3 - ball mill grinding

7/25/2019 3 - Ball Mill Grinding

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BALL MILLGRINDING



Ball Mill Grinding

2

LEARNING OBJECTIVES

At the end of the day the trainee shall e a le to !

Describe the ball mill grinding process

Describe ball mill internal equipment andtheir impact on performance

Des"ri e the #ro"ess #rin"i#les of $ill

se#arations and inter#ret the Tro$# "%r&e



3

BALL MILL

GRINDING'ROCESS



Ball Mill Grinding

4

Crushing is done by :

Cascade effect : the most efficient

grinding by rolling / crushing under pressure

material entering into the charge

Cataract effect : splitting up by impact

balls falling onto particles

ACTION O( T)E BALLS



Ball Mill Grinding

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CASCADING ACTION

Nipping Angle and Particle Size!



Ball Mill Grinding

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CATARACTING ACTION

Crushing by Impact



Ball Mill Grinding

7

Lift Zone

GrindingZone

1 2 3

1 - Cascading (tumbling)2 - Cataracting (free fall - max impact)3 - Excessive L ift (impact on l iner)

Liners d igs into charge.Some slip occurs.

Release Points

12

3

RotationRelease #oints Rotation

Lift*one

Grinding*one

+ , Cas"ading -t%$ ling./ , Catara"ting -free fall , $a01 i$#a"t2 , E0"essi&e Lift -i$#a"t on liner.

Liners digs into "harge1So$e sli# o""%rs

RELEASE 'OINTS AND GRINDING



Ball Mill Grinding

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Energy trans$itted y the Balls• Mass Ball sizes, Specific Weight

• Speed Movement, Mill Speed, Filling, ine!s

• "!o#a#ilit$ %&m#e!, Size, Mate!ial Filling,'ontact ($pe

Conta"t 'ata!act ) *mpact, o+ %&m#e!of contacts

'ascading ) F!iction, igh %&m#e!

of contacts

GRINDING 'ROCESS



Ball Mill Grinding

-

A&erage Ball 3eight

• (otal cha!ge +eight . (otal n&m#e! of #alls /0g.#all1S#e"ifi" S%rfa"e Area

• (otal s&!face a!ea . 'ha!ge +eight /m 2.t1

Coarse Balls , Large VoidsLo4 Retention

(ine Balls , S$all Voids)igh Retention

BALL C)ARGE , 'OROSIT5



Ball Mill Grinding

3

Inter#arti"le grinding o""%rs 4hen the &oids#a"e is #ro#erly filledThe "ollision of alls "a%ses a $o$entaryhigh #ress%re "o$#ression

%ip o! 'ontact points+he!e c!&shing ta0es

placeFo! filling !atios less than 3 6the!e s steel to steel contact

no g!inding

oids +he!e inte!pa!ticleg!inding ta0es place

Fo! filling !atios g!eate! than ,#alls a!e p&shed apa!t, c&shioningimpact

GRINDING VERS6S (ILLING



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BALL MILL



Ball Mill Grinding

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De#ending on their f%n"tion• a+ mill, additions 9slag, limestone, :

• 'ement Mill 9p&!e cement o! cement +ith additions:

• 'oal Mill

The $ore ada#ted te"hnology 4ill e %sed• ;i!)S+ept Mills 9mate!ial is so!ted #$ ai!:

• Mill +ith end discha!ge ) 'ompo&nd Mill

• Mill +ith cente! discha!ge ) Bi!otato!

T)E MILL



Ball Mill Grinding

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AirSweptMill

T)E MILL



Ball Mill Grinding

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ndischarge"all millwith

#Chamber

T)E MILL



Ball Mill Grinding

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"i$rotator

T)E MILL



Ball Mill Grinding

8

Inlet headReject returnchute

Fresh feed

Fresh air inlet

Trunnion

C1 linersC2 liners

Supports

Intermediate diaphragm

Shell

Central Ventilation ring grate

Central or entilation ring

!utlet diaphragm

"as # dustoutlet

$ischarge bo%

!utlet seal

&aterial discharge

Feed 'rrangements

&ill (eads&ill )earings$ri e Types&ill Shell

T)E BALL MILL



Ball Mill Grinding

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(EED ARRANGEMENTS



Ball Mill Grinding

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MILL )EADS



Ball Mill Grinding

2

MILL BEARINGS , TR6NNION



Ball Mill Grinding

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MILL BEARINGS 8 SLIDE S)OE



Ball Mill Grinding

2<

MILL DRIVE T5'E 8 GIRT) GEAR



Ball Mill Grinding

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MILL DRIVE T5'E 8 CENTRAL DRIVES



Ball Mill Grinding

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MILL DRIVE T5'E 8 GEARLESS DRIVES



Ball Mill Grinding

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'O3ER RANGES O( MILL DRIVES



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BALL MILLINTERNALS



Ball Mill Grinding

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Rotation

ROTATION

(or first "o$#art$ents only

Better 4ear "hara"teristi"s

Moderate lift

CONTIN6O6S LI(T OR STE' LINERS



Ball Mill Grinding

2-

)!*T*+SS ST+, C('&)+R1 *I-+R

*ess material spillage

' oids bolt brea.age

The step si e 0lifting po erdepends on

&ill rotation speed

03 Critical Speed

Volume load

"rindability of feed material

Dire"tion of rotationDire"tion of rotation



Ball Mill Grinding

<3

Rotation

Early release onbackslope cause smedia t o sl ip.

(or first "o$#art$ents only

Negati&e a"9 slo#eind%"es sliding

Ra"ing is "o$$on: 4ear life

is shortIt has good lift

D%olift has a s$all h%$# inet4een lifts to #re&ent this13earlife is $%"h etter1

D%olift is designed for $illsthat had lorrain liners efore

SINGLE 3AVE ; D6OLI(T LINERS



Ball Mill Grinding

<

%%&#'Chamber #

LORAIN BAR LI(T LINING

Chamber %# %&#'



Ball Mill Grinding

<2

INSTALLED D6OLI(T LINERS



Ball Mill Grinding

<<

iameter ( )*)m

iameter + )*)m

CLASSI(5ING LINERS



Ball Mill Grinding

<4

S, -. N $ MA-/.. A01 .2P

CA3MAN ,ININ-

E<AM'LES O( CLASSI(5ING T5'E LINERS

NA.A, 4.5IN P3/6I, .2P 7



Ball Mill Grinding

<5

-rinding media to be used in #nd

chamber + 89mm

RI''LE T5'E LINERS



Ball Mill Grinding

<6

Refer to the Best 'ra"ti"e

=Sele"tion of Shell Liners>

Refer to the Best 'ra"ti"e

=3hen to Change Shell Liners>

BEST 'RACTICES ON LINERS



Ball Mill Grinding

<7

'ARTITION ? O6TLET 3ALLDISC)ARGE ; / ND COM'ARTMENT VIE3



Ball Mill Grinding

<8

Outer Grate S egment

Inner Grate S egment

Center Hub or Cone

Center Screen (Mill Sweep)

Typical Chamber Filling Level

Feed E nd V iew of Partition with G rate S egments

Do% le 4all: f%ll liftered design is the $ost"o$$on

'ARTITION ? O6TLET 3ALL



ll ll d



Ball Mill Grinding

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Con entional Material.ransport

ffect of the Material6low Control

CONTROLLING MATERIAL LEVEL IN C+ ; C/

B ll Mill G i di



Ball Mill Grinding

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GRINDING CIRC6ITS

B ll Mill G i di



Ball Mill Grinding

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O'EN CIRC6IT

ustCollector

6resh6eed

6inishedProduct

Mill

6an

-asMaterial

B ll Mill G i di



Ball Mill Grinding

4<

*ittle or no control of fineness

-ot adapted to high fineness

,ossibility of o er grinding(igher temperature of products

)road particles si e distribution

*o er in estment costs

O'EN CIRC6IT

B ll Mill G i di



Ball Mill Grinding

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&ill

$ynamicSeparator

$ustCollector

FreshFeed Finished ,roduct

Rejects

StaticSeparator

$ust Collector

"as&aterial

Fan Fan

CLOSED CIRC6IT

B ll Mill G i di g



Ball Mill Grinding

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)etter regularity because of a real controlof the fineness(igh fineness is possible(igher fle%ibility and possibility of

optimisation by product,ossibility of higher mill entilation)etter control of the temperature 0coolingor drying is possible in the separator

(igher output4 better efficiency -arro particle si e distribution(igher in estment costs

CLOSED CIRC6IT

Ball Mill Grinding



Ball Mill Grinding

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DESIGN AS'ECTS

O(BALL MILL S5STEM

Ball Mill Grinding



Ball Mill Grinding

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*

*eff C1

*eff C2

$ $eff

*eff T!T256 7 */$ 7 852293 7 *ength of firstcompartment 7 8:3 milleffecti e lengthFirst Compartment,o er ; 6 to 1< .=h/t)all diameter in C1 from1<<>?< mm to 9<>@< mm)all diameter in C2 from@<>:< mm to 2<>19 mm

T)E BALL MILL

Ball Mill Grinding



Ball Mill Grinding

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, A * B Vcr

1529

jD Fr rpm

BB B BB BE2589?

d C

ABSORBED 'O3ER O( A MILLS, -. N 6/3M0,A :

=here G * > Hseful *ength of mill 0m

rpm > &ill Speed 0rpmVcr > The critical speed inside liners A 0E258/Fr <5:Fr > Internal $iameter 0inside liners 0mD > Ratio bet een the apparent ball olume and the internal olumej > 0158@ ; 152 B Dd > 'pparent density of load 0t/m8 G C1AE5: J C2AE5@

C > Constant depending on the material and the liners A 1152@2 ; For clin.er mill closed circuit ith Slegten eKuipment A 1<59< ; For Clin.er # Slag A 1251@ ; For ra mi%

Ball Mill Grinding



Ball Mill Grinding

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Nor$al &al%es for the ratio Net?Gross #o4er @1 @ Nor$ally for old and ineffi"ient $ills

@1 / 'olysi%s Co$ ifle0 Dri&e

@1 2 Girth gear dri&en $ill

@1 ,@1 Modern "entral dri&e $ill

6ne0#e"ted &al%es

@1 )igh #o4er losses #ossi ly d%e to $ill

"ha$ ers r%nning e$#ty1 @1 ,+1@@ Lo4 #o4er losses #ossi ly d%e to "harge

e0#ansion and?or %ild %# of "lin9er ni s

NET AND GROSS MILL 'O3ER



Ball Mill Grinding



Ball Mill Grinding

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Bond ! E %al N%$ er of Balls

Size= -3 . 83 . 73 . 63 mm

Fo! Smalle! Feed Size

43 A 25 A

23 A 5 A

Size= -3 . 83 . 73 . 63 mm

($pical ecommendation

43 A

<3 A 23 A

3 A

T5'ICAL BALL C)ARGE (OR C+

Ball Mill Grinding



Ball Mill Grinding

52

To# siFe de#ends on ho4 $%"h #re#aration is donein the first "ha$ er1 Re"o$$endation ! 2@ 111 @ $$

S$allest siFe de#ends on the dis"harge grate slotsiFe

• "!actical !&le of th&m#> smallest = 2 C slot +idth

• ? g slot +idth 8) 3 mm> smallest = 6)23 mm

Non,"lassifying liners li$its C/ to 2 siFes

Classifying liners allo4 a large &ariety of H s

Best 'ra"ti"e =Ball Charge O#ti$iFation>

BALL C)ARGE DESIGN 8 C/

Ball Mill Grinding



Ball Mill Grinding

5<

RELATION BALL SI*E 8 'ARTICLE SI*E

?< mm

E< mm

1: mm

<41 mm

8< mm

1 mm

Ball Mill Grinding



Ball Mill Grinding

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SLOT DESIGNS

Beyond here: the slotegins to 4iden

3ith the slotflared o%t:

$aterial "an#ass freely

4itho%t a$$ing

C3I. 3IA :

C% Slots ;

From @ to 6 mm

C# /utlet Slots ;

*arger by at least

2mm than thoseof C1 outlet

Ball Mill Grinding



Ball Mill Grinding

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MILL 3ATERINJECTION

Ball Mill Grinding



Ball Mill Grinding

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3ater In e"tion 8 Only if re %ired

%D *%E?'(*D%%D *%E?'(*D% *%E?'(*D%*%E?'(*D%*% ?(.D ( ?(*% ?(.D ( ?(

KCKC KCKC

Ball Mill Grinding



Ball Mill Grinding

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KCKC KCKC


Ball Mill Grinding



Ball Mill Grinding

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*nlet +ate! inGection Hiaph!agm +ate! inGection


Ball Mill Grinding



Ball Mill Grinding

5-

Different arrange$ents to "o$#ensate for different tr%nnions

Ball Mill Grinding



g

63


Ball Mill Grinding



g

6


Ball Mill Grinding



g

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BALL MILL

INTERNALCONDITION

Ball Mill Grinding



g

6<

,urposeInsuring proper cascadingof the balls and hencecrushing of material"eneral Condition of *iners

Plate conditions 4brea<s=chips= attachments7CriterionPerformance should bechec<ed when step + )9>of initial step 4wear?@9>7Correcti e &easure3eplacement

Step

3otation

CONDITIONS O( T)E LI(TING LINERS

Ball Mill Grinding



g

64

Measure on %&#step or plate

trans erse center

erticalMeasurement

Middle ABis

VOL6ME LOADING 8 C+ ; C/Purpose

Insure adeKuate si e reductionInsure proper ourput

uic< stimate$istance bet een charge and

lo er part of the trunnion$istance bet een charge andlo er part of the entilationscreen

Criterion)et een 263 and 8E3

Correcti e MeasureRegular recharging

Ball Mill Grinding



g

65

Best 'ra"ti"e =Ball Charge Le&el Manage$ent=

LEVEL MANAGEMENT

Vol%$e Load &s1 S#e"ifi" 'o4er

+@+

/@

/

+ /@ / 2@ 2Vol%$e load

S # e " i f i "

G r i n

d i n g

E n e r g y

L 9 3

h ? t N

Ball Mill Grinding



66

,urpose+ aluating ball charge ear $etecting a mechanical problem0brea.age of a diaphragm sector

CriteriaClean charge 0no scrapRound balls 0not deformed andof suitable si e

CleanCharge

PollutedCharge

BALL C)ARGE CONDITIONS IN C+ ; C/

Correcti e &easures

)all charge sorting in case of contaminationC1 ball sorting 0e ery :<<< > 9<<< hC2 ball sorting 0e ery 1<<<< > 1E<<< h

Ball Mill Grinding



67

,urpose*imit ear andinsure a good particle

si e reduction$etecting the

presence of spit ers

Luic. + aluation&aterial / ball le el

! erfilled compartment

MATERIAL LEVEL IN C+ ; C/

Ball Mill Grinding



68

Criterion&aterial le el A ball le elo er the entire compt5

Correcti e &easuresChange in the number ofsmall balls @< mm or :<mm in C1 and 2< mm or19 mm in C2

Scoop adjustmentsControl of the circulatingload +mpty compartment

Right le el

MATERIAL LEVEL IN C+ ; C/

Ball Mill Grinding



6-

Ma0i$%$ le&el -Ball "harge is "o&ered 4ith $aterial.fine material coarse material alls ha&e "onta"t alls loose "onta"tideal "ase in / nd "o$#1 &ery "riti"al in + st "o$#1

Nor$al le&el -Material is fo%nd in et4een alls.fine material coarse material alls ha&e "onta"t ideal "ase in +st "o$#%t still $aterial et4een the alls

Too lo4 le&el -fe4 $aterial in et4een alls.

high s#e"ifi" energy4ear and rea9age on alls and liners

MATERIAL LEVEL

Ball Mill Grinding



73

,urpose'dapts the charge granulometry tothat of the material

Criterion,rogressi e decrease of the ball si e

in C2Correcti e &easuresSorting and optimi ation of the ballchargeReplacing liners

Chec.ing the si e of slotsM@mm intermediate diaphragmM6mm outlet diaphragm

Hnclassified

Classified

BALL C)ARGE CLASSI(ICATION

Ball Mill Grinding



7

,urposeInsure gas flo,re enting balls from passing

bet een compartments"eneral Condition

Cleanliness

Criteria&a%imum permeability&echanical beha ior ith the ?< mm balls and screenN 7 E< mm in C1ScreenN 7 1: mm in C2 to pre ent 2<

mm balls from escapingCorrecti e &easures

Cleaning or replacement

-ood Permeability

.otal lac< of Permeability

VENTILATION SCREENS

Ball Mill Grinding



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,urpose,ro iding outlet for thematerial in thecompartments hile

retaining spit ers and ballsImpro ing entilation

"eneral conditions

Slot plugging,eening4 Clearances

DIA')RAGM SLOTS

Scrap

Slot

Didth

C% Side

Clearance

C% Side

Clearance



Ball Mill Grinding



74

Rotation

Slots defor$ed fro$one end

Center Defor$ation o&er slot s entirelength Center

Rotation

DIA')RAGM SLOTS

Ball Mill Grinding



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Conditions of *ifting *iners,erformance has to be loo.ed at if step 7 E<3of initial step 0 earA@<3

Volume *oading G #E> to 8)>

)all Charge Conditions G Clean4 round shape and suitable si e for thecompartmentC1 has to be sorted e ery :<<< to 9<<< hC2 has to be sorted e ery 1<<<< to 1E<<< h

S6MMAR5

Ball Mill Grinding



76

&aterial le el &aterial le el A ball le el o er the entire compartment

)all charge classification,rogressi e decrease of the ball si e in C2

$iaphragm slotsFirst compartment slots G @mm to 6mmSecond compartment outlet slots larger by at least 2mmthan those of first compartment

Ventilation screens

They ha e to ha e the ma%imum permeability to let thema%imum gas flo through the mill hile retaining the

balls

S6MMAR5

Ball Mill Grinding



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Target le&els for $aterial fineness efore theinter$ediate dia#hrag$

Basis , sie&e a o%t @1 , + 7g of $aterial ifthere are "lin9er ni s #resent1

Sie&e SiFe-$$.

C%$%lati&e Resid%e- .

/12

+ , +

Ball Mill Grinding

3 - ball mill grinding

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