min/Max RemarksSAG Power, kW 10093 11500 OKPebbles, ton/hr 369 400 OKBM Power, kW 4631 3730 KOProduct Size, P80 167.0 185.0 OKPump Capacity, P*Q 17554 30000 OKTotal Water, m3/hr 1470 2000 OK
PROCESS RESTRICTIONS
� In conjunction with other unit operation models, such as Conventional Ball Milling, Hydroclassification, Screening and Crushing, the referred SAG model can be applied, with Moly-Cop Tools, to represent fairly complex circuit arrangements.
1189 ton/hr, Fresh FeedMesh # 1 131488 F80
Opening 304800 2.90 % Moisture By-Pass 0.000 D50/Ds 1.00 1
m 100.00 Upper 0 ton/hrSplit 0.00
Mesh # 1 1Opening 304800 Lower 0 ton/hrBy-Pass 0.000 0.00 % of FeedD50/Ds 1.00 2.90 % Moisture
m 100.00 2
61.50 % - 1/2"
2
F80 131488 % - 1.5" 58.97
Water, m3/hr 271
Diameter, ft 35.30 Grate ScreenLenght, ft 15.00 5 10 Mesh #
Speed, % Critical 78.00 76200 13335 Opening Charge Level, % 26.00 0.070 0.017 By-Pass
Balls Filling, % 10.00 0.70 0.90 D50/D
⊕⊕⊕⊕
⊕⊕⊕⊕
∅∅∅∅
∅∅∅∅1
2
Simulation N° 0 Remarks
371 ton/hr Base Case Example31.19 % of Feed
2.90 % Moisture Ore Density, ton/m3 2.80
61.50 % - 1/2"
Split 0 ton/hr 1189 ton/hr (all mills)0.00 0.00 % of Feed 40.00 % Solids
62.52 % - 100#270.0 P80
# of Cyclones 4.00 357 d50cDiameter 26.00 0.260 Bpf
Height 78.00 0.273 BpwInlet 10.00
Opening Vortex 10.00 82.66 % SolidsApex 5.00
Circ.
Complex Circuit Simulation ... SABC-2Complex Circuit Simulation ... SABC-2
Balls Filling, % 10.00 0.70 0.90 D50/D % Solids (slurry) 76.00 3.00 4.00 m
App. Density, ton/m3 3.331 % Solids 73.45 Gross kW 10093 % - 100# 25.85
kWh/ton 8.49 T80 5052 m3/hr 588
Mesh Opening Fresh Crushed CrushedFeed Pebbles 1 Pebbles 2
1 12" 304800 100.00 100.00 100.00 m3/hr, Water 391 2 8" 203200 97.60 100.00 100.00
Size Distributions
Circ.% - 200# in psi 13.51 Load, %
Mill Discharge (Guess) 2.688 16.08 (Actual) 2.688
(Delta) 0.000
353 Water, m3/hr
2.00 # of Mills3 6" 152400 83.93 100.00 100.00 4 4.15" 101600 73.57 100.00 100.00 5 2.95" 76200 67.87 100.00 100.00 6 2.1" 50800 62.82 100.00 100.00 7 1.48" 38100 58.97 100.00 100.00 8 1.05" 26670 53.78 98.07 98.07 9 0.742" 18850 49.78 90.24 90.24
10 0.525" 13335 42.74 61.50 61.50 11 0.371" 9423 38.32 48.04 48.04 12 3 6680 34.00 31.84 31.84 13 4 4699 29.28 23.55 23.55 14 6 3327 25.65 18.08 18.08 15 8 2362 22.57 14.32 14.32 16 10 1651 20.19 11.53 11.53 17 14 1168 18.16 9.20 9.20 18 20 833 16.79 7.80 7.80 19 28 589 15.65 6.65 6.65 20 35 417 14.66 5.74 5.74 21 48 295 13.79 5.06 5.06 22 65 208 12.84 4.43 4.43 23 100 147 12.01 3.96 3.96 24 150 104 11.12 3.50 3.50 25 200 74 10.28 3.10 3.10
19.00 Diameter, ft 24.00 Lenght, ft 76.00 Speed, % Critical 38.00 Charge Level, % 38.00 Balls Filling, %
% Solids 64.12 72.00 % Solids (slurry) m3/hr 2009 5.395 App. Density, ton/m3
4631 Gross kW 7.79 kWh/ton
Current Min/Max RemarksSAG Power, kW 10093 11500 OKPebbles, ton/hr 371 400 OKBM Power, kW 4631 3730 KOProduct Size, P80 270.0 185 KOPump Capacity, P*Q 27155 30000 OKTotal Water, m3/hr 1759 2000 OK
PROCESS RESTRICTIONS
� In conjunction with other unit operation models, such as Conventional Ball Milling, Hydroclassification, Screening and Crushing, the referred SAG model can be applied, with Moly-Cop Tools, to represent fairly complex circuit arrangements.
Current Operational Trends inCurrent Operational Trends inCurrent Operational Trends inCurrent Operational Trends inSEMIAUTOGENOUS GRINDINGSEMIAUTOGENOUS GRINDINGSEMIAUTOGENOUS GRINDINGSEMIAUTOGENOUS GRINDING
200
400
600
800
1000
1200
Mill
Thr
ough
put,
ton/
hr5000
10000
15000
20000
25000
30000
Mill
Pow
er D
raw
, kW
22% Total Filling 26% Total Filling 30% Total Filling
Effect of % BALLS IN THE CHARGE
Effect of % BALLS IN THE CHARGE
� D = 36’φφφφL = 15’Vel. = 78% Crit.
SimulatedConditions
Max. Power
0
200
0 5 10 15 20
% Balls
Mill
Thr
ough
put,
ton/
hr
0
5000 Mill
Pow
er D
raw
, kW
Vel. = 78% Crit.% Solids = 76%F80 = 131448 micronsGrate = 0.5”Screen = 0.5”Ball Size = 5”Circuit Type = SABC-1
� One of the first “diversions” from Fully Autogenous Grindingwas the addition of large diameter balls with the purpose of increasing mill power draw and so providing extra grinding capacity, giving rise to the so-called Semi Autogenous option.
� Under any circumstances, Operators must be alert not to exceed the design Maximum Power of the mill motor and drive mechanism.
200
400
600
800
1000
1200
Mill
Thr
ough
put,
ton/
hr5000
10000
15000
20000
25000
30000
Mill
Pow
er D
raw
, kW
22% Total Filling 26% Total Filling 30% Total Filling
Effect of % BALLS IN THE CHARGE
Effect of % BALLS IN THE CHARGE
� D = 36’φφφφL = 15’Vel. = 78% Crit.
SimulatedConditions
Max. Power
0
200
0 5 10 15 20
% Balls
Mill
Thr
ough
put,
ton/
hr
0
5000 Mill
Pow
er D
raw
, kW
Vel. = 78% Crit.% Solids = 76%F80 = 131448 micronsGrate = 0.5”Screen = 0.5”Ball Size = 5”Circuit Type = SABC-1
� Even at the same mill power draw, balls would be more effective than rocks to convert the available power into actual grinding, thanks to their higher density and spherical shape.
11.5
12.0
12.5
13.0
13.5
14.0
kWh/
ton
200
400
600
800
1000
1200
Mill
Thr
ough
put,
tph
22% Total Filling 26% Total Filling
Effect of % BALLS IN THE CHARGE
Effect of % BALLS IN THE CHARGE
� D = 36’φφφφL = 15’Vel. = 78% Crit.
SimulatedConditions
11.0
11.5
2.0 3.0 4.0 5.0
Apparent Charge Density, ton/m 3
0
200 Mill
Thr
ough
put,
tph
26% Total Filling 30% Total Filling
� In some cases, it is possible to identify an Apparent Charge Density (determined by the balls/rocks ratio) that minimizes the overall Specific Energy requirement.
� If the feed contains large rocks – that essentially must grind themselves – we must assure that these large rocks get to absorb the necessary proportion of the total available energy, so the overall process can achieve optimal performance.
Vel. = 78% Crit.% Solids = 76%F80 = 131448 micronsGrate = 0.5”Screen = 0.5”Ball Size = 5”Circuit Type = SABC-1
11.5
12.0
12.5
13.0
13.5
14.0
kWh/
ton
200
400
600
800
1000
1200
Mill
Thr
ough
put,
tph
22% Total Filling 26% Total Filling
Effect of % BALLS IN THE CHARGE
Effect of % BALLS IN THE CHARGE
� D = 36’φφφφL = 15’Vel. = 78% Crit.
SimulatedConditions
11.0
11.5
2.0 3.0 4.0 5.0
Apparent Charge Density, ton/m 3
0
200 Mill
Thr
ough
put,
tph
26% Total Filling 30% Total Filling
� However, regardless of this ideal Apparent Charge Densitythat would optimize the energy efficiency (kWh/ton) of the process, the overall effectiveness (mill throughput) of the operation is always achieved at higher balls/rocks ratios, up to the limit imposed by the available motor and drive power.
Vel. = 78% Crit.% Solids = 76%F80 = 131448 micronsGrate = 0.5”Screen = 0.5”Ball Size = 5”Circuit Type = SABC-1
1000
1050
1100
1150
1200
1250
Mill
Thr
ough
put,
ton/
hr
Screen Opening = 1/2 inch Screen Opening = 3/4 inch
Effect of DISCHARGE GRATE OPENING
Effect of DISCHARGE GRATE OPENING
� D = 36’φφφφL = 15’Vel. = 78% Crit.
SimulatedConditions
950
1000
0.0 1.0 2.0 3.0
Grate Opening, inches
Mill
Thr
ough
put,
ton/
hrVel. = 78% Crit.% Solids = 76%F80 = 131448 microns% Filling = 28%% Balls = 16%Ball Size = 5”Circuit Type = SABC-1
� Another source of “diversion” of SAG milling technology has been the empirical confirmation that removing and crushing larger and larger pebbles (by opening the discharge grate slots) invariably translates into substantially improved mill grinding capacity.
� In plain words … it is like “the SAG mill is asking help from the Crushers”.
12001400160018002000220024002600280030003200
ton/
hr
SABC-1 SABC-1 plus +6 inch Crushing SABC-1 plus 6x2 inch Crushing
Effect of FRESH FEED SIZE DISTRIBUTION
Effect of FRESH FEED SIZE DISTRIBUTION
� D = 36’φφφφL = 17’Vel. = 76% Crit.% Solids = 78%
SimulatedConditions
21%21%
600800
10001200
20 30 40 50 60 70 80 90 100
% - 2" in SAG Mill Feed
Vel. = 76% Crit.% Solids = 78%% Filling = 28%% Balls = 12%Grate = 2”Ball Size = 5”Circuit Type = SABC-1
� It has been repeatedly demonstrated in actual operational practice that “getting rid of the rocks” ahead of the SAG mill brings substantial throughput benefits, raising questions about the effective contribution of such rocks to the overall grinding process.
� Taken from: J. E. Sepúlveda, “A SIMULATION ANALYSIS OF THE NET EFFECT OF FEED PARTICLE SIZE DISTRIBUTION ON SAG MILL PERFORMANCE”, Jan D. Miller Symposium, SME-AIME Annual Meeting, 2005.
2400
2500
2600
2700
2800
2900
3000
ton/
hr
SAG 1 SAG 2
Effect of Feed Size THE PELAMBRES CASE
Effect of Feed Size THE PELAMBRES CASE
21%21%
� D = 36’φφφφL = 17’Vel. = 76% Crit.% Solids = 78%
OperatingConditions
2200
2300
2400
40 45 50 55 60 65
% - 1.25" in SAG Mill Feed
� Actual data in support of the previous statement was provided by the PELAMBRES (Chile) operation, back in 2001, in the context of their “mine-to-mill” approach.
� Taken from: R. Palomo, Moly-Cop 2001: IX Mineral Processing Symposium.
Vel. = 76% Crit.% Solids = 78%% Filling = 23%% Balls = 15%Grate = 2”Ball Size = 5”Circuit Type = SABC-1
Effect of Feed SizeTHE COPPERTON CASE
Effect of Feed SizeTHE COPPERTON CASE
10001100120013001400150016001700180019002000
ton/
hr
Lines 1 - 3 Line 4
(*) D. King (2005), SME-AIME Annual Meeting
800900
1000
30 35 40 45 50 55 60
% - Fines in SAG Mill Feed (*)
Effect ofCIRCUIT CONFIGURATION
Effect ofCIRCUIT CONFIGURATION
100012001400160018002000220024002600280030003200
ton/
hr
DSAG SABC-1 SABC-1 plus +6 inch Crushing SABC-1 plus 6x2 inch Crushing SABC-2
� D = 36’φφφφL = 17’Vel. = 76% Crit.% Solids = 78%
SimulatedConditions
600800
1000
20 30 40 50 60 70 80 90 100
% - 2" in SAG Mill Feed
� The grinding capacity of any given circuit improves as its configuration evolves from DSAG to SABC-1 to SABC-2; that is, as the SAG mill contributes less and less to the overall grinding task!
� Also, as the larger feed rocks get to be pre-crushed, the Ideal Apparent Charge Density quickly approaches values close to the limiting maximum value corresponding to just ‘balls plus slurry’ (~5 ton/m3); that is, Conventional Grinding.
Vel. = 76% Crit.% Solids = 78%% Filling = 28%% Balls = 12%Grate = 2”Ball Size = 5”Circuit Type = SABC-1
Effect of Balls/Rocks RatioIDEAL APPARENT CHARGE DENSITY
Effect of Balls/Rocks RatioIDEAL APPARENT CHARGE DENSITY
� D = 36’φφφφL = 17’
SimulatedConditions
0
2000
4000
6000
8000
10000
12000
kW (Net)
Total
Balls
Rocks
Slurry
� As Total Mill Filling is increased (by the addition of large or mid size rocks), at constant Ball Filling, the Total Mill Power Draw increases, but the Net Power absorbed by the Ballsactually decreases.
� If one is to accept that rocks are less effective than balls as grinding media (not to say, totally ineffective), then Mill Throughput will be higher at lower Total Filling levels.
� This empirical finding has led operators to run at fairly low Total Filling (below 24%) and relatively high (up to 20%) Ball Filling levels.
L = 17’Vel. = 70% Crit.% Solids = 78%% Balls = 12%Grate = 0.5”Ball Size = 5”Circuit Type = DSAG
0
14 16 18 20 22 24 26 28 30 32 34 36 38
Total Mill Filling, %
Meanwhile ... Has theIDEAL MAKE-UP BALL SIZE
also been evolving?
Meanwhile ... Has theIDEAL MAKE-UP BALL SIZE
also been evolving?
� With the advent of the new century, SAG mill operators have been consistently 1200
1400
1600
1800
2000
2200
2400
Mill
Thr
ough
put,
ton/
hr
F80, mm
27
56
been consistently realizing the clear advantages of using larger and larger balls, regardless of the ore feed particle size.
800
1000
1200
3.5 4 4.5 5 5.5 6 6.5 7 7.5
Make-up Ball Size, inches
Mill
Thr
ough
put,
ton/
hr
120
131
� For every ‘grinding task’, there is an Ideal Make-up Ball Sizethat maximizes mill throughput.
� Quite often, this Ideal Make-up Ball Size turns out to be larger than the largest commercially available ball size and increases consistently for coarser and coarser feeds.
4.8
5.0
5.2
5.4
5.6
Ave
. SA
G B
all S
ize,
inch
es
Meanwhile ... Has theIDEAL MAKE-UP BALL SIZE
also been evolving?
Meanwhile ... Has theIDEAL MAKE-UP BALL SIZE
also been evolving?
� It should be noted that this trend of increasing make-up
4.0
4.2
4.4
4.6
'90 '92 '94 '96 '98 '00 '02 '04 '06 '08
Ave
. SA
G B
all S
ize,
inch
esincreasing make-up ball sizes has not yet been offset by the concurrent trend of feeding the mills with finer and finer particles.
� Based on Historical Sales Records of Moly-Cop Chile S. A.
So ...HOW ARE THEY RUNNING TODAY?
So ...HOW ARE THEY RUNNING TODAY?
Mill Mill Ball Total Ball F80 ChargeFacility Diameter, Length, Filling, Filling, Size, Size, D ensity, Circuit Type
ft ft % % in mm ton/m 3
Chuquicamata 32 15 15.0 28.0 5.0 120 3.75 SABC-1 Andina 36 15 14.0 30.0 5.0 76 3.54 SABC-2 Teniente SAG 1 36 15 14.0 33.0 5.0 170 3.46 SABC-2 Teniente SAG 2 38 22 15.0 31.0 5.0 100 3.64 SABC- 2 Collahuasi 32 15 12.0 25.0 5.0 152 3.56 SABC-1 MEL Laguna Seca 38 20 19.0 26.0 5.5 80 4.37 SABC-1 MEL Los Colorados SAG 1 28 14 13.0 23.0 5.0 80 3.88 SABC-1
� Data obtained from direct interviews to the listed operations.
MEL Los Colorados SAG 1 28 14 13.0 23.0 5.0 80 3.88 SABC-1 MEL Los Colorados SAG 2 28 14 13.0 23.0 5.0 80 3.88 SABC-1 MEL Los Colorados SAG 3 36 19 15.0 23.0 5.0 80 4.14 SABC-1 Candelaria 36 15 17.5 31.0 5.5 128 3.95 SABC-2 Mantos de Oro 28 14 14.0 30.0 6.0 64 3.52 Precrush ing Pelambres 36 17 19.5 30.0 5.5 90 4.10 Precrushing El Soldado 34 17 14.0 25.0 5.0 117 3.83 SAC Los Bronces SAG 1 28 14 17.0 30.0 5.0 60 3.88 Prec rushing Los Bronces SAG 2 34 17 17.0 30.0 5.0 60 3.88 Prec rushing
120
140
160
180
200
F80
Siz
e, m
m
Chuquicamata Andina Teniente Collahuasi Escondida Candelaria
So ...HOW ARE THEY RUNNING TODAY?
So ...HOW ARE THEY RUNNING TODAY?
Too manyballs!
FAGFAG
40
60
80
100
2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8
Charge Density, ton/m 3
F80
Siz
e, m
m
Candelaria MDO Pelambres Anglo
� Data obtained from direct interviews to the listed operations.
Not enoughballs!
BAGBAG
�� It is very likely that many of It is very likely that many of It is very likely that many of It is very likely that many of It is very likely that many of It is very likely that many of It is very likely that many of It is very likely that many of
the members of this audience the members of this audience the members of this audience the members of this audience the members of this audience the members of this audience the members of this audience the members of this audience
would would would would would would would would notnotnotnotnotnotnotnot share with me the share with me the share with me the share with me the share with me the share with me the share with me the share with me the
‘rightfulness’‘rightfulness’‘rightfulness’‘rightfulness’‘rightfulness’‘rightfulness’‘rightfulness’‘rightfulness’ of all of my of all of my of all of my of all of my of all of my of all of my of all of my of all of my
todays statements.todays statements.todays statements.todays statements.todays statements.todays statements.todays statements.todays statements.
�� For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just
CONCLUDING REMARK
CONCLUDING REMARK
�� For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just For now, in my defense, I just
wish to express that, in real wish to express that, in real wish to express that, in real wish to express that, in real wish to express that, in real wish to express that, in real wish to express that, in real wish to express that, in real
life ... life ... life ... life ... life ... life ... life ... life ...
nobody is free ofnobody is free ofnobody is free ofnobody is free ofnobody is free ofnobody is free ofnobody is free ofnobody is free of
making mistakes !!!making mistakes !!!making mistakes !!!making mistakes !!!making mistakes !!!making mistakes !!!making mistakes !!!making mistakes !!!