Coal Science

36 Petrography and Carbonization Characteristics of Some Western Canadian Coals A. R. CAMERON

1

Downloaded by NORTH CAROLINA STATE UNIV on December 31, 2017 | http://pubs.acs.org Publication Date: January 1, 1966 | doi: 10.1021/ba-1966-0055.ch036

Department

and J. C. BOTHAM

2

of Mines and Technical Surveys, Ottawa, Ontario,

Canada

Petrographic and carbonization studies were carried out on samples from two seams in the Crowsnest Pass area of British Columbia. Swelling was measured by the free swelling index test and fluidity by the Gieseler test; strength measurements were made on coke from the 500 lb. capacity, movable-wall test oven. Petrography is expressed in both macerals and microlithotypes. Of interest is the somewhat anomalous distribution of the fusinitic constituents in the size fractions of one of the seams examined. Fluidity correlates better with the content of the microlithotype vitrite than with the total vitrinite. Calculated stability factors on six cokes suggest that a textural variety of vitrinite, described as mylonitized or pitted, has a deleterious effect on coke strength.

paper covers some of the information revealed during a study made by the Department of Mines and Technical Surveys on the petrography and coking properties of two high rank coals from western Canada. T h e Geological Survey of Canada carried out the sampling and pétrographie evaluation while the chemical analyses and the carbonization tests were carried out by the Mines Branch. T h e coals i n question are L o w e r Cretaceous in age and occur i n the Crowsnest Pass area of the Canadian Rockies. They are marginal with respect to coking and are not typical of some of the better coking coals from this area. O n e of the coals is medium volatile bituminous, and the other is low volatile bituminous, by A S T M rank classification. T h e medium volatile coal w i l l be treated i n considerable detail. J h i s

' Geological Survey of Canada Mines Branch

2

564

Given; Coal Science Advances in Chemistry; American Chemical Society: Washington, DC, 1966.

36.

CAMERON AND BOTH AM

Experimental

Canadian Coals

565

Procedures

T w o lOOO-lb. samples of the medium volatile coal were collected at a fresh face underground and represent the top and bottom halves of a 12-foot thick seam. E a c h of these gross samples was screened into eight size fractions, namely, + 2 inch, 2 X 1 Vz inch, 1 % X 1 inch, 1 X % inch, % X k inch, Vz X VA inch, V4 X Vs inch, and —Vs inch. E a c h of these size fractions was weighed, and the results have been plotted in weight percent histograms on Figure 1. E a c h of the size fractions was crushed to 8 0 % —Vs inch, and each was sampled for pétrographie analysis, chemical analysis, a n d swelling a n d fluidity tests. T h e original gross samples were then reconstituted by blending the fractions back together.


x

WEIGHT

20

PCT.

40

SIZE

60

VOLUME P C T . 40 60 80 0

FRACTIONS OF T O P SAMPLE

WEIGHT

PCT.

60 + 2° SIZE

FRACTIONS

OF BOTTOM SAMPLE

VITRINITE SEMI-FUSINITE β FUSINITE

Figure 1.

Ml CRINITE MINERAL MATTER

Maceral compositions in size fractions of medium volatile coal

The chemical analysis and the bench-scale and technical-scale testing were carried out either by standard tests or by tests under consideration for stand?rdization by A S T M . Analytical data from these tests for the size frac tions of the medium volatile coal are given in Table I. In addition to the fluidity and swelling tests and the chemical analyses, three charges of the medium volatile coal were coked in the 500-lb. capacity test oven, one representing the top sample, one the bottom sample, and one a 50-50 blend of top and bottom. Also, three charges were coked of the low volatile coal. These represented three commercial size fractions—namely, + 1 % inch, 1 % X V4 inch, and — V A inch. Chemical analyses of these six samples, prior to coking, are given i n Table II. T h e technical-scale oven used for this part of the study is the movable-wall type and has been in service for the past three years. T h e coking chamber is approximately 38 inches deep, 34 inches high, and 12 inches wide. T h e walls of silicon carbide tile are heated electrically by (silicon carbide) heating elements. W i t h standardized operat ing conditions the quality of the cokes produced i n the test oven duplicates closely that of the commercial cokes made from the same coals under equiva lent conditions. Particle size, moisture, and bulk density are given i n Table


566

COAL SCIENCE Table I. Identification Screen Fraction, inch

Analyses of Screen Fractions for Top

+2

A

B 2X1%

C 1% X 1

Proximate analysis, %


Moisture Ash Volatile matter Fixed carbon

0.9 24.4 21.2 53.5

0.9 29.2 20.5 49.4

0.9 24.1 21.2 53.8

Free swelling index

7

5%

6%

Gieseler plasticity" Start, °C. Max. fluid temp. °C. Max. fluidity, ddm Melting range, °C.

443 469 13 46

447 477 8 49

444 471 14 49

1.0 22.7 22.8 53.5

0.9 35.3 21.2 42.6

1.2 31.9 20.8 46.1

Proximate analysis, % Moisture Ash Volatile matter Fixed carbon Free swelling index

8

6%

lk

Gieseler plasticity* Start, °C. Max. fluid temp., °C. Max. fluidity, ddm Melting range, °C.

445 475 27 54

433 472 16 57

442 470 17 53

l

" Constant torque plastometer; ddm—dial division per minute.

V I , and the heating rate was programmed according to the recommendations of Eddinger and Mitchell ( I ) . T h e pétrographie analyses of both the size fractions and the samples for carbonizing were carried out microscopically by reflected light on duplicate pellets, prepared in each case from — 2 0 mesh material. F o r each fraction, macérais and microlithotypes were identified and their proportion recorded. F o r the samples prepared for coking, only the macérais were recorded. T h e point count method was used to determine the maceral content, with 300 points being counted per pellet or a total of 600 per sample. T h e integrating stage was used to assess quantitatively the microlithotypes—60 m m . of coal were traversed per pellet, making a total of 120 m m . per sample. Petrography of Medium Volatile

Coal

Figure 1 shows the variations i n maceral distribution of the size fractions making u p the top and bottom samples. Also shown in weight percent histograms are the quantities of coal occurring i n each size fraction. Examining these diagrams shows that this is a very friable coal, with about 5 0 % of each gross sample occurring i n the —Vs inch fraction. T h e pétrographie plots show that i n this seam, fusinite and semifusinite are the major inert macérais and the most variable i n terms of proportions present in each fraction. T h e amount of micrinite is remarkably constant throughout the size fraction series of both samples. Fusinite and semifusinite are found in greatest quantity i n the inter-


36.

CAMERON AND

BOTH AM

Canadian Coals

567

and Bottom Samples of Medium Volatile Coal

1

D X %

£ % X Vz

F Vz X

VA

VA

G X Vs

H —Vs

Top


0.8 18.7 22.0 58.5

0.8 19.8 21.4 58.0

7

448 473 9 41

1.0 19.6 21.7 57.7

1.1 13.4 22.5 63.0

1.1 9.2 23.7 66.0

8

9+

5%

IVz

450 473 11 43

444 472 10 47

444 474 35 52

441 478 81 58

1.0 22.0 21.5 55.5

1.2 21.9 21.2 55.7

1.0 19.8 22.4 56.8

1.1 15.0 23.0 60.9

8

8

8

9

Bottom 1.1 26.1 21.2 51.6 7M» 444 474 23 54

447 478 19 55

443 477 17 52

440 476 39 56

438 473 73 60

mediate sizes and not in the fines. Vitrinite is least abundant in the intermediate sizes and most abundant in the — V s inch fraction, especially in the top sample. This concentration of vitrinite in the —Vs inch fraction, without an accompanying increase of fusinite, is a favorable feature of this coal. It represents a natural segregation of reactive and inert macérais in a coal that overall has an overabundance of inerts. Exinite was identified in all samples, but i n amounts that never exceeded 2 /c ; hence its distribution has not been plotted in Figure 1 . Table III presents the detailed maceral data for each size fraction. c

Because exinite is a minor constituent in this coal, the microlithotypes defined represent variations in a two-component system of vitrinite and the inert macérais semifusinite, fusinite, and micrinite. W h o l e particles were considered in the microlithotype analysis—i.e., the maceral composition of a particle was estimated, and on the basis of this estimation the whole particle was assigned to a particular microlithotype. Figure 2 shows the triangular arrangement of the microlithotypes, with the more heavily lined part on the right side being applicable in the present study. Vitrite and fusite were recognized, as well as carbargilite and shale; the remainder of the material fell into the category of vitrinertite, of w h i c h four varieties were noted—namely, vitrinertites 1 , 2, 3, and 4 . The boundaries of these four varieties of vitrinertite are so drawn that vitrinertite 1 corresponds


568

COAL SCIENCE

roughly to clarite, vitrinertite 2 to duroclarite, vitrinertite 3 to clarodurite, and vitrinertite 4 to durite. Figure 3 shows the compositions of the size fractions i n terms of the microlithotypes just described. T h e fractions of the top sample differ from those of Table II.

Analyses of Coals as Prepared for Carbonization in Test Oven


Identification

Med. Volatile Coal 50-50 Top Bottom Blend

Proximate analysis, % Moisture Ash Volatile matter Fixed carbon

1.1 11.9 25.5 61.5

0.8 18.0 23.1 58.1

Ultimate analysis, % Carbon Hydrogen Sulfur Nitrogen Ash Oxygen (by diff.)

76.85 4.57 0.54 1.41 11.92 3.65

70.41 4.29 0.39 0.98 18.15 5.19

Low Vohtile Coal + 1 % 1 % X VA inch inch —VA inch 0.6 15.7 18.2 65.5

0.8 15.3 18.7 65.2

0.4 14.3 19.6 65.7

0.49

75.00 4.06 0.23 0.92 15.66 3.52

74.66 4.23 0.63 0.89 15.33 3.49

76.05 4.19 0.45 0.95 14.27 3.69

0.9 16.0 22.8 60.3

— — —

Free swelling index

9

8

SVz

2%

4

IVz

Gieseler plasticity Start, °C. Max. fluid temp., °C. Max. fluidity, ddni Range, °C.

443 478 66 61

445 479 57 60

444 477 61 58

466 483 2 26

467 479 2 29

460 486 6 44

0

" Constant torque plastometer; ddm—dial division per minute.

Table III. Sample

Macérai Composition of Size Fractions of Medium Volatile Coal Vitrinite

Semifttsinite Fusinite

Micrinite

Exinite

Min. matter

Top

—Vs inch

63.4 65.3 65.9 65.0 55.0 65.9 70.0 80.1

3.7 4.2 3.0 3.3 5.8 2.1 1.8 1.8

13.3 9.5 8.5 16.8 92 7 1^8 14.4 6.7

8.3 7.1 10.4 8.1 8.0 9.9 9.7 6.1

0.8 0.9 1.2 2.0 1.5 1.8 1.9 1.3

10.5 13.0 11.0 4.8 7.0 7.5 2.2 4.0

Average "

73.7

2.3

9.8

7.6

1.4

5.2

-f2 inch 2 X IVz IVz X 1 1 X /4 yΑ χ % Vz X VA VA X VS —Ve inch

61.7 63.7 57.0 60.2 61.3 63.6 67.1 76.0

4.7 4.6 5.3 8.3 5.0 4.3 5.6 4.7

13.3 10.3 11.0 15.0 14.0 10.7 9.8 8.6

3.3 6.7 6.0 6.5 5.7 7.4 4.0 4.4

1.7 1.0 1.7 1.3 1.0 1.0 0.7 1.7

15.3 13.7 19.0 8.7 13.0 13.0 12.8 4.6

Average "

68.7

5.0

10.3

5.1

1.4

9.5

+ 2 inch 2 X IVz IVz X 1 1 X /4 % X Vz 3

VZXVA VA X Vs

Bottom

3

β

Calculated from compositions of fractions.


36.

CAMERON AND BOTHAM

Canadian Coals

569


VITRINITE

Figure 2.

Triangular diagram showing microlithotypes

20

40

+ 2 A β

VOLUME 60

TOP t

F G -Ι/β"Η

30

G

VOLUME

-l/B"H VITRITE VITRINERTITE I VITRINERTITES Ζ A 3

of

P C T. A B C D E F

M

ο E-l

maceral compositions

30 A B C 0

n

J

G H PCT.

J

Figure 3.

CARBARGILITE β

Microlithotypes in size fractions of volatile coal

SHALE

medium


COAL SCIENCE


570

the bottom sample i n certain details. There is more variation i n the vitrite content from the coarse fractions to the fine i n the top sample as compared with the bottom sample. There is also greater variation i n the contents of vitrinertites 2 and 3 and vitrinertite 4 and fusite i n the top sample. These last mentioned four microlithotypes concentrate i n the intermediate fractions of the top sample while no such concentration is apparent i n the bottom sample. Carbargilite and shale decrease i n a somewhat erratic fashion from coarse fractions to fine fractions i n both samples. Table I V gives the detailed composition of each fraction i n terms of microlithotypes. Relation of Fluidity

and Swelling to Petrography

F l u i d i t y data were determined by the Gieseler apparatus o n the 16 size fractions of the medium volatile coal. T h e values obtained were relatively low, ranging from 8 to 81 dial divisions per minute. A n attempt was made to correlate these results with pétrographie data. Some of the possible relations examined are shown i n Figure 4. A plot of the macérai vitrinite against fluidity shows considerable scatter as does a plot of the ash content vs. fluidity. T h e ash content was determined b y proximate analysis (see Table I) and is included here for comparison. 80

80

80

:4o

40

40

2 ο

-.Λ 50

70 90 TOTAL VITRINITE

50 70 90 VITRINITE (VIO, VII)

80,

25 ASH

40

80 TOP

ο ο

SAMPLES

·

BOTTOM SAMPLES Q

30

Ό

TOTAL

Figure 4.

50 70 VITRITE

40

20

40 60 VITRITE (VIO.VII)

Relation of fluidity (Gieseler) to some parameters

pétrographie

However, when the content of the mierolithotype vitrite was plotted against fluidity, the result was a considerable improvement though several points still fell off the trend line. T o examine this relation between vitrite content a n d fluidity further, we used reflectivity data that h a d been obtained on the vitrinitic portion of each size fraction. T h e reflectance types ranged from V I 0 to V I 3 . ( T h e term reflectance type as used i n this paper is equivalent to vitrinoid type as used by Schapiro et al. (2)). T h e vitrite content of


36.

CAMERON AND

Table IV.

Canadian Coals

571

Microlithotype Composition of Size Fractions of Medium Volatile Coal

Sample


BOTHAM

V/

Vitrite

Top + 2 inch 2X1% 1% χ 1 1 χ % % χ % % X VA VA X VB — % inch Average Bottom -1-2 inch 2X1% 1% χ 1 1 X % % X % VzX VA VA X VS —Vs inch Average 6

h

2

VI

Vh

Fusite

Carb.

Shale

:i

42.0 32.2 38.5 33.8 35.3 35.6 44.3 59.4 50.8

14.8 15.4 18.0 13.5 9.8 12.8 14.1 11.0 12.2

7.8 13.6 9.7 13.1 14.4 17.7 15.4 6.9 9.9

7.2 3.7 9.4 9.6 7.3 6.8 4.8 5.5 5.9

0.9 2.9 1.9 4.1 4.5 0.9 5.5 2.7 2.9

9.1 9.6 11.7 13.8 14.6 11.6 6.1 6.5 7.9

7.5 7.7 4.7 6.0 9.3 9.6 9.7 7.4 7.9

10.7 14.9 6.1 6.1 4.8 5.0 0.1 0.6 2.5

47.6 40.0 44.4 45.1 45.1 52.3 49.6 52.5 50.2

11.5 10.4 8.9 11.0 7.5 12.8 10.9 11.8 11.3

9.5 7.3 9.2 11.1 8.3 10.3 10.5 12.1 10.9

3.0 2.7 4.1 5.7 3.6 5.0 5.1 3.0 4.0

1.9 3.5 1.7 0.5 1.7 1.8 4.4 0.7 1.7

11.2 6.7 6.7 8.7 11.0 7.4 3.4 11.8 8.6

2.8 9.2 8.5 6.1 13.3 5.9 9.8 5.3 7.0

12.5 20.2 16.5 11.8 9.5 4.5 6.3 2.8 6.3

*» Vitrinertites 1, 2, etc. * Calculated from compositions of fractions.

each fraction was calculated to include only vitrite composed of reflectance types V I 0 and V I 1 . This calculation is based on an assumption that may be open to criticism, and the result is included here only because it seems to show the best relationship with fluidity of all the pétrographie parameters plotted. It was assumed that the reflectance types ( V 1 0 , V I 1 , etc.) are equally distributed i n all the microlithotypes—i.e., that the vitrinite of vitrite contains the same proportions of reflectance types as does the vitrinite of other microlithotypes, vitrinertite 2 for example. Because vitrite is virtually 100% vitrinite, it is possible to use the proportions of the various reflectance types to calculate that part of the vitrite content that is devoid of the higher reflectance types, V 1 2 and V 1 3 . The resulting calculation and the relation with fluidity are shown on the fifth graph of Figure 4. It seems to be an improvement over the graph in which total vitrite is plotted against fluidity. Figure 4 shows that a similar calculation for the maceral vitrinite failed to produce much improvement. These four plots of the maceral vitrinite and the microlithotype vitrite suggest that for this coal at least, the most significant relation as far as fluidity is concerned is shown not by the total vitrinite content but rather by that part contained in the larger bands and lenses, which part is expressed by the vitrite content. Furthermore, this relation seems to be improved if only a part of the vitrite content is considered—namely, that part made up in this coal of reflectance types V I 0 and V I 1 . The free swelling index ( F S I ) was determined on each of the size fractions; for the top samples the values ranged from 5 % to 9, whereas the bottom size fractions ranged from 6 % to 9 (see Table I ) . In each case the lowest values occur in the intermediate size fractions—namely, those ranging from 2 X 1 % inch to % X % inch. These show a rough relationship with the increase in fusinite and semifusinite and the decrease in vitrinite i n these


572

COAL SCIENCE


fractions. It is interesting that both the fluidity values a n d the swelling indices i n the size fractions of the bottom sample are higher than those of the corresponding size fractions of the top sample i n spite of the fact that the ash values (Table I) tend to be higher and the vitrinite values lower i n the former.

Figure 5. Photomicrographs of particles of medium volatile coal showing pitted vitrinite. (A) Particle composed of mylonitized or porous vitrinite (MT) in center. Note similarity of reflectance with particle of normally textured vitrinite (NT) at top center. (B) Pitted vitrinite particle (MT) in center. Smaller particle (NT) immediately helow is normally textured vitrinite. Both photomicrographs taken under oil, X 175


36.

CAMERON AND BOTHAM

573

Canadian Coals


50r

#

Ο

10

STABILITIES AFTER R E E V A L U A T I O N OF VITRINITE

' 20 30 40 PREOICTEO STABILITY

* 50

' 60

Figure 6. Relation of predicted to actual stabilities medium vofotile and low volatile samples

for

However, the vitrite values for the bottom size fractions are higher than the corresponding values for the top size fractions (Table I V ) . These differences i n the petrography of the top and bottom size fractions suggest the value of a microlithotype analysis. T h e microlithotype analysis provides some idea of the texture of the coals involved. T h e vitrinite contents of the bottom size fractions are lower than those of the top size fractions, yet the vitrite content is greater in the bottom than in the top. This indicates that a much higher proportion of the vitrinite in the bottom size fractions is con centrated i n relatively pure bands and lenses. This textural difference may be of considerable technological significance as indicated by the relation of swell ing (and especially fluidity) with vitrite content. Coke Stability and

Petrography

Pétrographie analyses, including reflectivity measurements, were made on the six charges coked i n the test oven, and stability factor predictions were calculated according to the method described by Schapiro, Gray, and Eusner ( 2 ) . In four of the six samples involved the predictions were higher than the actual values obtained. T h e samples were re-examined petrographically, and a portion of the material originally designated as vitrinite was recorded in a separate category. This is vitrinite with a pitted, sometimes granular texture, often heavily impregnated with mineral matter. Figure 5 shows photomicrographs of particles of this material compared with particles of more normally textured vitrinite. Some coal petrographers might place a part of this material in semifusinite, but at least some of it is mylonitized or crushed


574

COAL SCIENCE Table V. Vitrinite V13

Pétrographie Data

9

Sample


Medium Volatile Top(l)' Bottom (3) 50-50 (2)

νιο

Vll

V12

12.3 12.1 12.2

44.1 30.7 36.6

1.5 3.1 2.4

Low Volatile + 1 % inch (5) 1 % X VA (6) —Μι inch (4)

— — —

— —

— — —

0.1 0.1 10.0 6.2 9.8

V14

V15

vie

— —

—

—

6.4 7.6 6.7

0.7 1.3 1.0

22.7 29.3 34.3

« V10-V16, reflectance types; V Pitted, mylonitized vitrinite. Mineral matter calculated according to Parr's formula (2). P

b

Table VI.

Evaluation of Coal Samples in Movable-Wall Test Oven

Identification Condition of coal charged Moisture,% Size(Ve X 0 i n c h ) , % Oven bulk density ( dry ) lb./cu. ft Mean coke size, inches

Med. Volatile Coal 50-50 Top Bottom Blend 1.3 95.0 51.3

2.6 92.0 49.4

1.2 93.0 51.8

Loti; Volatile Coal + 1% 1 % X VA —VA inch inch inch 0.9 77.2 55.8

1.2 81.5 58.5

1.2 80.6 56.0

see Table II 3.2

3.4

3.2

3.6

3.6

3.4

Drop shatter test for coke 1%-inch sieve, %

81.8

79.8

80.8

72.8

79.0

74.2

Tumbler test for coke ( cumulative percent retained on ) Stability factor, 1-inch sieve Hardness factor, V4-inch sieve

40.7 63.4

24.3 50.3

32.5 58.3

20.2 66.3

13.6 58.6

26.4 66.1

0.93

—

—

—

1.1

1.5

1.2

3.8

Apparent specific gravity Carbonization pressure Maximum, p.s.i.g.

0.94

0.93

1.5

1.0

vitrinite, a constituent to be expected i n view of the tectonic history of these coals. The stability factors were recalculated, a n d the pitted or mylonitized vitrinite was treated as semifusinite with two-thirds of it being assigned to inerts. Figure 6 shows the relation of the predicted stabilities to the stabilities actually obtained on the coke. T w o sets of points are shown, one indicating the position of the stabilities as first calculated and the other the stabilities after re-evaluating the vitrinite. T h e second calculation is a considerable i m provement i n the relation of predicted to actual stabilities. T h e complete data upon which these calculations were made are shown i n Table V , while other data pertinent to the evaluation of the samples coked i n the movable-wall oven are given i n Table V I . T h e position of the coal represented b y point 5 was not improved b y recalculation. This coal gave an actual stability of 20.2.


36.

CAMERON


U s e d in S t a b i l i t y

AND BOT H AM

Canadian

Coals

575

Calculations

Semifus.

Fus.

Mic.

Ex.

M in. mat.

11.4 18.9 15.1

5.1 7.5 6.4

10.2 11.5 10.9

7.2 5.5 6.4

1.4 0.9 1.1

6.7 9.8 8.8

5.7 9.0 10.1

12.3 15.3 7.2

23.1 14.7 13.6

10.6 8.2 9.4

—

b

8.5 8.4 7.9

' (1). (2), etc., sample numbers on Figure S.

However, its high ash content and its high quantity of inert materials put it i n a category of coals where predictions of stability are difficult. A comparison of the F S I values (Table II) for the +1% inch material (point 5 i n Figure 5) with the 1% X V\ inch coal (point 6) suggests that the stability factor of the first-mentioned coal should be lower. This comparison substantiates to some degree the predictions made concerning the +1% inch coal. It is possible that the pitted or mylonitized component, because of its open porous structure, is more susceptible to oxidation than is the more normally textured vitrinite, and this could explain the apparently deleterious effect that this material has on coke quality. In addition to the relationships discussed, the data presented here suggest one further conclusion of a more general nature—namely, it is well to remember that coal seams have individual characteristics even though possessing many features i n common a n d being subject to many valid generalizations concerning their use. These characteristics are perhaps related to age, or type of parent material, or type of depositional environment, or tectonic history, therefore, the critical pétrographie or chemical details governing the utilization properties of one seam may not be as critical with another. Literature

Cited

(1) Eddinger, R . T., Mitchell, J., Trans. AIME 15, 148 (1956). (2) Schapiro, N . , Gray, R . J., Eusner, G . R., Trans. AIME 20, 89 (1961). R E C E I V E D January 25, 1965.

Discussion Marie-Therese M a c k o w s k y : Have you ever tried to plot the vitrite a n d clarite content against fluidity? Alexander Cameron: Yes, but the correlation with fluidity was not as good as with the vitrite content alone.


576

COAL SCIENCE


John H a r r i s o n : The method of mining can effect size distribution. W h a t method of mining was used for this coal? H a v e you been able to correlate the " p i t t e d " vitrinite with collinite? D r . C a m e r o n : The coal was dug by hand from a fresh face underground, and the screen analyses were carried out on this "mine r u n " coal. N o , we have not attempted this correlation.


Coal Science

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