Mineral Matter in Illinois and Other US Coals - American Chemical

2 Mineral Matter in Illinois and Other U.S. Coals Richard D . Harvey and Rodney R. Ruch

Downloaded by UNIV LAVAL on July 12, 2016 | http://pubs.acs.org Publication Date: April 2, 1986 | doi: 10.1021/bk-1986-0301.ch002

Illinois State Geological Survey, Champaign, IL 61820

This review (1) describes and classifies the geological, physical, and chemical occurrences of mineral matters in coal; (2) summarizes analytical methods used to characterize the mineral matter; and (3) compares the mineral-matter composition of Illinois coals with that of other U.S. coals. In Illinois coals the organic constituents generally vary vertically within seams by a factor of 2 to 3; many elements also vary laterally within the same seam. Similarly, variations are substantial from one seam to another within the Illinois Basin. There is a considerable overlap, however, in compositional ranges of coals from different U.S. basins. On a regional basis, the material variability of many elements, such as sulfur and chlorine, is the result of geological processes. Low-sulfur coals mined in many western states, southern West Virginia, southwestern Virginia, and eastern Kentucky underlie strata deposited from fresh water; whereas many high-sulfur seams underlie strata deposited from sulfate-bearing brackish or marine waters. Because of the high variability of coal, samples from all prospective deposits need to be analyzed. Methods for analysis of inorganic elements in coal are generally precise, but methods for quantitative analysis of mineral phases need to be improved.

M i n e r a l m a t t e r i s g e n e r a l l y c o n s i d e r e d t o b e t h e sum t o t a l o f a l l i n o r g a n i c m i n e r a l s ( d i s c r e t e p h a s e s ) and e l e m e n t s t h a t a r e present i n coal ( J J . Thus, a l l elements i n coal except o r g a n i c a l l y c o m b i n e d C , Η, 0 , N , a n d S a r e c l a s s i f i e d b y t h i s d e f i n i t i o n as m i n e r a l m a t t e r . T h i s a d e q u a t e l y c l a s s i f i e s most i n o r g a n i c e l e m e n t s i n c o a l s , t h o s e t h a t a r e s t r u c t u a l l y bound w i t h i n v a r i o u s m i n e r a l s , b u t some o t h e r e l e m e n t s a r e a l s o combined i n t h e o r g a n i c m a t t e r . F o r bituminous coals such e l e m e n t s i n c l u d e B, B e , B r , G e , S b , and V ( 2 - 5 ) ; f o r l o w e r r a n k c o a l s much o f t h e Ca i s c o m b i n e d a s a n o r g a n i c s a l t . In 0097-6156/ 86/ 0301 -0010508.75/ 0 © 1986 American Chemical Society

Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

2.

HARVEY AND

RUCH


a d d i t i o n , many o t h e r

Mineral

Matter

elements

in U.S.

11

Coals

are combined

in

both the

organic

and t h e m i n e r a l m a t t e r f r a c t i o n s . The c h e m i s t r y o f c o a l i s f u r t h e r c o m p l i c a t e d by t h e f a c t t h a t t h e o r g a n i c e l e m e n t s , e x c e p t n i t r o g e n , a l s o o c c u r i n one o r more m i n e r a l c o n s t i t u e n t s : carbon in carbonates; hydrogen in a b s o r b e d w a t e r and a s h y d r o x i d e i n c l a y m i n e r a l s ; o x y g e n i n w a t e r , q u a r t z and o t h e r s i m p l e o x i d e s , c l a y m i n e r a l s , c a r b o n a t e s , s u l f a t e s , and o t h e r t r a c e m i n e r a l s ; and s u l f u r i n p y r i t e , r e l a t e d s u l f i d e s , and s u l f a t e s . F o r s c i e n t i f i c and t e c h n o l o g i c a l p u r p o s e s , i t i s i m p o r t a n t t o know t h e o r g a n i c i n o r g a n i c a s s o c i a t i o n s of the elements in coals being studied or used i n i n d u s t r i a l p r o c e s s e s . C h a r a c t e r i z a t i o n of the mineral matter in coal i s important f o r a number o f r e a s o n s . B e c a u s e o f t h e way c o a l m u s t be m i n e d , t h e m i n e - r u n p r o d u c t a l w a y s i n c l u d e s some r o c k m a t e r i a l o t h e r than c o a l , thereby c o n t r i b u t i n g mineral m a t t e r to the mine product. M i n e r s o f a t h i n seam u s u a l l y h a v e t o r e m o v e some r o o f and f l o o r s t r a t a . Irregular bodies of roof shale or other rocks f r e q u e n t l y o c c u r w i t h i n c o a l seams and i n e v i t a b l y become p a r t o f t h e mine p r o d u c t . Some c o a l seams g r a d e u p w a r d s t o s h a l e c o a l o r c o a l y s h a l e s so t h a t t h e r e i s no c l e a r - c u t b o u n d a r y b e t w e e n c o a l and t h e r o o f r o c k s . In a d d i t i o n , many c o a l seams c o n t a i n o n e o r more m i n e r a l p a r t i n g s o f v a r i o u s t h i c k n e s s so t h a t m i n e r s must i n c l u d e t h e s e i n t h e mine p r o d u c t . It i s best f o r mining and s a l e s p u r p o s e s i f t h e a m o u n t s , t y p e s , and c h a r a c t e r i s t i c s o f t h e s e r o c k m a t e r i a l s be known p r i o r t o m i n i n g i n o r d e r t o p r o p e r l y d e s i g n t h e m i n e and p r e p a r a t i o n p l a n t . W h i l e i t h a s l o n g b e e n known t h a t m i n e r a l m a t t e r i s a n i m p o r t a n t d e s i g n f a c t o r f o r u t i l i t y and o t h e r l a r g e b o i l e r s (6-_ S) consumer p r e s s u r e f o r low e l e c t r i c b i l l s c o u p l e d w i t h more s t r i n g e n t regulations of s u l f u r emissions are causing u t i l i t i e s t o seek more e f f i c i e n t o p e r a t i o n o f e x i s t i n g c o a l - f i r e d power plants. T h u s , t h e r e i s r e n e w e d i n t e r e s t and c o n c e r n w i t h s u c h p r o b l e m s a s s l a g g i n g and f o u l i n g o f b o i l e r s ( 9 - 1 6 ) . Slagging i s the accumulation of mineral matter in a fused and h a r d e n e d f o r m on t h e w a l l s and o t h e r s u r f a c e s i n t h e f u r n a c e of b o i l e r s . S l a g g i n g r e d u c e s h e a t t r a n s f e r and c a u s e s e x c e s s i v e t e m p e r a t u r e o f t h e e x h a u s t gases as t h e y e x i t t h e f u r n a c e . The n e t e f f e c t o f s l a g g i n g i s t o add m a i n t e n a n c e c o s t s f o r b o i l e r o p e r a t i o n a s i t damages t h e m e t a l p a r t s on w h i c h t h e s l a g forms. B l o c k s o f s l a g h a v e b e e n known t o g r o w t o o v e r 5 f e e t t h i c k i n t h e t o p o f f u r n a c e s and e v e n t u a l l y t o f a l l o f t h e i r own w e i g h t , k n o c k i n g out t h e b o t t o m of t h e f u r n a c e . A v a i l a b i l i t y of t h e b o i l e r f o r g e n e r a t i n g e l e c t r i c power i s s i g n i f i c a n t l y r e d u c e d by s e v e r e s l a g g i n g . F o u l i n g i s t h e a c c u m u l a t i o n o f m i n e r a l - d e r i v e d a s h on t h e s u p e r h e a t e r and r e h e a t e r t u b e s i n t h e c o n v e c t i v e ( h e a t e x c h a n g e r ) s e c t i o n downstream from the f u r n a c e . Fouling r e s t r i c t s t h e f l o w o f e x h a u s t g a s e s and i m p e d e s h e a t t r a n s f e r t h r o u g h s u p e r h e a t e r t u b e w a l l s and t h e r e b y r e d u c e s t h e amount o f steam g e n e r a t e d . A b r a s i o n of metal p a r t s i n s i d e the b o i l e r i s a t h i r d d e l e t e r i o u s e f f e c t o f a s h p a r t i c l e s p r o d u c e d by some c o a l s . Ash p a r t i c l e s t h a t are e s p e c i a l l y hard w i l l cause e x c e s s i v e a b r a s i o n 9


12

M I N E R A L M A T T E R A N D A S H IN C O A L


when t h e y

i m p i n g e on t h e

furnace

and b o i l e r

surfaces.

At

plants

where a b r a s i o n i s s e r i o u s , i t c a u s e s f r e q u e n t s h u t - d o w n s . A f o u r t h i m p o r t a n t f a c t o r t h a t i n c r e a s e s o u t a g e s and maintenance costs i s the c o r r o s i v e e f f e c t s of a l k a l i elements, e s p e c i a l l y sodium, which i s associated with c h l o r i n e in c e r t a i n coals. The s p e c i f i c damage t o b o i l e r s b y c h l o r i n e i s n o t w e l l known, but t h i s m i n e r a l c o n s t i t u e n t c l e a r l y causes e x c e s s i v e rates of corrosion to coal handling equipment. T h i r t y - f o u r m i n o r and t r a c e e l e m e n t s a r e o f p o t e n t i a l environmental concern (17). S u l f u r i s the element of major c o n c e r n due t o i t s a b u n d a n c e i n f l u e g a s e s f r o m some c o a l b u r n i n g p l a n t s and i t s s u b s e q u e n t c o n t r i b u t i o n t o " a c i d r a i n . " S u l f u r as a c i d i c i o n s o f s u l f a t e c a n a l s o c o n t r i b u t e t o p o l l u t i o n o f s u r f a c e w a t e r and g r o u n d w a t e r . Other elements of g r e a t e s t c o n c e r n a r e A s , B, C d , P b , H g , Mo, and S e . With the e x c e p t i o n o f Β and S e , t h e s e e l e m e n t s a r e s t r o n g l y a s s o c i a t e d w i t h m i n e r a l m a t t e r i n t h e c o a l and a r e c o n c e n t r a t e d i n w a s t e p i l e s from coal p r e p a r a t i o n p l a n t s . I f the waste d i s p o s a l site i s n o t c o n s t r u c t e d as a c l o s e d s y s t e m , p o l l u t i o n o f n e a r b y groundwater i s p o s s i b l e . B o r o n and Se may c o n t r i b u t e t o t h e p o l l u t i o n r i s k as t h e y a r e a s s o c i a t e d w i t h b o t h m i n e r a l and organic components. On t h e o t h e r h a n d , c e r t a i n c o a l - m i n e w a s t e s h a v e p o t e n t i a l f o r r e c o v e r y o f v a l u a b l e m e t a l s s u c h a s z i n c and cadmium ( 1 8 ) . G e o l o g i c a l s t u d i e s of the d i s t r i b u t i o n (or v a r i a t i o n ) of m i n e r a l m a t t e r i n a l o c a l a r e a , s u c h as a l a r g e m i n e , as w e l l a s r e g i o n a l l y o v e r the e x t e n t o f a commercial seam, e n a b l e u s e f u l p r e d i c t i o n s o f t h e c o n c e n t r a t i o n s o f some i n o r g a n i c e l e m e n t s important to coal q u a l i t y . G e o l o g i c a l p r o c e s s e s t h a t formed the seam o p e r a t e d o v e r e x t e n s i v e a r e a s ; t h e r e f o r e , p a t t e r n s o f e l e m e n t a l d i s t r i b u t i o n e n a b l e q u a l i t y p a r a m e t e r s o f t h e c o a l bed t o be p r e d i c t e d i n some u n e x p l o r e d a r e a s ( 5 , 1 9 - 2 4 ) .

Coal

Geology

C o a l i s a brown t o b l a c k , c o m b u s t i b l e , s e d i m e n t a r y r o c k composed p r i n c i p a l l y o f c o n s o l i d a t e d and c h e m i c a l l y a l t e r e d p l a n t r e m a i n s (25)(Figure 1). The o r i g i n a l p l a n t s g r e w a b u n d a n t l y i n a n c i e n t swamps and t h e i r r e m a i n s a c c u m u l a t e d a s p e a t on t h e swamp f l o o r , m o s t l y under w a t e r , which r e s t r i c t e d d e c o m p o s i t i o n of the p l a n t debris. Commercial t h i c k n e s s e s o f c o a l a r e t h o u g h t t o have r e q u i r e d p o s s i b l y a c e n t u r y o r more o f u n u s u a l l y c o n s i s t e n t c l i m a t i c and h y d r o l o g i e c o n d i t i o n s t o a l l o w f o r t h e d e p o s i t i o n of the required t h i c k n e s s of peat. S t u d i e s h a v e shown t h a t p e a t : c o a l ( b i t u m i n o u s ) t h i c k n e s s r a t i o s r a n g e f r o m a b o u t 3:1 t o 30:1 ( 2 6 ) . C o T l seams i n t h e U n i t e d S t a t e s t h a t a r e o f m i n a b l e t h i c k n e s s and q u a l i t y r a n g e i n a g e f r o m t h e P e n n s y l v a n i a n t o t h e Tertiary geologic periods (Figure 2). A rough e s t i m a t e suggests t h a t t w o - t h i r d s to t h r e e - q u a r t e r s of the coal produced t o date i n t h e U n i t e d S t a t e s has b e e n b i t u m i n o u s c o a l f r o m P e n n s y l v a n i a n s t r a t a m i n e d f r o m seams i n t h e A p p a l a c h i a n , I l l i n o i s , a n d Western I n t e r i o r Basins ( F i g u r e 3 ) . Most o f t h e r e m a i n d e r has b e e n l i g n i t e and s u b b i t u m i n o u s c o a l m i n e d f r o m T e r t i a r y and


RUCH

Mineral

Matter

in U.S.

Coals


HARVEY AND

0 5 i_i

50 ι

μπη

F i g u r e 1. T h i n s e c t i o n o f a c o a l i n t r a n s m i t t e d l i g h t s l i c e d normal t o b e d d i n g s h o w i n g l a y e r e d s t r u c t u r e o f p l a n t d e b r i s and d i s s e m i n a t e d g r a i n s ( 2 - 4 ym) o f q u a r t z (Q) a n d p y r i t e ( Ρ ) .


MINERAL

Yrs (106)

Geologic Period

Subbituminous

Lignite

M A T T E R A N D A S H IN C O A L

Bituminous Medium volatile

High volatile

Low volatile

Anthra cite

Tertiary western

50-

:··.·:··Λ w e s t e r n states

100-

Cretaceous

150-

I

Jurassic


200Triassic

VA

Permian

ΤΧ,ΟΗ, PA, W V

250-

300-

Pennyslvanian

350-

Mississippian

East o f G r e a t Plains rWxWidely scattered a n d l i m i t e d coals:

F i g u r e 2. G e o l o g i c age ( p e r i o d ) and rank N o r t h A m e r i c a , a f t e r Cady ( 2 7 ) .

Figure

3. C o a l f i e l d s

of the United

of coal

States

deposits

(28,29).


in

2.

HARVEY A N D RUCH

Mineral

Matter

in U.S. Coals


C r e t a c e o u s s t r a t a i n t h e n o r t h e r n Great P l a i n s , t h e Rocky M o u n t a i n s ( i n c l u d i n g c e n t r a l Utah and n o r t h e a s t e r n A r i z o n a ) , W a s h i n g t o n , T e x a s and A l a s k a . In r e c e n t y e a r s p r o d u c t i o n f r o m t h e s e T e r t i a r y and C r e t a c e o u s d e p o s i t s h a s g r e a t l y i n c r e a s e d . F o r e x a m p l e , between 1972 and 1982 t h e p r o d u c t i o n f r o m t h e s e d e p o s i t s i n Wyoming i n c r e a s e d f r o m an a n n u a l t o n n a g e o f a b o u t 10 m i l l i o n t o n e a r l y 110 m i l l i o n , w h i l e p r o d u c t i o n i n I l l i n o i s d e c r e a s e d f r o m a b o u t 6 5 t o 61 m i l l i o n t o n s . O r i g i n o f Coal Seams. By a n a l o g y t o p r e s e n t - d a y d e p o s i t s and t o the l i t h o l o g i e character of associated s t r a t a , the ancient coal seams f o r m e d i n v a s t p e a t s w a m p s . The swamps w e r e l o c a t e d on coastal p l a i n s , often o n , or adjacent t o , major r i v e r d e l t a s . Some o f t h e swamps m i g h t h a v e b e e n 2 0 0 t o 4 0 0 m i l e s a c r o s s . O v e r a p e r i o d o f many c e n t u r i e s t h e swamp l a n d s l o w l y s u b s i d e d w h i l e m a i n t a i n i n g a dense f o r e s t a t o r near sea l e v e l . Layer upon l a y e r o f f a l l e n v e g e t a t i o n was c o n v e r t e d t o p e a t . Mineral m a t t e r was i n t r o d u c e d i n t o t h e swamps, m a i n l y by r i v e r s , a s s u s p e n d e d mud and d i s s o l v e d i o n i c s p e c i e s d u r i n g s t o r m s t h a t f l o o d e d t h e swamp, b y s e a w a t e r d u r i n g w i n d s t o r m s , a n d by d i s t a n t v o l c a n i c e r u p t i o n s t h a t r a i n e d d u s t o n t o t h e swamp. Some i n o r g a n i c e l e m e n t s w e r e d r a w n i n t o p l a n t t i s s u e s t h r o u g h t h e i r r o o t s f r o m t h e swamp w a t e r and p e a t y s o i l ; t h i s m a t e r i a l i s known a s " i n h e r e n t " m i n e r a l m a t t e r ( 3 0 ) i n t h e f i n a l coal. U l t i m a t e l y t h e swamp was d r o w n e d b y r i v e r s o r s e a w a t e r f r o m w h i c h s a n d and mud w e r e d e p o s i t e d o n t o t h e d y i n g f o r e s t . Peats c o v e r e d w i t h s e a w a t e r were i n j e c t e d w i t h s u l f a t e , b u t t h o s e c o v e r e d by t h i c k a n d i m p e r m e a b l e r i v e r muds ( f r e s h w a t e r ) r e m a i n e d more o r l e s s f r e e o f s u l f a t e . M o r e o f t e n t h a n n o t , o n c e a p e a t swamp was e s t a b l i s h e d on a c o a s t a l p l a i n o r d e l t a and l a t e r c o v e r e d b y s e d i m e n t s d u e t o l a n d s u b s i d e n c e , a s e c o n d swamp was e s t a b l i s h e d i n t h e same r e g i o n b y c y c l i c c h a n g e s i n s e a l e v e l and r e - e s t a b l i s h m e n t o f swamp-type v e g e t a t i o n . In t h i s w a y , m u l t i p l e l a y e r s o f p e a t a n d s u b s e q u e n t l y o f c o a l were f o r m e d . Coal i f i c a t i o n . The t r a n s f o r m a t i o n o f p e a t i n t o c o a l was a s l o w and c o m p l e x p r o c e s s t h a t b e g a n w i t h b a c t e r i a l r e d u c t i o n o f p l a n t d e b r i s d u r i n g t h e p e a t s t a g e ( F i g u r e 4 ) . As t h e p e a t was p r o g r e s s i v e l y b u r i e d u n d e r h u n d r e d s o f f e e t o f s e d i m e n t s , i t was c o m p a c t e d ; i t s i n h e r e n t m o i s t u r e was p r o g r e s s i v e l y f o r c e d o u t b y t h e p r e s s u r e o f o v e r l y i n g s e d i m e n t s and b y h e a t f r o m t h e e a r t h ' s interior. M e t h a n e and C 0 w e r e r e l e a s e d o r e n t r a p p e d w i t h i n pores o f t h e compacted o r g a n i c d e b r i s . Several chemical p r o c e s s e s b r i e f l y d e s c r i b e d as p e a t i f i c a t i o n , h u m i f i c a t i o n , g e l i f i c a t i o n , and v i t r i f i c a t i o n , a l t e r e d t h e r o o t s , b a r k , and o t h e r c e l l u l o s e and l i g n i n b e a r i n g d e b r i s t o v i t r i n i t e - - t h e m o s t abundant maceral c o m p r i s i n g b i t u m i n o u s c o a l s ( F i g u r e 4 ) . P l a n t s p o r e s , c u t i c u l e s , and r e s i n s a n d o t h e r l i p i d c o m p o n e n t s w e r e i n c o r p o r a t e d i n t o p e a t and t h e s e a r e c l a s s i f i e d a s t h e l i p t i n i t e group of macérais. Various oxidized (charred or f u s i n i z e d ) d e b r i s a r e c l a s s i f i e d as i n e r t i n i t e s ( F i g u r e 4 ) . With i n c r e a s i n g c o a l i f i c a t i o n ( r a n k ) , t h e s e m a c é r a i s become i n c r e a s i n g l y e n r i c h e d i n c a r b o n so t h a t a l l macérais i n a n t h r a c i t e h a v e e s s e n t i a l l y t h e same p r o p e r t i e s a s i n e r t i n i t e . 2



> ζ

ζ o

MACERAL COMPONENTS

Increasing carbon content

SPORES, L E A F CUTICLES, ROOTS, LIMBS. BARK . RESINS, A L G A E , ETC. , , C E L L U L O S E . LIGNIN

95%lo MOISTURE

v/tineral g r a i n s suspended in w a t e r or atmosphere

3

90%lo MINERAL COMPONENTS

Epigenesis

Deposition solution^ Syngenesis

Moisture and ionic compounds, including sulfur, d i s s o l v e d in w a t e r — IONS

INORGANIC COMPONENTS

Figure 4. Diagramatic representation of c o a l i f i c a t i o n processes i n v o l v i n g t h e c o n v e r s i o n o f p l a n t d e b r i s t o v a r i o u s macérais, and t h o s e i n v o l v i n g m o i s t u r e a n d g e n e t i c p r o c e s s e s o f m i n e r a l matter.

Swamps, s o m e lakes and lagoons

T r e e s , s h r u b s , reeds, grasses, algae, f u n g i , b a c t e r i a

ORGANIC COMPONENTS


η

Χ

CO

>

> Ζ α

25 H m

r

>

73

2.

HARVEY A N D RUCH

Mineral

Matter

in U.S.

Coals

Because o f t h e c o m p l e x i t y o f the coal i f i c a t i o n p r o c e s s e s , d i f f e r e n t measures are used t o d e f i n e d i f f e r e n t l e v e l s o f rank ( T a b l e I ) : h i g h m o i s t u r e , l o w h e a t i n g v a l u e , and n o n a g g l o m e r a t i n g c h a r a c t e r o f t h e c o a l d e f i n e t h e rank (group) w i t h i n t h e l i g n i t e and s u b b i t u m i n o u s c l a s s e s ; a n d v o l a t i l e m a t t e r ( o r f i x e d carbon) d e f i n e t h e v a r i o u s groups o f rank i n t h e b i t u m i n o u s and a n t h r a c i t e c l a s s e s . In a d d i t i o n t o t h e s e p r o p e r t i e s , the r e f l e c t a n c e of v i t r i n i t e , carbon content of the c o a l ( d r y , m i n e r a l m a t t e r f r e e ) , and some o t h e r p r o p e r t i e s change p r o p o r t i o n a t e l y as rank i n c r e a s e s (Table I ) .


Mineral

Occurrences

i n Coal

Seams

Over 125 d i f f e r e n t m i n e r a l s have been r e p o r t e d i n c o a l ( 3 2 ) ; h o w e v e r , o n l y about 25 have been r e c o g n i z e d as o c c u r r i n g i n s i g n i f i c a n t amounts ( T a b l e I I ) . M i n e r a l s i n c o a l o c c u r as d i s c r e t e g r a i n s o r f l a k e s o r a g g r e g a t e s i n one o f f i v e p h y s i c a l modes ( 3 1 ) : ( 1 ) as m i c r o s c o p i c a l l y d i s s e m i n a t e d i n c l u s i o n s w i t h i n macérais; (2) as l a y e r s o r p a r t i n g s w h e r e i n f i n e - g r a i n e d c l a y m i n e r a l s u s u a l l y p r e d o m i n a t e ; ( 3 ) as n o d u l e s i n c l u d i n g l e n t i c u l a r and s p h e r i c a l c o n c r e t i o n s ; ( 4 ) a s f i s s u r e s , i n c l u d i n g c l e a t and o t h e r f r a c t u r e o r v o i d f i l l i n g s ; ( 5 ) a s r o c k f r a g m e n t s — m e g a s c o p i c masses o f rock m a t e r i a l found w i t h i n t h e c o a l bed as a r e s u l t o f f a u l t i n g , s l u m p i n g , o r r e l a t e d d i s t u r b a n c e s . T h i s c l a s s i f i c a t i o n i s u s e f u l i n t h a t t h e removal o f m i n e r a l s f r o m c o a l i n p r e p a r a t i o n p l a n t s i s s t r o n g l y i n f l u e n c e d by t h e m i n e r a l ' s p h y s i c a l mode o f o c c u r r e n c e . Fine-grained quartz, c l a y , and p y r i t e d i s s e m i n a t e d w i t h i n m a c é r a i s a r e l e a s t s u s c e p t i b l e t o removal by p h y s i c a l c l e a n i n g m e t h o d s ; whereas r o c k f r a g m e n t s and m i n e r a l s i n l a y e r e d , n o d u l a r , and f i s s u r e modes b r e a k f r e e and a r e more e a s i l y r e m o v e d . Origin of Mineral Matter. A genetic c l a s s i f i c a t i o n of mineral m a t t e r p r o v i d e s t h e b e s t means t o p r e d i c t t h e q u a l i t y o f c o a l i n a r e a s a h e a d o f m i n i n g and e x p l o r a t i o n . We c o n s i d e r t h r e e m a i n g e n e t i c p r o c e s s e s t o be r e s p o n s i b l e f o r m i n e r a l s i n c o a l : d e t r i t a l d e p o s i t i o n , syngenesis, or epigenesis (see the r i g h t s i d e o f F i g u r e 4 ) . D e t r i t a l g r a i n s were i n t r o d u c e d i n t o t h e swamp by r i v e r s , t i d a l ( s t o r m ) w a v e s , a n d w i n d ( v o l c a n i c dusts). S y n g e n e t i c m i n e r a l s were formed d u r i n g t h e peat s t a g e o f c o a l f o r m a t i o n , b e f o r e t h e p e a t was "1 U n i f i e d " t o l i g n i t e . T h r e e d i f f e r e n t s u b c l a s s e s o f s y n g e n e t i c m i n e r a l s c a n be d i s t i n g u i s h e d on t h e o r e t i c a l g r o u n d s . ( a ) m i n e r a l s formed by c r y s t a l l i z a t i o n o f i n o r g a n i c e l e m e n t s t h a t were i n c o r p o r a t e d i n t o t h e t i s s u e s o f the l i v i n g plants (the inherent mineral matter referred to above). ( b ) m i n e r a l s f o r m e d by b a c t e r i a l r e d u c t i o n o f a q u e o u s s u l f a t e s by c r y s t a l g r o w t h i n m i c r o s c o p i c p o r e s within the plant remains. (c) m i n e r a l i z a t i o n around n u c l e i or o t h e r c e n t e r s , forming nodules; these include coal b a l l s ( p e r m i n e r a l i z e d p e a t ) and o t h e r p l a n t r e p l a c e m e n t forms. It i s r a r e l y p o s s i b l e t o u n e q u i v o c a l l y d i s t i n g u i s h type (a)


17

Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986. \

Meta-anthracite

Anthracite

Semianthracite

L o w volatile bit. c o a l

M e d . volatile bit. c o a l

1

1 I

Reproduced with permission from Ref. 31. Copyright 1984,

> 14.000

/

No

• Yes

No

No

No

Agglomerating

Plenum Press.

>32.5

>32.5

30.2-32.5

13.000-14.000*

H i g h volatile Β bit. c o a l >14,000

26.7-30.2 Ϊ

10.500-13.000*

H i g h volatile C bit. c o a l

H i g h volatile A bit. c o a l

24.4-26.7 J

19.3-22.1 j 22.1-24.4

9.500-10.500*

Subbituminous C coal

14.6-19 3 1

10.500-11.500*

8.300-9.500*

Lignite A

Subbituminous A coal

6.300-8.300*

Lignite Β

-14.6

Subbituminous Β coal

Undefined-6.300*

" A i r dried. » W e l l - s u i t e d for rank d i s c r i m i n a t i o n in range indicated. ' Moderately well-suited for rank d i s c r i m i n a t i o n .

Anthracitic

Bituminous

Subbituminous

Lignite

class

1

(moist, m m f)

group

ASTM

7.0-9.3

MJ/kg (moist.mmf)

Btu/lb

ASTM

H e a t i n g value

%R

22-31*

1-2»

i-r >94'

90-97' 0.5-2 2.2-5.0*

2-8*

1-3

2-4' >4.5»

2-4»

3-5' 89-93' C/3

>

m 73

H

r

>

m 73

00

Vorres; Mineral Matter and Ash in Coal ACS Symposium Series; American Chemical Society: Washington, DC, 1986. 3

10

4

10

2

2

2

3

4

10

4

4

3

2

2

2

3

3

Mn,Ce,Sr,U K.Mg

Na, Sr, Pb,

Mn, Ti Ca

—

Mn, Ti

__

Mn, Zn, Sr

As, Co, Cu, A other chalcophile elements

Na.Ca.Fe.Li ,Ti ,Mn,F h other lithophile elements

Common Moderate Moderate Moderate Rare Rare Moderate Rare

Common Cjmmon Common

Trace Trace Trace Minor Minor Trace Trace Trace

Abundant Minor-trace Trace

Abundant Trace Mi nor

Ν 0,L D D,F F D D D

D, L, Ν Ν D

Ν,F N,L Ν

d,s(?)

d,s(?) s d(?)

e,s s ,e s ,e

s ,e s(?) s(?) e e

n,N,F D(?) η F F

Variable Trace Trace Minor-trace Trace

Rare-common Rare-moderate Rare Rare Rare Rare-common Moderate Rare

d,e,s(' d

L,F L

Abundant Moderate

d,s(?)

d,s(?)

Common Rare

D,L

0,L

Abundant

Abundant

Common

1

Chief occurrences Genetic Physical*

Common

Concentration in min. matter

Frequency of occurrence in coal seams

*n-disseminated, L-layers (partings), N-nodules, F-fissures (cleat). First listed is the most common occurrence. **d-detrital, s-syngenetic, e-epigenetic, w-weathering. First listed is the most common occurrence; ? indicates there is divergence of opinion about the genetic occurrence.

5

4

4

4

4

2

FeOOH K(Nz)AlSi 0o ZrSi0 CaS0 .2H 0 BaS0 FeS0 .H 0 Ca (P0 ) (F,Cl,0H) NaCl

2

3

Others goethite/1imonite feldspar zi rcon sulfates: gypsum barite szomolnokite apatite halite

3

SiOo

3

3

2

Fe 0 /Fe 0 Ti0

2

CaC0 CaMg[C0 ) FeC0

x

FeS (isometric) FeSÔ (orthorhombic) Fe S Zn S PbS/CuFeS

2

a

2

Al Si 0.(0H) Mg|AlfATSi 0 (OH)

2

Al Si 0 (0H) -H 0

2

KAl (AlSi 0 )(OH)

Composition

Carbonates cal cite dolomite (ankerite) siderite Oxides quartz magneti te/hemati te rutile A anatase

kaolinite group chlorite Sulfides pyrite marcasite pyrrhotite sphalerite galena/chalcopyrite

Mineral Clay minerals i l l i t e (sericite) smectite (including mixed layered)

Common minor and trace element associations

Table II. Minerals Frequently Occurring in Coals, Their Stoichometric Compositions, Relative Abundances, and Modes of Occurrences


>

Ci

Co

3

s

ί

C η χ

70

D

> ζ

m -

Mineral Matter in Illinois and Other US Coals - American Chemical

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