Dusty Jacobson

7/27/2019 Dusty Jacobson

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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

Dusty Jacobson

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