Steep Seam Coal Mining in Western Canada 1984

8/9/2019 Steep Seam Coal Mining in Western Canada 1984

1/16

aj K. S i n g h a l

C an ad a C e n t r e f o r M i n e r a l a nd E n e rg y Te ch n ol o gySydney Nova S c o t i a Canada

Dave G Osborne

K i l b o r n E n g i n e e r i n g B . C . ) L t d .Va nc o uv e r B r i t i s h C o lu m bi a

Canada

For p r e s e n t a t i o n a t t h e SME-AIME An nu al M eet ingL os A n g e l e s C a l i f o r n i a - F e b r u a r y 26-March 1 984

Permission is hereby given to publish with appropriate acknowledgmentsexcerpts or summaries not to exceed one-fourth of the entire text of the paper.Permission to print in more extended form subsequent to publication by the Institutemust be obtained from the Executive Director of the Society of Mining Engineersof AIME.

If and when this paper is published by the Society ~f Mining Engineers of AIME itm y embody certain changes made by agreement between the Technical Publications

ommittee and the author so that the form in which it appears here is not necessarilythat in which i t may be published later.

These preprints are available for sale. Mail orders to PREQRINTS Society of MiningEngineers Caller No. D Littieton Colorado 80l27

PREPRtNT AVAILABILITY LlST IS PUBLISHED PERIODICALLY tMINING ENGINEERING


2/16

A b s t r a c t . C an ad a p r od u ce s c l o s e t o 42 m i l l i o ntonnes of co al pe r annun of which some 38 m i l l i o ntonnes i s produced by s ur fa ce mining methods.The two k es te rn Canadian prov inc es , Alb er ta andB r i t i s h C o lu mb ia , p r od u c e 3 1 m i l l i o n t o n n e s ofc o a l by s u r f a c e m i n i ng . These two provincesp r ov i de t h e b u l k of t h e m e t a l l u r g i c a l c o a l f o re x p o r t .

The g e o l o g i c a l c o n d i t i o n s i n t h e We s te rnp r ov i nc e s p a r t i c u l a r l y i n t h e m ou nt ai n r e g i o na r e c om pl ex . The c o a l s a r e f r i a b l e an d t h e s ea msa r e s t e e p l y i n c l i n e d , s h ea r ed , i n t e n s e l y f o ld e dand fa u lt ed . There may be as many s 1 5 t o 20c o a l s ea ms p r e s e n t w i t h t r u e t h i c k n e s s r a n g in gfrom 2.5 m t o o v e r 8 m.

This paper rev iews th e sur fac e min ing methodsu se d t o e x t r a c t s u c h s ea ms . The d i f f i c u l t i e sa s s o c i a t e d w i t h s t e e p s e a m a n d m u l t i p l e s e a mm in in g of f r i a b l e c o a l r e s u l t i n g i n l ow er c o a lr e c o v e r y, h i g h d i l u t i o n a n d t h e pr ob le m ofc l e a n i n g f i n e c o a l i n t h e w ash p l a n t h av e be en

h i g h l i g h t e d .

G e o l o g i c a l S t r u c t u r e

F i g u r e ( 1 ) s ho ws t h e d i s t r i b u t i o n o f C a n ad ia nC o a l f i e l d s w h e re a s F i g u r e 2) shows the coa ld e p o s i t s of A l b e r t a a nd B r i t i s h C ol um bi a. S e v e r a lCanadian provinces have coa l resources bu t Alber tai s e s t i m at e d t o h av e t h e l a r g e s t r e s e r v e s ofb i tuminous and sub-b ituminous coa l .

The prov inc e of Albe r ta i s d i vi d ed i n t o t h r e er e g i o n s e a c h c o n t a i n i n g d e p o s i t s o f s i m i l a r a g ea nd c h a r a c t e r i s t i c s . T he s e a r e t h e M ou nt ai n,F o o t h i l l s a nd P l a i n s r e g i o n s .

T h e X o u n t a i n R e g i o n e x t e n d s a l o n g t h e e a s t e r nf l an k of theRocky Mounta ins ; t c o n t a i n s n o s t l ym e d i u m a n d l o w v o l a t i l e b i t u m i n o u s c o a l d e p o s i t smain ly of Upper Ju ra ss ic and Lower Cre taceous ag eT he c o a l s a r e commonly f r i a b l e . The c o a l b e a r i n gs t r a t a a r e h ig h l y f o l d e d and f a u l t e d wh ic h h asc u as e d c o n s i d e r a b l e t e c t o n i c t h i c k e n i n g a ndt h i n n in g o f c o a l s eam s i n c e r t a i n l o c a t i o n s .

The F o o t h i l l s Re gi on a d j o i n s t h e e a s t e r n e d g eof th e Mounta in Region and con ta in s main ly h igh lyv o l a t i l e b i t u m in o u s c o a l s o f U p pe r C r e t a c eo u s a n dLower Te r t i a r y a g es . L ik e t h e i r c o u n t e r p a r t s i nt h e Mo un ta in R e gi on t h e s e c o a l f i e l d s h a v e b ee ns h e a r ed , f a u l t e d a nd f o l de d , and i n c e r t a i n l oc a-t i o n s show c o n s i d e r a b l e t h i c k e n i n g a nd t h i n n i n gof c oa l seams.

The P la ins Region coa l i s mostly sub-bituminous

i n rank mainly of Upper Cretac eous and LowerTe r t i a r y ag e . M ost o f t h e s ea ms o f t h i s r e g i o na r e f l a t - ly i n g e x c e p t t h o s e c l o s e t o t h e s u r fa c et h a t h a ve be en g l a c i a l l y d i s t u r b e d .

A s c a n be s e e n i n F i g u r e 2 ) c o a l d e p o s i t s o ft h e p r o v i n c e o f B r i t i s h C ol um bia a r e w i d e l ys c a t t e r e d .

The c o a l d e p o s i t s o f s o u t h e a s t e r n B r i t i s hC ol um bi a ( C ro w s ne s t C o a l f i e l d ) a r e U pp er J u r a s s i ci n ag e a nd a r e p a r t of t h e s o u t h e r n e n d of t h eM ou n ta in R eg io n a s d e s c r i b e d f o r A l b e r t a , w i t ht h e n o t a b l e d i f f e r e n c e t h a t t h e y c o n t a i n c on s i-de rab ly more seams t h a t a r e of g r e a t e r t h i c k n e s st h a n i n a d j o i n i n g a r e a s of A l b e r t a . The c o a ld e p o s i t s o f n o r t h e a s t e r n B r i t i s h C o l u m b i a a r e

h ow ev er C r e t a c e o u s i n a g e a n d a r e t h e n o r t h e r ne x t e n s io n o f t h e c o a l s t h a t o c c u r i n t h e Xo un ta inR e gi on o f A l b e r t a . S e v e r a l s m a l l b a s i n s ofTe r t i a r y c o a l oc c ur i n t h e s o u t h - c e n t r a l p a r t o ft h e p r o v i n c e i n c l u d i n g Tul an ee n P r i n c e t o n , X e r r i t t

and Hat Creek . Most o f the se bas ins co nta in coa ls ea ms wh ic h a r e i n t e n s e l y f o l d e d , f a u l t e d , andi r r e g u l a r i n t h ic k ne s s .

The Energy, Xines and Resources Canada ReportER-79-9 by BIELXHSTEIK e t 21 p r o v i d e s f u r t h e rd e t a i l s on t h e g e o l o g i c a l e n vi r on m e nt ofC a na di an c o a l d e p o s i t s .

Coal Reserves, Recovery and Mining Losses

T he e s t i m a t i o n o f m in e a b l e c o a l r e s e r v e s ,m i n i n g r e c o v e r i e s a n d d i l u t i o n i s a f a i r l y c om plexp r o c e s s p a r t i c u l a r l y w he re t h e r e a r e a num be r o fs ea ms s e p a r a t e d by i n t e r b u r d e n o f v a r i o u s t h i c k -n e s s e s and l i t h o l o g i e s . t i s even more d i ff icu l tf o r t h e s t e e p d i p p i n g s ea ms s u rr o un d ed by d i s t o r t -e d m o un ta in ou s s t r a t a . The i n i t i a l e s t i m a t e s ofm i ne ab le r e s e r v e s , r e c o v e r i e s an d d i l u t i o n a r eb a s ed o n e x p e r ie n c e t o b e v e r i f i e d l a t e r b ya c t u a l f i e l d e x p e r ie n c e a nd b ac k a n a l y s i s b u ti t i s n o t a n e a s y t a s k . Eve n t h e e s t i m a t i o n

method va r i e s f rom mine to mine depending on thec o m p l e x i t i e s o f t h e g e o l o g i c a l e n v i r on m e nt .

Some t y p i c a l g u i d e l i n e s u s e d f o r m in e a bl e c o a lres erv e es t i ma tes , by way of example, a r e :

a ) A l l s e a m s g r e a t e r t h a n 1 . 5 m i n t h i c k n e s sa r e m i ne a b le ;

b ) p a r t i n g s g r e a t e r t h a n 1 . 5 n i n t h i c k n e s sc an b e s e l e c t i v e l y m ined a n d r e j e c t e d ;

C) mining lo s s fo r each seam: 10 cm from th etop of th e seam and 10 m from the bottom.

A t a n o t h e r p r o j e c t i n B r i t i s h C olum bia w h er et h e c o a l b e a r i n g s t r a t a c o n t a i n e d a p pr o xi m at e ly20 c o a l s ea ms o r s p l i t g r ou p w i t h a n a g g r e g a t ec o a l t h i c k n e s s o f a b o u t 90 m t h e f o l l o w i n gc r i t e r i a we re a p p l i e d i n r e s e r v e e s t im a t i o n :

a. Coal Mining Member one o r more co a ls p l i t s o r s ea ms o fmore than 60 cm tr u ethicicness eachs e p a r a t e d by o n e o rmore rock par t ings ofl e s s t h a n 9 0 cm t r u et h i c k n e s s e a c h

b . C oa l i n P l a c e t h e sum of a l l Co al?lin ing Yembers

c. Mining Loss 30 m of c o a l a t t h ehanging wa l l o f eachCoal Mining Member

d. Raw Coal Coal i n Pl ac e minusEiining Loss (b-c)

e. Di lu ti on 15 cm of rock from

t h e f o o t w a l lOne o f t h e m os t c r i t i c a l f a c t o r s i n s t e e p s eam

m i n in g i n t h e m o u n t ai n s i s t h e m in in g l o s s .Mining los se s occur when top c oa l is removed witho v e rb u rd e n o r b o tt om c o a l l e f t i n p l a c e . Somef a c t o r s w hic h a f f e c t m in in g l o s s e s a r e t h e c o a lt h i c k n e s s , i n t e r b u r d e n , d i p of t h e s ea m s, m in i ngo f m u l t i p l e se a ms , p r o x i m i t y o f se am s , s p i l l a g e ,s i z e and type of min ing equipment used and t heg e o l o g i c a l c o m p l e x i t i e s .

s a g e n e r a l r u l e 80 t o 9 0 p e r c e n t o f c o a l 6srecove red f rom major seams d ipping t o up t o 30and not unduly d i s turbed by geology. From seamssandwiched be tween the d i s tor ted and brokens t r a t a , d e pe nd in g on t h e s eam t h i c k n e s s , r e c o v er -

i e s o f 4 0 t o 50 p e r c e n t a r e o b ta i ne d . I n s u chc a s e s d i l u t i o n i s v e r y h i g h . I n c a s e of t h i n n e rs ea ms wh ic h a r e i n c l o s e p r o x i m i t y t o m a jo r s e a ms ,r e c o v e r i e s ( fr om t h e t h i n se am s) c a n b e a s l o w a s20 p e r c e n t t o n o t h i n g .


3/16

r p l n c ec vh c re s t r uc tu r a l dc fom n t io n hno r c -su l t ed Ln thickening of co nl seams [up t o 15 t o20 n t h i c k ) i n p r o v m e n t i n c o a l r c co v cr y a nd c o a lr cocrv c c s t i n a cc c a r c of ecn no t ed .

Con1 Qual i ty

The f o m c i o n p r oce s s o f Canadi an coa l s unde rs c v c r e g c o l o g i c n l d i s t u r b n n c e a s d e s c r i b e d h a sr c s u l c c d i n a s c a m s t r u c t u r e t h a t i s vcryd i f f c r cn t f ro m co kx ng co n l depo s i t s e l s ewhe re.?luch of th e coa l i s s ev e rc l y shea red and t her e s u l t a n t c o n l s a r e p or ou s , p ro ne t o o x i d a t io nand mass ive ly f r ac tu re d on a micro-scnle . Therei s , t h e r e fo r e , a w ide r ange of me t a l l u rg i ca lcoking coa l i n t er m s of i nd i v idu a l p rop e r t i e scomparable in some resp ec ts wi th the C S highand low vola t i le coals and Aust ra l ian medium andlow v o l a t i l e c o a l s . T h i s r a n g e i s o f p a r t i c u l a ri n t e r e s t t o co a l p u rchase r s s e ek ing optimumbl ends fo r m e t a l l u r g i c a l coke manufac tu re . Thes t r u c t u r e of t h e s e c o a ls g r e a t l y i n f l u e n c e s t h eph y s i c a l , me ch an i c a l and chemica l p rope r t i e s suc ha s f r ~ a b i l i t y , m o i s tu r e c apac i t y, deg ree o fox l da c io n and cok in g p rope r t i e s . A l l o f t h e semay i n t u r n i n f l u e n c e impor t an t product coa lp rop e r t i e s i n s u bse quent m in ing , hand l i ng ,b e n e f i c l a t i o n and p r o c e s s i n g .

The e f f e c t s of h a n d l i ng a nd c l e a n i n g f r i a b l eRocky Xo un t ai n b i t uminous co a l s on s i z e d i s t r i bu -t l o n c a n b e s e en i n Ta b le 1. The amount of f i n ecoa l r e su l t i n g from mining and t r an s po r t i ng rawc o a l t o t h e c o a l p r e p a r a t i o n p la n t c an be s e e n i nTable 2

In te rms of coking proper t ies , Rocky Xounta inco a l s ( b e i ng t y p i ca l o f non -mar ine coa l s ) a r ec h a r a c t e r i z e d by t o t a l s u l p h u r c o n t e n t of l e s sthan one perc ent and raw co al as h conten t of10 to 30 percent by weight .

Th i s m i n e ra l m a t t e r i s composed primarily ofka ol in i t e and qua r tz . The pe t r ogra phic composi-t i on s of most of t he co king co al s show them to ber i c h i n i n e r c i n i t e m a ce r al s , ma c r in i t e, f u s i n i t eand s e m i f u s i n i t e , w hich a r e p r o p e r t i e s r e s u l t i n gi n st ro ng coke. When th e mean maximum re fl e c -t a nc e of v i t r i n i t e i n o i l Ro m a i s u se d a s t h ec o a l ra nk p a ra m et e r, t h i s h ig h i n e r t i n i t e c o n t e n ti s f u r t he r c h a r a c t e r i z ed by co rr e spond ing ly lowv o l a t i l e m a t t e r c o n t e n t s , l ow er f r e e s w e l li n gind ice s (F .S . I . ) , lower maxintum d i la ta t i o n andf l u i d i t i e s t ha n o t h e r U S a n d A u s t r a l i a n c o a lof t he same rank. The Canadian co al s ar e howeverr i c h e r i n t h e r e a c t i v e m a ce ra l s, v i t r i n i t e ,ex in i t e an d s em i f u s in i t e . These combined p roper-t i e s of Rocky Xountain coking c oa ls have been amajor r eas on why such co al s have been i n demandby t h e J a pa n es e s t e e l i n d u s t r y a s a m a j or c o keblend component.

Ta b l e 3 shows a c l a s s i f i c a t i o n of m k i n g c o a lqu a l i t y by g roup .

Mining Methods

I n t h e p ro v in ce s o f B r i t i sh Columbia andA l b e r t a most s u r f a c e c o a l mi ne s a r e o pe n p i tt e r r a c e o p e r at i o ns . The o p e r a t i o n s u s e t y p i c a lt r uck - s h ove l m ethods ex t r a c t i ng mu l t i p l e coa lseams f rom se ve ra l mul ti -bench work face s . Onlyo ne o p e r a t i o n u s e s a d r a g l i n e a s t h e pr im e e a r t hmover.

F o r t h e t o p s o i l r em ov al s c r a p e r s a r e pr e -f e r r e d .

In soz c nrcna where pio nc eri ng work ouch asc l e a r i n g r r c c s a nd b r us h i s involved, f rone-endlondero , hyd rnul ic ohoveln and dozcrs a re uecd.To p so i l i s s t o c kp i l ed f o r l a t c r u se i n r c-c l m n t i o n . U n co nso l i da t ed ov e rbu rde n s r m o v c dby si m il a r type of cquipmcnt.

Hard consol ida ted ovcrburdcn is d r i l l c d n n db l a s t e d . B l a s t h o l e s a r e d r i l l e d w i th r o t a r yc r a v l c r mounted r i g s u s i n g b i t s i n t h e 22 cnt o 3 1 cn d i a me t e r r ang e. Typ i ca l ho l e dc p rh s a r ci n t h e r a n g e of 1 2 t o 1 8 m t o ncconn odn t e t h e p i tb ench he ig h t s o f 1 2 t o 15 m. For a a highbench a t y p i c a l h o l e w i l l be 16.6 m i n d e p t hi n c l u d i n g t h e s u b g ra d e d r i l l i n g of 2 6 n.Ty p i c a l l y, h al f o f t h i s h o l e w i l l be powdercolumn and half w i l l be s t e m ed . Fo r a 1 5 .2 mb en ch a t y p i c a l h o l e w i l l be up t o 18.3 n i nd e pt h i n c l u d i n g t h e s ub g ra d e d r i l l i n g .

T yp ic al d r i l l i n g p a t t e r n s a r e 9 m spacing and9 n bu rde n. Dep ending on l o c a l g eo log i c a lc o n d i t i o n s and h o l e d i am e te r s e l e c t e d d r i l l i n gp a t t e r n s of 8 m r 8 m 8.5 n 7.3 m ands t a g g e r e d p a t t e r n s o f 11 m 5.5 m and 7.3 m3.7 m e t c . a r e be i ng u s e d.

The p r ima r y e xp lo s iv e u sed f o r b l a s t i n g i sANFO. I n wet hol es which can be dewate red th eh o l e s a r e l in e d w i th a p l a s t i c l i n e r a nd t h enload ed wit h ANFO. Wet ho le s which can no t bed ew at er ed a r e l o ad e d w i t h a w a t e r g e l s l u r r y . I nhar de r rock, e.g. sa nd sto ne , alu mini zed ANFO( c o n t a i n i n g t o 7 p e r c e n t o f Al o r s t r a i g h ts l u r r y i s used. ANFO and s l u r r y e x p l o si v e s a r ed e l i v e r e d i n b u l k l o a d i n g t r u c k s .

Ty p i ca l powder f a c t o r s ( k il o gr a m o f ~ u p l o s ip e r BQl broke a r e i n th e range of 0 .36 kg/bmt o 0.70 kg/bm .

Overburden i s exca va t ed mos tl y by co nve n t i on a ls h o v e l s a nd f ro n t- e nd l o a d e r s ; r e c e n t l y t h eh y d r a u l i c s h o v e l h a s g a i n e d c o n s i d e r a b l e a c c e p -t an ce j. Z l e c t r i c c a b l e s h o v e l s w i t h 11 19 and

3 m r o c k d i p p e r s f o rm t h e n a j o r e x c a v a t i o n u n i t .However on a dipping seam a wedge of waste i s n o ta c c e s s i b l e t o a s h o v e l . T h i s wedge i s dozed downa nd l oa de d i n to t r u ck s by fron t -end l oad e r s a ndh y d r a u l i c s h o v e l s .

Of ten more than one fa ce i s a c t i ve on a ny onebench and sometimes work i s i n p r o g r e s s o nse v e ra l be nc h es s im u l t an e ous ly u s ing a co mbi na ti onof equipment descr ibed.

Overburden i s h au le d t o w as te d i s p o s a l s i t e se i t h e r i n t h e p i t o r o u t s i d e of i t i n rock-bodyt r uc ks . T he mos t pop u l a r s i z e i s 15 4 t on n e bu tt ru ck s of 90 tonne , 110 tonne , 180 tonne and i none case even 315 tonne a r e be ing used .

A s has b een n o t ed Wes t e rn Ca na d i an c os l s a r ef r i a b l e an d do n o t r e q u i r e d r i l l i n g a nd b l a s t i n g .Coal i s u s ua l l y l o ad ed by t h e fron t- en d l oad e r sa n d / o r h y d r a u l i c s h o v e l s i n t o c o a l b ody t r u c k s .Fronfj-end loa de rs and hy dra ul i c shovel s of up t o19 m b u c k e t c a p a c i t y a r e b e in g u s e d .

An e a r l i e r p r a c t i c e of d o z i ng c o a l down t h efo o t wa l l on m ode ra te l y p i t ch ing s eams (up t o 30i n c l i n a t i o n ) i s b e i n g g r a d u a l l y d i s c a r d e d .Tr a v e l o f d o z e r on t h e c o a l be d r e s u l t s i n ex-c e s s i v e g e n e r a t i o n of f i n e s c a u s i n g s e v e r ep ro bl em s i n t h e c o a l wash p l a n t . F o r t h i s r e a s o nhy d rau l i c s hov e l / ba ck f ioe i s being used on ani n c r e a s i n g s c a l e f o r mi n in g o f m od e r a te l yd ipp in g co a l s e ams .

In s eam s o f v a r y ing q u a l i t y w here b le nd ing i sn e c e ss a r y t o me et t h e c o n t r a c t s p e c i f i c a t i o n s , ad oz e r w i l l n o r ma l ly push co a l ob l i qu e ly ac ro s s


4/16

t h e s e am t o a c h i e v e b l e n d i n g o f t h e f o o t w a l l a ndh a n g i n g w a l l c o a l . T he d i g g i n g a c t i o n o f ah y d r a u l i c s h o v e l p r o v i d e s t h e same e nd r e s u l t .

I n m o d e r a te l y d i p p i n g s ea ms o f t e n f o o t w a l l i sf o l lo w e d . I n s t e e p e r c o a l s e am s (3 0 t o 90 )b e n c h in g of t h e f o o t w a l l i s o f t e n n e c e s s a r y.Even i n s u c h s i t u a t i o n s a h y d r a u l i c s h ov e l/ b ac k -

hoe i s p r e f e r r e d . I n n u l t i p l e sea m m i ni n g,p a r t i c u l a r l y i n t e c t o n i c al l y d i s t u rb e d s t r a t a ,a h y d r a u l i c s h o v e l p e r m i t s g r e a t e r d e g r e e ofs e l e c t i v e m in in g. I n a c ou p l e of i n s t a n c e s o fs t e e p sea m c o a l mi n in g s m a l l e r c r a w l e r d r a g l i n e shave been used t o remove p i t bo ttom coa l .

Ty p i c a l l y b en c h h e i g h t s i n We st e rn C a na d ia np i t s a r e 1 2 t o 1 5 m o v e r a l l p i t s l op e s 4 j0 t o50 w i t h s ome l o c a l i z e d s t e e p e r s l o p e s . I n seamsd i p p i n g g r e a t e r t h a n 30 f o o t w a l l i s o f t e nb en c he d t o c r e a t e s a f e t y b er ms . I n som e c a s e sd e w a t e ri n g h a s b ee n n e c e s s a r y t o r e l i e v ea r t e s i a n p r e s su r e and s t a b i l i z e t h e p i t w a l ls ;i n o t h e r s r o ck b o l t i n g o f t h e f o o t w a l l ha s b ee nc o n s i d e r e d .

H a u la g e r o a d w i d t h s d e t e r m i n e d by t h e s i z e o ft h e eq ui pm e nt i n u s e a r e 25 30 m wide and gradebetween 6 t o 1 0 p e r c e n t . B e c au s e of t h emounta inous topography, s wi t ch back haulag e roadsa r e u s e d i n some p i t s . S a f e t y ra mp s f o r s t o p p i n grun-away t ru ck s a r e provided .

D ep en di ng u po n t h e t o po g ra p hy a t t h e m in e s i t eend t ip p i ng and a re a dumping (d um pin g i n l a y e r s )of th e overburden i s c a r r i e d o u t. I n t h emounta inous reg io n more of t en i t i s e n d t i p p i n g .End t ip p i ng normal ly does no t pe rmi t compact iono f t h e d is p o se d m a t e r i a l and t h i s r e s u l t s i nocc as i ona l dump fa i l u r es . Waste dumps a r eu s u a l l y t e r r a c ed and s e t t l e t o t h e a n g l e ofr e p o s e o f t h e w a s t e m a t e r i a l be t we e n 35 t o 37O.

G u i d e l i n e s a n d g o v e r n m e n t r e g u l a t i o n s e x i s t

r e l a t i n g t o t h e r e c l a m a ti o n of m ine d o ut p i t s ,w a s t e a r e a s a nd o t h e r a r e a s d i s t u r b e d by t h em i n in g a c t i v i t y. Was te dumps a r e r e q u i r e d t o b es lo ped t o an ov er a l l maximum of 27 f o r rec lama-t i o n . B a c k f i l l i n g of t h e p i t i s u s u a l l y c a r r i e do u t a s s o o n s s p a c e i s a v a i l a b l e . I n a lm os t a l lc a s e s o v e r b u r d e n i s d e p o s it e d e x t e r n a l l y t o t h ep i t f o r t h e f i r s t few y e a rs .

C o a l P r e p a r a t i o n a n d H a n d l i n g

The f i r s t wave o f l a r g e c o a l p re p a r a t i o np l a n t s i n Wes te rn Canada we re b u i l t i n t h e e a r l y1 97 0 s. B a s i c a l l y t h e y u s e d t h e s t a n d a r d B r i t i s hand U S t echnology.

t q u i c k l y be cam e e v i d e n t t h a t t h e s e f l o ws h e e t s w er e n o t s u i t a b l e f o r t h e Wes te rnC a n a d i a n c o a l s c h a r a c t e r i z e d b y h i g h f i n e s c o n -t e n t a nd i n c o n s i s t e n t f r o t h f l o t a t i o n p r o p e r t i e s .T he s e f a c t o r s c o mb in ed w i t h t h e s e v e r i t y o f t h eC a n ad i an w i n t e r c a u s e d many s e r i o u s a n d c o s t l yproblems.

M aj or d e s i g n c ha n ge s i n t h e p r e p a r a t i o n p l a n t sa nd t h e r m a l d r y e r s we r e ma de. T he r e s u l t h a sb e e n t h e d ev e lo p m en t of a f l o w s h e e t t h a t h a sa l mo s t become a s t a n d a r d f o r t r e a t i n g t h e s ec o a l s .

Us ing many of th e less on s le arn ed , t he secondg e n e r a t i o n p l a n t s o f t h e e a rl :? 1 9 8 0s h a v e b e e na b l e t o a v o id many p r ob le m s a nd p i t f a l l s . Afu r t he r change has been t he need f o r some of themt o p r e p a r e a t he r m al c o a l f o r e x p o r t a s w e l l a st h e t r a d i t i o n a l c ok in g ( m e t a l l u rg i c a l ) c o a l .The new p l a n t s a r e i n t h e C r ow s ne st P a s s a r e a o f

B r i t i s h C ol um bi a G r e e n h i l l s ( We s t a r ) , L i neCreek (S he l l ) and Byron Creek (Esso) and i n th ePeace River Area Qu in te t te (Denison) andBullmoose (Teck) .

he e f f e c t s of m u l t is e am mixin r e s u l t i n g i nv a r i a b l e p ro d uc t c o a l y i e l d s a nd f l u c t u a t i o n i nt h e amount of ou t- of- se am d i l u t i o n a r e e f f e c t i v eovercome by some form of homog enizat ion of th era w c o a l . Th e e x t e n t t o w hi ch t h i s i s a p p l i e d ,b ei ng c l o s e l y r e l a t e d t o t h e v a r i a b i l i t y o f t h er a w c o a l , i s u s u a l l y g r e a t l y a s s i s t e d bysched ul ing and handl ing of co a l f rom the openp i t t o th e p l an t s i t e . No c u r r en t l y o p er a ti o na lmine employs blending bed methods with complexs t a c k e r / r e c l a i m e r e q ui pm e nt l a rg e l y be c a u s e o ft h e f a v or a b l e w a s h a b i l i t y c h a r a c t e r i s t i c s o f t h ec o a l . E ac h o f t h e c o n t r i b u t i n g c o a l s ea m s,w h e th e r c o ns i d e r ed i n d i v i d u a l l y o r m ix ed , c r e a t ef ew c l e a n i n g p r o b le m s a nd t h i s o b v i a t e s t h e ne e df o r a s o p h i s t i c a t e d b l e n d in g a p p ro a c h.Accord ingly, homogeniza t ion i s l a rge ly accompl i*ed by means of n at ur al mixing c re at ed by a com-

b i n a t i o n o f r aw c o a l ha n d l i ng a nd s i l o s t o r a g ea n d r e c l a m a t i o n .I n g e n e r a l t h e c o a l s a r e r e a d i l y c le an e d

w i th o u t t e c h n i c a l d i f f i c u l t y , p r o vi d in g t h a t t h ei n d i v i d u a l raw c o a l f e e d s t o e ac h of t h e c o a lc l e a n i n g s tr e a m s a r e a d e q u a te l y s i z e d a n d l o rc l a s s i f i e d p r i o r t o c l ea n in g . .

Ta b l e 4 shows t h e w a s h a b i l i t y a n a l y s i s f o r a38 mm by 0.5 mm raw co a l t yp ic a l o f RockyMounta in c oa l , re ad i l y c leaned by dense mediumcyclone .

F i g u r e s how s a s i m p l i f i e d f l ow s h e e t f o rone of th e newly c ons t ruc ted p l an ts which may ber e g a r de d a s b e i n g t y p i c a l o f most p l a n t sp r od u ci n g m e t a l l u r g i c a l co k in g c o a l . I i e t a l l u r -g i c a l c o a l p r o d uc t a s h c o n t e n t i s u s u a l ly 7 t o9 . 5 p e r c e n t .

The c le an i ng of the rmal coa l i s c a r r i e d o u tby a p a r t i a l c l e a n i n g a p p r oa c h i n t h e c a s e o fLine Creek and Byron Creek p l an ts (c oa l p lu s 6t o 8 mm i s washed; co al minus 6 t o i sb l e n d e d w i t h w as h c o a l w i t h o u t c l e a n i n g ) . A tQ u i n t e t t e t h e t h e rm a l c o a l i s cle ane d i n a Baumj i g and a t G r e en h il l s a c i r c u i t s i m i l a r t oF i g u r e i s used exc lud ing th e dense mediumb a t h . T he rm a l c o a l p r o d u c t a s h c o n t e n t i su s u a l l y 1 2 t o 1 6 p e r c e n t .

F i n e c o a l c l e a n i n g of m e t a l l u r g i c a l c o a l i sc a r r i e d o u t u s i n g o n e o f t wo , mo re o r l e s s ,s t an d a rd c i r c u i t s . F or c o a l s e nc ou n te ri ng l i t t l eo r no o x i d a t i o n o r w e at h er i ng c h a r a c t e r i s t i c s ,

th e minus 0 .5 mm c o a l p a s s e s f ro m f l o t a t i o n w i t ht h e c o n c e n t r a t e s b e i n g s u b s e q u e n t l y d e w at e re d bye i t h e r vacuum d i s c f i l t e r s o r s c r e e n bowlc e n t r i f u g e s . F o r c o a l s w i t h t h e s e p ro bl em s , t h ef i n e s a r e c l a s s i f i e d a t 0 .15 mm a nd t h e 0 . 5by 0.15 mm f r a c t i o n i s cleaned by two-stagewater-only cyc lo ne whi le th e minus 0 .15 mmf r a c t i o n i s e i t h e r c l e an ed by f r o t h f l o t a t i o n o re l s e d i s c a rd e d . The r e as o n f o r t h i s i s t h a t t h ec o a r s e f r a c t i o n h a s b e e n show n t o b e p o o r l yr e s p o ns i v e t o f l o t a t i o n an d y e t r e a d i l y c l ea n edby cyc lones . The converse i s t r u e f o r t h e0 .15 mm f r a c t i o n . The two c l e a n c o a l f u n c t i o n sa r e t he n combined f o r f i l t r a t i o n o r c e n t r i f u g a ld e w a t e r i n g .

Conclus ions

The m a j o r p r ob l em s f a c e d by t h e o p e r a t o r s i n


5/16

t h e We st cr n Cn nn di an c o n l f i e l d s a r e r e l n t c d t othc recovery of in s i c u con l . P roper min ing andq u a l i t y c o n t r o l p r oc e du r es a r e e s r a b l i s h c d i n t h ep i t to nm in i zc coa l r ecovery f rom che senm nndmin imize d i lu t i on . There i s no one method of es-t i m a t i n s m i n ea b l e p i t r e s e r v e s , r e c o v e r i e s , &g

l o s s e s and d i l u t i o n . T h i s i s t o b e e x pe c t ed a sg e o l o g i c a l c o n d i t i o n s a r e v e r y v n r i e d f ro m on emine s i t e to nno ther. Even wi th i n the same p i ta vn r i e t y o f seam(s ) con f igur a t ion s cnn be seen .

The open pi t s of Western Canada a r e highlymechnnized and us e t he most modern of minin gequipment . Hydrau l ic shove l s and b e l t conveyorsf o r l o ng d i s t a n c e t r a n s p o r t a t i o n a r e two i t em swhich have gained remarkable acceptance within avery sh or t time. High break-out fo rc e and capac-i t y f o r s e l e c t i v e m in in g ha s c o n tr i b u t e d l a r g e l yt o t h e s u c c e s s of t h e h y d r a u l i c s h o ve l . T h e reare some 20 s u c h ma c hi ne s i n o p e r a t i o n i n We st e rnCanada.

Only one coa l oper a to r i n t he mountains uses adr ag l i ne . Dragl ines have not found t h a t much ofa c c ep t a nc e a l t h ou g h s e v e r a l a r e b e in g o p e r a t e d i nt h e s u r f a c e c o a l mi ne s i n t h e P l a i n s R eg io n.

The g r e a t e s t c o n s t r a i n t t o o v e r a l l m in in g i nthe p rov inces o f B r i t i sh Columbia and Alber ta i sthe topography. The rugged mounta in t e r r a i np laces numerous cons t ra in t s on mine p lann ing ,m a t e r i a l s h a n d l i n g a nd i n f r a s t r u c t u r e d ev e lo pm e ntThe m in es a r e l o c a t e d a t e l e v a t i o n s o f u p t o2 4 0 0 m a bo ve t h e s e a l e v e l . Te m pe r a tu r e s d u r i n gt h e w i n t e r d i p as low a s -450C.

T h i s t y p e o f c l i m a t e r e q u i r e s t h a t some s p e c i a ls p e c i f i c f e a t u r e s b e i n c o rp o r at e d i n t h e b a s i cmachines. For example, most lo ad be ar in g compo-n e n t s a r e made f ro m c o l d w e a t h e r s t e e l . P r o vi -s i o n i s made f o r h e a t i n g o f t h e e n g i n e c o o l a n t

when t h e machine i s off -du ty. Hea t ing e lementsf o r h e a t i n g t h e h y d r a ul i c o i l a f t e r ma ch in e s t op -pages and pre- heat i ng of ba t t er i es by means ofh o t p l a t e s a r e a l s o r e q ui r e d, The f u e l o i lwarmer fwate r separa to rs and a i r- sys tem de ice rs ys t em s a r e a l s o e s s e n t i a l f o r c o l d we a t he r o pe r-a t i o n .

The Wes tern Canad ian mines have l e a r n t t o de a lw i th t h e pr ob le m o f f r i a b l e c o a l . I n p i t mi ni ngtechn iques have been deve loped to min imize t hep r o du c t io n o f f i n e s . Tr i a l s w i th v a r i o u s s e t s o ff i n e c o a l c le a ni ng c i r c u i t s h ave l e d t o t h e a d o pt i o n o f f r o t h f l o t a t i o n an d w a t e r o nl y cy c l on e s .

The p r o c es s p l a n t s i n c o r p o r a t i n g t h e t h r e ec lea n ing c i r cu i t s , e .g . dense medium, hydrocy-c l o n e s and f r o t h f l o t t i o n t en d t o be r e l a t i v e l yc ompl ex wi t h a h i g h c a p i t a l c o s t b u t o f f e r ag r e a t d e a l of f l e x i b i l i t y i n terns of f e e d v a r i -a b i l i t y and p r od u ct q u a l i t y.

On a ny c o a l mi ni n g p r o j e c t i n t h e m ou n t ai n st h e c h a l l e n g e s f a c i n g t h e m in e p l a n n e r s a r e en or -mous. The concur rent mining of se ve ra l seamso f t e n p r o v i d e s a b a t c h o f r a w c o a l o f h i g h l y mri-a b l e q u a l i t y . The raw coa l f rom these ba tchesm us t b e b le n d ed t o p r o v i d e a u n i f o r m f e e d f o r t h ec o a l p r o c e ss i n g p l a n t w i t h t h e a i m o f a c h i e v i n ga washed c o a l o f a s p e c i f i c q u a l i t y f o r t h eexpor t marke t .

S e v e r a l mi ni ng a l t e r n a t i v e s m us t b e e v a l u a te di n o r d e r t o f i n d a n o p t i m a l t r a d e - o f f b et we e np r o du c t io n c o s t , s e l l i n g p r i c e , r e s o u r c e co ns e r-v a t i o n , p r o d u c t q u a l i t y a n d e n v i r o n m e n r a l p r o t e c -t i o n .

Rcfc rences

1 Bn ll , C.W., Er.?lorntion and Geo log ica l Scruc-tu re o f Coal Nensures i n Wes te rn ~nn oda , oalE x a l o r n t io n , P r o ce e d in g s o f t h e F i r s t I n t e r n a -t ionnl Con1 Explorat ion Symposiurc, 2l i l ler

Freeman Pub l ic a t i ons Inc . , 1976 .2 Bie len s te in , H.U. e t a l . , Coa l Resources and

Re se rv es of Canada, P.eport ER 79-9, Ene rg y,M ne s and Resource s Canada, December 1979.

3 But che r, S.G., Osborne, D.G. and k' al te rs , A.D.Des im . C o d s s i o n i n ~ nd Opera t ion o f P lan t s

~ r e a t ? n g H ig hl y ~ r i a b i e a n ad i o n C oa l s' ' , P np e rG3. V I I I I n t e r n a t i o n a l C oa l P r e ~ a r a t i o n on-g r e s s , USSR Don ets k, May 1979.

4 . Mikha i l , M X and Pa tch ing , T . Size Degrada-t ion of Bituminous Coal from Western Canada ,CL I B u l l e t i n , Flay 1980.

5 . Pear son, D.E., The Qu al i t y of Western CanadianCoking Coals , CEI Bul le t in , January 1980 .

6. Rance, D.C., The Qui nt et te Coal Pr oj ec t , MBul le t in , Vol . 76 , No . 853 llay 1983.

7 S c m EA a al. The Coa l f i e ld s o f Smheas te rnBr i t i s h Columbia , >l ining Magazine, &ust 1983.

8. Singh al , R.K., Course no te s: Mine Plan ning andM a t e r i a l s H a nd l i ng i n S u r f a c e ? li n i ng , U ni ve r -s i t y of Al be rt a, Edmonton, November 1980.

9. Sin gha l , R.K., Grassy blountain Coal Pr oj ec t ,Unpublished R epo rts , Home Oi l Co. Ltd.,

Calgary, 1982.

XI Walters A.D., Coal Pr ep ar at io n Technology i nBr i t i s h Columbia , P roceed ings o f 8 t h AnnualCLhi Di s t r i c t 6 Meet ing, Smi thers , Br i t i s hColumbia, October 1983.


6/16

Table 1 Si ze Di st ri bu ti on s of Rocky Xountain Coking Coal

S i z e F r a c t i o nm

Plus 50

-50 +25

-25 +13

-13 6

- 6 + 3

- 3 0 . 5

0.5 0.15

Hinus 0.15

Mass

aw CoalA s Hined

Raw CoalI n t o P l a n t

Ash Co nte nt ?lass Ash Co nt ent

Clean CoalA f t e r D r y i n g

(Reference 3 B u tc h er e t a l . , 1 97 9)

Table 2 . Prop or t i on of F ines i n Rocky Mountain Coals

Mine

AverageVo l a t i l e A s h

Hardgrove Matter ContentG r i n d a b i l i t y ( mf

A (Semi-Anthracite) 7 9

B 8 9

96

D 8 9

E 82

91

G 10

CinesContent

-28 Yesh

(Reference 4 Hi kha i l and Patching , 1980)


7/16

Table 3. Coking Properties of Rocky Mountain Coals

I n e r t aximum MaximumN ip po n S t e e l Rank C o nt e nt D i l a t a t i o n F l u i d i t y

group in^ Ro max d dpm

Keystone 1.50 8 t o 30 0 t o 70 5-100

P i t t s t o n 1 . 0 - 1.4 8 t o 3 0 80 t o 260 1500-30000Moura 0.9 - 1 .2 25 t o 45 -10 t o +lo0 3-2500

Balmer 1 2 - 1 5 2 5 t o 4 5 - lO t o + l O O 3-1500

Predominantly Canadian Rocky Mountain Coals

Vo l a t i l e~ atter

FSI (dmmf)

(Ref eren ce 5. Pea rson , 1980)

Tab l e 4 . Example: Wa sh ab il it y of Rocky >fou ntai n Coking Coal

R e l a t i v e D e n s i t y

F l o a t s 1 . 3 0

-1.30 + 1.35

-1.35 + 1.40

-1.40 + 1.45-1.45 + 1 , 5 0

-1.50 + 1.55

-1.55 + 1.60

-1.60 + 1.65

-1.65 + 1.70

-1.70 + 1.75

-1.75 + 1.80

-1.80 1.85

-1.85 + 1.90

Sinks 1 .90

F r a c t i o n a l

Y i e l d A s h

6.14 2.28

9.89 7.80

9.03 11.34

5.72 15.45

3.20 19.66

3.11 23.17

2.05 27.75

1.54 31.91

1.50 35.80

1.29 40.37

1.24 44.24

1.37 48.64

1.33 52.27

23.09 79.25

Cumularive

Yield Ash

6.14 3.28

46.03 3.47

55.06 4.76

60,28 5.69

63.48 6.39

66.59 7.17

68.64 7.79

70.18 8.32

71.68 8.89

72.97 9.45

74.21 10.03

75.58 10.73

76.91 11.45

100.00 27-10

(Referenc e 10 . Wal te rs , 1983)


8/16

F i g u r e 1 Coal i n Canada from Ref. 2 .

pper retaceous


9/16

Eigures and 4 Typical geological sections showing coal seamstructure in the Western Canadian MountainousRegion


10/16


11/16


12/16

F i g u r e 7 T he f o o t w a l l o f a m o de r a t e l y d i p p i n g s ea m i s

b e i n g c l e a n e d by t h e d o z er .

F i g u r e 8. The coal dozed down i s b e i ng l o a de d i n t ot r u c k s by a fr o n t e n d l o a d e r.

F i g u r e 10 The m o un t ai no u s t o p o gr a p hy o f t e n n e c e s s i t a t e so v e r b u r d e n d i s p o s a l b y e n d t i p pi n g .


13/16


14/16

rnl z s ;

ue K1 MhRCU W H E K55-..-

n

R4W COAL

i A l L l ~ GD15P 54L

CLEAN COAL

C O N V E Y C R

D l C A R D CONV Er i aKc J aJOADOUT

DISCARD

F i g u r e 11 Example: Coal Prepara t ion Plant f low sheet for Western Canadian c o a l


15/16

Figu re 12 Belt conveyors are gaining rapid acceptance This m long

svstem snow n is at the Gree nhil ls mine in arit ish Columbia


16/16

Documents

Steep Seam Coal Mining in Western Canada 1984