BALL MILL GRINDING
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Ball Mill Grinding
LEARNING OBJECTIVES At the end of the day the trainee shall e ale to ! Describe
the ball mill grinding process
Describe
ball mill internal equipment and
their impact on performance Des"rie
the #ro"ess #rin"i#les of $ill se#arations and inter#ret the Tro$# "%r&e
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BALL MILL GRINDING 'ROCESS
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Ball Mill Grinding
ACTION O( T)E BALLS 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 4
Ball Mill Grinding
CASCADING ACTION
Nipping Angle and Particle Size! 5
Ball Mill Grinding
CATARACTING ACTION
Crushing by Impact
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Ball Mill Grinding
RELEASE 'OINTS AND GRINDING RRotation ot at i on
Rel ea s eP o i n t s Release #oints 3 2 1
1
2
3
Lift Li f tZone *one
Gr i ndi ng Grinding Zone *one
1-Ca s ca di n g( t u mb l i n g) + , Cas"ading -t%$ling. 2-Cat ar act i ng( f r eef al l-maxi mpact ) / , Catara"ting -free fall , $a01 i$#a"t 3-Exc ess i veLi f t( i mpactonl i ner ) 2 , E0"essi&e Lift -i$#a"t on liner.
Liners digs into "harge1 Li ner sdi gsi nt oc har ge. So$e So mes l i p sli# o c c ur o""%rs s .
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Ball Mill Grinding
GRINDING 'ROCESS Energy trans$itted y the Balls
• Mass • Speed
Ball sizes, Specific Weight
Movement, Mill Speed, Filling, ine!s
• "!o#a#ilit$
%&m#e!, Size, Mate!ial Filling,
'ontact ($pe Conta"t
'ata!act
) *mpact, o+ %&m#e! of contacts
'ascading ) F!iction, igh %&m#e!
of contacts 8
Ball Mill Grinding
BALL C)ARGE , 'OROSIT5
Coarse Balls , Large Voids Lo4 Retention
(ine Balls , S$all Voids )igh Retention
A&erage Ball 3eight • (otal cha!ge +eight . (otal n&m#e! of #alls /0g.#all1 S#e"ifi" S%rfa"e Area • (otal s&!face a!ea . 'ha!ge +eight /m 2.t1 -
Ball Mill Grinding
GRINDING VERS6S (ILLING Inter#arti"le grinding o""%rs 4hen the &oid s#a"e is #ro#erly filled The "ollision of alls "a%ses a $o$entary high #ress%re "o$#ression %ip o! 'ontact points +he!e c!&shing ta0es place Fo! filling !atios less than 36 the!es steel to steel contact no g!inding
oids +he!e inte!pa!ticle g!inding ta0es place
Fo! filling !atios g!eate! than , #alls a!e p&shed apa!t, c&shioning impact
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Ball Mill Grinding
S'EED AND LINERS T5'E
Ball Mill Grinding
)O3 A 'ARTITION 3ALL 3OR7S Fe edEndVi e w ofPa r t i t i on wi t houtGr at eSegment s
Si deVi ew ofaPar t i t i on
3.Mat er i al gr av i t ydr ops t hr ought hecent erhub andi nt ot henex t compar t ment . 2.Mat er i al i sl i f t ed bymi l l r ot at i on.
.
1.Mat er i al fi l l st he c h amb er ,i nbe t we en t hes l ot t edpl at esand bl i ndpl at es
Mat er i al i sl i f t edby mi l l r ot at i onandi s t hengr av i t ydr opped i nt ot hene x t compar t ment .
sFl ow 1 Ga
2
BM Loa dL ev el Mat er i al pas s es t hr ought hes l ot s andfi l l st h el i f t er chamber .
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BALL MILL
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Ball Mill Grinding
T)E MILL 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! 4
Ball Mill Grinding
T)E MILL
Air Swept Mill
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Ball Mill Grinding
T)E MILL
nd ischarge "all mill with # Chamber
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Ball Mill Grinding
T)E MILL
"i$rotator
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Ball Mill Grinding
T)E BALL MILL
"as # dust outlet
Intermediate diaphragm !utlet diaphragm Reject return Inlet head C2 liners C1 liners chute
$ischarge bo%
Fresh feed !utlet seal &aterial discharge
Shell Central or entilation ring Fresh air inlet Central Ventilation ring grate Supports Trunnion
Feed 'rrangements &ill (eads &ill )earings $rie Types &ill Shell 8
Ball Mill Grinding
(EED ARRANGEMENTS
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Ball Mill Grinding
MILL )EADS
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Ball Mill Grinding
MILL BEARINGS , TR6NNION
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Ball Mill Grinding
MILL BEARINGS 8 SLIDE S)OE
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Ball Mill Grinding
MILL DRIVE T5'E 8 GIRT) GEAR
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Ball Mill Grinding
MILL DRIVE T5'E 8 CENTRAL DRIVES
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Ball Mill Grinding
MILL DRIVE T5'E 8 GEARLESS DRIVES
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Ball Mill Grinding
'O3ER RANGES O( MILL DRIVES
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BALL MILL INTERNALS
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Ball Mill Grinding
CONTIN6O6S LI(T OR STE' LINERS (or first "o$#art$ents only Better 4ear "hara"teristi"s Moderate lift ROTA TI ON
Ro t a t i o n
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Ball Mill Grinding The step sie 0lifting poer depends on &ill
rotation speed
03 Critical Speed Dire"tion of rotation
Volume
load
"rindability
of feed material
)!*T*+SS ST+, C('&)+R 1 *I-+R *ess
material spillage
'oids
bolt brea.age
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Ball Mill Grinding
SINGLE 3AVE ; D6OLI(T LINERS Ea r l yr el ea s eo n b ac k s l o pec a u s es medi at os l i p.
(or first "o$#art$ents only Negati&e a"9 slo#e ind%"es sliding Ra"ing is "o$$on: 4ear life is short
Ro t a t i o n
It has good lift D%olift has a s$all h%$# in et4een lifts to #re&ent this1 3earlife is $%"h etter1 D%olift is designed for $ills that had lorrain liners efore
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Ball Mill Grinding
LORAIN BAR LI(T LINING
# %& #'
% %& #'
Chamber %
Chamber #
<
Ball Mill Grinding
INSTALLED D6OLI(T LINERS
<2
Ball Mill Grinding
CLASSI(5ING LINERS iameter + )*)m
iameter ( )*)m
<<
Ball Mill Grinding
E
CA3MAN ,ININ-
S,-.N $ MA-/..A01 .2P
NA.A, 4.5IN P3/6I, .2P7 <4
Ball Mill Grinding
RI''LE T5'E LINERS -rinding media to be used in # nd chamber + 89mm
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Ball Mill Grinding
BEST 'RACTICES ON LINERS Refer to the Best 'ra"ti"e
=Sele"tion of Shell Liners>
Refer to the Best 'ra"ti"e
=3hen to Change Shell Liners>
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Ball Mill Grinding
'ARTITION ? O6TLET 3ALL DISC)ARGE ; /ND COM'ARTMENT VIE3
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Ball Mill Grinding
'ARTITION ? O6TLET 3ALL Do%le 4all: f%ll liftered design is the $ost "o$$on F e e dEn dVi e wo fPa r t i t i o nwi t hGr a t eSe g me n t s
Ou t e rGr a t eSe g me n t I n ne rGr a t eSe gme nt Ce n t e rHu bo rCo ne Ce nt e rSc r e e n( Mi l l Swe e p)
T y pi c al Ch a mb e rFi l l i n gL e v e l
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Ball Mill Grinding
SLEGTEN ADJ6STABLE 'ARTITION S"oo# Asse$ly
N%$er of o#en s"oo#s reg%lates the $aterial flo4
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Ball Mill Grinding
CONTROLLING MATERIAL LEVEL IN C+ ; C/
Conentional Material .ransport
ffect of the Material 6low Control 43
Ball Mill Grinding
GRINDING CIRC6ITS
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Ball Mill Grinding
O'EN CIRC6IT
-as Material
ust Collector
6an
6resh 6eed Mill
6inished Product 42
Ball Mill Grinding
O'EN CIRC6IT
*ittle or no control of fineness
-ot adapted to high fineness
,ossibility of oer grinding
(igher temperature of products
)road particles sie distribution
*oer inestment costs
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Ball Mill Grinding
CLOSED CIRC6IT Fan $ynamic Separator
$ust Collector
Fan $ust Collector
Static Separator Rejects
Fresh Feed
Finished ,roduct &ill
&aterial "as
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Ball Mill Grinding
CLOSED CIRC6IT )etter regularity because of a real control of the fineness (igh fineness is possible (igher fle%ibility and possibility of optimisation by product ,ossibility of higher mill entilation )etter control of the temperature 0cooling or drying is possible in the separator (igher output4 better efficiency -arro particle sie distribution (igher inestment costs 45
Ball Mill Grinding
DESIGN AS'ECTS O( BALL MILL S5STEM
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Ball Mill Grinding
T)E BALL MILL *eff C2 *eff C1
256 7 */$ 7 852 293 7 *ength of first compartment 7 8:3 mill effectie length First Compartment ,oer ; 6 to 1< .=h/t )all diameter in C1 from 1<<>?< mm to 9<>@< mm )all diameter in C2 from @<>:< mm to 2<>19 mm
*eff T!T $
$eff
*
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Ball Mill Grinding
ABSORBED 'O3ER O( A MILL S,-.N 6/3M0,A :
, A *B =here G * rpm Vcr Fr D j d C
rpm
1529
2589? D B j B Fr B d B C B B E Vcr
> Hseful *ength of mill 0m > &ill Speed 0rpm > The critical speed inside liners A 0E258/Fr<5: > Internal $iameter 0inside liners 0m > Ratio beteen the apparent ball olume and the internal olume > 0158@ ; 152 B D > 'pparent density of load 0t/m8 G C1AE5: J C2AE5@ > Constant depending on the material and the liners A 1152@2 ; For clin.er mill closed circuit ith Slegten eKuipment A 1<59< ; For Clin.er # Slag A 1251@ ; For ra mi%
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Ball Mill Grinding
NET AND GROSS MILL 'O3ER Nor$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
@12
Girth gear dri&en $ill
@1,@1
Modern "entral dri&e $ill
6ne0#e"ted &al%es @1
)igh #o4er losses #ossily d%e to $ill "ha$ers r%nning e$#ty1
@1,+1@@ Lo4 #o4er losses #ossily d%e to "harge e0#ansion and?or %ild %# of "lin9er nis 4-
Ball Mill Grinding
BALL C)ARGE DESIGN 8 C+ E$#hasis on "r%shing and less on grinding Ty#i"al to# siFe! • 83 mm = if eas$ to c!&sh, small feedsize • -3 mm = is the most common • 33 mm = in !a!e cases> ve!$ ha!d, coa!se feed Coarser all "harges: gi&es good "r%shing "a#aility %t! • (oo po!o&s ) sho!te! !etention • ess s&!face, less g!inding • 'an !es< in poo! p!epa!ation fo! second cham#e! if $o& ove!feed 9&s&all$ fo!ced to &nde!feed: • ?@t!a +ea! 53
Ball Mill Grinding
T5'ICAL BALL C)ARGE (OR C+ ($pical ecommendation 43 A
<3 A
Fo! Smalle! Feed Size
43 A
25 A
23 A 23 A
5 A
3 A Size = -3 . 83 . 73 . 63 mm
Size = -3 . 83 . 73 . 63 mm
Bond ! E%al N%$er of Balls 5
Ball Mill Grinding
BALL C)ARGE DESIGN 8 C/ To# siFe de#ends on ho4 $%"h #re#aration is done in the first "ha$er1 Re"o$$endation ! 2@ 111 @ $$ S$allest siFe de#ends on the dis"harge grate slot siFe
• "!actical !&le of th&m#> smallest = 2 C slot +idth • ?g slot +idth 8)3 mm> smallest = 6)23 mm Non,"lassifying liners li$its C/ to 2 siFes Classifying liners allo4 a large &ariety of Hs Best 'ra"ti"e =Ball Charge O#ti$iFation> 52
Ball Mill Grinding
RELATION BALL SI*E 8 'ARTICLE SI*E
?< mm
8< mm
1: mm
E< mm
1 mm
<41 mm
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Ball Mill Grinding
SLOT DESIGNS C3I.3IA : C% Slots ; From
@ to 6 mm
C# /utlet Slots ;
3ith the slot flared o%t: $aterial "an #ass freely 4itho%t a$$ing
*arger
by at least 2mm than those of C1 outlet
Beyond here: the slot egins to 4iden
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Ball Mill Grinding
MILL 3ATER INJECTION
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Ball Mill Grinding
3ater Ine"tion 8 Only if re%ired *%E?'(*D% *%?(.D(?(
%D *%E?'(*D%
KC
KC
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Ball Mill Grinding
3ater Ine"tion 8 Only if re%ired
KC
KC
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Ball Mill Grinding
3ater Ine"tion 8 Only if re%ired
*nlet +ate! inGection
Hiaph!agm +ate! inGection 58
Ball Mill Grinding
Different arrange$ents to "o$#ensate for different tr%nnions
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Ball Mill Grinding
Different arrange$ents to "o$#ensate for different tr%nnions
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Ball Mill Grinding
Different arrange$ents to "o$#ensate for different tr%nnions
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Ball Mill Grinding
BALL MILL INTERNAL CONDITION
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Ball Mill Grinding
CONDITIONS O( T)E LI(TING LINERS ,urpose Insuring proper cascading of the balls and hence crushing of material "eneral Condition of *iners Plate conditions 4brea of initial step 4wear?@9>7 Correctie &easure 3eplacement
Step
3otation
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Ball Mill Grinding
Purpose
VOL6ME LOADING 8 C+ ; C/
Insure adeKuate sie reduction Insure proper ourput uic< stimate $istance beteen charge and loer part of the trunnion $istance beteen charge and loer part of the entilation screen Criterion )eteen 263 and 8E3 Correctie Measure Regular recharging
Measure on %&# step or plate transerse center
ertical Measurement
Middle ABis
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Ball Mill Grinding
LEVEL MANAGEMENT Vol%$e Load &s1 S#e"ifi" 'o4er y / g r e n E /@ g N n t ? i d h n 3+ i r 9 G L " +@ i f i " e # S
+
/@
/
2@
2
Vol%$e load
Best 'ra"ti"e =Ball Charge Le&el Manage$ent= 65
Ball Mill Grinding
BALL C)ARGE CONDITIONS IN C+ ; C/ ,urpose +aluating ball charge ear $etecting a mechanical problem 0brea.age of a diaphragm sector Criteria Clean charge 0no scrap Round balls 0not deformed and Clean of suitable sie Charge Correctie &easures )all charge sorting in case of contamination C1 ball sorting 0eery :<<< > 9<<< h C2 ball sorting 0eery 1<<<< > 1E<<< h
Polluted Charge
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Ball Mill Grinding
MATERIAL LEVEL IN C+ ; C/ ,urpose *imit ear and insure a good particle sie reduction $etecting the presence of spiters Luic. +aluation &aterial / ball leel
!erfilled compartment
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Ball Mill Grinding
MATERIAL LEVEL IN C+ ; C/ Criterion
&aterial leel A ball leel oer the entire compt5
Correctie &easures
Change in the number of small balls @< mm or :< mm in C1 and 2< mm or 19 mm in C2 Scoop adjustments Control of the circulating load
Right leel
+mpty compartment 68
Ball Mill Grinding
MATERIAL LEVEL Ma0i$%$ le&el -Ball "harge is "o&ered 4ith $aterial. fine material coarse material alls ha&e "onta"t alls loose "onta"t ideal "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" energy 4ear and rea9age on alls and liners 6-
Ball Mill Grinding
BALL C)ARGE CLASSI(ICATION ,urpose 'dapts the charge granulometry to that of the material Criterion ,rogressie decrease of the ball sie in C2 Correctie &easures Sorting and optimiation of the ball charge Replacing liners Chec.ing the sie of slots M @mm intermediate diaphragm M 6mm outlet diaphragm
Classified
Hnclassified
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Ball Mill Grinding
VENTILATION SCREENS ,urpose
Insure gas flo ,reenting balls from passing beteen compartments
-ood Permeability
"eneral Condition
Cleanliness
Criteria
&a%imum permeability &echanical behaior ith the ?< mm balls and screenN 7 E< mm in C1 ScreenN 7 1: mm in C2 to preent 2< mm balls from escaping
.otal lac< of Permeability
Correctie &easures
Cleaning or replacement 7
Ball Mill Grinding
DIA')RAGM SLOTS ,urpose ,roiding outlet for the material in the compartments hile retaining spiters and balls Improing entilation "eneral conditions Slot plugging ,eening4 Clearances
Scrap
C% Side Clearance
Slot C% Side Didth Clearance
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Ball Mill Grinding
DIA')RAGM SLOTS Criteria C1
slots from @ to 6 mm
,eened slots
C2
outlet slots larger by at least 2 mm than those of C1 outlet
Correctie &easures Filing
and cleaning
$iaphragm replacement
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Ball Mill Grinding
DIA')RAGM SLOTS Rotation Rotation
Slots defor$ed fro$ one end
Center
Defor$ation o&er slots entire length Center
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Ball Mill Grinding
S6MMAR5 Conditions of *ifting *iners ,erformance has to be loo.ed at if step 7 E<3 of initial step 0earA@<3 Volume *oad *oading ing G #E> to 8)> )all Charge Conditions G Clean4 round shape and suitable sie for the compartment C1 has to be sorted eery :<<< to 9<<< h C2 has to be sorted eery 1<<<< to 1E<<< h 75
Ball Mill Grinding
S6MMAR5 &aterial leel &aterial
leel A ball leel oer the entire compartment
)all charge classification ,rogressie
decrease of the ball sie in C2
$iaphragm slots First
compartment slots G @mm to 6mm Second compartment outlet slots larger by at least 2mm than those of first compartment
Ventilation screens They
hae to hae the ma%imum permeability to let the ma%imum gas flo through the mill hile retaining the balls 76
Ball Mill Grinding
Target le&els for $aterial fineness efore the inter$ediate dia#hrag$ Sie&e SiFe -$$.
C%$%lati&e Resid%e -.
/12
+
, +
Basis , sie&e ao%t @1 , + 7g of $aterial if there are "lin9er nis #resent1 77
