crushing principles of mechanical crushing
TRANSCRIPT
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Crushing- Principles of Mechanical Crushing
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Per Svedensten
Manager Crushing Chamber and
Materials Development
Product Development Center
Crushing (R&D)
Master of Science in Mechanics,
specialized in mechatronics
Ph.D 2007, Chalmers Universi ty
Partly funded by Sandvik
Modeling, simulation and
optimization of crushing plants
Technical-EconomicOptimization
Sandvik employee since 2004
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Objective
Explain the interactionbetween
rock material
and
crusher
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Take home messages
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Agenda
Cone Crusher Operating Principal
Crusher Operation
Rock Breakage Behavior
Crushing Forces
Optimization and Crusher Performance Map Conclusions
NCC, Borås, Sweden
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I m pl em en t a t i on s
Scientific Approach
Hypothesis / System behavior
Prediction of performance
Utilize results for improvement
Choice of method and/or modeling
Study and/or prediction of system behavior
Verification
Problem / Research Question
Customer Values
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Cone Crusher
Why Cone Crusher?
The cone crusher designconcept is an effective and smartway of realizing compressive
crushing Aggregate Production
Mechanical Liberation ofValuable Minerals
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Product
Feed
Power
Operating Principle
Heat
Noise
Lube
Oil
Hydraulic
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Operating Principle
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Operating Principle
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Operating Principle
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Operating Principal
Opening Phase == Transport
Closing Phase == Crushing
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Transport
Crushing
Mantle
Concave
Operating Principal
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Operating Principal
10 Indentations
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Crushing
Mantle
Concave
Operating Principal
Transport
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Mantle
Concave
Crushing
s
b
b: Bed Height
s: Compression
s/b: Compression Ratio
Operating Principal
Crushing Zone
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Mantle
Concave
Single Particle Breakage SPB
Inter Particle Breakage IPB
Operating Principal
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Operating Principal
In a cone crusher the stones are crushed with both SPB and IPB as thematerial moves down through the chamber.
The relative amounts of IPB and SPB depends on factors like chamberdesign, crusher geometry, speed, css, eccentric throw, and others.
SPB IPB
Fines Less More
Shape Flaky Cubic
Force Low High
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Operating Principal Capacity
Cross section area
0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.22-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
i
Area [m2]
Area function
Choke level
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Operating Principals
0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.2 0.21 0.-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
Nominal Cross-Sectional Area
Y - c o o r d i n a t e [
m ]
Area [m2]
Choke level
Choke zone
Capacity
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Operating Principals
Standard
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Crusher operation
As the market demand shifts can the crusher operation be modified?
The crusher is likely to be installed for maximum production. Can it bechanged to maximum efficiency?
Understanding how breakage and capacity is effected by Eccentric Throw
Speed
Closed Side Setting
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Crusher operation
Running the crusher at different eccentric throws
ECC 0.6” (16 mm)51 tph
ECC 1.0” (25 mm)75 tph
ECC 1.4” (34 mm)97 tph
-0.08”: 16%
0.08”-0.5”: 80%+0,5”: 4%Fines/Product: 0.20
-0.08”: 19%
0.08”-0.5”: 74%+0,5”: 7%Fines/Product: 0.25
-0.08”: 20%
0.08”-0.5”: 73%+0,5”: 7%Fines/Product: 0.27
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Crusher operation
Running the crusher at different eccentric throws, CSS optimized
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
16 36
P r o d u c t i o n [ % ]
ECC [mm]
Product
Fines
Re-circulation
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Crusher operation
Running the crusher at different speeds
280 rpm106 tph
360 rpm104 tph
440 rpm96 tph
-0.08”: 13%
0.08”-0.5”: 69%+0,5”: 18%Fines/Product: 0.19
-0.08”: 17%
0.08”-0.5”: 71%+0,5”: 12%Fines/Product: 0.24
-0.08”: 21%
0.08”-0.5”: 71%+0,5”: 8%Fines/Product: 0.30
Changing speed can have mechanical effects on the crusher and motor
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Chamber DesignDesign drawings
FineCoarse
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Crusher operation
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Crusher operation
Chamber selection
Fine Medium Coarse Extra Coarse
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Crusher Operation
Relation between CSS andShape
The size were the best shapecan be found is at CSS
It is very difficult for cubicalstones larger then CSS to passthe chamber
Breakage of stones creates flakyparticles. Smaller flaky stoneswill more easily find its way
through the chamber
F a
n e s s
n e x [ % ]
Particle size [mm]
Increasing CSS
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Crusher Operation
Relation between Feed size andShape
The greater reduction ratio theworse particle shape.
Inter particle breakage improvesshape. When crushing a bed ofmaterial weaker particles willbreak first. Flaky or elongatedparticles are weaker then round.
Breaking round particles gives
flaky material.
F l a k i n e s s i n d e x [ % ]
Particle size [mm]
Increasing average feed size x
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OptimumCSS
Reduction
Crusher Operation
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Process Capacity
Design capacity: 200 tph
Crusher Capacity: 300 tph
Choke fed Crusher operation(300 tph):
Material in surge bin runs out at evenintervals
Consequence:
Crusher is operated choke fed 66% oftotal operating time feeding the screen
with 300 tphScreen overload
Solution: Adjust throw in order to reach200 tph capacity
32
200
200
200
66% Capacityutilization
300
300
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Rock Breakage Behavior
33
SPB IPB
Compression ratio Compression ratioDistribution width
Laboratory investigation of breakage modes
Compressive crushing with hydraulic press.
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Rock Breakage Behavior
Short fraction
Long fraction
Compression ratio
Packing limit
S e l e c t i o n
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Rock Breakage Behavior
Dolerite
Gneiss
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Crushing Force
s
b
b: Bed heights: compression
s/b: compression ratio
F: ForceF = f(s/b, σ )σ: Fraction length
F
F
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Crushing Force
( ) 2 2 2 2 21 2 3 4 5 6, p s a s a s a s a s a s a s
size distribution width
σ σ σ σ σ
σ
ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ ℵ
ℵ
= + + + + +
=
Multi (inter) particle
-pressure response Packing!
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Crushing Force
( ) ( )32 1 2, k F s d d k s k s
s compression ratiod particle size
ℵ ℵ ℵ
ℵ
= +
=
=
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35
0
500
1000
1500
2000
2500
3000
3500
4000
quartzite 16-19
o tests- simulations
Single particle
-force response
F o r c e
[ N ]
Compression ratio
O ti i ti f Fi l C hi St
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Optimization of a Final Crushing Stage
Who is control of your process
performance? What tools have been provided
to make the production efficient?
Optimi ation of a Final Cr shing Stage
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Optimization of a Final Crushing Stage
The crushers are the last sizereduction stage in the valuechain.
Over crushing is common.
The connection between crushersetting and yield is oftenunknown
The rock cannot be repaired.
We need to control the crusher
carefully.
O ti i ti f Fi l C hi St
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Optimization of a Final Crushing Stage
Optimization of one parameter(CSS) can be done by samplingand analysis
The invested time and lost
production will quickly be repaidby increased productivity
Combine product yield andeconomic aspects
This can be done by taking
samples and making theanalysis in MS Excel
Planning Sampling Analysis Optimization
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Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
Run the crusher at different settings
Take at least one sample at eachsetting. (Multiple samples are oftenuseful)
Special Attention to Safety when takingsamples!!
Position of point were samples aretaking.
Ensure that the conveyor will not start byaccident.
Planning Sampling Analysis Optimization
Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
Particle Size Distribution Plots
If taking single samples on eachCSS the risk of getting
inconsistent results might makethe graph look strange.
Impossible to determine optimumsetting by only using particle size
distribution graphs
Planning Sampling Analysis Optimization
Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
If taking single samples on eachCSS the risk of gettinginconsistent results might make
the graph look strange.
Impossible to determine optimumsetting by only using particle sizedistribution graphs
Planning Sampling Analysis Optimization
Optimization of a Final Crushing Stage
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0
10
2030
40
50
60
70
80
90100
0.001 0.01 0.1 1 10
p e r c e n t p a s s i n g
sieve size ['']
Particle Size Distribution at CSS 0.79''
0,79
Optimization of a Final Crushing Stage
0
50
100
150
200
250
0.50 0.60 0.70 0.80 0.90 1.00
C a p a c i t y [ t p h ]
CSS ['']
Capacity and CSS
Planning Sampling Analysis Optimization
Combine the particle size distribution and capacity.
Percentage of final product times the capacity gives the production capacity ofeach product.
Example 0.08’’-0.16’’ mm at CSS 0.79’’:
Percentage of crusherproduction
20% - 11% = 9%
Crusher capacity
193 tph
Total Production:
193 tph x 9% = 17 tph
Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
Entering all the values into MSExcel makes this easy to getproduction capacities.
Still difficult to determine theoptimal setting
Planning Sampling Analysis Optimization
Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
Use the price* per ton for allproducts:
0-0.08’’: $ 0 (by-product)
0.08-0.16’’: $ 12.30
0.16-0.32’’: $ 13.85
0.32-0.64’’: $ 16.90
0.64-0.87’’: $ 10.80
Make an income graph bycombining prices with capacity
Planning Sampling Analysis Optimization
*All prices are estimates based on publicly available data
Optimization of a Final Crushing Stage
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Optimization of a Final Crushing Stage
What difference does it make?
Running the crusher 0.08’’ off:
Decrease the profit by 58.5 $/h
Running the crusher at 1600hours per year:58.5*1600=$93600
Planning Sampling Analysis Optimization
Crusher Performance Map
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Crusher Performance Map
Planning Sampling Analysis Optimization
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Crusher Performance Map
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