ball mill inspection fin

8/17/2019 Ball Mill Inspection Fin

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Ball Mill Optimization

The Ball Mill


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2March 2004The Ball mill / ATC Process

The Ball Mill

Inlet headReject return

chute

Fresh feed

Fresh air inlet

Trunnion

C1 linersC2 liners

Supports

Intermediate diaphragm

Shell

Central Ventilation ring grate

Central or ventilation ring

Outlet diaphragm

Gas dust

outlet

!ischarge "o#

Outlet seal

$aterial discharge

Drive types

Feed ArrangementsMill HeadsMill Bearings

Mill hell


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!March 2004The Ball mill / ATC Process

%

%eff C1

%eff C2

! !eff

%eff TOT

The Ball Mill

" #/D $ %atio &et'een ! and (

" #ength o) C*/Total #ength $ ratio &et'een 2+ and 40, e-cept )or &irotators

" Ball diameter in C* )rom *00".0 mm to +0"0 mm 4 / !"*/21 to 2"*/2 / 21

" Ball diameter in C2 )rom 0"(0 mm to 20"*+ mm 2"*/21 / 21 to !/4 / (/31


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Conditions of the lifting liners

Purpose ns5ring proper cascading o)

the &alls and hence cr5shing o)material

General condition of liners

Plate conditions &rea6s7 chips7attachments

Criterion Per)ormance sho5ld &e

chec6ed 'hen step 8 40,o) initial step 'ear90,

Corrective measure %eplacement

Step

rotation


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(March 2004The Ball mill / ATC Process

BOLTLESS STEP CHAMBEBOLTLESS STEP CHAMBE

! L"#E! L"#E

Less material spillageLess material spillage

Avoids $olt $rea%ageAvoids $olt $rea%age

The step si&e 'lifting po(er)The step si&e 'lifting po(er)

depends ondepends on

Mill rotation speed '*Mill rotation speed '*

critical speed)critical speed)

+olume load+olume load

Grinda$ilit, of feedGrinda$ilit, of feedmaterialmaterial

-irection of rotation-irection of rotation


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March 2004The Ball mill / ATC Process

E.ample of $olted liner


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Effect of dela,ed mill maintenance

%eplacing 'orn o5t liners in a cement mill

:increase o) the mill o5tp5t ;*(,

:decrease o) the electricity cons5mption

Delayed replacement o) li)ting liners 8!0,initial :%es5lts a)ter replacement

Average cons5med speci)ic energy

" &e)ore /0 %1h2t

" a)ter 34 %1h2t lin%ed to a return to normal mill output


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C! and C5 +olume Loading

Purpose

ns5re ade


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>-ample )or an over)illed compartment


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As an e-ample7 'hat is the e))iciency loss associatedto a poor &all vol5me loading ?

1986 1993 Gap

@ol5me loading in C* !0, 2*, "!0,

Mill o5tp5t t/h 3( (. "!0,

6h/t 2+7 !.7* ;42,


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Purpose >val5ating &all charge 'ear

Detecting a mechanical pro&lem &rea6age o) a diaphragmsector

Criteria Clean charge no scrap

%o5nd &alls not de)ormedand o) s5ita&le si=e

Corrective measures Ball charge sorting in case o)

contamination

C* &all sorting every (000 " +000 h

C2 &all sorting every *0000 " *4000 h

Ball charge conditions in C! and C5

Clean charge &olluted charge



Material level in C! and C5

Purpose #imit 'ear and ins5re a

good particle si=e

red5ction

Detecting the presence o)spit=ers 'aves

6uic% evaluation Material / &all level

Overfilled compartment


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Material level in C! and C5

Criterion Material level 9 &all level

over the entire compt

Corrective measures

Change in the n5m&er o)small &alls 0 mm 2"*/21 or (0 mm 21 inC* and20 mm !/41 or *+ mm(/31 in C2

coop ad5stments Control o) the circ5lating

load'mpt( compartment

Right level



conventional

material

transport

effect of the

material flow

control

Controlling material level in C! and C5


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Ball Charge Classification

Purpose Adapts the charge gran5lometry to

that o) the material

Criterion Progressive decrease o) the &all si=e

in C2

Corrective measures orting and optimi=ation o) the &all

charge %eplacing liners Chec6ing the si=e o) slots

mm intermediate diaphragm 3mm o5tlet diaphragm

)nclassified

Classified


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Classif,ing liners

-iameter 7898m

-iameter :898m


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rinding media to &e 5sed in 2nd cham&er 8!0mm

ipple t,pe liner for ;fine Grinding<



Effect of dela,ed mill maintenance

Ball sorting done a)ter ! years Too late 9 20000h

%es5lts a)ter &all charge sorting

= to !0* o5tp5t increase on average )or all prod5cts

Average cons5med speci)ic energy E

&e)ore 35 %1h2t

a)ter 8= %1h2t


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*.March 2004The Ball mill / ATC Process

Ho( are the liners and the $all charge>

ear o) the liners and &all charge has to &e loo6ed a)ter in order to avoid per)ormance losses

Worn out state Normal state* Gap

rindingenergy !. 6h/t !2 6h/t "*3,

Mill o5tp5t ( t/h .2 t/h ;40,

a)ter the replacing o) liners and &all charge


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+entilation Screens Purpose

ns5re gas )lo' Preventing &alls )rom passing &et'een

compartments

General condition Cleanliness

Criteria Ma-im5m permea&ility Mechanical &ehavior 'ith the .0 mm

!"*/21 &alls and screenG 8 40 mm*"!/41 in C*

creenG 8 *( mm (/31 in C2 to prevent

20 mm !/41 &alls )rom escaping Corrective measures

Cleaning or replacement

Good permeability

Total lack of permeability


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2*March 2004The Ball mill / ATC Process

Purpose

Providing o5tlet )or the material

in the compartments 'hile

retaining spit=ers and &alls

mproving ventilation

General conditions lot pl5gging

Peening7 clearances

-iaphragm Slots

Scrap

lot 'idth

C5 side clearance

C! side clearance


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Meas5ring the Diaphragm details


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2!March 2004The Ball mill / ATC Process

-iaphragm Slots

Criteria C* slots )rom mm to

3 mm C2 o5tlet slots larger &y at least 2 mm than

those o) C* o5tlet

Corrective measures Filing and cleaning Diaphragm replacement

&eened slots


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Compartment Samples

Purpose

rinding

assessment

C* and C2

Determiningspit=er locations

6uic% evaluation

amples ta6en at

the discharge end

o) the compartment

CO$&*RT$'+T +,2CO$&*RT$'+T +,1

C!! 5 4 8 3 /

C5! 5 4 8 3

amples

Direction o) rotation

Charge-./m


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2(March 2004The Ball mill / ATC Process

E?ual positioning for

sample collection andmedia grading 'measure

80 media $alls at each

position)9


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Second cham$er

sample collection usingsieve9


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2+March 2004The Ball mill / ATC Process

Meas5ring media

diameter 5sing

vernier caliper


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@ineness evolution in the mill

0

20

40

0

30

*00

* 2 ! 4 ( + 3 . *0 ** *2

Sample #um$er

* Cumulated reects

40 Im ! Im *00 Im 200 Im (00 Im

* mm 27( mm ( mm Diaphragm Diaphragm

Compartment Samples

Criteria 8(, retained on 2

to 2( mm or 3mesh sieve at thediaphragm

Progressivedecrease all alongthe mill

Corrective measure Adapting the

charge

gran5lometry Changing the

length

Inade0uate grinding

&resence of grains


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2.March 2004The Ball mill / ATC Process

Summar,

Conditions o) li)ting liners Per)ormance has to &e loo6ed at i) step 8 40, o) initial step 'ear90,

@ol5me loading $ 23, to !4, Ball charge conditions $

Clean7 ro5nd shape and s5ita&le si=e )or the compartment C* has to &e sorted every (000 to +000 h C2 has to &e sorted every *0 000 to *4 000 h


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GOP EEC"SE

1HAT CA# DO SEE >


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!2March 2004The Ball mill / ATC Process

1hat are (e loo%ing at >>>>>

As6 yo5rsel) Jhat?Jhere?

JCondition?

Bac6 side o) intermediate diaphragm

Klder type diaphragm

ap in

diaphragm

#o' permea&ility

lots LL


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!!March 2004The Ball mill / ATC Process

Hard )aced croll at mill inlet


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lotted &ac6 plates7

this is 5ndesira&le


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!(March 2004The Ball mill / ATC Process

@ery lo' permea&ility


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irth gear drive 7

B5c6et elevator mill


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!+March 2004The Ball mill / ATC Process

ntermediate diaphragmBloc6age d5e to e-cessive heat 'ithin mill

lot pro)ile is circ5m)erential and is there)ore o6

Central ventilation grid permea&ility o6


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K5tlet side o) intermediate diaphragm sho'inge-cessive 'ear


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!.March 2004The Ball mill / ATC Process

orn mill )eed inlet 7

Plant 5sed initiative 5ntil replacement availa&le


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Badly &loc6ed and

'orn central ventgrid

High 'ear

Media &loc6age

o) radial slots


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4*March 2004The Ball mill / ATC Process

Tramp material7Thiso)ten res5lts in slot

&loc6age


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4!March 2004The Ball mill / ATC Process

orn classi)ying liner

n 2nd

cham&er


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Badly )itting head 'all

liners


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4(March 2004The Ball mill / ATC Process

Cham&er 2 side o) intermediate diaphragm

ndesira&le slots &loc6ed 'ith

mall media


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@ery small ventilation grid )itted

ith 2 s5pport &ars d5e to past

damage


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4+March 2004The Ball mill / ATC Process

Central ventilation gridBloc6ed 'ith tramp material

>ntered 'ith the mill )eed

Circ5m)erential

slots


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Damaged ventilation grid

Note the ne' mesh )itted on

Kther side


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4.March 2004The Ball mill / ATC Process

%ipple liner in 2nd cham&er


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(0March 2004The Ball mill / ATC Process

Kld type o) material transportation

De)lectors


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(*March 2004The Ball mill / ATC Process

Flo' control mechanism o) modern intermediate

Diaphragm 7 Ocoops1 Ad5sta&le &y rotation

ood ventilation grid


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OBloc6ing o))1 in order To control )lo'


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(!March 2004The Ball mill / ATC Process

mall media contamination

n *st cham&er


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Dann5lar ring 7 these &ecome sa)ety iss5es


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((March 2004The Ball mill / ATC Process

Mill inlet sho'ing no area )or air inlet


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ntermediate diaphragm *st cham&er

ho'ing sectioned plates desired 7 radial

lots 5ndesired and &adly )itting


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(+March 2004The Ball mill / ATC Process

tep ch5te inlet 7 good area

For air)lo'


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onic ear 5sed )or control


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(.March 2004The Ball mill / ATC Process

Bro6en head 'all liners

Ca5sed &y over tightening

K) &olts


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tep ch5te )eeder

ater inection no==le


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*March 2004The Ball mill / ATC Process

%emova&le vent grid

ap si=e may &e 'rong


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Brea6 *( mins


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* + o l u m e l o a d

AT"O H2-

Ball mill volume load estimation

50

45

40

5

0

25

20

15

10

5

0!50 0!55 0!"0 0!"5 0!#0 0!#5 0!$0 0!$5

'IGT *3OV'

C*RG'

! I+T'R+*% !I*.


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+OLME LOA- @OMLA+OLME LOA- @OMLA

H HE"GHT ABO+E CHAGE 'M)

- M"LL "#TE#AL -"AMETE "#S"-E L"#"#G 'M)

, @ol5me #oad 9

400/P02(Cos2H/D"0(

"H/D"0(H/D"H/D20(


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Changes in apparent volume loaddue to charge e.pansion

H! Height a$ove charge FMill Crash Stop

%pparent &'ar(e density &ase )Volume load

t/m

!*1 +1 &ras' ,top $)

+ 1 + 2

H5 Height a$ove charge F Mill un Out

4!50 +2 -it'out Material)

&'ar(e .xpansion 5)


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March 2004The Ball mill / ATC Process

Target levels for material fineness$efore the intermediate diaphragm

,ieve sie ) &umulative

esidue2!" mm 1 )

1!1$ mm " )

00 um 20)

asis sieve about 0!5 1 3( of material if

t'ere are clinker nibs present!


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+March 2004The Ball mill / ATC Process


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.March 2004The Ball mill / ATC Process


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+*March 2004The Ball mill / ATC Process

Mill po(er calculationF -A1# @ormula

#ETT 1 095=8/ -A1#

-'ere

"nternal -iameter of Mill

A !904 F I

'1here I @ractional +olume Load i9e9 if +L 40* then I 094)

Charge (eight in Tonnes

# Mill speed in PM

-

1


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#ormal values for the ratio #et2Gross po(er 09J0 #ormall, for old and inefficient mills

09J5 Pol,sius Com$ifle. -rive

09J4 Girth gear driven mill

09J8 F09J3 Modern central drive mill

ne.pected values

09== High po(er losses possi$l, due to mill

cham$ers running empt,9

09J F !900 Lo( po(er losses possi$l, due to charge

e.pansion and2or $uild up of clin%er ni$s9

"f une.pected values occur K revie( the mill data

#et and Gross mill po(er


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+!March 2004The Ball mill / ATC Process


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