Horizontal_Vertical Mill Comparison-2

8/7/2019 Horizontal_Vertical Mill Comparison-2

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Horizontal & Vertical Mills

Comparisons &Lab Testing Methods


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The Netzsch Disc Mill

Operation Mode

Normally one or two passesdepending on the product

ApplicationsInks; paints; pigments;textile dyes; magneticcoatings; paper coatings;agriculture chemicals; ores;minerals; technical ceramicsand utility ceramics;pharmaceutical; cosmetics;

food; bio technology


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Development of Wet GrindingMachines

18961896 19581958 19631963

19741974 19851985 19951995

19741974 19911991 20002000

Netzsch has been making finegrinding mills for over 100 years


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coolable grinding

chamber

Separation

system

Agitator shaft

Horizontal & Vertical Disc Mills

Netzsch makes bothNetzsch also make P in type Mills

Have different advantages for Inks, Paints, Etc


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Horizontal & Vertical Mills

Energy Efficiency - kWh/ t What determines Energy Efficiency?

Energy Efficiency is determined by ore characteristics, mediasize/ type and classification efficiency, when energy input and

other operating parameters (density, etc) are held constant

Decreased media size improves energy efficiency (manystudies-200+, eg: McIvor, 1997, Weller,1999, Jankovic, 2002,Nesset, 2006) and type/ quality (Kwade, 1996, Curry,

Clermont, 2005, Yang, 2006) Improved classification efficiency (sharper cut) improves

energy efficiency (many studies, eg: McIvor, 1988,Morrell,2008)

Power measurement and sample segregation in lab mills needto be carefully measured and/ or controlled, or lab results w illbe misleading compared to full scale operation


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Horizontal & Vertical MillsEnergy Efficiency - kWh/ t

Disc vs P ins

Same Energy Efficiency for same conditions

P ins have increased power draw per set, and increased

wear/ decrease life Disc have more wear surface

Signature Plot

10.0

100.0

1000.0

1.0 10.0 100.0 1000.0Size (um)

Spec

ificEnergy(kWh/t)

P98 - Pin

P80 - Pin

P98 - Disk

P80 - Disk


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Horizontal vs Vertical

Same Energy Efficiency for same conditions

Beware size segregation if mill load sized, PSD larger

But operating differences affect performance at full scalecontinuous operation

Signature Plot P80

1

10

100

1000

1 10 100

Particle Size (micron)

SpecificEnergy(kWh/t)

Vertical Test Horizontal Test Vertical Test 2

Horizontal Test

Vertical Test

Vertical Lab Test

Size Segration Vertical Lab Test

Result when all mill

load is sized


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Batch Lab Test sub-sampling from top or part of chargemeasures finer result than bulk mill load need to empty milland size complete charge, at each sampling time. Generally

not practical. Continuous Throughput Testing Sample segregation still an

issue need to ensure there is no retention of coarse in themill

Recommend passing minimum of THREE times the volume of

solids through the mill, compared to Mill volume to ensuresteady state discharge of feed sample

Can be tested by making large feed sample and pump throughmill at testing feed rate, w ith no media, but stirrer running calculate the volume of feed required to achieve milldischarge at original feed PSD.

Isamill testing is conducted w ith 25L of slurry 6-8L of solids being passed through a mill w ith 2L of net volume (3.5L-1.5L media) Volume of solids is THREE times mill volume.

Horizontal & Vertical MillsLab Testing Methods


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Isamill Maxmises Energy Efficiency by

Finer Media Sizing

Energy efficient media types

Improved classification, sharper product size distribution,due to plug flow through 8 chambers and patentedproduct separator

Weller, Gao - 1999

Media Size Tests


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Isamill Maxmises Energy Efficiency by

Finer Media Sizing

Energy efficient media types

Improved classification, sharper product size distribution,due to plug flow through 8 chambers and patentedproduct separator

KOC RoC Regrind Test - MT1 Media - Open Circuit

0

20

40

60

80

100

0.1 1 10 100 1000Size (um)

Cumulativ

e%Passing

Feed

20 kWh/t

36.7 kWh/t

57.4 kWh/t

79.1 kWh/t

Narrow ing Size Distributionw ith increased IsaMilling

Minimal over-grinding

Sharp

ClassificationReduce Top Size,

With M inimalFines Production


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IsaMil l Horizontal Layout - Benefits

Wide operating range.Continuous turn-down.

Relatively equal media distributionalong the length of the shaft.

Best access to all wear parts.Relatively low lifting weights assingle components can be removed.

Horizontal configuration enables

large scale designs up to 3.0 MW.

Shell on wheels. Easy maintenance.Single component lifts.

Low breakaway torque.

Restart after crash stop is noproblem. No need to dump media ona mill stop like some vertical mills.

Suitable for coarse and high SGproducts which tend to

sedimentation.

M10,000 M3000 M1000


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Limitations of Vertical Mills

High risk of sedimentation and fine-coarse particle separation in the mill,especially at low flow rates.

Media distribution unequal due to unbalanced drag and gravity forces.

Maximum breakaw ay torque due to high media compression at the bottom. Hardto restart under load.

Limited shaft speed. Vortex generated. Vortexing at high density - lowersgrinding volume. Vortex changes repose angle as density changes mill can gofrom low fill and low pow er draw to slurry being spun out from the top of milland high power draw as density is lowered.

Heavy components to lift. Exchange of wear parts preferably in the workshop.

Limited in mill capacity/ motor size.

Media floats at high density

Needs cyclones and density control.

Screen discharge :

Short circuit of feed for top fed.

Media block feed pipe for bottom fed.

Screens blocks w ith media.


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IsaMill Product Separator

Patented product separator keeps mediainside grinding chamber allow ing onlyproduct and consumed media to exit.

Invention of product separator eliminatesscreens from ultra-fine grinding - deliversprocess with robustness required by miningindustry.

Typical Fine Screen on Vertical Mill Patented IsaMill P roduct Separator


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IsaMill Internals

8 grinding chambers in series no short circuiting

Product separator retains media without fine screens

PRODUCT SEPARATORGRINDING DISCS


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IsaMill Product Separator

Advantages

No screen to block.

Centrifugal forces higher than a cyclone 60G.

Retains media and classifies product.

Sharp cut, fine P98.

Minimal over-grinding.

Media does not blind the screens since worn media simply

discharges from mill when fine enough.

Media does not w ear out the screens, as media not pushagainst screens.


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Stirred Mill - lab vs ful l scale - Century

Lab. v. Continuous SMDs

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100 1000Size (m)

CumulativeP

ercentPassing(

Lab SMD

Continuous SMD

Numbers provided by Laurie Reemeyer, Concentrator Manager, Century

The difference in P98 may not be important in flotation, where coarse particles still float, but is crucial in leaching sincethe coarse particles may not leach.

Plant P98 38 um

Lab 98 19.5 um

Same P80 8um


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Impact of Product Separator on Size Distribution

Lab. v. Continuous SMDs

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100 1000Size (m)

CumulativePercentPassing(

Lab SMD

Continuous SMD

MRM IsaMill

Discharge

MRM plant IsaMills:

P80 9.5

P98 19.5

Century plant

P80 8

P98 38

Century Lab scale

P80 8

P98 19.5


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End

Horizontal_Vertical Mill Comparison-2

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