Electron Probe Microanalysis - American Chemical Society

9 Electron Probe Microanalysis A Means of Direct Determination of Organic Sulfur in Coal ROBERT RAYMOND, JR.

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on March 9, 2016 | http://pubs.acs.org Publication Date: November 12, 1982 | doi: 10.1021/bk-1982-0205.ch009

Los Alamos National Laboratory, Earth and Space Sciences Division, Los Alamos, N M 87545

An analytical method of measuring organic sulfur directly by use of the electron probe microanalyzer (EPM) avoids the uncertainty of calculating organic sulfur by difference. The EPM enables rapid, nondestructive determination of the organic sulfur content of individual macerals. Thus, total organic sulfur content of a coal may be computed by a mean modal analysis of the macerals. Twenty-nine coals, collected from 13 states within the contiguous USA, and ranging in rank, age, and organic sulfur content (0.2 to 5.3 wt% dmmf) have been analyzed. When plotting organic sulfur content of the coals vs organic sulfur content of respective vitrinite components, the best linear fit of the data has a correlation coefficient of 0.99, a slope of 0.98, and a y-intercept of -0.03. Empirically, organic sulfur content of a coal (dmmf) essentially equals organic sulfur content of its vitrinite. Note that analyzed samples contained as little as 41.9 wt% vitrinite macerals (dmmf). For EPM organic sulfur analysis representative samples (-20 to -100 mesh) are potted in epoxy pellets, polished, and carbon coated. Vitrinite grains are identified during analysis by shape and texture, with resulting organic sulfur contents equivalent to those determined when using oil-immersion, reflectance techniques for vitrinite identification. According to t-statistics, analyzing 15 vitrinite grains achieves a maximum variability of less than 0.20wt%in the coals that contain less than 2.00 wt% organic sulfur. Instrument time to analyze 15 grains, and therefore to determine the organic sulfur content of a sample, is less than 10 minutes. To test the EPM method, 0097-6156/82/0205-0191$06.00/0 © 1982 American Chemical Society

Fuller; Coal and Coal Products: Analytical Characterization Techniques ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

192

COAL

AND COAL

PRODUCTS


we chose coals containing either no inorganic sul fur (organic sulfur = total sulfur), or for which ASTM organic sulfur values were corrected for unextracted iron (which takes into account any unextracted pyrite). These 13 samples contained up to 2.09 wt% organic sulfur and variations between EPM and ASTM values were less than 0.16 wt%. As o u r need f o r e f f i c i e n t c o a l u t i l i z a t i o n i n c r e a s e s , i n a b i l i t y to i n t e r p r e t the occurrence and the amount o f s u l f u r i n c o a l becomes i n c r e a s i n g l y s e r i o u s . The e f f e c t that s u l f u r has on c o a l u t i l i z a t i o n , and on the environment i s s t a g g e r i n g . We can t h e o r i z e that s u l f u r form and content vary w i t h i n a c o a l as a d i r e c t r e s u l t o f the geochemistry o f precursor peatforming environments, source areas surrounding the peats, and d i a g e n e t i c c o n d i t i o n s o c c u r r i n g l a t e r during c o a l i f i c a t i o n . S t i l l , we have l i t t l e knowledge about the emplacement o f s u l f u r i n peats, and o f the t r a n s i t i o n s i t goes through during c o a l maturation. Largely because o f t h i s l a c k o f knowledge i s our b a s i c i n a b i l i t y t o a n t i c i p a t e and c o n t r o l the e f f e c t s o f s u l f u r during c o a l u t i l i z a t i o n . The American S o c i e t y f o r T e s t i n g and M a t e r i a l s (ASTM) Stan dard Test Method D2492-68 f o r s u l f u r a n a l y s i s i n c o a l s p e c i f i e s the a n a l y t i c a l determination o f values f o r t o t a l , p y r i t i c and sulfate sulfur. Organic s u l f u r i s c a l c u l a t e d by s u b t r a c t i n g p y r i t i c and s u l f a t e s u l f u r from the t o t a l . The procedures a r e aimed at p r o v i d i n g r a p i d , inexpensive, and r e p r o d u c i b l e data f o r coal u t i l i z a t i o n . The p y r i t i c , s u l f a t e , and organic s u l f u r contents reported by the processes adequately r e f l e c t the amount of s u l f u r that can be removed by s i z i n g , s p e c i f i c g r a v i t y separa t i o n , and hindered s e t t l i n g techniques. But any e r r o r i n t o t a l , p y r i t i c or s u l f a t e s u l f u r determination w i l l show up as an e r r o r i n organic s u l f u r determination. Reasons f o r e r r o r i n p y r i t i c s u l f u r determinations are reported by Edwards e t a l . (J.) and Greer ( £ ) . The e l e c t r o n probe microanalyzer (EPM) uses a f i n e l y focused e l e c t r o n beam that impinges on a p o l i s h e d sample, g e n e r a l l y a t 15-20 keV, producing χ rays c h a r a c t e r i s t i c o f the elements pres ent i n the sample. In g e n e r a l , EPM r e s u l t s are accurate and r e p r o d u c i b l e to ±2% o f the amount present f o r most major e l e ments. R e l a t i v e accuracy decreases with decreasing elemental concentrations. For elemental c o n c e n t r a t i o n s o f about 1 w t i , r e l a t i v e accuracy should be w i t h i n ±5$. The EPM r e v o l u t i o n i z e d p e t r o l o g y and geochemistry, but the p a u c i t y o f published papers r e p o r t i n g i t s use i n c o a l and peat s t u d i e s shows that EPM has been neglected i n c o a l r e s e a r c h . E l e c t r o n m i c r o a n a l y s i s o f c o a l g e n e r a l l y has been l i m i t e d t o the scanning e l e c t r o n microscope (SEM) with energy d i s p e r s i v e x-ray (EDX) c a p a b i l i t y . The unique c a p a b i l i t i e s o f the EPM can provide i n f o r m a t i o n that i s i n a c c e s s i b l e through other methods. Examples are x-ray chemical s h i f t



9.

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Electron Probe Microanalysis

193

determinations, l i g h t element d e t e c t i o n , and r e s o l u t i o n o f x-ray l i n e s that have EDX i n t e r f e r e n c e s by wavelength d i s p e r s i v e x-ray (WDX) techniques. Modern c o m b i n a t i o n EPM-SEM i n s t r u m e n t s equipped with both EDX and WDX c a p a b i l i t i e s are e s p e c i a l l y powerf u l tools for coal analysis. EPM has important advantages over c o n v e n t i o n a l methods o f a n a l y s i s f o r organic s u l f u r i n c o a l : a n a l y s i s by EPM i s done d i r e c t l y , thus a v o i d i n g problems a s s o c i a t e d with calculating organic s u l f u r content by d i f f e r e n c e ; organic s u l f u r contents o f i n d i v i d u a l macérais can be measured i n s i t u i n a sample; and organic s u l f u r a n a l y s i s with the EPM i s n o n - d e s t r u c t i v e and rapid. The f o l l o w i n g shows how the EPM may be used f o r q u a n t i t a t i v e a n a l y s i s o f organic s u l f u r i n c o a l . Background I n i t i a l l y Raymond and Gooley (3.) c a l c u l a t e d the organic s u l f u r content o f a c o a l with the EPM using a mean modal a n a l y s i s technique. For t h i s work well-documented samples from the Pennsylvania State u n i v e r s i t y Coal Bank were analyzed. The samples had p r e v i o u s l y been ground to -20 mesh s i z e . Upon r e c e i p t , the samples were s p l i t , potted i n epoxy, and made i n t o p o l i s h e d 2.5 cm rounds, approximately 120 μ m t h i c k . The rounds were mounted on 27x46 mm g l a s s s l i d e s , and photomicrograph mosaics o f p o r t i o n s o f the samples were prepared at approximatley 400X m a g n i f i c a t i o n . Mosaics are necessary s i n c e the samples must be carbon-coated f o r conduction during e l e c t r o n bombardment, and once the samples are carbon coated, r e f l e c t a n c e l e v e l s are obscured and i d e n t i f i c a t i o n o f a l l the v a r i o u s macérais i s extremely d i f f i c u l t . Coal macérais present i n the mosaics were i d e n t i f i e d by o i l - i m m e r s i o n , r e f l e c t e d l i g h t techniques. Where p o s s i b l e , 15 examples o f each maceral type w i t h i n the s e c t i o n were l o c a t e d . In most cases l e s s than 15 p i e c e s o f one or more p a r t i c u l a r macérais could be found, and so fewer than 15 were t h e r e f o r e i n c l u d e d i n the a n a l y s i s . Our EPM has a 400X m a g n i f i c a t i o n o p t i c a l system, and using morphology o f the v a r i o u s c o a l g r a i n s i n c o n j u n c t i o n with the mosaics, the p o i n t s o f EPM analys i s could be e x a c t l y l o c a t e d . S t a n d a r d i z a t i o n datum f o r EPM a n a l y s i s i s determined as an average o f seven background and matrix c o r r e c t e d i n t e n s i t i e s on a r e c e n t l y developed petroleum coke standard (A). A f t e r each c o a l a n a l y s i s the computer p r i n t s x-ray i n t e n s i t i e s and wt% s u l f u r as determined by comparison with the x-ray i n t e n s i t y o f the p e t r o leum coke standard. X-ray i n t e n s i t y o f i r o n i s c o n t i n u a l l y monitored during a n a l y s i s and any i n t e n s i t i e s i n excess o f background l e v e l s are assummed to r e s u l t from contamination by p y r i t e , so those r e s u l t s are r e j e c t e d . At the same time, an energy d i s p e r s i v e system output i s monitored f o r any elements that might suggest the presence o f other s u l f i d e s or s u l f a t e m i n e r a l s . Theref o r e our reported s u l f u r contents are most l i k e l y o r g a n i c .



194

COAL AND

COAL

PRODUCTS

Another p o s s i b i l i t y i s elemental s u l f u r , but the homogeneous d i s t r i b u t i o n of s u l f u r throughout each maceral i s i n d i c a t i v e o f organic r a t h e r than elemental s u l f u r . The r e s u l t s of a sample a n a l y s i s i n c l u d e a number o f organic s u l f u r measurements f o r a l l macérais present i n the sample. An example of the a n a l y s i s of a high v o l a t i l e A bituminous (hvAb) c o a l can be seen i n Table I . The mean organic s u l f u r content (S ) f o r each maceral-type determined by EPM was m u l t i p l i e d by the wt* o f that maceral i n the dry c o a l sample. The Pennsylvania State U n i v e r s i t y Coal S e c t i o n determines the wtjC o f i n d i v i d u a l macérais i n the c o a l by m u l t i p l y i n g maceral d e n s i t y by volume % i n the c o a l . Volume % i s determined by counting 1000 p o i n t s , a method that the Pennsylvania State U n i v e r s i t y Coal S e c t i o n has been able to show has a r e p r o d u c i b i l i t y o f 2-3*. The s u l f u r contents c o n t r i b u t e d to the t o t a l organic s u l f u r content o f the c o a l by the i n d i v i d u a l macérais i s a l s o shown i n Table I . The summation o f the c o n t r i b u t i o n s o f the i n d i v i d u a l macérais g i v e s the t o t a l organic s u l f u r c o n c e n t r a t i o n (dry) as determined by EPM. To measure the v a l i d i t y o f the EPM technique c o a l s were chosen i n which s u l f a t e s u l f u r as determined by ASTM methods equaled zero and i n which p y r i t i c s u l f u r was minimal as d e t e r mined by ASTM methods and as observed by o p t i c a l microscopy. Since i n o r g a n i c s u l f u r contents are s m a l l , any d i s c r e p a n c i e s between EPM and ASTM organic s u l f u r contents due to i n a c c u r a t e p y r i t e or s u l f a t e a n a l y s i s a l s o should be s m a l l . As can be seen i n Table I I the EPM analyses very c l o s e l y approach those o f the ASTM. The comprehensive EPM method discussed above i s extremely time consuming. The method r e q u i r e s point counting the sample to determine the wt* o f the v a r i o u s macérais. An oil-immersion photomosaic has to be prepared f o r i d e n t i f i c a t i o n o f a n a l y t i c a l s i t e s once the sample has been placed i n the EPM. Finally, g r e a t e r than 60 EPM analyses must be performed to determine the organic s u l f u r content o f a s i n g l e c o a l sample. Data d e r i v e d from a n a l y s i s o f numerous c o a l s using the comprehensive method, Table I: Comprehensive EPM method o f organic s u l f u r a n a l y s i s o f L. Elkhorn, KY, hvAb c o a l ( a f t e r 3.).

UACEBAL Vitrinite Pseudovitrinite Fusinite Semifusinite Sporinite Micrinite Macrinite

MACERAL wtjt S / wt* S MACERXL wt* 0.61° 52.8 0.32 16.4 0.56 0.09 0.02 6.2 0.27 0.44 6.2 0.03 0.04 0.64 6.0 0.02 2.8 0.59 0.51 0.7 (0,004) Total S (dry) = 0.52 wt$


9.

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195

Electron Probe Microanalysis Table I I : ASTM/EPM comparative study ( a f t e r (3.) ; a l l contents as dry wt% )


lAHK U. Elkhorn #3 Ohio #5 L. Elkhorn Hazard #7 U. Sunnyside B l i n d Canyon D i e t z #3

hvAb subC hvAb hvAb hvAb hvAb subC

ASTM PYRITIC S 0.01 0.01 0.03 0.03 0.06 0.13 0.13

ASTM ORGANIC S

EPM ORGANIC S

0.61 0.92 0.52 0.51 0.59 0.33 0.15

0.63 0.94 0.52 0.58 0.66 0.41 0.18

t h o u g h , p r o v i d e d us w i t h a b e t t e r and more c o n f i d e n t EPM approach. The comprehensive method was performed on 29 c o a l s that represented 27 seams from 13 s t a t e s i n the contiguous USA. Rank o f the c o a l s ranged from subbituminous C to low v o l a t i l e ; t o t a l s u l f u r contents ranged from 0.28 t o 8.60 wtj ( d r y ) ( T a b l e I I I ) . The organic s u l f u r contents o f the c o a l s determined by the comprehensive EPM method are p l o t t e d vs the organic s u l f u r content o f r e s p e c t i v e v i t r i n i t e components ( F i g u r e 1). The best l i n e a r fit of the data has a c o r r e l a t i o n c o e f f i c i e n t o f 0.99, a y - i n t e r c e p t o f -0.03, and a slope o f 0.98. E m p i r i c a l l y , the organic s u l f u r content o f a c o a l e s s e n t i a l l y equals the organic s u l f u r content of i t s v i t r i n i t e . Raymond (5.) showed that a general r e l a t i o n s h i p e x i s t s i n most c o a l s with respect to organic s u l f u r contents o f the macérais: s p o r i n i t e , r e s i n i t e Σ m i c r i n i t e , v i t r i n i t e > psuedov i t r i n i t e Σ s e m i f u s i n i t e Σ m a c r i n i t e > f u s i n i t e (Table I V ) . How then can the v i t r i n i t e organic s u l f u r content be r e p r e s e n t a t i v e of a l l macérais present i n a c o a l sample? In most o f the 29 c o a l s discussed above (as i s the case i n most c o a l s ) the v i t r i n i t e macérais dominate (Table I I I and V). Thus the v i t r i n i t e organic s u l f u r content has a major i n f l u e n c e on the organic s u l f u r content o f the c o a l . But what o f the c o a l s c o n t a i n i n g as l i t t l e as 41.9 wtjt v i t r i n i t e macérais? Table VI c o n t a i n s the wt* of the v a r i o u s macérais found i n two c o a l s and the organic s u l f u r contents o f those macérais. As can be seen i n Table VI, the v i t r i n i t e organic s u l f u r contents approximate the organic s u l f u r contents determined from the weighted mean o f the other macérais present. Therefore, as w e l l as commonly being the most dominant maceral, the v i t r i n i t e contains an organic s u l f u r content approximately equivalent to the mean of a l l the macérais. Two f a c t o r s make i t advantageous to measure the organic s u l f u r content o f v i t r i n i t e i n order to f i n d the organic s u l f u r content of a c o a l . The most obvious i s that the number o f EPM analyses w i l l be fewer. For each o f the c o a l samples l i s t e d i n



196

COAL AND

COAL

PRODUCTS

Figure 1. Organic sulfur content of coal vs. organic sulfur content of respective vitrinite components for coals listed in Table III (dmmf wt %). All measurements by EPM.


Fuller; Coal and Coal Products: Analytical Characterization Techniques ACS Symposium Series; American Chemical Society: Washington, DC, 1982. 0.46 0.54

hvAb η η η tl

2.93 3.73 5.64 6.55

ft ft ft ft

2.62

0.65 1.96 2.34

ft

ft ft

0.82 1.62

mvb η

0.55 0.62

U. U.

3.29 6.01

Canyon

L. Clarion Clarion

Pittsburgh Pittsburgh L. K i t t a n n i n g

Americana

H a z a r d #7 L. E l k h o r n U. E l k h o r n U. S u n n y s i d e Clintwood

Blind

Sewell U. F r e e p o r t

Kittanning Hartshorne Kittanning

L.

2.07

lvb tt η

Seam Name

PA PA

PA W.VA PA

KY KY KY UT VA ALA

UT

W.VA PA

OK PA

PA

State

83.9 72.6

68.7 83.6 75.1 85.0

64.5

70.9 75.9 41.9 89.8

88.5

66.9 87.6

76.0 92.2 76.4

ÎV

11.0 16.9

24.9 13.7 20.9 11.8

17.5 38.9 8.5 31.2

9.8 20.1

28.7 9.1

23.5

24.0 7.8

$1

0

S

0

1.28 1.64

1.07

1.32 1.08 2.41

0.71 0.81

0.55 0.67

0.43 0.74

0.65 0.48

0.46 0.84 0.74

Mod.

S„ ο

1.23 1.50

1.19 2.65 1.14

1.52

0.73 0.75 0.88

0.77 0.61

0.44

0.77 0.52

0.89 0.78

0.48

Vit

Continued on next page.

5.1 10.5

2.7 4.0 3.2

1.7 4.3 5.4

1.7 9.0 6.6 19.2

3.3

4.4

0.0 0.0 0.1

*L

V a r i o u s c h a r a c t e r i s t i c s o f t h e 29 c o a l s a m p l e s o n w h i c h t h e c o m p r e h e n s i v e EPM method was p e r f o r m e d ( T o t a l S on d r y b a s i s ; a l l o t h e r v a l u e s on dmmf b a s i s ) , V = vitrinite macérais, I = i n e r t i n i t e macérais, L = l i p t i n i t e macérais, S Mod. = o r g a n i c s u l f u r v a l u e d e t e r m i n e d b y m a c e r a l mean m o d a l a n a l y s i s , S V i t . = organic sulfur value d e t e r m i n e d by v i t r i n i t e a l o n e .

Tot. S

III:

Rank

Table


Î

ο

Ο Ο

ι

VO


Tot. S

3.39 3.60 4.55 5.85 7.27 2.59 3.86 6.14 8.60 0.28 0.93 1.78

Rank

hvBb tt tt tt tt hvCb tt η tt subB subC tt Ohio #5 Wildcat

D i e t z #3

I l l i n o i s #6 I l l i n o i s #5 L. Cherokee unknown

Ohio #4 I l l i n o i s #2 Kentucky #14 Bevier Tebo

Seam Name

TABLE I I I (continued)

OH TX

WY

IL IL ΙΑ ΙΑ

OH IL KY MO MO

State

84.6 88.8

83.8

84.7 89.2 74.3 89.4

75.0 78.3 83.4 69.6 75.3

%V

10.0 10.0

15.6

10.9 10.1 22.3 9.3

17.7 18.4 12.0 28.7 19.1

ÎI

5.4 1.2

0.6

4.4 0.7 3.4 1.3

7.3 3.3 4.6 1.7 5.6

%L

1.04 1.50

0.19

2.26 2.80 5.29 4.08

2.80 3.02 1.16 2.97 3.13

S^ Mod. -2


1.16 1.59

0.21

2.28 2.96 5.10 4.31

2.93 3.09 1.13 3.08 3.55

S Vit. _2

Fuller; Coal and Coal Products: Analytical Characterization Techniques ACS Symposium Series; American Chemical Society: Washington, DC, 1982. Coal L. K i t t a n n i n g U. Sunnyside B l i n d Canyon Americana Tebo Ohio #5

lvb hvAb hvAb hvAb hvBb subC

-

0.56 0.70 1.23 4.07 4.99 0.87

-

0.53 0.53

_

0.57 0.69 0.48 1.07 3.87 1.28

0.48 0.75 0.44 1.52 3-55 1.16

_5L

0.53 0.40 1.30 2.81 0.35

0.82

-

0.39 0.43 0.30 0.83

-Ha 0.36 0.47 0.30 0.71 1.03 0.32

0.30 0.39 0.26 0.57 0.75 0.20

JL

General r e l a t i o n s h i p between macérais and organic s u l f u r contents f o r high and low s u l f u r c o a l s (S wt$ on dmmf b a s i s ) S = s p o r i n i t e , R = r e s i n i t e , Mi = m i c r i n i t e , V = v i t r i n i t e , Pv = p s e u d o v i t r i n i t e , Ma = m a c r i n i t e , S f = s e m i f u s i n i t e , F = f u s i n i t e ( a f t e r 5.).

Rank

Table IV:


200

COAL

Table V:

COAL

PRODUCTS

A n a l y s i s o f maceral c o n s t i t u e n t s f o r 29 c o a l s (maceral wt* on a dmmf b a s i s ) * wtf Vitrinite Inertinite Liptinite


AND

78.5 17.3 3.7

MUSK 41.9-92.2 7.8-38.9 0.0-19.2

Table V I I , Raymond et a l . (&) analyzed up to 400 v i t r i n i t e g r a i n s for organic s u l f u r content both with and without the a i d o f photomosaics. Using a t - s t a t i s t i c approach they c a l c u l a t e d the number o f analyses (n) f o r each run necessary to g i v e a d e s i r e d maximum v a r i a b i l i t y o f 10*, at the 95* confidence l e v e l , from the true mean as defined by 100 analyses. As can be seen i n Table VII, i n no case was i t necessary to analyze more than 14 v i t r i n i t e areas. The second advantage to a n a l y z i n g o n l y v i t r i n i t e i s that Raymond et a l . (&) were able to achieve e s s e n t i a l l y i d e n t i c a l r e s u l t s both with and without the use o f photomosaics. Using texture and morphology to i d e n t i f y areas o f v i t r i n i t e a f t e r the sample had been placed i n the EPM was as s u c c e s s f u l as i d e n t i f y i n g the v i t r i n i t e using oil-immersion microscopy p r i o r t o analysis. I t should be noted that only two o f the four researches were f a m i l i a r with the EPM. T h i s , combined with the v a r i e t y o f c o a l s chosen, supports the unbiased nature o f the t e s t even though the sample set c o n s i s t e d o f only four c o a l s . Thus the need f o r photomosaics i s e l i m i n a t e d .

The Rapid EPM Method EPM a n a l y s i s f o r organic s u l f u r content can be performed e a s i l y on -20 to -100 mesh c o a l samples. Samples need o n l y be mounted i n epoxy and p o l i s h e d s i m i l a r to how c o a l samples are commonly prepared f o r pétrographie examination. 15 areas w i t h i n non-contiguous v i t r i n i t e g r a i n s are analyzed with the EPM. Without the need to produce a photomosaic, the organic s u l f u r content of v i t r i n i t e , and t h e r e f o r e o f a c o a l , may be determined i n l e s s than 10 minutes. To t e s t the EPM method c o a l s were analyzed f o r which the ASTM organic s u l f u r values were c o r r e c t e d f o r unextracted i r o n . As discussed by Suhr and Given (2) such a c o r r e c t i o n would take i n t o account the e f f e c t o f any p y r i t e that remained unextracted f o l l o w i n g the ASTM Standard Method D2492-68. As can be seen from the data i n Table V I I I , the EPM o r g a n i c s u l f u r contents are yery c l o s e to those o f the c o r r e c t e d ASTM v a l u e s .

Plgovisslon The chemistry o f a c o a l may vary g r e a t l y w i t h i n a seam, both from the top to the bottom and t r a n s v e r s e l y throughout i t . These v a r i a t i o n s are r e a l , and they represent d i f f e r e n t c o n d i t i o n s that



V i t . =0.73

0

S

V i t . =2.93

S

wt* of sample wt* o

S

0.30

7.1

Ε

3.9 0.73

3.0 2.56

0.64

0.60

13-3

Mi

1.51

5.7

Sf

0.92

0.3

Ma

7.3

7.8

S c o a l = 2.80 ο

3.89

S

2.90

1.03

2.4

&_

S^ c o a l = 0.69

0.94

17.6

S

Mi

(wt'd x) remaining macérais = 2 . 5 0

2.93

72.0

F

Pv

0

tfe

13.2

Ohio #4 hvBb Coal V

S

0.38

5.3

Si

(wt'd x) remaining macérais = 0 . 6 7

0.45

0.73 A

2.2

38.9

S

EY

_Ji

U. Elkhorn hvAb Coal

R e l a t i o n s h i p between o r g a n i c s u l f u r contents o f v i t r i n i t e , remaining macérais, and whole c o a l ( a l l wt* on dmmf b a s i s ) V = v i t r i n i t e , Pv = p s e u d o v i t r i n i t e , F = f u s i n i t e , S f = semif u s i n i t e , Ma = m a c r i n i t e , Mi = m i c r i n i t e , S= s p o r i n i t e , R = resinite.

wt* o f sample wt* S ο

Table V I :


202

COAL


Table V I I :

AND

COAL

PRODUCTS

Number o f analyses (n) necessary to g i v e a maximum d e s i r e d v a r i a b i l i t y when a n a l y z i n g f o r organic s u l f u r with EPM ( a f t e r £ ) .

£QAL

JBAHK

Tebo Ohio #5 U. Sunnyside L. K i t t a n n i n g

hvBb subC hvAb low v o l

Table V I I I :

SULFUR wt*

(drv)

7.27 0.93 0.65 2.07

_π_ 13-14 10-12 5-6 7-9

Coals c o n t a i n i n g p y r i t e - EPM S vs documented ASTM S (ASTM data a f t e r (1); a l l contents as dry wt*). Q

L. KITTANNING hvAb/hvBb COAL ASTM SAMPLE

1273 1276 1277 1279 1282 1299

S

Q

(diff.)

1.54 2.12 2.09 0.55 0.61 1.28

EPM S

Q

(corr.)

1.49 2.07 2.04 0.44 0.53 1.19

S

Q

1.50 2.09 2.08 0.60 0.57 1.09

occur during c o a l maturation processes. Using the EPM method, the p o t e n t i a l e x i s t s to achieve very r a p i d , m u l t i p l e organic s u l f u r analyses, which i n t u r n w i l l allow f o r r a p i d , d e t a i l e d measurements o f v a r i a t i o n s i n organic s u l f u r content o c c u r r i n g across c o a l seams. Indeed, Raymond (8) and Raymond and Davies (9) have been able to apply the EPM method to the L. K i t t a n n i n g c o a l seam and have been able to show how organic s u l f u r values f o r that seam c o r r e l a t e with organic s u l f u r values f o r recent peats deposited under s i m i l a r c o n d i t i o n s i n F l o r i d a Bay. The EPM o f f e r s the opportunity to i n v e s t i g a t e the occurrence o f organic s u l f u r i n c o a l , on a maceral or whole c o a l b a s i s , that h e r e t o f o r e was shrouded i n the heterogeneity o f the sample and the com p l e x i t y o f the a n a l y s i s . Acknowledgments I would l i k e to thank the Pennsylvania State U n i v e r s i t y Coal S e c t i o n f o r the samples they provided f o r EPM a n a l y s i s , and f o r the c o n s t i t u e n t maceral data and ASTM analyses on those samples.



9.

RAYMOND

Electron Probe Microanalysis

203

I would e s p e c i a l l y l i k e t o thank Dr. Peter Given f o r p r o v i d i n g me with s p l i t s o f the L. K i t t a n n i n g samples l i s t e d i n Table V I I I . Over the past four years Tom Gregory, Roland Hagan, and Dave Mann, Los Alamos N a t i o n a l Laboratory, have provided the t e c h n i c a l a s s i s t a n c e i n sample p r e p a r a t i o n and a n a l y s i s necessary t o keep the development o f the EPM organic s u l f u r technique on l i n e . Ron Gooley, Los Alamos N a t i o n a l Laboratory, and Tom Davies, Exxon Production Research, provided the s c i e n t i f i c e x p e r t i s e t o ques t i o n v a r i o u s aspects o f the EPM procedure, and by so doing, helped t o make the procedure that much stronger. The general a s s i s t a n c e o f Tom Davies, Roland Hagan, and Alan A l l w a r d t , UC Santa Cruz, i n the s t a t i s t i c a l analyses i s t r u l y a p p r e c i a t e d . T h i s work was performed a t the Los Alamos N a t i o n a l Laboratory and supported by the Department o f Energy under c o n t r a c t W-7405-ENG36.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. 9.

Edwards, A. H., Jones, J. Μ., Newcombe, W. Fuel 1964, 43, 55-62. Greer, R. T. in "Scanning Electron Microscopy/1977/I," O. Johari (ed.), ITT Research Institute, Chicago, 1977, 79-93. Raymond, R., Jr.; Gooley, R. in "Scanning Electron Micros copy /1978/I," O. Johari (ed.), SEM Inc., AMF O'Hare, IL, 1978, 93-107. Harris, L. Α., Raymond, R., Jr.; Gooley, R. in "Microbeam Analysis," D. B. Wittry (ed.), San Francisco Press, San Francisco, 1980, 147-148. Raymond, R., Jr. in "Microbeam Analysis," Ε. E. Newbury (ed.), San Francisco Press, San Francisco, 1979, 105-110. Raymond, R., Jr.; Davies, T. D.; Hagan, R. C. in "Microbeam Analysis," D. B. Wittry (ed.), San Francisco Press, San Francisco, 1980, 149-150. Suhr, N.; Given, P. H. Fuel 1981, 60, 541-542. Raymond, R., Jr. Compte Rendu of the IX Inter. Cong. of Carb. Strat. and Geol., Urbana, IL (in press). Raymond, R., Jr.; Davies, T. D. GSA Abst. with Progs., 1979, V. 11, no. 7, p. 501.

RECEIVED May 17, 1982


Electron Probe Microanalysis - American Chemical Society

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