Mineral Matter and Ash in Coal - ACS Publications - American

8 Reactions and Transformations of Coal Mineral Matter at Elevated Temperatures G . P. Huffman and F. E. Huggins

Downloaded by FUDAN UNIV on April 26, 2017 | http://pubs.acs.org Publication Date: April 2, 1986 | doi: 10.1021/bk-1986-0301.ch008

Technical Center, U.S. Steel Corporation, Monroeville,PA15146

An overview is presented of the reactions and transformations of the inorganic constituents of coal at elevated temperatures. Following a brief review of the types of inorganic matter in Eastern and Western coals, reactions and transformations of mineral matter that are of importance in coal combustion are discussed. The importance of ash melting and the utilization of phase diagrams are emphasized in the discussion of slagging behavior and slag deposition. In the section on fouling deposits, emphasis is placed on the reactions of volatile alkalies that give rise to molten phases (alkali sulfates and alkali silicates). Finally, a very brief discussion of the role of mineral matter in other coal conversion processes (liquefaction, carbonization, gasification) is given. Throughout the chapter, the importance of modern analytical techniques (Mössbauer spectroscopy, X-ray absorption spectroscopy, computer-controlled scanning electron microscopy) in the analysis of complex assemblages of minerals and mineral derivatives is stressed.

Coal contains a v a r i e t y of inorganic constituents that e x h i b i t d e l e t e r i o u s b e h a v i o r i n most p r o c e s s e s t h a t attempt t o c o n v e r t t h e energy i n c o a l t o a u s e f u l form. As c o a l i s h e a t e d , t h e i n o r g a n i c phases undergo t r a n s f o r m a t i o n s and r e a c t i o n s t h a t y i e l d a complex m i x t u r e o f s o l i d , m o l t e n , and v o l a t i l e s p e c i e s . These s p e c i e s g i v e r i s e t o s l a g g i n g and f o u l i n g d e p o s i t s , c o r r o s i o n , p o l l u t i o n , and other problems. A l t h o u g h s u c h problems a r e u s u a l l y a s s o c i a t e d w i t h t h e combustion o f c o a l t o produce e l e c t r i c a l power, t h e y a r e a l s o common i n c o a l g a s i f i c a t i o n and l i q u e f a c t i o n , cokemaking, and i r o n production. Conversely, c e r t a i n inorganic constituents ( a l k a l i e s , c a l c i u m , and i r o n - b e a r i n g phases) can have s i g n i f i c a n t and v a l u a b l e c a t a l y t i c a c t i v i t y i n c o a l g a s i f i c a t i o n and l i q u e f a c t i o n . The c u r r e n t c h a p t e r w i l l b r i e f l y r e v i e w r e s e a r c h on t h i s t o p i c . 0097-6156/86/ 0301 -0100$06.00/0 © 1986 American Chemical Society

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

8.

H U F F M A N A N D HUGGINS

Reactions

and Transformations

of Mineral

Matter

101

Nature o f t h e I n o r g a n i c C o n s t i t u e n t s o f C o a l I t i s common p r a c t i c e t o make a d i s t i n c t i o n between the i n o r g a n i c c o n s t i t u e n t s o f s o - c a l l e d " E a s t e r n " and "Western" c o a l s . By d e f i n i t i o n , Western c o a l s a r e those f o r which t h e CaO+MgO c o n t e n t exceeds t h e F e 0 content o f the ash, while the reverse i s true f o r Eastern coals [ J J . The i n o r g a n i c c o n s t i t u e n t s i n E a s t e r n c o a l s , which a r e p r i n c i p a l l y b i t u m i n o u s i n r a n k , a r e p r e d o m i n a n t l y i n t h e form o f d i s c r e t e m i n e r a l p a r t i c l e s . Clay minerals ( k a o l i n i t e , i l l i t e ) a r e u s u a l l y dominant, f o l l o w e d by q u a r t z and p y r i t e . The range and t y p i c a l v a l u e s o f t h e m i n e r a l d i s t r i b u t i o n and a s h c h e m i s t r y o f E a s t e r n c o a l s a r e shown i n T a b l e I . These d a t a were determined from c o m p u t e r - c o n t r o l l e d s c a n n i n g e l e c t r o n m i c r o s c o p y (CCSEM), Mossbauer s p e c t r o s c o p y , and o t h e r measurements on over a hundred c o a l s .


2

3

Table I .

Inorganic Constituents of Eastern Coals

Mineral Distribution Mineral Range

Typical

T y p i c a l Ash C h e m i s t r y Weight % Species 54

Quartz

5-44

18

Si0

Kaolinite

9-60

32

A1 0

3

Illite

2-29

14

Fe 0

3

Chlorite

0-15

Mixed

5-31

Silicates

2

2

2

29 8 2

2

CaO

17

MgO

1

Pyrite

1-27

8

κο

2

Calcite

0-14

3

Na 0

1

Siderite/Ankerite

0-11

2

Ti0

Other

Minerals

0-12

4

2

2

P

2

2°5

so

3

1 0.2 2

Western c o a l s a r e u s u a l l y l i g n i t e s o r subbituminous c o a l s . The range and t y p i c a l v a l u e s o f t h e i n o r g a n i c phase d i s t r i b u t i o n and a s h c h e m i s t r y o f a p p r o x i m a t e l y 20 Western c o a l s examined i n t h i s l a b o r a t o r y a r e shown i n T a b l e I I . In a r e c e n t paper, we d i s c u s s e d t h e d i f f e r e n c e s between the i n o r g a n i c c o n s t i t u e n t s o f low-rank c o a l s and t h o s e o f b i t u m i n o u s c o a l s [2J· These d i f f e r e n c e s o c c u r i n t h e c a l c i u m - , i r o n - , and a l k a l i - c o n t a i n i n g p h a s e s . I n bituminous c o a l s , t h e c a l c i u m c o n t e n t i s t y p i c a l l y low (CaO ^ 3

4

(3)

3

where M = Na o r K. T h i s p o i n t o f view i s s u p p o r t e d by the work o f C o a t s e t a l . [17] which e s t a b l i s h e d t h a t l i q u i d m e l t s c o n t a i n i n g up t o 90 p e r c e n t p y r o s u l f a t e can be formed from N a S 0 - K S 0 mixtures in S0 p r e s s u r e s of 100 t o 300 ppm a t t e m p e r a t u r e s down t o 335°C. Such SO l e v e l s can be r e a d i l y r e a c h e d v i a c a t a l y t i c o x i d a t i o n o f S0 i n the p r e s e n c e o f F e 0 [10]. CCSEM a n a l y s e s o f f o u l i n g d e p o s i t s from a b o i l e r f u r n a c e i n which a N o r t h Dakota l i g n i t e had been f i r e d a r e g i v e n i n T a b l e I I I . A l t h o u g h the d e p o s i t s c o n s i s t e d p r i n c i p a l l y o f c a l c i u m - e n r i c h e d a l u m i n o s i l i c a t e s , t h e y a l s o c o n t a i n e d s m a l l but s i g n i f i c a n t amounts of a l k a l i s u l f a t e s , intermixed with c a l c i u m s u l f a t e . R e c e n t l y , we c o n d u c t e d p o t a s s i u m K-edge X - r a y a b s o r p t i o n s p e c t r o s c o p y (XAS) measurements on t h e s e and r e l a t e d samples a t the S t a n f o r d S y n c h r o t r o n R a d i a t i o n L a b o r a t o r y . The X - r a y a b s o r p t i o n near-edge s t r u c t u r e s , o r XANES, were found to e x h i b i t c h a r a c t e r i s t i c forms t h a t c o u l d be used to i d e n t i f y the s u l f a t e s p r e s e n t . F i g u r e 4 shows the XANES s p e c t r a o b t a i n e d from the s e c o n d a r y s u p e r h e a t e r d e p o s i t ( t o p ) and from a dep o s i t c o l l e c t e d i n a combustion r i g (bottom) t h a t was f i r i n g a N o r t h Dakota l i g n i t e . The XANES o f t h e s u p e r h e a t e r d e p o s i t was found to be v e r y s i m i l a r to t h a t o f p o t a s s i u m b i s u l f a t e , KHSOit. KHSOu m e l t s at 212°C, and c o n v e r t s r a p i d l y t o K S 0 above 350C. The XANES s p e c t r u m o f t h e combustion r i g d e p o s i t , c o l l e c t e d a t a temperature 2

lt

2

1|

3

3

2

2

3

2

2

?




ι

Reactions

ι

ι

ι

and Transformations

ι

ι

ι

ι

ι

of Mineral

ι

Matter

ι

V, mm/s F i g u r e 3 Comparison o f t y p i c a l Mossbauer s p e c t r a o b t a i n e d from E a s t e r n ashes quenched from h i g h temperatures i n r e d u c i n g ( t o p ) and o x i d i z i n g (bottom) atmospheres. τ

-2

1

0

1

1

2

ι

4

ENERGY (EV) χ 10 F i g u r e 4 P o t a s s i u m K-edge XANES s p e c t r a o b t a i n e d from f o u l i n g d e p o s i t s r e s u l t i n g from l i g n i t e c o m b u s t i o n .


108

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

Table I I I .

CCSEM

CCSEM A n a l y s e s o f F o u l i n g D e p o s i t s

Category

Sec. Superheater, 990-1050°C 55 7 2 4 3 10 2 2 3 5 7

Ca-rich aluminosilicate* Ca- and F e - r i c h a l u m i n o s i l i c a t e * * Alkali sulfate*** Calcium s u l f a t e + a l k a l i s u l f a t e Si0 Ca-rich Hematite Ca-Fe f e r r i t e Ca-Mg s u l f a t e Al-Si rich U n i d e n t i f i e d , mixed phases 2


Preheater 750°C 63 6 2 6 2 6 1 1 2 2 5

*Approximate average c o m p o s i t i o n (mole %) determined from CCSEM energy d i s p e r s i v e X - r a y f l u o r e s c e n c e s p e c t r a was 37% Ca, 8% Mg, 4% F e , 41% S i , 10% A l (elements w i t h Ζ > 12, o n l y ) . **Average c o m p o s i t i o n - 31% Ca, 7% Mg, 21% Fe, 32% S i , 9% A l . ***Average c o m p o s i t i o n - Na~~Ca,,K~S, . ft

of 1090°C, c o u l d be s i m u l a t e d r a t h e r w e l l by weighted a d d i t i o n o f the XANES s p e c t r a from I^SO^ ( 6 0 % w e i g h t ) and K - a l u m i n o s i l i c a t e g l a s s ( 4 0 % w e i g h t ) . A more d e t a i l e d d i s c u s s i o n w i l l be g i v e n e l s e where [18J. S p i r o e t a l . [19J have used p o t a s s i u m K-edge XAS t o i n v e s t i g a t e combustion p r o d u c t s and c y c l o n e d e p o s i t s from a f l u i d i z e d bed combustor f i r i n g an E a s t e r n c o a l ( P i t t s b u r g h #8). They observed o n l y K - a l u m i n o s i l i c a t e g l a s s w i t h no e v i d e n c e o f any s i g n i f i c a n t potassium s u l f a t e content. These i n i t i a l r e s u l t s i n d i c a t e t h a t XAS w i l l be a v e r y u s e f u l method o f i n v e s t i g a t i n g t h e s t r u c t u r e o f i n d i v i d u a l elements i n complex d e p o s i t s . R e a c t i o n s and T r a n s f o r m a t i o n s o f I n t e r e s t Processes

f o r Other C o a l

Conversion

In t h i s s e c t i o n , examples o f t h e h i g h - t e m p e r a t u r e b e h a v i o r o f i n o r g a n i c phases i n o t h e r c o n v e r s i o n p r o c e s s e s w i l l be g i v e n . L i q u e f a c t i o n . Montano e t a l . [20] have i n v e s t i g a t e d the t r a n s f o r mation of p y r i t e to p y r r h o t i t e i n c o a l l i q u e f a c t i o n environments. They conducted i n s i t u Mossbauer s p e c t r o s c o p y measurements on c o a l s m a i n t a i n e d a t 1.24 MPa n i t r o g e n p r e s s u r e and observed changes i n the isomer s h i f t a t a p p r o x i m a t e l y 300°C t h a t s i g n a l l e d t h e b e g i n n i n g o f the t r a n s f o r m a t i o n o f p y r i t e t o p y r r h o t i t e . The t r a n s f o r m a t i o n a c c e l e r a t e d between 300 and 400°C, and from 20 t o 80 p e r c e n t o f the p y r i t e i n f o u r d i f f e r e n t c o a l s was t r a n s f o r m e d a f t e r one hour a t 440°C. From e x a m i n a t i o n o f b o t h t h e i n s i t u s p e c t r a and t h e s p e c t r a o f c o o l e d r e s i d u e s , t h e y c o n c l u d e d t h a t t h e p y r r h o t i t e underwent c o v a l e n t bonding t o the c o a l m o l e c u l e s , c a u s i n g a c a t a l y t i c e f f e c t on c o a l l i q u e f a c t i o n .


8.


Reactions

and Transformations

of Mineral

Matter

109


C a r b o n i z a t i o n . When c o a l i s h e a t e d t o temperatures ^900 t o 1200°C i n the absence o f a i r , most o f t h e v o l a t i l e m a t t e r i s d r i v e n o f f , l e a v i n g a c h a r , o r , i n the case o f m e t a l l u r g i c a l b i t u m i n o u s c o a l , a coke. The atmosphere i n a coke oven c o n s i s t s p r i n c i p a l l y o f h y d r o gen and methane. C o n s e q u e n t l y , p y r i t e i s reduced to a m i x t u r e o f i r o n s u l f i d e ( t r o i l i t e and p y r r h o t i t e ) and i r o n m e t a l [21 ] . The amount o f i r o n m e t a l formed depends on b o t h the temperature and the c o m p o s i t i o n o f t h e coke-oven g a s . The r e d u c t i o n o f i r o n s u l f i d e t o i r o n m e t a l i s d e s i r a b l e s i n c e b l a s t f u r n a c e o p e r a t i o n i s more e f f i c i e n t w i t h low s u l f u r coke. C a l c i t e reacts with the l i b e r a t e d s u l f u r to form c a l c i u m s u l f a t e , thus r e t a i n i n g s u l f u r i n the c o k e . C a l c i u m XANES s p e c t r a o f coke produced from P i t t s b u r g h seam c o a l i n which a l l c a l c i u m i s i n i t i a l l y p r e s e n t as c a l c i t e i n d i c a t e t h a t a p p r o x i m a t e l y 70 p e r c e n t o f t h e c a l c i t e i s c o n v e r t e d to c a l c i u m s u l fate during coking. XAS and e l e c t r o n m i c r o s c o p y measurements e s t a b l i s h t h a t p o t a s sium i n coke i s p r e s e n t p r i m a r i l y i n the form of K - a l u m i n o s i l i c a t e g l a s s d e r i v e d from i l l i t e . P o t a s s i u m i n coke i s o f g r e a t c o n c e r n because o f i t s b e h a v i o r i n a b l a s t f u r n a c e d u r i n g i r o n m a k i n g . In the combustion o r "raceway" zone o f the b l a s t f u r n a c e , p o t a s s i u m can become v o l a t i l i z e d . The v o l a t i l e p o t a s s i u m s p e c i e s condense on coke, b r i c k w o r k , and m e t a l s u r f a c e s i n the c o o l e r upper r e g i o n s o f the b l a s t f u r n a c e c a u s i n g s e v e r a l a d v e r s e e f f e c t s , i n c l u d i n g e x c e s s i v e coke r e a c t i v i t y , a l k a l i a t t a c k on b r i c k w o r k , and a l k a l i i n i t i a t e d d e p o s i t s and c o r r o s i o n . As d i s c u s s e d e l s e w h e r e [22,23], XAS measurements can p r o v i d e i n s i g h t i n t o the r e a c t i o n mechanisms o f p o t a s s i u m i n a b l a s t f u r n a c e . F o r example, the XAS d a t a o b t a i n e d from a b r i c k t h a t was s e v e r e l y damaged by a l k a l i a t t a c k i n a b l a s t f u r n a c e a r e shown i n F i g u r e 5. The XANES spectrum from the b r i c k i s compared to a s i m u l a t e d spectrum o b t a i n e d by weighted a d d i t i o n o f the XANES o f KC1 (50% weight) and K S 1 0 (50% w e i g h t ) i n F i g u r e 5a, w h i l e the r a d i a l s t r u c t u r e f u n c t i o n d e r i v e d from the EXAFS (extended X-ray a b s o r p t i o n f i n e s t r u c t u r e ) o f the p o t a s s i u m atoms i n t h e b r i c k appears i n F i g u r e 5b. Peaks due to the CI and Κ n e i g h b o r s h e l l s i n KC1 and to the 0 and S i n e i g h b o r s h e l l s i n K - a l u m i n o s i l i c a t e are labeled. From these r e s u l t s , i t appears t h a t the mechanism of a l k a l i a t t a c k i n v o l v e d v a p o r - d e p o s i t i o n o f KC1 f o l l o w e d by K - f l u x i n g o f the a l u m i n o s i l i c a t e b r i c k . The r e s u l t s o f an i n v e s t i g a t i o n o f t h e r e a c t i o n o f p o t a s s i u m w i t h coke u s i n g XAS and e l e c t r o n m i c r o s copy w i l l be g i v e n elsewhere [ 2 3 ] . 2

3

Gasification. Iron e x h i b i t s a great d i v e r s i t y of r e a c t i o n s at e l e v a t e d temperatures when the r e a c t i o n environment encompasses b o t h r e d u c i n g and o x i d i z i n g c o n d i t i o n s a t d i f f e r e n t s t a g e s o f the p r o c e s s . For example, i t i s n o t u n u s u a l t o o b s e r v e f i v e o r s i x d i f f e r e n t i r o n - b e a r i n g compounds i n t h r e e d i f f e r e n t o x i d a t i o n s t a t e s i n char and ash samples o b t a i n e d from c o a l - g a s i f i c a t i o n systems. In F i g u r e 6, the Mossbauer spectrum o f a c h a r r e s i d u e from a benchs c a l e g a s i f i c a t i o n system a t the I n s t i t u t e o f Gas Technology i s shown. The i n p u t atmosphere to t h e g a s i f i e r was a p p r o x i m a t e l y 5.2% 0 , 21.2% H 2 O , and the remainder N , and the average temperature was 1800°F. As i n d i c a t e d i n F i g u r e 6, s i x i r o n - b e a r i n g phases e x h i b i t ing three d i f f e r e n t o x i d a t i o n s t a t e s are observed: i r o n metal, i r o n s u l f i d e ( p r i n c i p a l l y FeS), f a y a l i t e ( F e S i 0 ) , magnetite ( F e 0 ) , h e m a t i t e ( F e 2 0 ) , g l a s s , w u s t i t e , and p o s s i b l y o t h e r minor p h a s e s . 2

2

2

1 |

3


3

u

110

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

A B S O R P T I O N (x 1 ( T ) 1


8 ΐ

4 r

-20

0

40

20 E N E R G Y (EV)

M A G N I T U D E (χ 1 0 ) 1

10

-i

b

1

1

—ι

CI A

8

K - A T T A C K E D BRICK

6

4

i Λ

:

2

0 0

ΙΛΛΑΑΛ ' I 2

1 4

1 6

1 8

Ζ—y. 10

RADIUS ( A )

Figure 5 of a b l a s t KC1 + 50% potassium K-attacked

(a) Comparison o f the potassium K-edge XANES spectrum f u r n a c e b r i c k t o a s i m u l a t e d XANES spectrum ( 5 0 % K Si0 ). (b) R a d i a l s t r u c t u r e f u n c t i o n o f d e r i v e d by F o u r i e r t r a n s f o r m i n g the EXAFS o f the brick. 2

3




Reactions

and Transformations

of Mineral

Matter

V E L O C I T Y , mm/ne

Figure 6 F e Mossbauer s p e c t r a o f g a s i f i c a t i o n c h a r r e s i d u e showing peaks from h e m a t i t e ( Η ) , m a g n e t i t e (Μ) , i r o n m e t a l (Fe), i r o n sulfides (FeS), f a y a l i t e (Fay), glass + wustite ( G l ) , and an unknown phase ( ? ) . 5 7


112

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

A more d e t a i l e d d i s c u s s i o n o f t h i s work has been g i v e n by Mason e t a l . [24]. A l k a l i e s and a l k a l i n e e a r t h s s e r v e as e f f e c t i v e c a t a l y s t s i n c o a l g a s i f i c a t i o n p r o c e s s e s [ 2 5 ] . I n low r a n k c o a l s , c a l c i u m bound to oxygen a n i o n s i n c a r b o x y l groups i s m o l e c u l a r l y d i s p e r s e d throughout t h e macérais [ 2 , 3 ] . S i m i l a r l y , i n K - e n r i c h e d cokes t r e a t e d a t h i g h t e m p e r a t u r e s , a more o r l e s s u n i f o r m l y d i s p e r s e d K-C phase i s observed [22,23 ]. Such u n i f o r m d i s p e r s i o n s g r e a t l y i n c r e a s e the a c t i v i t y o f t h e c a t a l y t i c s p e c i e s .


Conclusions Even from t h i s b r i e f o v e r v i e w , i t i s c l e a r t h a t much remains t o be done i n t h e a r e a o f u n d e r s t a n d i n g m i n e r a l - m a t t e r b e h a v i o r i n c o a l combustion and o t h e r c o n v e r s i o n t e c h n o l o g i e s and even more i n comb a t i n g t h e s t i c k y problems a r i s i n g from t h i s component i n c o a l . In p a r t i c u l a r , t h e r e i s g r e a t need f o r more d e t a i l e d i n v e s t i g a t i o n s o f f u l l - s c a l e t e c h n o l o g i c a l p r o c e s s e s , e s p e c i a l l y now t h a t a number o f r e l a t i v e l y new and s o p h i s t i c a t e d t e c h n i q u e s a r e a v a i l a b l e t h a t can be used to c h a r a c t e r i z e m i n e r a l - m a t t e r r e l a t e d phenomena i n ways t h a t were n o t p o s s i b l e a few y e a r s ago. Such t e c h n i q u e s i n c l u d e Mossbauer and EXAFS s p e c t r o s c o p i e s , which we have h i g h l i g h t e d i n t h i s a r t i c l e , t h a t have the a b i l i t y t o f o c u s on s p e c i f i c c r i t i c a l elements ( F e , K, S, e t c . ) , and r e v e a l v e r y d e t a i l e d i n f o r m a t i o n about t h e b e h a v i o r o f t h a t e l e m e n t . However, t h e o b s e r v e d phenomena i n f u l l - s c a l e p r o c e s s e s w i l l a l s o need t o be i n t e r p r e t e d i n terms o f b o t h k i n e t i c ( e . g . , d r o p - t u b e e x p e r i m e n t s [ 1 5 ] ) and thermodynamic ( e . g . , phase diagram a n a l y s i s [ 1 1 ] ) a p p r o a c h e s , as w e l l as t o take i n t o account the form o f the m i n e r a l m a t t e r and i t s d i s t r i b u t i o n i n the o r i g i n a l c o a l . These s h o u l d be i m p o r t a n t areas f o r r e s e a r c h on m i n e r a l - m a t t e r r e l a t e d problems i n the f u t u r e . Acknowledgments We a r e g r a t e f u l to a number o f c o l l e a g u e s f o r p r o v i d i n g many o f t h e samples d i s c u s s e d i n t h i s paper. These c o l l e a g u e s i n c l u d e Ken Ho o f the Babcock and W i l c o x Company; Dave Mason o f t h e I n s t i t u t e o f Gas T e c h n o l o g y ; Steve Benson, Mike J o n e s , and H a r o l d Schobert o f the U n i v e r s i t y o f N o r t h Dakota Energy R e s e a r c h C e n t e r ; and Mike M i l i t z e r of U. S. S t e e l C o r p o r a t i o n . We would a l s o l i k e t o acknowledge t h e S t a n f o r d S y n c h r o t r o n R a d i a t i o n L a b o r a t o r y (SSRL) f o r p r o v i d i n g beamtime f o r the XAS e x p e r i m e n t s and o u r c o l l a b o r a t o r s i n those e x p e r i ments, F. W. L y t l e and R. B. Greegor o f t h e Boeing Company. SSRL i s s u p p o r t e d by DOE, NSF, and NIH. The m a t e r i a l i n t h i s paper i s i n t e n d e d f o r g e n e r a l i n f o r m a t i o n o n l y . Any use o f t h i s m a t e r i a l i n r e l a t i o n t o any s p e c i f i c a p p l i c a t i o n s h o u l d be based on independent e x a m i n a t i o n and v e r i f i c a t i o n o f i t s u n r e s t r i c t e d a v a i l a b i l i t y f o r such u s e , and a d e t e r m i n a t i o n o f s u i t a b i l i t y f o r the a p p l i c a t i o n by p r o f e s s i o n a l l y q u a l i f i e d p e r s o n n e l . No l i c e n s e under any U n i t e d S t a t e s S t e e l C o r p o r a t i o n p a t e n t s o r o t h e r p r o p r i e t a r y i n t e r e s t i s i m p l i e d by t h e p u b l i c a t i o n o f t h i s paper. Those making use o f o r r e l y i n g upon t h e m a t e r i a l assume a l l r i s k s and l i a b i l i t y a r i s i n g from such use o r r e l i a n c e .


8.

HUFFMAN AND HUGGINS

Reactions and Transformations of Mineral Matter

113

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1.

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Mineral Matter and Ash in Coal - ACS Publications - American

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