Mill Grinding

I nt r oduc t i ont oCe me ntMa nuf ac t ur i ng

T a bl eofCont e nt s MI LLGRI NDI NG THEORY

1.

2.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I nt r oduct i onandOve r vi ew.

3

1. 1

I nt r o duc t i ont oGr i ndi ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

1. 2

Gr i ndi ngMi l l Ci r c ui t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 2. 1 Open-Ci r c ui tGr i ndi ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 2. 2 Cl os ed-Ci r c ui tGr i ndi ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 2. 3 Pr i nc i pl esofCl os edCi r c ui tGr i ndi ng. . . . . . . . . . . . . . . . . . . . . . . . . .

4 4 4 8

1. 3

T y pesofMi l l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 3. 1 Bal l Mi l l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 3. 2 Rol l erPr e s sMi Mi l l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. 3. 3 Rol l erorBowl Mi l l s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8 9 9 9

I nt er nalBal lMi l lPar t s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

2. 1

Par t i t i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 1. 1 Pur p os eofPar t i t i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 1. 2 Doubl eWal l Di aphr agm Par t i t i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . 1 . 3 Op er a t i o nan dRe pa i ro ft h eDi a ph r a gm Pa r t i t i o n. . . . . .

12 12 12 1 6

2. 2

Li ner s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 2. 1 Pur p os eof Li ner s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 2. 2 T y pesofLi ner s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. 2. 3 Li nerQual i t y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17 17 18 24

C. T . S T e c h ni c a lT r a i ni ng


3.

Ball Mill Grinding and Related Topics

25

3. 1

Bal l Mi l l i ngPr oc es s( Bas i c sandFundament al s ) . . . . . . . . . . . . . . . . . . . . . 3. 1. 1 Si z eReduc t i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 2 BedMov ement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 3 Fac t or sI nfl uenc i ngSi z eReduc t i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 4 Mi l lCr i t i c al Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 5 Bal l Si z eandBr eak ageRat es. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 6 Bal l Mi Mi l l Li ner s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 7 Mi l l SweepI nfl uenc eonGr i ndi ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 1. 8 Mi l l Mas sT r ans por tandBy pas s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25 25 26 27 28 29 31 31 33

3. 2

Gr i ndi ngMedi a. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 2. 1 Bal l T y pesandWear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 2. 2 Bal lCoat i ng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 2. 3 Bal l Char g eDes i gn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

39 39 41 41

3. 3

Bal l Mi l l andCi r c ui tEv al uat i onsandT es t s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 3. 1 Mi l l Mat er i al Lev el s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 3. 2 Fi nenes sEv al uat i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 3. 3 Mi l l Ret ent i onTi me. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 3. 4 Ci r c ul at i ngLoad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

52 52 54 54 57

3. 4

Bal l Mi l l Cont r ol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 1 Bas i cBal l Mi l l Cont r ol Theor y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 2 Mi l l Mot ork W Cont r ol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 3 Mi l l SoundCont r o l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 4 Di s c har geBuc k etEl ev at orMot ork W. W. . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 5 Rej ec t sFl owr a t e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3. 4. 6 Rul eBas eMi l l Cont r ol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

58 58 58 61 62 63 64



4.

Air Separators

67

4. 1

I nt r oduc t i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

4. 2

T y pes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 2. 1 St at i cGr i t Separ a t or . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 2. 2 St ur t ev antSepar a t or s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 2. 3 Ray mondSepar at or s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 2. 4 Hi ghEffic i enc ySepar at or s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67 68 72 77 79

4. 3

Separ a t orEffic i enc y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 3. 1 Tr o mpCur v e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87 87

4. 3. 2 Ros i nRamml erNumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

92

4. 4

Mi l l Ci r c ul at i ngLoads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 4. 1 Defi ni t i on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 4. 2 Ci r c ul at i ngLoadandPr oduc t i onRat es . . . . . . . . . . . . . . . . . . . . . . 4. 4. 3 L/ DRat i oandCi r c ul at i ngLoad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. 4. 4 Ci r c ul at i ngLoadCal c ul at i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

93 93 94 96 97

4. 5

Qf / QaPr i nc i pl e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4. 5. 1 By pas sandQf / Qa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102



3.

MI LLGRI NDI NGTHEORY

For ewor d Th et e x to ft h ef o l l o wi n gs e c t i o no n Mi l lGr i n di n g wa sa da pt e df r om a l a r g er doc umentent i t l ed: Laf ar geMi l l Gr i ndi ngRef er enc e,Edi t i on1 Vol ume1:Pr ac t i c al Fundament al sofBal l Mi l l i ngandSepar at i on

Reader swi s hi ngt os t udyt het opi ci ngr eat erdept handdet ai lar eenc our agedt o obt ai nac opyoft hi sandot herappr opr i at ev ol umeswhi c har ea v ai l abl ef r om CTS i nhar dc opyorondi s k et t ef orMac i nt os h.

Ot herv ol umest hatwi l lbeav ai l abl ei nt heLaf ar geMi l lGr i ndi ngRef er enc es er i es ( al l ofwhi c hwi l l beav ai l abl ebef or et heendof1992)ar e: Vol ume2:Aux i l i ar yEqui pmenti nMi l l Ci r c ui t s Vol ume3:Pr ocessMet hodsandTheor y Vol ume4:Rol l erMi l l sandRol l erPr es s es Vo l u me5:We tPr o c es sGr i n di n g

Vo l u me s1& 2we r eme an tt ob ep r a c t i c a lr e f e r e nc ea ndi d eab oo k sf o rp l a nt pe op l e ;t oh el ps o l v et h ed i z z ya r r a yofp r o bl e mst h eye nc o un t er e d. Th en ex t t hr eet ex t sspec i al i z eandi nc l udemor et heor ywher eappr opr i at e. Re ad ers h ou l du nd er s t a nd t h att h et e x tp r e s e nt e dh er eh as b e en e di t e d, s ubs t ant i al l y ,t os ui tt he t i me al l ot t ed i nt hi sc our s e" I nt r oduc t i on t o Pr oc es s Eng i neer i ng " . Real i s t i c al l ywe c anno tpr es entand t eac ht hi ssegmentwhi c h nor mal l yr equi r es9 wor k i ng d ay s( f orPr od uc t i on Super v i s or s ) . Qui t es i mpl y


4-4


t h er ei st o o mu c h ma t e r i a l . Re co gn i z et h att h et op i c" Mi l lGr i n di n ga nd Separ at i on"i sf armor ec ompl e xt hanmos tofusr eal i z eandi nan ys hor tc our s e onec anonl yc ov ert hehi ghl i ght swhi c hnev erd el v esi nt ot hei nt r i c ac i esoft hi s wh ol efi el d.Wec anon l ye nc ou r a gey out oas kq ue s t i o nsa nddi s c o v er . Sam Fuj i mot o

Paul Uk r ai net z

Pr oc es sEngi neer

Pr oc es sEngi neer

Laf ar geCanadaI nc .

Laf ar geCa nadaI nc .


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1.

Introduction and !er!ie"

1. 1

I nt r oduc t i ont oGr i ndi ng

I nt h ec e me n ti n du s t r y we s p e nd a l o to fe ff or ta nd mo ne yi n t os i z e r educ t i onatv ar i ouss t agesi nt hewhol epr oc es s .Ateac hoft hes es t eps wet r yt ogr i ndmat er i al sv er yfi nel yandwi t hi nas pec i fi cs i z eands ur f ac e ar ear ange.Wh y ? Agi v enpar t i c l e' ss i z e( ormes h)a nds ur f ac ear ea( or b l a i n e) s i g ni fi c a nt l yi n fl ue nc e st h es p ee da nd c o mp l e t e ne s so ft h e c h emi c alr e ac t i o n wi t ht h atp ar t i c l e . Fo re x ampl eap ou nd o fc o ur s e par t i c l eswi l lhav eamuc hs mal l ert ot als ur f ac ear eaandwi l lr eac ts l ower t ha nap ou ndo fv e r yfi nep ar t i c l e swh i c hwo ul dh av eamuc hl ar ge rt o t a l s ur f ac ear ea.Mor eov erwi t ht hel ar gerpar t i c l es ,t her ei st hec hanc et hat t he r eac t i on wi l lno tc ons ume t he whol e par t i c l e,l ea v i ng t he c ent er s u nt o uc h ed . Gr i n di n ga l l o wst h ec e me ntma nu f a c t u r e rt oi n fl ue nc ea nd t ai l ort hepr oc es st oac hi ev et hedes i r edr es ul t . I nr aw mi xgr i ndi ng,t hepar t i c l es i z ehasani mpor t antr ol ei nt heabi l i t y and e as et o pr oduc ec l i nk er ,t he c l i nk e rqual i t ya nd t he effic i enc ywi t h wh i c hwea c c omp l i s ht hi si nt h ek i l n . Mos tp l a nt sus ea% p as s i n g2 00 mes h( o r75mi c r o ns i z e )t a r g eta st h ei nd ext ode t er mi n e,wh et h ert h e p r o duc th asb ee np r o pe r l yg r o un d.Se eal s o" TheI mpa c to fRa w Gr i n di n g onKi l nOper at i on" . Forc oalmi l l s ,mos tpl ant sus et he200mes ht ar getaswel l .Thepar t i c l e s i z ei nf u el shasap r of o un deff ec to nt h efl a me ' ss ha pe,t e mp er a t ur ea nd s t abi l i t y ,whi c hul t i mat el yi nfl uenc est hec l i nk erqual i t y . Fo rc e me ntfi n i s hmi l l s ,weu s eb ot ha3 25me s h( 4 5mi c r o n)a ndb l a i n e ( ors u r f ac e ar ea)t ar ge t s . Di ff er entt ar ge t sand di ff er entemphas i sar e u s e dd ep en di n go nt h et y p eo fc e me ntb ei n gp r o du c e da ndt h ed es i r e d p er f o r ma nc e . Fo re x amp l e,ASTM T y pe1c e me nt sc ha r a c t e r i s t i c a l l yh as v e r yg oo dea r l yd ays t r e ng t hga i n sbu ts l o wsdo wna t28 d ay s .Th e3 25 mes hi nc ement ss t r ongl yi nfl uenc esl at eda ys t r engt hsandt her ef or emos t pl ant sf oc us esont hi st ar getc l os el y .ForASTM T y pe3wet y pi c al l yr ai s e t h eb l a i n eo rs ur f a c ea r e a( t h ea mo un to fs u pe rfi ne s )i no r d ert o dr amat i c al l yr ai s et he1and3da ys t r engt hper f or manc e.


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I ns hor tho w wegr i ndmat er i al satt hepl ant sateac hs t agepl a y sav e r y maj orr ol ei nours uc c es si npr oduc i ngc ons i s t ent l yhi ghqual i t yc ement s . Ther ef or ewemus tal lunder s t andgr i ndi ngt hor oughl yi fwear et os t ayi n bus i nes s .Wes hal l b egi nt hatpr oc es sher e.

1. 2

Gr i ndi ngMi l l Ci r c ui t s

A mi l lc i r c u i ti sac omb i n at i o na ndp r o pera r r a nge me nto fo neormo r e gr i ndi ngmi l l sandt heaux i l i ar i esr equi r edt oc onv ey ,c l as si f yandt oc ol l ec t t hegr o undpr oduc t . Letusfir s tl ookatt heBal lMi l lgr i ndi ngc i r c ui t s .Onc eac i r c ui ti sdefi ned asei t herWET orDRY gr i ndi ng,i tneedbef ur t herdefinedasOPEN or CL OSEDc i r c u i t .

1. 2. 1

OpenCi r cui tGr i ndi ng

Wher et hemi l lpr oduc ti ss entt os t or ages i l oswi t houts i z i ngorr et ur ni ng t heov er s i z et ot hemi l lf orf ur t hergr i ndi ng.Fi gur e4. 1. 2. 1i sas ket c hofan openc i r c ui tmi l l .Si nc es i z er educ t i onmus tbeac c ompl i s hedi nonepas s , openc i r c ui tmi l l st endt obev er yl ong.

1. 2. 2

Cl osedCi r cui tGr i ndi ng

Wher et hemi l lpr oduc ti ss entt ot hes epar at orandt heov er s i z er et ur ned t ot he mi l lf orf ur t herg r i ndi ng. The o v er s i z e mat er i alc an be c al l ed REJECTS,TAI LI NGSorCI RCULATI NG LOAD.Fi gur e4. 1. 2. 2i sask et ch ofac l os edc i r c ui tmi l l .Fi gur e4. 1. 2. 3i sav ar i at i ons howi ngfl as hdr y i ng.


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5

g n i d n i r G t i u c r i C n e p O 1 . 2 . 1 . g i F

l l i m t i u c r i c n e p o n a f o h c t e k S

t n e l l o i l m i o m e l s i c s d g m d r n e i u n e e d s f k u n p l n i l o i i y r r l C G M G G . . . . . 1 2 3 4 5

4

3

2

1


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Fi g.1. 2. 2-Cl osedCi r cui tGr i ndi ng

Separ at orF eed( A)

Separ at or

Rej ec t s( R)

Fi nes( F)

F r e s hF e ed( K)

Mi l l


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Fi g.1. 2. 3-Cl osedCi r cui tGr i ndi ng Wi t hDr yi ngofFeed

Sepa r at orF e ed( A)

Separ at or

F r es hF eed( K)

Rej ec t s( R)

Fi nes( F)

Mi l l


4-10


1.2.3

#rinciples o$ %losed %ircuit Grinding

Formos tr a w mi xandc ementgr i ndi ngweus edc l os edc i r c ui tgr i ndi n g. I nac l os ed c i r c ui ts y s t em,t he mi l lpr oduc ti sc onv ey ed t oac l as s i fi er ( s epar at or )andt hemat er i alc oar s ert hant her equi r edmax i mum s i z ei s r e t ur nedt ot hemi l lf eed.Thes epar at orr emo v est hefi ne( Fi ni s hPr oduc t ) , wh i c hi st henpumpedt os t or agea ndt hec oar s e par t i c l es( r ej ec t s )a r e r e t ur nedt ot hemi l l .Suffic i entnew f eedmat er i ali saddedasr equi r edt o mai nt ai nt hec har gewi t hi nt hemi l l att heoper at i ngc apac i t y . Fr om t hec os ts t andpoi nt ,i ti sl es sex pens i v et ogr i ndi nopenc i r c ui ti ft he r eq ui r e dp r o du ctd oe sn ote x c ee da pp r o x i ma t e l y33 00Bl a i n e. Th e mi l l s ys t em i nopenc i r c ui ti ss i mpl er ,buti ti snotaseffic i entasc l os edc i r c ui t gr i ndi ng. I n gener alt he yt end t oo v er gr i nd t he pr oduc tt o mai nt ai na c er t ai nmes ht ar get . I nt hec l os edc i r c ui t ,t hemi l lhasagr eat erc apac i t yandt hefi ni s hpr oduc t c ont ai nsl i t t l eornoov er s i z e,dependi ngupont headj us t ment smadet ot he s epar at or .Al s of orqual i t yc ont r ol ,c l os ed c i r c ui ts y s t ems off ermor e opt i ons t o adj us t t he pr oduc tp ar t i c l es i z e di s t r i but i ons f oropt i mum p er f o r ma nc e .

1. 3

T y pesofMi l l s

Thegr i ndi ngmi l li st hemai npi ec eofequi pmentus edi nt het ot alfi ni s h gr i ndi ng s y s t em. Gr i nd i ng mi l l sc an be c l as s i fi ed i nt ot he f ol l o wi ng c at egor i es : 1. 3. 1 Bal l Mi l l s . 1. 3. 2 Rol l erPr es sMi l l s . 1. 3. 3 Rol l erorBo wl Mi l l s .


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1.3.1

Ball Mills

A bal lmi l li sac yl i ndr i c aldr um wi t hv ar y i ngr at i oofdi amet ert ol engt h, ( a l s oc al l e dt ub e mi l l s ) . I th as e i t h er o ne ,o rt wo c ompa r t men t s , ( s ome t i mest hr eec ompt . ) . Thegr i ndi ngmed i aar eus ual l ys t eelorc as t i r onbal l sofdi ffer entdi amet er s . Wi t hi nLaf ar ge,t hev as tmaj or i t yoft he g r i n di n gi sa c c o mp l i s h e d wi t hs u c h mi l l sa nd c o me i nav a r i e t yo f ar r angement sr efl ec t i ngt het ec hnol ogyoft het i meandwhati ti ss uppos ed t obegr i ndi ng.

1. 3. 2

Rol l erPr essMi l l s

Ar o l l e rp r e s sa ss ho wno nt h ea t t a ch edd i a gr a mi sno t h i n gmo r et h ana pai rorr ol l spl ac edi noppos i ngpos i t i onwi t has mal l gapbet weent her ol l s . Oneoft her ol l si ss t at i onar y( fi x edr ol l )andon( mov eabl er ol l )i smount ed ons l i di nggui deway s ,wi t hhy dr aul i cc yl i nder sappl y i ngf or c et owar dt he fi x edr ol l .Themov eabl er ol loft her ol l erpr es si sunderc ons t antl oadf r om t hehy dr aul i ccy l i nder s .I ti sanol di dea,r ei nv ent edf oranewappl i c at i on. Thus f ar i ns t al l at i ons ha v e been app l i ed t oe x i s t i ng b al lmi l l s ,t o dr amat i c al l yi mpr ov egr i ndi ngr at es .Howev ert heyar edi ffic ul tt obal anc e a ndc a nb ee x pe ns i v et oma i n t a i n .

1. 3. 3

Rol l erorBowl Mi l l s

Rol l erMi l l sc ons i s tofwheel s( orr ol l er s )mount edabov ear ot at i ngt abl e. Fr e s hf e edi sdr op pedi n t ot h et a bl ei sgr o un d be t we ent h e wh eel san d t abl east het abl et ur ns .Of t ent hes emi l l sar eai rs weptandus ual l yc ome wi t ht her e own bui l ti ns epar at or . Man y oft he i ns t al l at i ons i n Nor t h Amer i c a ar ef org r i ndi ng c oal ,wi t haf e w gr i ndi ng r a w mat er i al s( eg. Bal c ones ,Da v enpor tan d Demopo l i s ) .I ns t al l at i onsar eus ual l yc ompac t andar ei dealf orr el at i v el ys of tmat er i al s ,butnor mal l yhav ec ompl exhot gasc i r c ui t sas soc i at edwi t ht hem.


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Rol l e rPr e ssConfigur a t i on Thebas i cc onfi gur at i onoft her ol l erpr es sc ons i s t sof : •

2r ol l er s

•

Fr ame

•

Rol l ersu ppor tbear i ngs

•

Hydr aul i ccy l i nder s

•

Hy dr aul i ca c c umul at or

Hy dr aul i c ac c u mu l a t o r

Bear i ngbl oc k s Hy dr aul i c c y l i nder

T ens i on member

T ens i onmember Mo v eabl er ol l


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Fi x edr ol l

Fr ame end pi ec e


Cl as s i fi ers haf t Dr i v enb y Var i abl es peeddr i v e

Pr oduc t Di s c har gepor t

Cl as si fi er Bl a de

Ra wmat er i al

T o t al l yenc l os ed hou s i ng

F eedspout Rol l ers uppor t Rol l erhous i ng

Loadi ngr od ( oneoft hr ee)

Gr i ndi ngr ol l er Por t edai rr i ng

Gasi nt ak epor t Ho tg a s ( Rec l ai medf r om k i l n pr eheat erorc ool er )

Gasp l en i um Wear i ngr i ng Ro t at i nggr i ndi ngt abl e Hi g hs p ee ds h af t

Hy dr aul i cl oadi ng c y l i nder( oneoft hr ee)

Speedr educer


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2.

Internal Ball Mill #arts

2. 1

Par t i t i ons

2. 1. 1Pur pos eofPar t i t i ons Thei rpr i mar ypur pos ei st os epar at et hedi ffer ents i z esoft hebal lc har ge i nor dert or oughl ymat c ht hebal ls i z et opar t i c l es i z ebei nggr ound.For e x ampl e,man y open c i r c ui tmi l l s wer e or i gi nal l ys upp l i e d wi t ht hr ee c o mp ar t me nt s .Ho we v e rmo s tc o mp ar t me nt e dmi l l si nLaf a r g et o da yha v e j us tt wo. The mat er i albei ng gr ound i nt he fi r s tc ompar t mentpas s es t hr ought hegr at es l ot si nt hepar t i t i ont oent ert hes ec ondc ompar t ment , t henl eav est hemi l l t hr ought hedi s char gegr at e. As ec ondar ypur pos ef oradoubl ei nt er medi at epar t i t i oni st or et ai nt he i ns uffic i ent l ygr oundmat er i ali nt hefi r s tc ompar t ment ,byr egul at i ngt he mat er i al l ev el i ni t .Pr oper l ydes i gnedt hepar t i t i ondet er mi nest hefl owr at e f r o mo nec o mp ar t me ntt ot h en ex ta ndt h er e byhe l p st oma i n t a i nag oo d fi l l i ngr at i o. Ofc our s ei tal s or oughl ysepar at esandr et ai nst hel ar gemat er i alpar t i c l es i nt hefi r s tc ompar t ment .

2. 1. 2

Doubl eWal l Di aphr agm Par t i t i ons

Thes epar t i t i onsar eequi ppedwi t hl i f t er swhi c hr egul at et hefl ow r at eof t hemat er i a lf r o mt hefi r s tt ot h es ec o ndc o mp ar t me nt . Th eb ac kpl a t e s ar ebl i nd.


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As mill rotates, material is lited and dropped through the opening in the center hub.

Fee d End View of Partition

Material Discharged

Airfow

$iter or Scoop "lind #late

Air Sweep enter Screen enter !ub or one Slotted Grate Segment

In the lower hal, material is pushed through the s lots, lling the empty liter chamber.

Si deVi e w

St andar dLi f t er edPar t i t i ons These ar ec ommon and mos t l ysufferf r om t he s ame pr obl em. The por os i t yoft hefi r s tc ompar t mentc har gei shi ghandwi t h af ul l y l i f t er ed par t i t i on( l i f t er sr i ghtt ot hes hel l )t hemat er i alfi l l i ngr at i o( U)i spul l eddown wel lbel ow 0. 9andbal lweari sac c el er at ed. Us ual l yi ti sbel ow t he0. 6 poi ntatwhi c hmat er i albr eak ager at esar er educ ed. ( I not herwor dst he v oi dsar et ooempt y-s eeal s os ec t i ononMat er i alFi l l i ngRat i o. ) Thi si s ev i denc edbynomat er i alv i s i bl eont hebal l satt hepar t i t i on,s omet i mes onemus tdi g18"ormor et o' hi t ' c ement . The Fr ench have at t empt ed t o over come t hi st hr ough bal lc har ge mo di fi c a t i o ns ( mo r es ma l l e r ba l l s )a nd r e du c i n gt h es l o ts i z e . At De mo po l i sl a r g eh ol e sh av eb ee nc u ti nt h el i f t e r st or e du c et h ei r effic i enc y .Nei t hermet hodhasbeenhi ghl ys uc c es s f ul .Changi ngs l ots i z e


4-16


andc ut t i ngl i f t er sar ei r r ev er s i bl eandpl ant shav eex per i enc edv er yl i mi t ed s uc ces s. Addi ngs mal lbal l st oi nc r eas et hefi l l i ngr at i oi sO. K.unt i lt he c i r c ul at i ngl oadormat er i algr i ndabi l i t yc hanges ,atwhi c ht i mey oumus t s t ar t ov er . Ot herpl ant sha v ei ns t al l edpar t i t i onswhi c har emul t i s egment ed. Thes e al l ow y out or epl ac es l ot t eds egment swi t hbl i nds ec t i onsont hei nl ets i de andt her ebyc ont r ol l i ngt het o t als l otar ea.TheGr oupdoesnothav eal ot ofe xper i enc ewi t ht hi st y pebuti tappear sdi ffic ul tt omak ec hangesandi t a l s oc h ok e soffmi l l s wee p.

Adj us t abl eDoubl eWal l Di a phr agm Par t i t i ons Th i si sa d ou bl e wa l lp ar t i t i o n wi t ha dj u s t a bl es c o op sd ev e l op ed b y SL EGTEN,a ndl a t e ro ffe r e db yot h erma nu f a c t u r e r s . Thegr i ndi ngeffic i enc yofami l l dependsdi r ec t l yont het i meofr et ent i onof t hemat er i alwi t hi nt hebal lc har ge.Thi sr egul at i ngpar t i t i ont husper mi t s adj us t mentoft hemat er i all e v eli nt hefi r s tc ompar t mentb yus i ngs c oops l o c at ed b et wee nt h es l o t t e dg r a t e sa ndt h eb l i n dg r a t e so nt h es ec o nd c o mp ar t me nts i d e.


4-17


SLEGTENDOUBLE -DI APHRAGM PARTI TI ON Ac t ual i ns t al l at i onsoft heSLEGTENr egul at i ngdi aphr agm onfi ni s hmi l l si n t h eGr o upar e : • Bous s ens • Vald' Az er gues • Po r t l a No uv e l l e • Cont es • LeHav r e • Al pena • Bal c ones • Bat h • Whi t ehal l • Wos s i ngen • L . F . I .atDu nk e r q ue,Fos ,a ndNo r f ol k Th eGr o u ps t r o ng l yr e c o mme nd sSL EGTEN d i a ph r a gm p ar t i t i o nso v e ra l l o t her s .I n addi t i on,t he SLEGTEN di aphr agm par t i t i on i smec hani c al l y v er y wel ldes i gned i nt hati th as a s i mpl es t r uc t ur e,wel ladap t ed t o s t r es s es c aus ed by t he r ot at i on oft he mi l ls h el l ,es pec i al l yi nl ar ge


4-18


di amet ermi l l s . Howev er ,r ec ogni z et hatt hei ns t al l at i on ofa r egul at i ng di aphr agm r equi r esal ongc ommi s s i oni ngper i od,s y s t emat i c al l ymak i ng adj us t ment soft hegr i ndi ngc har geandpar t i t i ont os eeani mpr o v ement .

2. 1. 3

Oper at i onandRepai roft heDi aphr agm Par t i t i on

The di aphr agm and gr at es ar ear at herweak ( per haps t he weakest ) el ementi ns i det hemi l l .I ft heyar ei npoors hape,t hemi l lwi l lf unc t i on poor l y . • Sl o t si nba ds h ap eb l o c kea s i l y . • Hi g hp r e ss ur el o ssc au s espoo rv e nt i l a t i o n. • Ho l e s ,e x c e s s i v ep l a yb et we ent h ep l a t e s ,wo r na nde nl a r g ed s l ot s ,al lpas sc l i nk erpar t i c l es( 2,5,10mm)whi c hpr ev entt he effic i entac t i onoft hes ec ondc ompar t mentb al l c har ge. I ti st her ef or enec es sar yt oc onduc tadet ai l edi ns pec t i onev er yt i met he mi l l i sent er ed. Thepr operoper at i onoft hemi l lpar t i t i onc anbebet t erunder s t oodbyt he f ol l owi ngt wopr oc es sel ement s : • Fi neness cur v es of s ampl es t aken al ong t he bal lchar ge, ( gr anul omet r y ) .I ft heyshow t oomanyl ar gepar t i c l es( 2,5,10 mm)i nt hes ec ondchamber ,t hepar t i t i onneedsat t ent i on. • Th el e v e lo ft h e ma t e r i a li nt h efi r s tc o mp ar t me nt . A we l l adj us t edpar t i t i onwi l lk eepal ev elofmat er i alequalt ot hel ev el oft hebal l s( ev ens l i ght l yhi gher )i nt hefi r s tc ompar t ment . I ft hi si snott hec as e,t heny oumus tpl aywi t h: • t hepos i t i onoft hes c oops ,i fi ns t al l ed • t hedi mens i onsoft hel i f t er s ,i fpos si bl e


4-19


• t h en umb era nd / o rt h ed i me ns i o nso ft h es l o t s


4-20


2.2

&iners

2. 2. 1

Pur pos eofLi ner s

Thepur pos eofmi l ll i ner si snotonl yt opr ot ec tt hemi l ls hel lbutt heymus t al s o" gr i p"t hegr i ndi ngbal l sandr el eas et hem att her i ghthei ghtt oobt ai n t hec as cadi ngort umbl i ngt hatmax i mi z est hegr i ndi ngr at e.I ft hebal l sar e c ar r i edt oohi ght heywi l lgett hr ownagai ns tt hemi l ll i ner sont heoppos i t e s i dewher et hebal l sorl i ner smaybr eak .I naddi t i on,t hegr i ndi ngac t i on c oul dbel i mi t edt ot het oeoft hemi l ll oad.I ft hebal l sar enotc ar r i edhi gh enought hent hei mpac tener g i eswhi l et umbl i ngar egr eat l yr educ ed,t hus r et ar di ng t he gr i ndi ng ac t i on. I n addi t i on,r ec ogni z et hats ome s l i di ng c ont ac twi l l oc curwhi c hi nc r eas esl i nerwear . Manyofusl os es i ghtoft hef ac tt hatt hebal l sshoul dnotbes l i di ngast hey ar ebei ngl i f t edup. Sl i di ngbet weenbal l sandl i ner si nc r eas eswearand c anl eadt opr emat ur ef ai l ur es .Ev i denc eoft hi sc anbes eeni nt hef or m of " r ac i ng" .Rac i ngar et hegr oov esorr i ngswor ni nt ol i ner sandi sar es ul tof s l i di ng c ont ac tbet ween bal l sand l i ner s . Ex c es si v er ac i ng wi l li nt ur n p r o mo t emo r es l i di n gc on t a cta nd t h usa c ce l e r a t i ngt h e wh ol epr oc e s s. Rec ogni z et hought hatast hel i nerr ot at esar oundandent er si nt ot het oe oft hebal lc har ges omes l i di ngc ont ac twi l loc curunt i lt hel i nerhasgr i pped t hebal lc har ge,t ol i f ti t .Somemanuf ac t ur er st ak eadv ant ageoft hi sand mar k e tg r oo v ed l i n er s whi c ha r ed es i g ne dt od oe x t r ag r i n di ng i nt h e g r o ov e st h ems el v e sa st h el i n er se nt e rt h e ba l lc h ar ge . Ex a mpl e sa r e Ma no i r ,Ar mc o De l l o y e ,a n dOwe nCo r p . Li nerd es i gn i sc r i t i c alt o good gr i ndi ng ac t i on and wearl i f e. Car ef ul c ons i der at i onmus tal s obegi v ent obal lc har gedes i gn,mat er i al ,mat er i al l o ad a nd t he g r i ndi ng ac t i on r equi r ed i nt hatc ompar t menti n or dert o des i gnt heappr opr i at el i ner .


4-21


2.2.2

T'pes o$ &iners

A)Fi r s tComp ar t me nt Th ewo r kdo nei nt hi sc omp ar t me nti sdo neb yi mpa c t ,t hu ss o mec a l lt h i s t hec r us hi ngc ompar t ment . Ther ef or et hel i ner smus tbel i f t i ngandar e pr es enti ns ev er alf or ms ,bl oc k ,wedgebar ,Lor r ai neandDuol i f t . Thei r j obi ss i mpl e.Li f tt hebal l shi ght oej ec tt hem f r om t hec har ges ot heyf al l f ar t herandhi thar der .Thi si ss howni nt hef ol l owi ngdr awi ngs howi ngt he det ac hmentpoi ntoft hebal l sf r om t hel i ni ngf ora0. 75m Ø t es tmi l l ,75% c r i t i c als peed,25% v ol umel oad,30mm bal l s ,mat er i alfi l l i ngr at i o1. 0, f eed<3. 15mm.


4-22


Smooth %&*()

$iters %&'()

Groo+ed %&()

Th er ef o r es a t u r a t i n gi ss u pp or t e da ndt h ef r a ct ur eme c ha ni s m en ha nc ed . Thi smeanst hatbr eak ager at eswi l l bes hi f t edt owar dst hec oar s erpar t i c l e s i z es ,att hee x pe ns eofbr eak ager at esont hefi neron es . Thi si scl ear l yshownbyt es t sconduc t edbyRoger setal .( " . . Effec tofLi ner De s i gno n Per f o r man c e ofa . . . We tBa l lMi l l " )o n a0 . 91m Ø mi l l . The l i f t er smo v et hepeakbr eak agepoi ntt oac oar s ers i z e,f r om 1. 5t o4mm. Th eb r e ak a ge o ffi ne r ma t e r i a li s mu c hl o we r wi t hl i f t e r st h an wi t h c o r r u ga t e d l i ne s . Th er e f or e l i f t er s d on ' tb el on g i n t he s e c on d compar t ment .


4-23


$ining -ype +s "reaage '(

0 n i m 2 ' / i S , e t a 1

Lifters

'

e g a . a e r " c f i c e p S

orrugated Spiral Angular .' .'

'

'(

Material #article Diameter /mm0

Th us t h i si st h et y pe ofl i n erwh i c hi st h efi r s tc h oi c e ma ny p l an t s , ( s omet i mesc al l eds hi pl oadorwedgeors t eppedl i ner ) .


4-24


(!en so) t*ere are ot*er t'pes still in use in +ort* A,erica.

Forwedgebar ,l or r ai ne,bl oc kt y pel i ner st her at i oofhei ghtt os pac i ngi n bet ween ( us ual l y mat c hes bol t i ng pat t er ns )i sc r i t i c alt o ac hi ev i ng t he c or r ec tt r aj ec t or i es .Sur pr i s i ngl ymanysuppl i er sdonothav es ophi s t i c at ed met hodst ode t er mi net hi s .Ho we v ert hi sgr oupofl i nert y pess eemst obe i deal i nSAG mi l l sus edi nmi ni ngorf ormi l l swi t hv er yl ow% c r i t i c al s peed. Mos ts i ngl ewav el i ner sgener al l yhadgoodl i f tc har ac t er i s t i c s,howev eron t hedo wns l opes i de,me di at endedt os l i dewhi c hv a st l ya cc el er at eswear . The new “ DuoLi f t ”l i ner devel oped by SLEGTEN coul d pr ovi de an i nt er es t i ngr es ul t s .

TheDuol i f ti ses pec i al l ydes i gnedt omai nt ai nt hes amel i f tc har ac t er i s t i c s t hr ough90% ofi twearl i f ebyc ont r ol l i ngt hewearpat t er n. I ndoi ngs o


4-25


Sl e gt enc l ai mst hatt hea bs or bedpowerandgr i ndi ngeffic i enc ywi l lr emai n mor ec ons i s t ent ,andwearl i f egr eat l yex t ended. Pr es ent l yt hi sl i neri s bei ngt r i edi nDemopol i sandWhi t ehal l .

B)SecondCompar t ment Co r r u ga t e d/ Wa v eL i n i n gs Thes ear et hes t andar dl i ni ngsi nNor t hAmer i c at hator i gi n alc omewi t h mos tmi l l s .Aswi t hl i f t er st heycomei nal l v er s i onsandper v er s i ons ,wav e, s i mpl ewa v e,doubl ewa v e,et c .Thei rpur pos ei st oas s i s ti nt hec as c adi ng ac t i on oft he bal l s . Ther ef or et heyas si s ti nt he at t r i t i on mec hani s ms , c hi ppi ngandabr as i on,onsmal l ers i z edpar t i c l es .Thi smeanst he ydonot b el o ng i nafi r s tc o mp ar t me nt ,b utr a t h eri nt h es e c on d. Th ey a r e , h owe v e r ,n ott h er e c omme nd eds ec o ndc omp ar t me ntl i n er s .

Cl as si f y i ngLi ni ngs Thi st y peofl i nerhass ev er al i mpor t antadv ant ages : •bal l s i z emat c hespar t i c l es i z eal ongt hemi l l ; •r ev er s eanddoubl er ev er s ec l as si fi cat i oni sav oi ded. Th eyha v ea l s ob eens h ownt oi n c r ea s emat e r i alt r a ns po r to pp os e dt oa nonc l as si fi edc har ge.Thi si sduet ot hei nc r eas edpor os i t y( bi gbal l s )i n t hear easwher et hepar t i c l esar el ar gerandl es s' fl ui d' .Thi smeansi ti s t heor et i c al l ypos si bl et or educ et hefi nalbal ls i z ei nt hemi l li nc ompar i s on t oanunc l as si fi edc har gef orbet t er' fi t 'bet weenbal l sandmat er i alwi t hout mat er i al t r ans por tpr obl ems . Thi sfi ti sobv i ous l yt hebes twhen' pl ugfl ow'i spr es ent .Thi smeanst hat mat er i alfl owst hr ought hemi l last houghi napi pel i neandi s n' tmi x edt oo mu c h.Th el o ng erL / Di nt h es e c on dc o mp ar t me ntg i v e sRTD' s( r e s i d en c e


4-26


t i medi s t r i but i ons )whi c har ec l os ert ot hepl ugfl owl i mi tt hant hes hor tL/ D fi r s tc ompar t ment . Th ea dv a nt a ge so fac l a s s i fi e dc h ar g ea r eg r e at e s twhe ni ta l l o wsawi d e r angeofbal ls i z est obeus ed. Thef ac tt hatonl y3t o4bal ls i z esar e p r e se nti nt h e mo r emi x e dfi r s tc ompa r t men tr e du c est ob en efi t soft hi s l i ni ngi nt hatar ea.

Foreac hl i ners t epf orc l as si f y i ngl i ner si nl ar gemi l l sov er4met r es( 13 f eet )i ndi amet er ,us et wol i ner spers t ep,l engt hwi s eoft hemi l l .

L ar g eme di a,5 0t o7 0mm ( 2t o23 / 4i n )d i ame t e r ,c anb ep uti nt hesa me c o mp ar t me nta ss ma l lme di a ,a ss ma l la s1 5mm ( 5 / 8i n )d i a me t e ri na n openc i r c ui tmi l l .I ns uc hac ompar t ment ,t hegr i ndi ngchar gec anac c ept av er ycoar s ef eed. Cl as si f y i ngl i ner sper mi tadet er i or at i ngoper at i oni n t hefi r s tc ompar t ment ,ori nt hedi aphr agm par t i t i on. Fur t her mor e,t he y


4-27


al l ow a bet t ero v er al lgr i ndi ng per f or manc ei n a mi l lwhos e par t i t i on di aphr agm l oc at i oni snoti deal . Ex c epti ns pec i alc as es ,whi c hmus tbee x ami nedwi t hc ar e,c l as s i f y i ng l i n i n gsa r er e c omme nd edf o rt h es e c on dc o mp ar t me nt ,a ndl o ngs i n gl e c o mp ar t me nt mi l l s wi t h l o we rc i r c u l a t i n g l o ad s ,b ut n ot f o rfi r s t compar t ment s.

2. 2. 3

Li nerQual i t y

I nNor t hAmer i c a,mos tl i ner st oda yar ewhi t ec as ti r onswi t hhi ghc hr ome c o nt e nt sal t h ou ght h er es e emst ob eag en er a lmo v e me ntt oh i g hc a r b on t ools t eelbas e.Di ff er ental l o yi ngel ement saswel lasc ar bonandc hr ome c o n t e nt sa r eu s e d,we s u s p ec t ,t oa c h i e v ed e s i r e dp r o pe r t i e sa nd p er f o r ma nc e ,b utwi t h i nt h ec o nfi ne so ft het e c hno l o gyu s eda td i ff er e nt f o un dr i e s .Th i sa pp ea r st ov a r ye v e n wi t h i nt h es a me c o mp an y . Th e o bs er v a t i o ni sun c on fi r me dma i n l yb ec a us en on eo ft h es u pp l i er swi s ht o di v ul get r ades ec r et s ,howev ernoneofoure xper i enc edi s put est hi s . I ngener al ,al ll i ner sat t emptt opr oduc egr ai nsofc hr omi um c ar bi de,whi c h ar eex t r emel yabr as i onr es i s t ant ,hel di namar t ens i t i cs t eel( t hehar des t f or m ofs t eel )mat r i x .Al s ot hebes tper f or mi ngl i ner sgener al l yhav ev er y fi n eg r a i n mi c r o s t r u c t u r e s( a c hi e v ed t hr o ug hh eatt r e at me nta nd p r o pe r quenc hi ng)whi c hi nc r eas esov e r al l har dnes sandabr as i onr es i s t anc e.By v ar y i ng t he c ar bi de c ont ent ,al l o yi ng e l ement s ,and mi c r os t r uc t ur es s uppl i er sc an al t ert he l i nerper f or manc e wi t hr es pec tt o abr as i on and i mpac tr es i s t anc et os ui tt heappl i c at i on. Howev er ,f oundr yqual i t yc ont r oli sv i t alt ogoodl i nerper f or manc e. Thi s s e emst ov a r ymo r ewi d el yi nNor t hAme r i c at h ani nEu r o pe ;t ot h ep oi n t wher es omepl ant swi l l s pec i f yt hef oundr yatwhi c ht hel i neri st obec as t .


4-28

Mill Grinding

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