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Cavity Levels Effect on ConeCrusher Performance and
ProductionDusty Jacobson, Metso
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Material Flow as Cavity Empties
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Theory Behind Study Higher cavity increases capacity A head of material pushes material down, improving flow
Higher particle density in chamber
Higher cavity improves reduction Gives higher particle density increased interparticle crushing Crushing action starts at top of chamber Low cavity can result in single layer crushing
Higher cavity increases power Increased capacity, increased particle density, higher reduction
*These are general statements that do not account for abnormalities in the feed size/cavity profile/oreproperties/etc.
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Theoretical Cavity Level EffectsCavityLevel
ParticleDensity
Flow ThruChamber
Capacity Power Draw
Reduction CrushingEfficiency
Low + + + + + +
Near-Full ++ ++ ++ ++ +++ ++
Super Choked
+++ +++ +++ +++ +++ ++
Capacity is proportional to the Cavity Density and Flow Through the Chamber
Power Draw is proportional to the Cavity Density and Capacity
Reduction is proportional to the Cavity Density and Power Draw
Crushing Efficiency is proportional to the Capacity and Reduction, and isinversely proportional to the Power Draw
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Test Background In May 2010, testing was conducted at the
Mineral Research & Test Center in Milwaukee,WI, USA
An HP200 was used with multiple settings Two different materials were tested
Hard-Trap Rock 25% CR 18 W.I. Soft- Limestone 41% CR 12 W.I.
Three cavity levels were investigated 42 tests were run with 76 samples
taken
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Test Procedure
Tests were run in tertiary (shorthead) position Four CSSs were investigated Cavity level was visually confirmed and recorded Power draw was steady (~+/-3%) for 30 seconds
before sampling Power, capacity, and particle size distribution
(PSD) were evaluated for every test
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Cavity Level Indication
HC, F, and SC cavity levels areshown to the right.
HC had material level at 5/8 of the
way up from the bottom of the cavity F was material level to the top of the
feed plate
SC was 12 (300mm) above the feedplate This was measured and visually
consistent during testing
Half Cavity Super ChokedFull Cavity
Half Cavity
Full Cavity
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Results - Summary Super-Choked gave slightly better performance than Full-Cavity,but there was a large drop-off with the Half-Cavity tests As the cavity level increased from HC, the capacity (+23-25%) and
power (+43-50%) increased while the discharge became finer The average specific energy to produce a 0-13mm product was 3-
5% less with F or SC, respectively, when compared to HC The average specific energy to produce a 0-6.7mm product was
10-13% less with F or SC, respectively, when compared to HC
Table 1: Relative production and specific energy based on half cavity results
Condition MTPH kW kWh/TThroughput
MTPH13mm x 0
kWh/T13mm x 0
MTPH6.7mm x 0
kWh/T6.7mm x 0
Super Choked 1.25 1.50 1.21 1.59 0.95 1.75 0.87Full Cavity 1.23 1.43 1.16 1.49 0.97 1.62 0.90Half Cavity 1.00 1.00 1.00 1.00 1.00 1.00 1.00
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Results Summary (cont) Real benefits were seen to operate with a full cavity at awider CSS (1/8 or 3mm) instead of tighter with a half cavity
(see below) The effect of cavity level was greater when looking at finer
size fractionsNOTE: These results are machine dependant. The effects with larger machines may be more pronounced. But, the general trends seen areuniversal to high speed cone crushing.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.0 0.1 1.0 10.0
% P
a s s
i n g
Size (relative to CSS)
NormalizedPSD Based on Cavity Level
Super Choked Average
Full Cavity Average
Half Cavity Average
Table 2: Operating data - Similar discharge PSD of super choked at wider CSS than half cavity
CSS (mm) MTPH kW kWh/T P80 P50Super Choked 22 1.36 1.10 0.81 1.02 1.04Full Cavity 22 1.33 1.02 0.76 1.10 1.10Half Cavity 19 1.0 1.0 1.0 1.0 1.0
Super Choked 19 1.42 1.16 0.82 1.05 0.99Half Cavity 16 1.0 1.0 1.0 1.0 1.0
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Average Results Relative toSuper-Choked Condition
CavityLevel
Capacity Power Draw
P80 P50 %PassingCSS
%Passing of CSS
Super
Choked
1.00 1.00 1.00 1.00 77% 41%
FullCavity
0.93 0.92 1.05 1.09 75% 38%
Half Cavity
0.78 0.65 1.17 1.30 68% 32%
This table and following graphs show results from the base tests as well asa small number of tests ran with a relatively finer feed (1.5 x ).
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HFS Comparison
Half Cavity
ChokeFeed
SuperChoked
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Practical Lessons
The crusher is more efficient with a full or super-choked chamber Therefore, keeping a full chamber consistently is more energy efficient Smaller or fewer crushers can be used by operating near max capacity
Bins/feeders/control packages will prove to be beneficial Liner life and sustainable profile improve with a consistently full cavity A higher cavity level will generally give a more consistent power draw
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Final Note
Each crusher/liners/feed material/application is differentand the effect of the cavity level will vary. The trends of this study are valid, but the magnitude of productiondifferences can only be seen with testing trials with theactual machine and feed.
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THANK YOU
Dusty Jacobson, MetsoPeter Janssen, MetsoVictor Urbinatti, Metso