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Dependence of coal liquefaction behaviour on coal characteristics. 2. Role of petrographic composition
Dependence of coal liquefaction behaviour on coal characteristics. 2. Role of petrographic composition Peter H. Given*, Donald C. Cronauert, Alan Davis* and Bimal Biswas*
William Spackman*,
Harold L. LoveIl*,
“College of Earth and Mineral Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA tGulf Research and Development Co., Pittsburgh, Pennsylvania, USA (Received 5 June 1974)
The techniques used were the same as those used in Part 1 (p 34). Comparison of the liquefaction behaviour of two lithotypes from a Kentucky bituminous coal indicated that of sets of maceral in this process pseudovitrinite is a reactive maceral. The hydrogenation concentrates obtained from a New Mexico sub-bituminous and a Kentucky bituminous coal showed fair correlations between conversion and the total concentration of the presumed reactive macerals (vitrinite, pseudovitrinite and sporinite). Similar concentrates from a Montana lignite showed no such correlation; the one sample that showed a high conversion was a high-density fraction that had a high mineral-matter content and in which nearly all the pyrite in the coal had accumulated. Two samples that have boghead and cannel characteristics gave quite different results on hydrogenation. Both were highly aliphatic in structure and had unusually high hydrogen contents and volatile matter. One, which contained appreciable proportions of sporinite, alginite and resinite, gave essentially no conversion to oil. The other, predominantly vitrinitic but containing alginite as the second most abundant maceral, gave an excellent yield of an oil of low viscosity and aromaticity. It was concluded that although rank, petrographic composition and perhaps geological history are important factors determining liquefaction behaviour, there are other characteristics of coals that may at times override these basic parameters, and the composition of the inorganic matter may be the most significant of these other characteristics.
The objectives and experimental methods of this study have been described in Part l’, which dealt with the liquefaction behaviour of a suite of vitrinite-rich coals of several rank levels and coal provinces. Here we consider the role of the various mace& of which coals are composed, particularly those other than vitrinite.
RESULTS Special
AND
DISCUSSION
fractions
prepared
by
‘beneficiation’
procedures
It is well known that coal mace& differ in their grindability, so that different size fractions of a crushed coal differ in petrographic composition; float-and-sink separations of the size fractions bring about further degrees of fractionation of the coal components. Advantage has been taken of these facts to prepare a number of fractions of widely differing petrographic composition. The liquids used for the float-and-sink separations were mixtures of halogenated hydrocarbons. The size fractions were 318 in X l/4 in, l/4 in X 16 mesh (Tyler), 16 mesh X 30 mesh, 30 mesh X 100 mesh, and -100 mesh. For the study described here, fractions were prepared in
40
FUEL
1975,
Vol 54, January
this way from sample PSOC-151, a sub-bituminous coat from the lower split of the Blue Seam, McKinley Mine, Gallup,NewMexico, andfromPSOC-90 and 91, which were respectively a channel sample and a clarainic lithotype from the Lower Lignite seam, Tongue River member, Savage Mine, Savage, Montana. The size and density fractions used, and the ash yields and petrographic analyses Data of the products, are given in Tables I and 2. characterizing the rank of the whole coals (before fractionation) are shown in Table 3. It will be seen that the exinite and micrinite contents in the fractions of the New Mexico coal are small in all cases, and we have in the set of samples a good inverse relation between vitrinite and fusinite contents. The product analyses are collected in Table 4, and in Figure I the solvation yield is plotted against the total content of vitrinite + exinite. It is seen that a fair correlation exists between yield and content of what are presumed to be the reactive macerals. There is no evident correlation between filtrate viscosity and petrographic composition; but it is worth noting that the viscosities of the products from the two heavy fractions which contain the largest concentrations of detrital minerals (C6b and A6b) are both very low compared with the others.
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Loveli, A. Davis and 6. Bisws: Coal liquefaction behaviour (2) Table I PSOC No. (151-)
Maceral analysis of Blue Seam, New Mexico, sub-bituminous coal samples Coal maceral analysis (%, mmf) Gravity fraction
Size fraction
1.20 float 1.20- 1.23 1.20- 1.23 l-20- 1.23 1.23- 1.25 1.23- 1.25 1.28- 1.30 l-25- 1,28 1.28-1~30 1.30 sink I.30 sink
Bla ?a in X Y! in f/4inX 16mesh A2b Ysin X t/4in A2a C2a “/8in X 44 in ?sinX gin A3a YeinX sin B3a A5b ‘/4in X 16 mesh ?/sin X ?ain A4a YsinX t/,in B5a ‘/4 in X 16 mesh C6b f/4inX 16mesh A6b 33:65 blend of B5a and C6b
Vitrinite
Exinite(‘)
96
1 3 2 3 2 1 2 2 3 5 2 4
91 91 89 89 85 83 81 70 61 63 64
Ash (%, dry basis)
Micrinite 1 2 0 1 1 2 1 1 4 1 4 2
2 4 7 7 8 12 14 16 23 33 31 30
2.5 21 3.0 3.15 3.5 3.6 4.4 4.1 7.8 24.0 233 183
1:; Includes sporinite and resinite Includes semifusinite
Table 2
Composition of fractions of lignite from Savage, Montana
Coal maceral analyses (% mmf) PSOC No.
Size fraction
90-C-5 91-C2a 90-C-l 90-B-3 91-B4b 90-A-7 90-A-3 90-A-8
‘/4 in X “/8in X “/sin X ?ain X ‘/,in X f/4in X “/8in X ‘/4in X
* + $
16 mesh $ in f/4in 44in 16 mesh 16 mesh ‘/4 in 16 mesh
Gravity fraction
Vitrinite*
Exinite+
Fusinitez
1.25 float 1.25- 1.30 1.25 float 1*30-1.40 1.40 sink 1*30-1.40 1.30- 1.40 1.40 sink
81 87 71 70 69 61 54 45
15 5 20 8 1 4 8 3
3 4 6 15 27 27 28 43
Micrinite
Total S (wt 56)
Ash (%, dry basis)
1 4 3 7 3 8 10 9
0.39 0.38 940 932 2.25 0.29 0.31 0.92
4.4 4.8 4.6 6.8 14.4 6.2 7.1 14.8
Includes pseudovitrinite Includes sporinite and resinite Includes semifusinite
Tab/e 3
Rank and other parameters of coals subjected to beneficiation procedures
Sample PSOC No.
Type of sample
Mean max. reflectance (in oil) of vitrinite (%)
C (wt%, dmmf)
Calorific value, moist mmf (Btu/lb) (MJ/kgj
Mineral matter (wt%)
Volatile matter (%)
Vitrinite content (%)
151 90 91
Channel Channel Lithotype
0.40 0.29 0.30
78.3 72.5 71.4
27.6 17.3 16.95
5.7” 108” 8.2”
45 60 59
79 61 66
*
Concerning
methods of determining
mineral
matter,
11845 7435 7295
see Appendix
The trends in composition of the lignite fractions are more complex, because the exinite and micrinite contents are more variable and do not correlate with contents of the other macerals. The liquefaction data in Table 5 show considerable differences in yield at 385”C, though less at 400°C. No correlation is evident, however, with vitrinite or vitrinite + exinite contents. Consideration of the ash compositions shown in Table 6
strongly suggests that with these lignite fractions various effects of the inorganic constituents are superimposed on the effects of the maceral composition of the organic matter. There is an obvious tendency for mineral materials (i.e. the larger particles) to concentrate in the heaviest fractions, as with fractions 91-B4b and 90-A-8. The high sulphur and iron contents of 91,B4b show that most of the pyrite in the coal has accumulated in this fraction.
FUEL, 1975, Vol 54, January
41
Coal liquefaction behaviour (2): P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas Table 4
Gulf liquefaction results with Blue Seam, New Mexico, samples Yields (% dmmf basis)
Coal No. IPSOC -151-I
Temperature (“C)
Bla 385 A2b 385 A2a 385 C2a 385 A3a 385 %3a 385 A5b 385 A4a 385 85a 385 C6b 385 A6b 385 Average of 385°C runs Blend (see 425 Tattle 7) A5b
385
Solvation
%enzeneinsolubles
Asphaltenes
Saturates
85-O
56.0 53.2 50.8 60-6 48.2 49-2 406 43.3 49.8 44.1 32.6 48.0 50.7
14.7 21.4 12.3 11.3 21.5 17-o 207 18.7 18.9 15-3 18.1 17.3 28.4
2.3 2.1 1.9 2.0 2.1 2.0 2.0 2.0 1.9 2.1 1.6 2.0 3.2
43.1
26.3
13.5
1.6
(%I 93.6 951 82.6 91.5 72.7 87-9 83.4 73.3 63.7 42-6 64.1
Filtrate viscosity @ 100°C (mm2/s)* 32 25 37 27 46 23 17 49 38 13 7 4.5
noncatalytic l
1 mmZ/s = 1 cSt
Table 5
Gulf liquefaction results with Savage, Montana samples Yields (%. dmmf basis)
Coal No. (PSOC-1
Temperature
Solvation
RI
90-c-5
Filtrate viscosity @ 100°C (mm2/s)
(96)
Benzeneinsolubles
Asphaltenes
Saturates
385
43.4
-
-
-
-
91-C2a WC-1 908-3 91-%4b
385 385 385 385
45-2 51.2 45.3 71.2
163 14.9 -
13.7 25.0 -
1.0 1.1 -
4.6 4.6 -
90-A-7 90-A-3
385 385
48.7 53.5
18.7
19.9
1.7 -
4.7 -
90-A-B
385
48.7
14.6
23.0
1.9 _-
3.5 -
Average of 385°C runs
509
16.1
20.4
1.4
4.4
90-c- 1 90-B-3 91-B4b 90-A-7 90-A-3 WA-8
63.6 66.4 84.4 65.5 72.6 77.7
31.9 27.4 25.0 29.7 29.3 26.5
19.5 16.6 39.0 197 19.6 32.0
1.1 2.2 1.4 1.8 I.9 2.1 -
6.0 5.5 4.4 6.1 5.4 4.3 -
71.7 69.2
28.3 29.0
24.4 21.5
I.7 1.8
5.3 5.5
___400 400 400 400 400 400
Average of 4&C runs Average of 4O@C runs with 91-B4b excluded
However, some mineral grains in any coal are very small and encased within organic matter, so that these will not be greatly concentrated by float-and-sink operations, though, as is clear from the data in Table 6, the various fractions
42
FUEL, 1975, Vol54,
January
may well contain
different assemblies of minerals, which could have different catalytic effects; the variations in SiOz/A1203 ratio are notable. Fraction 91-C2a has very high contents of calcium and
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davisand B. Biswas: Coal liquefaction behaviour (2) Tab/e 6 Composition of inorganic matter in fracxions of Savage, Montana Lignite, PSOC-90 and 91 Sample Ash composition (%) SiO2 A1203
Fe203 CaO MgO TiO2 MnO Na20 K20 Fe (% of coal feed)
91-C2a
91-i34b
90-A-8
8.0 17.1 03 34-7 13-9 0.59 O-12 0.20 0.15 O-01
17.5 10.4 23-4 14-2 59 O-37 O-06 O-12 0.08 2.36
38.0 167 2.8 20-5 7.8 0.77 009 O-15 042 O-29
content, may well be the high pyrite content of this sample. Pyrite would be expected to be reduced to pyrrhotite, or even to metallic iron, under liquefaction conditions, and either may ~11 be an important co-catalyst. Table 6 gives the contents of iron that could be formed from the three fractions, and it is seen that 2.36% could be produced from 91-B4b. Fraction 90-A-8, the other fraction with a high mineral content, has only about onetenth as much iron (and it also has 43.5% fusinite, a further reason for a relatively low conversion). The molecular structural parameters, shown in Table 7, for two fractions of the sub-bituminous coal of quite different petrographic composition are very similar to each other and to values for the product from the unfractionated coal (PSOC-151). The asphaltenes from the lignite fraction (PSOC-90) are of low aromaticity and the number of alkyl substituents per average molecule is particularly high, the products from the two fractions again being quite similar. high total mineral-matter
I
I
I
I
80
90
I
60 Vitrinite
50
70 + exinite
( %I
Figure I Dependenceof solvation yield from a sub-bituminous (PSOC-151) on content of reactive macerals
coal
magnesium,and we should probably infer that the carboxylic acid groups in the coal have accumulated these metals by cation exchange with ground waters. It was shown in Part 1 that the association of sodium ions with the acid groups has a marked effect on the viscosity of the oil produced on hydrogenation; we do not yet know the effect of Ca’+ or Mg++ similarly associated. In many ways, the feature of the liquefaction data that seems most puzzling is that fraction 91-B4b, containing 27% fusinite and only 69.6% reactive macerals, gives much the best yield of oil. The significant point, apart from the
Table 7
Lithotypes from Elkhom No.3 Seam, No.22 Mine, Deane, Kentucky The coal from this seam is of high-volatile A bituminous rank, the carbon content
(dmmf) being about 84% and the
Molecular-parameter analysis of asphaltenes from coats of various petrographic compositions, by proton n.m.r.
Sample No.
Fraction No.
Fract. aromatic C
Arom. rings/ average mol
Alkyl substits./ average mol
C atoms/ alkyl substit.
Aromatic group type (%I mono di tri
151 151 151 90 90 12 13 1 2 105 106 155
A2b A6b Whole C-l A-7 * -
0.57 0.51 0.54 0.38 0.44 0.56 0.55 0.67 0.69 0.62 0.61 0.36
1.6 1.6 1.5 1.3 1.5 1.5 1.6 1.7 1.8 1.4 1.7 1.1
2.8 3.8 3.1 5.4 4.7 3.3 4.3 2.3 2.3 2.4 2-6 4.9
2.2 2.2 2.2 2.2 2.1 1.9 1.6 1.9 1.7 2.0 2-2 2.3
52-4 59.7 70-t 67.3 67.6 73.2 44.5 54.9 51.0 74.5 55-6 94.3
*
Hydrogenation
at 400°C;
35-3 21.5 14-3 32.7 8.9 50 46-3 20’1 22.3 7.7 18.9 1.2
12-3 18.8 15.6 0.0 13-5 21.8 9.2 251 266 17.8 25.5 4.5
all others at 385”
FUEL, 1975, Vol54,
January
43
Coal liquefaction behaviour (21: P. H. Given, D. C. Cronauar, W. Spackman, H. L. Lovell, A. Davis and B. Bisws Table 8
Petrographic composition of lithotypes from Elkhorn No.3 Seam (vol %, dmmf)
Sample PSOC No.
Vitrinite
Exinitez
Fusinite
Semi-fus.
Granular
Massive
Reactives*
1 2 2c 2D 4 6C 6D
57 31 48 13 77+ 62 11
23 35 21 38 14 9 41
4 13 3 0 2 7 4
4 4 5 8 0 3 3
7 8 17 7 6 10 2
5 9 6 34 1 9 39
79 66 69 51 89 71 52
l
+ *
Micrinite
Sum of vitrinite, pseudovitrinite and sporinite Includes 15% of pseudovitrinite;other lithotypes in this set contained only O-l% Primarily contains sporinite, but also small amounts of resinite and cutinite
mean maximum reflectance of the vitrinite mostly in the range O-8-0-9%. The seam contains a number of very obviously distinct lithotypes, which were collected separately, and two of these were further separated into less obviously distinct lithotypes by hand picking. Six of the lithotypes have been studied by the Penn State group, and two by the Gulf workers. The petrographic compositions of the lithotypes are shown in Table 8, and data from the liquefaction runs in Tables 9 and 13. Chemical analyses are collected in Table 10. The mineral-matter contents are low (2-6%). It will be seen from Table 8 that the lithotypes cover a wide range of petrographic compositions. The ready decomposition of sporinites on pyrolysis at temperatures
Table9 Penn State autoclave runs with lithotypes from Elkhorn Seam (wt%, dmmf 1 Sample Conversion Asphaltenes Oil No.
Gas + H20
2 2c 2D 4 6C 6D
3.7 5.9 9.8 8.4 7.6 4.8
65.1 64.5 55.5 77.6 64.9 64.5
Tab/e 10
34.0 34.9 26.7 41.1 32.6 35.9
26.8 23.7 18.9 28.1 24.7 23.8
pseudovitrinite
Chemical-analytical data for selected iithotypes (%, dry basis)
(%, dmmf)
Sample No.
Total S
mm
VM
C
H
N
S
1 2 2c 2D 4 6C 6D 12 13 105 105A 106 122 123 124 155
0.78 0.61 0.63 0.55 0.86 O-64 0.67 0.59 935 2.21 1.70 0.59 0.92 0.68 0.99 0.56
4.85” 4.5 4.7 7.8 2.8” 25 6.9 3.45” 1*7* 13.4 9.3” 14.7” 14*4* 19.8” 9.7” 27.1 l
38.1 37.3 395 37.4 363 39.5 403 34.3 32.5 37.6 40.0 38.0 48.0 38.0 52.5 66.4
84.4 85.5 84.8 86.6 84.4 84.1 86.1 85.8 85.4 81.9 82.8 83.0 84.3 85.7 83.8 77.9
5.4
1.5
0.71
7.9
5.6 5.7 5.5 5.8 5.5 5.3 5.7 5.4 5.6 5.8 5.3 6.6 5.6 6.9 6.9
1.5 0.6 1.05 1.55 0.95 1.15 1.4 1.35 0.4 1.1 0.55 1.4 1.1 1.4 1.4
0.62 0.65 0.58 0.67 0.65 0.71 0.56 0.32 1.06 1.12 054 l-07 0.76 0.74 0.99
6.8 8.3 6.3 7.5 8.8 6.8 6.5 7.5 11.0 9.2 106 6.7 6.9 7.2 12.7
l
44
Concerning
methods
of determining
FUEL, 1975, Vol 54, January
mineral
matter,
see Appendix
0
p. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (2)
below 400°C to a highly fluid liquid, and their typically very high hydrogen contents and volatile-matter yields295, suggest that they should be very desirable constituents of feeds to liquefaction processes. Micrinite is inert in the coking process, and is thought to be highly aromatic and of low volatile-matter yield29617, though it cannot be said that the nature and properties of granular and massive micrinite are really understood. It is therefore unfortunate that where the sporinite content of the Elkhom lithotypes is high, the micrinite content is also high (we have so far not found any sporinite-rich durains like those found in many European seams, which may contain 60-70% sporinite). In Figure 2 we have plotted conversions from Table 9 against the sum of the vitrinite, pseudovitrinite and sporinite contents, treating these as ‘reactives’ (concerning pseudo vitrinite, see below). It seems unlikely that the reactivities of vitrinite and sporinite are in fact equal, and it cannot be assumed that both forms of micrinite are totally unreactive. Nevertheless, the correlation in Figure 2 is quite good. The fact that sample 6D is more reactive than would be predicted from the rectilinear correlation plot may indicate that sporinite is indeed more reactive than vitrinite, this lithotype having the highest sporinite content of the set.
Tab/e 7 7 Sample No. 12 13 105 105A 106 122 123 124 155
Tab/e 72
401
30
50
40
60
Total ‘reactive’
Figure2
Salvation
of
lithotypes
70
80
macerals from
the
90
100
(% 1 Elkhorn
No.3
seam,
Kentucky
The differences in solvation of samples 1 and 2 observed by the Gulf group (Table 14) are consistent with the differences in total reactives (in the above sense). The molecular structural parameters of the asphaltenes from the two samples (Table 7) are closely similar.
Sampling localities for lithotypes studied
Liquefaction behaviour of other selected lithotypes Other, smaller, sets of lithotypes have been selected for study to investigate certain specific points. The sampling locations are tabulated in Table II, their petrographic analyses in Table 12, and their chemical analyses in Table 10. In the latter, the macerals of the exinite group (sporinite, resinite, alginite, cutinite) were determined using U.V. fluorescence microscopy; it was found that determinations of these macerals in some coals could be considerably in error if made by conventional techniques based on reflection of visible light. Samples PSOC-12 and 13 were chosen for study in order to characterize the behaviour of pseudovitrinite; sample 13 containing nearly 40% of this maceral. The maceral has only been identified comparatively recently’, and its
Seam, Mine, Town, State C Seam, Mine No.1, Benham, Kentucky Another lithotype of same Channel, Indiana No.1 Block, Old Glory Mine, Jefferson Township, Indiana Lithotype of same Lithotype of same No.5 Block, G. Ready Mine, Bickmore, West Virginia Lithotype of same Lithotype of same Seam name unknown, abandoned site on north fork of Virgin River, Southern Utah
Petrographic composition of selected lithotypes (vol %, mmf)
Sample PSOC No.
Vitrinite
Pseudovit.
Fusinite
Semifus.
Massive
Granular
Sporinite
Resinite
Alginite
Cutinite
Mean max. reflectante* (%I
12 13 105 105A 106 122 123 124 155
50 35 63 58 25 48 16 18 74
6 37 0 0 0 0 6 0 0
2 4 6 3 10 4 5 6 3
6 3 3 6 12 3 5 2 0
6 4 3 5 20 5 14 9 1
IO 7 4 11 6 9 11 25 2
19 IO 18 15 23 26 33 26 4
1 0 1 2 3 2 6 5 7
0 0 0 0 0 3 3 7 9
0 0 2 0 1 0 1 2 0
I.2 0.98 0.56 0.48 0.63 0.75 0.71 0.55 0.44
l
Micrinite
Of vitrinite
in oil
FUEL, 1975, Vol 54, January
45
Coal liquefaction behaviour (2): P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas
principal distinguishing characteristic of practical significance is that, unlike vitrinite, it is unreactive in the coking process. A comparison of the liquefaction behaviour of the two lithotypes (Tables 13 and 14) shows that with both the Penn State and Gulf techniques, the pseudovitrinite-rich sample (13) actually gives somewhat higher conversion than the sample containing much vitrinite but very little pseudovitrinite. The viscosities of the product filtrates are similar, but the distributions of aromatic group types (Table 7,)are markedly different. At any rate it appears that pseudovitrinite is not unreactive in liquefaction, a conclusion supported to some extent by the data already presented (Table 9) for the Elkhom lithotype, PSOC4, which contained 15% of the maceral and gave excellent conversion. Two of the sets of lithotypes studied include ‘block coals. This is a miner’s term, and refers to the fact that block coals are particularly tough and do not readily form cracks;when they do break, they tend to show a conchoidal fracture. Generally speaking, their petrography suggests that they were formedin relatively open water environments where algal populations flourished and contributed their cells or cellular contents to the accumulating peat; the maceral known as ‘alginite consists of coalified algal cells. In these circumstances, contributions from the higher plants would mostly have been transported in from adjacent land areas. Thus vitrinite contents tend to be low and significant contents of the more resistant plant components (spores, resins, cuticle) to be preserved. It cannot be pretended that block coals are of wide occurrence in the major
Table 13 Liquefaction State data)
data for selected lithotypes (Penn
(%, dmmf) Sample Conversion Asphaltene Oil No.
Gas + Hz0
12 13 105A 106 122 123 124
7.0 7.8 6-2 2.5 6.2 52 6.3
l
68.9 73.0 62.7 55.3 75 65 36”
Initial
37.3 39.4 33.1 27.5 36.7 32.1 27.1
pressure of hydrogen,
Tab/e 74
24.6 25.7 23.4 23.3 32.1 27.2 2.8 13.4 MPa
coal basins of the U.S.,.but seams containing them can be of very considerable lateral extent (there are very large reserves of the No.5 Block Seam in West Virginia and the Indiana No.1 Block, both studied here). Insofar as they are known, the properties of cutinite, resinite, andalginite, like those of sporinite, are characterized by high hydrogen contents and volatile-matter yields, low decomposition temperatures and high fluidity during pyrolysis2~3~9+11. Thus one would expect all of them to be very desirable constituents of feedstocks for coal liquefaction. The total content of exinitic macerals in the lithotypes of the Indiana No.1 Block coal is not high (samples 105, 105A, 106) and indeed little or no alginite could be detected. It is still possible in principle that chemical components of algae, such as lipids, had diffused into the other macerals and combined with them; that is, that there could be an aIga1 contribution not detectable under the microscope. In agreement with this suggestion, the reflectance of vitrinite in PSOC-IOSA is surprisingly low, but the hydrogen contents and volatile-matter yields of none of this set of samples is specially high (Table 10). The liquefaction behaviour of the lithotype (106) richest in exinitic macerals (total, 27%) was distinctly poorer than that of the other lithotype (105A, see Table 13) or of the channel sample (105, Table 14). However, any beneficial effect of the presence of the exinitic mace&s is presumably nullified by the large proportion of inert macerals in sample 106 (48%). The relative proportions of the aromatic-group types is appreciably different for samples 105 and 106 (Table 7). The No.5 Block coal from Bickmore, West Virginia, presents a number of puzzles. It is the bottom bench of this seam (PSOC-124) that has the classical ‘block’ properties. The total of 40% exinitic mace& includes 7.4% alginite. Its hydrogen and volatile matter values are particularly high (Table IO), as also is the yield of alkanes on solvent extraction (2.1%) and the intensity of aliphatic C-H vibrations in the infrared spectrum. However, even allowing for the presumably high hydrogen content of the exinitic macerals (average S%?), the hydrogen content and aliphatic character of the whole lithotype seem to be higher than would be expected, in view of the fact that a total of42% of micrinitic and fusinitic macerals is also present. It seems most probable therefore that algal lipid derivatives, such as hydrocarbons and fatty acids have accumulated in the coal, as they do in a petroleum source rock and by much the same mechanism, and also as in a source rock they have partly condensed into a kerogen-like material.
Liquefaction data for selected lithotypes (Gulf data) (96, dmmf)
Sample No.
Solvation
Benzene-insol.
Asphaltenes
Saturates
2 12 13 105 106 124
86-9 78.4 80.3 87.6 808 50.6 Not filterable
28.0 26.9 33.2 37.9 24.7 31.5 -
46.5 44.8 37.8 34.1 38.2 15.9 _
1.1 1.0 1.9 1.4 0.9 I.0 -
155
92.8
1.6
6.4
6.3
1
46
FUEL, 1975, Vol 54, January
Filtrate viscosity at 100°C (mm2/s) 12 12 13 16 8.1 8.3 >lOOO at 150°C 4.7
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (2)
Some evidence that this can happen is provided by the studies of Given (unpublished) on jet occurring near Whitby (Yorkshire, England). Jet occurs in thin bands in a Jurassic marine shale that is rich in organic matter (13% organic C). It is believed to have formed from the metamorphism of logs of wood that floated down rivers into the sea, sank, and became incorporated in the marine sediment. From the point of view of the coal petrographer jet is a chemically modified vitrinitic maceral, and it is anomalous in the same way as a block coal - low reflectance, high hydrogen and volatile matter. From a comparison of the analysis of the materials extractable from the jet and from the surrounding shale, Given concluded that they were very similar and had a common origin in marine organisms. The residue after extraction was hydrogen-rich and highly aliphatic, from which it was concluded that some of the material from marine organisms had combined chemically with the vitrinite so that it was no longer removable by extraction (and, of course, not detectable by microscopy). The lithotype 124 behaved disappointingly in the liquefaction experiments of both the Penn State and Gulf groups. Under the usual conditions essentially no oil was obtained, and in the Gulf experiment the sample absorbed all the vehicle so that a tarry solid was produced. In the Penn State experiment in which a higher than normal initial pressure was used, some liquid product was obtained, but it had a very high asphaltene-to-oil ratio. The condensation of algal materials into the maceral structure could cause cross-linking of coal molecules, thus altering mechanical properties and giving the coal the observed poor swelling, fluidity and coking properties. It could also reduce solvation and make liquefaction difficult. On the other hand, the channel sample of the whole seam (PSOC-122), containing the block lithotype, showed a quite respectable conversion, with a particularly low asphaltene-to-oil ratio (1: 1 compared with an average value of 1:l.S). The other lithotype from this seam (123) contained more sporinite and less alginite than 124, and its hydrogen and volatile matter are not especially high (Table 12). It gave a lower conversion than the channel sample (122), though much higher than 124. It should be noted that the whole seam contains another bench in addition to the lithotypes 122 and 123, and no information about this is available at present. Finally, we must consider the extremely interesting coal from Utah, PSOC-155. Petrographically, this sample has some of the characteristics of a block coal, having 9% alginite, yet its vitrinite content is 74% (Table 12). Its calorific value would put it in the high-volatile C bituminous class on the ASTM system, though it is not clear whether this is significant. Its hydrogen content and volatile matter are very high, as are the intensities of the aliphatic C-H vibrations in the infrared spectrum. The reflectance of the vitrinite is about that of a subbituminous coal (0.44%). We must again presume the presence of molecularly dispersed algal material, not extractable and not visible under the microscope, and here chiefly associated with the vitrinite. In Gulf liquefaction tests the coal gave an excellent yield of oil containing very little benzene-insolubles or asphaltenes, implying that most of the product was pentaneThe filtrate viscosity was among the lowest soluble. found in this series of experiments. The yield of saturates (6%) was much higher than that found with any other sample. This yield was also considerably higher than the
quantity of alkanes extractable from the coal before hydrogenation, suggesting that the long-chain molecules had indeed been condensed into the structures of the coal macerals. In the molecular-parameter analysis (Table 7), the aromaticity of the small yield of asphaltenes was found to be very low, the alkyl substituents per average molecule very high, and 94% of the aromatic systems contained only one benzene ring. This Utah coal is certainly unique in the set of samples available to us, and its characteristics raise interesting geochemical points. The petrographic composition of the coal shows that woody tissue was the major contributor to the organic matter, and algal cells the next most abundant source. It is difficult to envisage circumstances in which this could have happened, with so little introduction of spores or formation of micrinite. Since we do not understand the circumstances in which a coal with the characteristics observed here might have originated, we cannot say how often similar circumstances may have arisen elsewhere. Since the Cretaceous and Tertiary bituminous coals of the western U.S. have been much less exploited commercially and studied geologically than the older coals of the east, other coals similar to the Utah sample may well exist, and they should be sought. The chemical analyses of the West Virginia Block lithctype and of the Utah coal are in some respects similar, and they have some features of their petrography in common. A major difference is the level of vitrinite contents; in the latter case algal molecules must be condensed only into vitrinite structure, whereas in the former they must be at least partly associated with other mace&, including micrinite and fusinite.
CONCLUDING
REMARKS
The data presented in this and the preceding paper show that the relation of coal characteristics to behaviour in liquefaction processes is complex. 1. Rank is certainly important, but we can as yet define only a broad range of rank as desirable. 2. The geological history of a sample is probably relevant, at least in some cases, but m&e w&k is needed to establish this. In a number of cases, the maceral distribution is quite clearly an important factor determining liquefaction behaviour, though we do not yet understand the effects of the various macerals well enough to make confident predictions. In most cases, such properties of a coal lithotype as volatile matter and hydrogen content can be seen to be consistent with the maceral composition of the sample and such knowledge of the properties of individual macerals as is available in the literature. It is worth noting, however, that a few cases have been identified where this is not so and the presence of components not detectable by microscopy must be suspected. There are factors other than rank, geological history and petrography that affect or may even determine liquefaction behaviour, and in some instances the nature of the inorganic constituents of the sample is undoubtedly one of these factors.
FUEL, 1975, Vol 54, January
47
Coal liquefaction behaviour (2):
P. H. Given, D. C. Cronauer, W.Spackman, H. L. Lovell,A. Davisand B. Biswas
It is the superimposition of the effects of the factors noted in statement 5 on the effects of the factors noted in items l-4 that make the data difficult to interpret fully. The properties that are likely to be relevant to liquefaction behaviour, other than those already referred to, are chemical structure, solubility in solvents, and the nature of the porosity. It is not clear to what extent these are independent variables.
ACKNOWLEDGEMENTS The greater part of the work carried out by the Penn State group was performed under Contract 14~1-0001-390 from the Office of Coal Research, U.S. Department of the The contribution made by the Gulf group was Interior. supported solely by the Corporation until June 1973, from which time the concluding stages of the work and the preparation of this paper was supported by the RANN Division (Research Applied to National Needs) of the National Science Foundation, to which we express our gratitude. A number of persons have contributed to this work in various ways, and we wish to acknowledge our indebtedness to all of them: Mr. Harold Beuther, for general guidance and for important discussions; R. G. Ruberto for analytical services;C. P. Dolsen, R. H. Ford, R. J. Carson, D. A. Eckley and Maria Fedale for sample collection and petrographic analyses; R. N. Miller, R. Yarzab and Joann Robuck for determinations of mineral-matter contents of coals.
mining mineral-matter contents of coals. For many of the samples studied in this investigation, we have’determined mineral-matter contents by acid demineralization1’*i8, which appears to be the most reliable means available. Data marked with a superscript c in Table I of Part 1 and an asterisk in Tables 3 and 10 of Part 2 were determined by this procedure. Data not so marked were corrected by a modified mineral-matter formula as described below. The formula is mm=1~13asht0~47Spy,t0~5C1
(1)
It was derived in essentially the same way as the Parr formula, but (a) Millott’s value for the average water of decomposition of the clays is adopted, (b) only the pyritic sulphur is considered, and (c) the correction for chlorine is adopted from the KMC formula. For the purpose of correcting organic carbon in the elementary analysis when direct CO2 data are not available, carbonates (as calcium salt) are assumed to represent 10% of total mineral matter (this is based on actual CO2 determinations for some 60 U.S. coals). This gives: C
erg
= Cdet - (0.014 ash t 0.0055 S,,)
(2)
The same assumption, combined with equation (1) and the correction to as-received volatile matter due to Leighton and Tomlinsonls, gives: VM = VMd, - (O-165 ash t 0.21 SpYr t 0.7 Cl - O-2)(3)
APPENDIX Determination of mineral-matter contents associated corrections to coal analyses
and
The well-known Parr formula for correcting ash to mineral matter assumes that all sulphur is pyritic, and is open to a number of other objections. The King-MariesCrossley mineral-matter formula’* is free from most of the objections to the Parr but in common with all such conversion formulae has to assume a constant average value for the water of decomposition of the clay minerals. Millott13 found that the average for 80 British coals was appreciably higher than King ef al had assumed, and corrected their formula accordingly. Corresponding changes were made in formulae for correcting organic carbon for CO;! from carbonates, organic hydrogen for Hz0 from clays and volatile matter for a variety of effects’4*15. Brown, Durie and Shafer16 found that the average water of decomposition of clays reported by Millott was valid for coals from one Australian basin, but not for coals from two others. We have found widely varying water yields from the clays in a selection of 20 American coals. These findings constitute a serious objection to the use of any mineral-matter formula. In experiments using an oxygen-plasma low-temperature asher, we have found that even at low power levels when no pyrite is oxidized the sulphate content of the ash is frequently higher than would correspond to the sulphate content of the original coal. We infer that organic sulphur forms sulphuric acid in the asher, and this would not be volatile under the conditions (1 torr or 133 Pa total pressure, maximum temperature about 1 SO’C). Sulphuric acid would react with carbonates. We are not satisfied, therefore, with low-temperature ashing as a method for deter-
48
FUEL, 1975, Vol 54, January
A corresponding simplification of a correction hydrogen due to the same authors gives: Ho, = H,
- (0.014 ash - O-0 17 S,,
to organic
- 0.02)
(4)
The constant 0.02 in equation (4) has been found to represent a good average for the algebraic sum of three terms present in the full Leighton-Tomlinson correction: -0.025 CO;! - 0.03 (Sati - Sso4), where Sso, represents the sulphatic sulphur content of the original coal. These various devices cannot be defended strongly; their principal justification is that they give better approximations than no corrections at all. Comparison of the mineral-matter content calculated by equation (1) with values determined by acid demineralization is available for 91 samples. The frequency distribution of differences, A = (calculated) - (direct), is as follows:
Range of A
No. of samples
Range of A
No. of samples
+0.5-0 1.oo-0.5 1 1.50-1.01 >+1.50
19 15 12 9
0 to 0.5 -0.51 to -1.00 -1.01 to -1.50 <-1.50
18 11 4 3
It will be noted that in 63 cases (69%) the difference is less than l%, and is more or less equally distributed between positive and negative values. The differences greater than 1.5% (range l-5-2.8%) all correspond to coals of high mineral-matter content (15-45%) and in these cases the formula tended to over-estimate more often than it underestimated.
p. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (21
REFERENCES
9
4
Given, P. H., Cronauer, D. C., Spackman, W., Lovell, H. L., Davis, A. and Biswas, B. Fuel, Lond. 1975,54, 34 Van Krevelen,D. W. Coal, 2ndedn, Elsevier, Amsterdam, 1961 Fenton, ti. W. and Smith, A. H. V. Gas World (Coking Section) 1959, 149, (May), 81 Given, P. H., Peover, M. E. and Wyss, W. F. Fuel, Lond.
5
Given, P. H., Peover, M. E. and Wyss, W. F. Fuel, Lond.
6
Brown, J. K. BCURA Monthly Bull. 1959,23, 1 Oelert, H. H. Fuel, Lond. 1970,49, 119 Benedict, L. G., Thompson, R. R., Shigo, J. J. and
1960,39,
323
1965,44,425
8
10 11 12 13 14 15 16 17 18
Aikman, R. P. Fuel, Lond. 1968,47,125 Murchison, D. G. Coal Science, Adv. in Chem. Series No.55, Amer. Chem. Sot., 1964, p 307 Murchison, D. G. and Millais, R. Fuel, Land. 1969,48,247 Neavel, R. C. and Miller, L. V. Fuel, Lond. 1960.39, 217 King, J. G., Maries, M. B. and Crossley, H. E. J. Sot. them Ind. 1936, 55T, 277 Millott, J. O’N. Fuel, Lond 1958, 37, 71 Ward, D. L. and Millott, J. O’N. Fuel, Lond. 1960, 39, 293 Leighton, L. H. and Tomlinson, R. C. Fuel, Land. 1960, 39, 133 Brown. H. R.. Durie. R. A. and Shafer, H. N. S. Fuel, Lond. 1960,39,59 Bishop, M. and Ward, D. L. Fuel, Lond. 1958, 37, 191 Radmacher, W. and Mohrhauer Gliickauf 1953,89,503
FUEL, 1975, Vol 54, January
49
William Spackman*,
Harold L. LoveIl*,
“College of Earth and Mineral Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA tGulf Research and Development Co., Pittsburgh, Pennsylvania, USA (Received 5 June 1974)
The techniques used were the same as those used in Part 1 (p 34). Comparison of the liquefaction behaviour of two lithotypes from a Kentucky bituminous coal indicated that of sets of maceral in this process pseudovitrinite is a reactive maceral. The hydrogenation concentrates obtained from a New Mexico sub-bituminous and a Kentucky bituminous coal showed fair correlations between conversion and the total concentration of the presumed reactive macerals (vitrinite, pseudovitrinite and sporinite). Similar concentrates from a Montana lignite showed no such correlation; the one sample that showed a high conversion was a high-density fraction that had a high mineral-matter content and in which nearly all the pyrite in the coal had accumulated. Two samples that have boghead and cannel characteristics gave quite different results on hydrogenation. Both were highly aliphatic in structure and had unusually high hydrogen contents and volatile matter. One, which contained appreciable proportions of sporinite, alginite and resinite, gave essentially no conversion to oil. The other, predominantly vitrinitic but containing alginite as the second most abundant maceral, gave an excellent yield of an oil of low viscosity and aromaticity. It was concluded that although rank, petrographic composition and perhaps geological history are important factors determining liquefaction behaviour, there are other characteristics of coals that may at times override these basic parameters, and the composition of the inorganic matter may be the most significant of these other characteristics.
The objectives and experimental methods of this study have been described in Part l’, which dealt with the liquefaction behaviour of a suite of vitrinite-rich coals of several rank levels and coal provinces. Here we consider the role of the various mace& of which coals are composed, particularly those other than vitrinite.
RESULTS Special
AND
DISCUSSION
fractions
prepared
by
‘beneficiation’
procedures
It is well known that coal mace& differ in their grindability, so that different size fractions of a crushed coal differ in petrographic composition; float-and-sink separations of the size fractions bring about further degrees of fractionation of the coal components. Advantage has been taken of these facts to prepare a number of fractions of widely differing petrographic composition. The liquids used for the float-and-sink separations were mixtures of halogenated hydrocarbons. The size fractions were 318 in X l/4 in, l/4 in X 16 mesh (Tyler), 16 mesh X 30 mesh, 30 mesh X 100 mesh, and -100 mesh. For the study described here, fractions were prepared in
40
FUEL
1975,
Vol 54, January
this way from sample PSOC-151, a sub-bituminous coat from the lower split of the Blue Seam, McKinley Mine, Gallup,NewMexico, andfromPSOC-90 and 91, which were respectively a channel sample and a clarainic lithotype from the Lower Lignite seam, Tongue River member, Savage Mine, Savage, Montana. The size and density fractions used, and the ash yields and petrographic analyses Data of the products, are given in Tables I and 2. characterizing the rank of the whole coals (before fractionation) are shown in Table 3. It will be seen that the exinite and micrinite contents in the fractions of the New Mexico coal are small in all cases, and we have in the set of samples a good inverse relation between vitrinite and fusinite contents. The product analyses are collected in Table 4, and in Figure I the solvation yield is plotted against the total content of vitrinite + exinite. It is seen that a fair correlation exists between yield and content of what are presumed to be the reactive macerals. There is no evident correlation between filtrate viscosity and petrographic composition; but it is worth noting that the viscosities of the products from the two heavy fractions which contain the largest concentrations of detrital minerals (C6b and A6b) are both very low compared with the others.
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Loveli, A. Davis and 6. Bisws: Coal liquefaction behaviour (2) Table I PSOC No. (151-)
Maceral analysis of Blue Seam, New Mexico, sub-bituminous coal samples Coal maceral analysis (%, mmf) Gravity fraction
Size fraction
1.20 float 1.20- 1.23 1.20- 1.23 l-20- 1.23 1.23- 1.25 1.23- 1.25 1.28- 1.30 l-25- 1,28 1.28-1~30 1.30 sink I.30 sink
Bla ?a in X Y! in f/4inX 16mesh A2b Ysin X t/4in A2a C2a “/8in X 44 in ?sinX gin A3a YeinX sin B3a A5b ‘/4in X 16 mesh ?/sin X ?ain A4a YsinX t/,in B5a ‘/4 in X 16 mesh C6b f/4inX 16mesh A6b 33:65 blend of B5a and C6b
Vitrinite
Exinite(‘)
96
1 3 2 3 2 1 2 2 3 5 2 4
91 91 89 89 85 83 81 70 61 63 64
Ash (%, dry basis)
Micrinite 1 2 0 1 1 2 1 1 4 1 4 2
2 4 7 7 8 12 14 16 23 33 31 30
2.5 21 3.0 3.15 3.5 3.6 4.4 4.1 7.8 24.0 233 183
1:; Includes sporinite and resinite Includes semifusinite
Table 2
Composition of fractions of lignite from Savage, Montana
Coal maceral analyses (% mmf) PSOC No.
Size fraction
90-C-5 91-C2a 90-C-l 90-B-3 91-B4b 90-A-7 90-A-3 90-A-8
‘/4 in X “/8in X “/sin X ?ain X ‘/,in X f/4in X “/8in X ‘/4in X
* + $
16 mesh $ in f/4in 44in 16 mesh 16 mesh ‘/4 in 16 mesh
Gravity fraction
Vitrinite*
Exinite+
Fusinitez
1.25 float 1.25- 1.30 1.25 float 1*30-1.40 1.40 sink 1*30-1.40 1.30- 1.40 1.40 sink
81 87 71 70 69 61 54 45
15 5 20 8 1 4 8 3
3 4 6 15 27 27 28 43
Micrinite
Total S (wt 56)
Ash (%, dry basis)
1 4 3 7 3 8 10 9
0.39 0.38 940 932 2.25 0.29 0.31 0.92
4.4 4.8 4.6 6.8 14.4 6.2 7.1 14.8
Includes pseudovitrinite Includes sporinite and resinite Includes semifusinite
Tab/e 3
Rank and other parameters of coals subjected to beneficiation procedures
Sample PSOC No.
Type of sample
Mean max. reflectance (in oil) of vitrinite (%)
C (wt%, dmmf)
Calorific value, moist mmf (Btu/lb) (MJ/kgj
Mineral matter (wt%)
Volatile matter (%)
Vitrinite content (%)
151 90 91
Channel Channel Lithotype
0.40 0.29 0.30
78.3 72.5 71.4
27.6 17.3 16.95
5.7” 108” 8.2”
45 60 59
79 61 66
*
Concerning
methods of determining
mineral
matter,
11845 7435 7295
see Appendix
The trends in composition of the lignite fractions are more complex, because the exinite and micrinite contents are more variable and do not correlate with contents of the other macerals. The liquefaction data in Table 5 show considerable differences in yield at 385”C, though less at 400°C. No correlation is evident, however, with vitrinite or vitrinite + exinite contents. Consideration of the ash compositions shown in Table 6
strongly suggests that with these lignite fractions various effects of the inorganic constituents are superimposed on the effects of the maceral composition of the organic matter. There is an obvious tendency for mineral materials (i.e. the larger particles) to concentrate in the heaviest fractions, as with fractions 91-B4b and 90-A-8. The high sulphur and iron contents of 91,B4b show that most of the pyrite in the coal has accumulated in this fraction.
FUEL, 1975, Vol 54, January
41
Coal liquefaction behaviour (2): P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas Table 4
Gulf liquefaction results with Blue Seam, New Mexico, samples Yields (% dmmf basis)
Coal No. IPSOC -151-I
Temperature (“C)
Bla 385 A2b 385 A2a 385 C2a 385 A3a 385 %3a 385 A5b 385 A4a 385 85a 385 C6b 385 A6b 385 Average of 385°C runs Blend (see 425 Tattle 7) A5b
385
Solvation
%enzeneinsolubles
Asphaltenes
Saturates
85-O
56.0 53.2 50.8 60-6 48.2 49-2 406 43.3 49.8 44.1 32.6 48.0 50.7
14.7 21.4 12.3 11.3 21.5 17-o 207 18.7 18.9 15-3 18.1 17.3 28.4
2.3 2.1 1.9 2.0 2.1 2.0 2.0 2.0 1.9 2.1 1.6 2.0 3.2
43.1
26.3
13.5
1.6
(%I 93.6 951 82.6 91.5 72.7 87-9 83.4 73.3 63.7 42-6 64.1
Filtrate viscosity @ 100°C (mm2/s)* 32 25 37 27 46 23 17 49 38 13 7 4.5
noncatalytic l
1 mmZ/s = 1 cSt
Table 5
Gulf liquefaction results with Savage, Montana samples Yields (%. dmmf basis)
Coal No. (PSOC-1
Temperature
Solvation
RI
90-c-5
Filtrate viscosity @ 100°C (mm2/s)
(96)
Benzeneinsolubles
Asphaltenes
Saturates
385
43.4
-
-
-
-
91-C2a WC-1 908-3 91-%4b
385 385 385 385
45-2 51.2 45.3 71.2
163 14.9 -
13.7 25.0 -
1.0 1.1 -
4.6 4.6 -
90-A-7 90-A-3
385 385
48.7 53.5
18.7
19.9
1.7 -
4.7 -
90-A-B
385
48.7
14.6
23.0
1.9 _-
3.5 -
Average of 385°C runs
509
16.1
20.4
1.4
4.4
90-c- 1 90-B-3 91-B4b 90-A-7 90-A-3 WA-8
63.6 66.4 84.4 65.5 72.6 77.7
31.9 27.4 25.0 29.7 29.3 26.5
19.5 16.6 39.0 197 19.6 32.0
1.1 2.2 1.4 1.8 I.9 2.1 -
6.0 5.5 4.4 6.1 5.4 4.3 -
71.7 69.2
28.3 29.0
24.4 21.5
I.7 1.8
5.3 5.5
___400 400 400 400 400 400
Average of 4&C runs Average of 4O@C runs with 91-B4b excluded
However, some mineral grains in any coal are very small and encased within organic matter, so that these will not be greatly concentrated by float-and-sink operations, though, as is clear from the data in Table 6, the various fractions
42
FUEL, 1975, Vol54,
January
may well contain
different assemblies of minerals, which could have different catalytic effects; the variations in SiOz/A1203 ratio are notable. Fraction 91-C2a has very high contents of calcium and
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davisand B. Biswas: Coal liquefaction behaviour (2) Tab/e 6 Composition of inorganic matter in fracxions of Savage, Montana Lignite, PSOC-90 and 91 Sample Ash composition (%) SiO2 A1203
Fe203 CaO MgO TiO2 MnO Na20 K20 Fe (% of coal feed)
91-C2a
91-i34b
90-A-8
8.0 17.1 03 34-7 13-9 0.59 O-12 0.20 0.15 O-01
17.5 10.4 23-4 14-2 59 O-37 O-06 O-12 0.08 2.36
38.0 167 2.8 20-5 7.8 0.77 009 O-15 042 O-29
content, may well be the high pyrite content of this sample. Pyrite would be expected to be reduced to pyrrhotite, or even to metallic iron, under liquefaction conditions, and either may ~11 be an important co-catalyst. Table 6 gives the contents of iron that could be formed from the three fractions, and it is seen that 2.36% could be produced from 91-B4b. Fraction 90-A-8, the other fraction with a high mineral content, has only about onetenth as much iron (and it also has 43.5% fusinite, a further reason for a relatively low conversion). The molecular structural parameters, shown in Table 7, for two fractions of the sub-bituminous coal of quite different petrographic composition are very similar to each other and to values for the product from the unfractionated coal (PSOC-151). The asphaltenes from the lignite fraction (PSOC-90) are of low aromaticity and the number of alkyl substituents per average molecule is particularly high, the products from the two fractions again being quite similar. high total mineral-matter
I
I
I
I
80
90
I
60 Vitrinite
50
70 + exinite
( %I
Figure I Dependenceof solvation yield from a sub-bituminous (PSOC-151) on content of reactive macerals
coal
magnesium,and we should probably infer that the carboxylic acid groups in the coal have accumulated these metals by cation exchange with ground waters. It was shown in Part 1 that the association of sodium ions with the acid groups has a marked effect on the viscosity of the oil produced on hydrogenation; we do not yet know the effect of Ca’+ or Mg++ similarly associated. In many ways, the feature of the liquefaction data that seems most puzzling is that fraction 91-B4b, containing 27% fusinite and only 69.6% reactive macerals, gives much the best yield of oil. The significant point, apart from the
Table 7
Lithotypes from Elkhom No.3 Seam, No.22 Mine, Deane, Kentucky The coal from this seam is of high-volatile A bituminous rank, the carbon content
(dmmf) being about 84% and the
Molecular-parameter analysis of asphaltenes from coats of various petrographic compositions, by proton n.m.r.
Sample No.
Fraction No.
Fract. aromatic C
Arom. rings/ average mol
Alkyl substits./ average mol
C atoms/ alkyl substit.
Aromatic group type (%I mono di tri
151 151 151 90 90 12 13 1 2 105 106 155
A2b A6b Whole C-l A-7 * -
0.57 0.51 0.54 0.38 0.44 0.56 0.55 0.67 0.69 0.62 0.61 0.36
1.6 1.6 1.5 1.3 1.5 1.5 1.6 1.7 1.8 1.4 1.7 1.1
2.8 3.8 3.1 5.4 4.7 3.3 4.3 2.3 2.3 2.4 2-6 4.9
2.2 2.2 2.2 2.2 2.1 1.9 1.6 1.9 1.7 2.0 2-2 2.3
52-4 59.7 70-t 67.3 67.6 73.2 44.5 54.9 51.0 74.5 55-6 94.3
*
Hydrogenation
at 400°C;
35-3 21.5 14-3 32.7 8.9 50 46-3 20’1 22.3 7.7 18.9 1.2
12-3 18.8 15.6 0.0 13-5 21.8 9.2 251 266 17.8 25.5 4.5
all others at 385”
FUEL, 1975, Vol54,
January
43
Coal liquefaction behaviour (21: P. H. Given, D. C. Cronauar, W. Spackman, H. L. Lovell, A. Davis and B. Bisws Table 8
Petrographic composition of lithotypes from Elkhorn No.3 Seam (vol %, dmmf)
Sample PSOC No.
Vitrinite
Exinitez
Fusinite
Semi-fus.
Granular
Massive
Reactives*
1 2 2c 2D 4 6C 6D
57 31 48 13 77+ 62 11
23 35 21 38 14 9 41
4 13 3 0 2 7 4
4 4 5 8 0 3 3
7 8 17 7 6 10 2
5 9 6 34 1 9 39
79 66 69 51 89 71 52
l
+ *
Micrinite
Sum of vitrinite, pseudovitrinite and sporinite Includes 15% of pseudovitrinite;other lithotypes in this set contained only O-l% Primarily contains sporinite, but also small amounts of resinite and cutinite
mean maximum reflectance of the vitrinite mostly in the range O-8-0-9%. The seam contains a number of very obviously distinct lithotypes, which were collected separately, and two of these were further separated into less obviously distinct lithotypes by hand picking. Six of the lithotypes have been studied by the Penn State group, and two by the Gulf workers. The petrographic compositions of the lithotypes are shown in Table 8, and data from the liquefaction runs in Tables 9 and 13. Chemical analyses are collected in Table 10. The mineral-matter contents are low (2-6%). It will be seen from Table 8 that the lithotypes cover a wide range of petrographic compositions. The ready decomposition of sporinites on pyrolysis at temperatures
Table9 Penn State autoclave runs with lithotypes from Elkhorn Seam (wt%, dmmf 1 Sample Conversion Asphaltenes Oil No.
Gas + H20
2 2c 2D 4 6C 6D
3.7 5.9 9.8 8.4 7.6 4.8
65.1 64.5 55.5 77.6 64.9 64.5
Tab/e 10
34.0 34.9 26.7 41.1 32.6 35.9
26.8 23.7 18.9 28.1 24.7 23.8
pseudovitrinite
Chemical-analytical data for selected iithotypes (%, dry basis)
(%, dmmf)
Sample No.
Total S
mm
VM
C
H
N
S
1 2 2c 2D 4 6C 6D 12 13 105 105A 106 122 123 124 155
0.78 0.61 0.63 0.55 0.86 O-64 0.67 0.59 935 2.21 1.70 0.59 0.92 0.68 0.99 0.56
4.85” 4.5 4.7 7.8 2.8” 25 6.9 3.45” 1*7* 13.4 9.3” 14.7” 14*4* 19.8” 9.7” 27.1 l
38.1 37.3 395 37.4 363 39.5 403 34.3 32.5 37.6 40.0 38.0 48.0 38.0 52.5 66.4
84.4 85.5 84.8 86.6 84.4 84.1 86.1 85.8 85.4 81.9 82.8 83.0 84.3 85.7 83.8 77.9
5.4
1.5
0.71
7.9
5.6 5.7 5.5 5.8 5.5 5.3 5.7 5.4 5.6 5.8 5.3 6.6 5.6 6.9 6.9
1.5 0.6 1.05 1.55 0.95 1.15 1.4 1.35 0.4 1.1 0.55 1.4 1.1 1.4 1.4
0.62 0.65 0.58 0.67 0.65 0.71 0.56 0.32 1.06 1.12 054 l-07 0.76 0.74 0.99
6.8 8.3 6.3 7.5 8.8 6.8 6.5 7.5 11.0 9.2 106 6.7 6.9 7.2 12.7
l
44
Concerning
methods
of determining
FUEL, 1975, Vol 54, January
mineral
matter,
see Appendix
0
p. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (2)
below 400°C to a highly fluid liquid, and their typically very high hydrogen contents and volatile-matter yields295, suggest that they should be very desirable constituents of feeds to liquefaction processes. Micrinite is inert in the coking process, and is thought to be highly aromatic and of low volatile-matter yield29617, though it cannot be said that the nature and properties of granular and massive micrinite are really understood. It is therefore unfortunate that where the sporinite content of the Elkhom lithotypes is high, the micrinite content is also high (we have so far not found any sporinite-rich durains like those found in many European seams, which may contain 60-70% sporinite). In Figure 2 we have plotted conversions from Table 9 against the sum of the vitrinite, pseudovitrinite and sporinite contents, treating these as ‘reactives’ (concerning pseudo vitrinite, see below). It seems unlikely that the reactivities of vitrinite and sporinite are in fact equal, and it cannot be assumed that both forms of micrinite are totally unreactive. Nevertheless, the correlation in Figure 2 is quite good. The fact that sample 6D is more reactive than would be predicted from the rectilinear correlation plot may indicate that sporinite is indeed more reactive than vitrinite, this lithotype having the highest sporinite content of the set.
Tab/e 7 7 Sample No. 12 13 105 105A 106 122 123 124 155
Tab/e 72
401
30
50
40
60
Total ‘reactive’
Figure2
Salvation
of
lithotypes
70
80
macerals from
the
90
100
(% 1 Elkhorn
No.3
seam,
Kentucky
The differences in solvation of samples 1 and 2 observed by the Gulf group (Table 14) are consistent with the differences in total reactives (in the above sense). The molecular structural parameters of the asphaltenes from the two samples (Table 7) are closely similar.
Sampling localities for lithotypes studied
Liquefaction behaviour of other selected lithotypes Other, smaller, sets of lithotypes have been selected for study to investigate certain specific points. The sampling locations are tabulated in Table II, their petrographic analyses in Table 12, and their chemical analyses in Table 10. In the latter, the macerals of the exinite group (sporinite, resinite, alginite, cutinite) were determined using U.V. fluorescence microscopy; it was found that determinations of these macerals in some coals could be considerably in error if made by conventional techniques based on reflection of visible light. Samples PSOC-12 and 13 were chosen for study in order to characterize the behaviour of pseudovitrinite; sample 13 containing nearly 40% of this maceral. The maceral has only been identified comparatively recently’, and its
Seam, Mine, Town, State C Seam, Mine No.1, Benham, Kentucky Another lithotype of same Channel, Indiana No.1 Block, Old Glory Mine, Jefferson Township, Indiana Lithotype of same Lithotype of same No.5 Block, G. Ready Mine, Bickmore, West Virginia Lithotype of same Lithotype of same Seam name unknown, abandoned site on north fork of Virgin River, Southern Utah
Petrographic composition of selected lithotypes (vol %, mmf)
Sample PSOC No.
Vitrinite
Pseudovit.
Fusinite
Semifus.
Massive
Granular
Sporinite
Resinite
Alginite
Cutinite
Mean max. reflectante* (%I
12 13 105 105A 106 122 123 124 155
50 35 63 58 25 48 16 18 74
6 37 0 0 0 0 6 0 0
2 4 6 3 10 4 5 6 3
6 3 3 6 12 3 5 2 0
6 4 3 5 20 5 14 9 1
IO 7 4 11 6 9 11 25 2
19 IO 18 15 23 26 33 26 4
1 0 1 2 3 2 6 5 7
0 0 0 0 0 3 3 7 9
0 0 2 0 1 0 1 2 0
I.2 0.98 0.56 0.48 0.63 0.75 0.71 0.55 0.44
l
Micrinite
Of vitrinite
in oil
FUEL, 1975, Vol 54, January
45
Coal liquefaction behaviour (2): P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas
principal distinguishing characteristic of practical significance is that, unlike vitrinite, it is unreactive in the coking process. A comparison of the liquefaction behaviour of the two lithotypes (Tables 13 and 14) shows that with both the Penn State and Gulf techniques, the pseudovitrinite-rich sample (13) actually gives somewhat higher conversion than the sample containing much vitrinite but very little pseudovitrinite. The viscosities of the product filtrates are similar, but the distributions of aromatic group types (Table 7,)are markedly different. At any rate it appears that pseudovitrinite is not unreactive in liquefaction, a conclusion supported to some extent by the data already presented (Table 9) for the Elkhom lithotype, PSOC4, which contained 15% of the maceral and gave excellent conversion. Two of the sets of lithotypes studied include ‘block coals. This is a miner’s term, and refers to the fact that block coals are particularly tough and do not readily form cracks;when they do break, they tend to show a conchoidal fracture. Generally speaking, their petrography suggests that they were formedin relatively open water environments where algal populations flourished and contributed their cells or cellular contents to the accumulating peat; the maceral known as ‘alginite consists of coalified algal cells. In these circumstances, contributions from the higher plants would mostly have been transported in from adjacent land areas. Thus vitrinite contents tend to be low and significant contents of the more resistant plant components (spores, resins, cuticle) to be preserved. It cannot be pretended that block coals are of wide occurrence in the major
Table 13 Liquefaction State data)
data for selected lithotypes (Penn
(%, dmmf) Sample Conversion Asphaltene Oil No.
Gas + Hz0
12 13 105A 106 122 123 124
7.0 7.8 6-2 2.5 6.2 52 6.3
l
68.9 73.0 62.7 55.3 75 65 36”
Initial
37.3 39.4 33.1 27.5 36.7 32.1 27.1
pressure of hydrogen,
Tab/e 74
24.6 25.7 23.4 23.3 32.1 27.2 2.8 13.4 MPa
coal basins of the U.S.,.but seams containing them can be of very considerable lateral extent (there are very large reserves of the No.5 Block Seam in West Virginia and the Indiana No.1 Block, both studied here). Insofar as they are known, the properties of cutinite, resinite, andalginite, like those of sporinite, are characterized by high hydrogen contents and volatile-matter yields, low decomposition temperatures and high fluidity during pyrolysis2~3~9+11. Thus one would expect all of them to be very desirable constituents of feedstocks for coal liquefaction. The total content of exinitic macerals in the lithotypes of the Indiana No.1 Block coal is not high (samples 105, 105A, 106) and indeed little or no alginite could be detected. It is still possible in principle that chemical components of algae, such as lipids, had diffused into the other macerals and combined with them; that is, that there could be an aIga1 contribution not detectable under the microscope. In agreement with this suggestion, the reflectance of vitrinite in PSOC-IOSA is surprisingly low, but the hydrogen contents and volatile-matter yields of none of this set of samples is specially high (Table 10). The liquefaction behaviour of the lithotype (106) richest in exinitic macerals (total, 27%) was distinctly poorer than that of the other lithotype (105A, see Table 13) or of the channel sample (105, Table 14). However, any beneficial effect of the presence of the exinitic mace&s is presumably nullified by the large proportion of inert macerals in sample 106 (48%). The relative proportions of the aromatic-group types is appreciably different for samples 105 and 106 (Table 7). The No.5 Block coal from Bickmore, West Virginia, presents a number of puzzles. It is the bottom bench of this seam (PSOC-124) that has the classical ‘block’ properties. The total of 40% exinitic mace& includes 7.4% alginite. Its hydrogen and volatile matter values are particularly high (Table IO), as also is the yield of alkanes on solvent extraction (2.1%) and the intensity of aliphatic C-H vibrations in the infrared spectrum. However, even allowing for the presumably high hydrogen content of the exinitic macerals (average S%?), the hydrogen content and aliphatic character of the whole lithotype seem to be higher than would be expected, in view of the fact that a total of42% of micrinitic and fusinitic macerals is also present. It seems most probable therefore that algal lipid derivatives, such as hydrocarbons and fatty acids have accumulated in the coal, as they do in a petroleum source rock and by much the same mechanism, and also as in a source rock they have partly condensed into a kerogen-like material.
Liquefaction data for selected lithotypes (Gulf data) (96, dmmf)
Sample No.
Solvation
Benzene-insol.
Asphaltenes
Saturates
2 12 13 105 106 124
86-9 78.4 80.3 87.6 808 50.6 Not filterable
28.0 26.9 33.2 37.9 24.7 31.5 -
46.5 44.8 37.8 34.1 38.2 15.9 _
1.1 1.0 1.9 1.4 0.9 I.0 -
155
92.8
1.6
6.4
6.3
1
46
FUEL, 1975, Vol 54, January
Filtrate viscosity at 100°C (mm2/s) 12 12 13 16 8.1 8.3 >lOOO at 150°C 4.7
P. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (2)
Some evidence that this can happen is provided by the studies of Given (unpublished) on jet occurring near Whitby (Yorkshire, England). Jet occurs in thin bands in a Jurassic marine shale that is rich in organic matter (13% organic C). It is believed to have formed from the metamorphism of logs of wood that floated down rivers into the sea, sank, and became incorporated in the marine sediment. From the point of view of the coal petrographer jet is a chemically modified vitrinitic maceral, and it is anomalous in the same way as a block coal - low reflectance, high hydrogen and volatile matter. From a comparison of the analysis of the materials extractable from the jet and from the surrounding shale, Given concluded that they were very similar and had a common origin in marine organisms. The residue after extraction was hydrogen-rich and highly aliphatic, from which it was concluded that some of the material from marine organisms had combined chemically with the vitrinite so that it was no longer removable by extraction (and, of course, not detectable by microscopy). The lithotype 124 behaved disappointingly in the liquefaction experiments of both the Penn State and Gulf groups. Under the usual conditions essentially no oil was obtained, and in the Gulf experiment the sample absorbed all the vehicle so that a tarry solid was produced. In the Penn State experiment in which a higher than normal initial pressure was used, some liquid product was obtained, but it had a very high asphaltene-to-oil ratio. The condensation of algal materials into the maceral structure could cause cross-linking of coal molecules, thus altering mechanical properties and giving the coal the observed poor swelling, fluidity and coking properties. It could also reduce solvation and make liquefaction difficult. On the other hand, the channel sample of the whole seam (PSOC-122), containing the block lithotype, showed a quite respectable conversion, with a particularly low asphaltene-to-oil ratio (1: 1 compared with an average value of 1:l.S). The other lithotype from this seam (123) contained more sporinite and less alginite than 124, and its hydrogen and volatile matter are not especially high (Table 12). It gave a lower conversion than the channel sample (122), though much higher than 124. It should be noted that the whole seam contains another bench in addition to the lithotypes 122 and 123, and no information about this is available at present. Finally, we must consider the extremely interesting coal from Utah, PSOC-155. Petrographically, this sample has some of the characteristics of a block coal, having 9% alginite, yet its vitrinite content is 74% (Table 12). Its calorific value would put it in the high-volatile C bituminous class on the ASTM system, though it is not clear whether this is significant. Its hydrogen content and volatile matter are very high, as are the intensities of the aliphatic C-H vibrations in the infrared spectrum. The reflectance of the vitrinite is about that of a subbituminous coal (0.44%). We must again presume the presence of molecularly dispersed algal material, not extractable and not visible under the microscope, and here chiefly associated with the vitrinite. In Gulf liquefaction tests the coal gave an excellent yield of oil containing very little benzene-insolubles or asphaltenes, implying that most of the product was pentaneThe filtrate viscosity was among the lowest soluble. found in this series of experiments. The yield of saturates (6%) was much higher than that found with any other sample. This yield was also considerably higher than the
quantity of alkanes extractable from the coal before hydrogenation, suggesting that the long-chain molecules had indeed been condensed into the structures of the coal macerals. In the molecular-parameter analysis (Table 7), the aromaticity of the small yield of asphaltenes was found to be very low, the alkyl substituents per average molecule very high, and 94% of the aromatic systems contained only one benzene ring. This Utah coal is certainly unique in the set of samples available to us, and its characteristics raise interesting geochemical points. The petrographic composition of the coal shows that woody tissue was the major contributor to the organic matter, and algal cells the next most abundant source. It is difficult to envisage circumstances in which this could have happened, with so little introduction of spores or formation of micrinite. Since we do not understand the circumstances in which a coal with the characteristics observed here might have originated, we cannot say how often similar circumstances may have arisen elsewhere. Since the Cretaceous and Tertiary bituminous coals of the western U.S. have been much less exploited commercially and studied geologically than the older coals of the east, other coals similar to the Utah sample may well exist, and they should be sought. The chemical analyses of the West Virginia Block lithctype and of the Utah coal are in some respects similar, and they have some features of their petrography in common. A major difference is the level of vitrinite contents; in the latter case algal molecules must be condensed only into vitrinite structure, whereas in the former they must be at least partly associated with other mace&, including micrinite and fusinite.
CONCLUDING
REMARKS
The data presented in this and the preceding paper show that the relation of coal characteristics to behaviour in liquefaction processes is complex. 1. Rank is certainly important, but we can as yet define only a broad range of rank as desirable. 2. The geological history of a sample is probably relevant, at least in some cases, but m&e w&k is needed to establish this. In a number of cases, the maceral distribution is quite clearly an important factor determining liquefaction behaviour, though we do not yet understand the effects of the various macerals well enough to make confident predictions. In most cases, such properties of a coal lithotype as volatile matter and hydrogen content can be seen to be consistent with the maceral composition of the sample and such knowledge of the properties of individual macerals as is available in the literature. It is worth noting, however, that a few cases have been identified where this is not so and the presence of components not detectable by microscopy must be suspected. There are factors other than rank, geological history and petrography that affect or may even determine liquefaction behaviour, and in some instances the nature of the inorganic constituents of the sample is undoubtedly one of these factors.
FUEL, 1975, Vol 54, January
47
Coal liquefaction behaviour (2):
P. H. Given, D. C. Cronauer, W.Spackman, H. L. Lovell,A. Davisand B. Biswas
It is the superimposition of the effects of the factors noted in statement 5 on the effects of the factors noted in items l-4 that make the data difficult to interpret fully. The properties that are likely to be relevant to liquefaction behaviour, other than those already referred to, are chemical structure, solubility in solvents, and the nature of the porosity. It is not clear to what extent these are independent variables.
ACKNOWLEDGEMENTS The greater part of the work carried out by the Penn State group was performed under Contract 14~1-0001-390 from the Office of Coal Research, U.S. Department of the The contribution made by the Gulf group was Interior. supported solely by the Corporation until June 1973, from which time the concluding stages of the work and the preparation of this paper was supported by the RANN Division (Research Applied to National Needs) of the National Science Foundation, to which we express our gratitude. A number of persons have contributed to this work in various ways, and we wish to acknowledge our indebtedness to all of them: Mr. Harold Beuther, for general guidance and for important discussions; R. G. Ruberto for analytical services;C. P. Dolsen, R. H. Ford, R. J. Carson, D. A. Eckley and Maria Fedale for sample collection and petrographic analyses; R. N. Miller, R. Yarzab and Joann Robuck for determinations of mineral-matter contents of coals.
mining mineral-matter contents of coals. For many of the samples studied in this investigation, we have’determined mineral-matter contents by acid demineralization1’*i8, which appears to be the most reliable means available. Data marked with a superscript c in Table I of Part 1 and an asterisk in Tables 3 and 10 of Part 2 were determined by this procedure. Data not so marked were corrected by a modified mineral-matter formula as described below. The formula is mm=1~13asht0~47Spy,t0~5C1
(1)
It was derived in essentially the same way as the Parr formula, but (a) Millott’s value for the average water of decomposition of the clays is adopted, (b) only the pyritic sulphur is considered, and (c) the correction for chlorine is adopted from the KMC formula. For the purpose of correcting organic carbon in the elementary analysis when direct CO2 data are not available, carbonates (as calcium salt) are assumed to represent 10% of total mineral matter (this is based on actual CO2 determinations for some 60 U.S. coals). This gives: C
erg
= Cdet - (0.014 ash t 0.0055 S,,)
(2)
The same assumption, combined with equation (1) and the correction to as-received volatile matter due to Leighton and Tomlinsonls, gives: VM = VMd, - (O-165 ash t 0.21 SpYr t 0.7 Cl - O-2)(3)
APPENDIX Determination of mineral-matter contents associated corrections to coal analyses
and
The well-known Parr formula for correcting ash to mineral matter assumes that all sulphur is pyritic, and is open to a number of other objections. The King-MariesCrossley mineral-matter formula’* is free from most of the objections to the Parr but in common with all such conversion formulae has to assume a constant average value for the water of decomposition of the clay minerals. Millott13 found that the average for 80 British coals was appreciably higher than King ef al had assumed, and corrected their formula accordingly. Corresponding changes were made in formulae for correcting organic carbon for CO;! from carbonates, organic hydrogen for Hz0 from clays and volatile matter for a variety of effects’4*15. Brown, Durie and Shafer16 found that the average water of decomposition of clays reported by Millott was valid for coals from one Australian basin, but not for coals from two others. We have found widely varying water yields from the clays in a selection of 20 American coals. These findings constitute a serious objection to the use of any mineral-matter formula. In experiments using an oxygen-plasma low-temperature asher, we have found that even at low power levels when no pyrite is oxidized the sulphate content of the ash is frequently higher than would correspond to the sulphate content of the original coal. We infer that organic sulphur forms sulphuric acid in the asher, and this would not be volatile under the conditions (1 torr or 133 Pa total pressure, maximum temperature about 1 SO’C). Sulphuric acid would react with carbonates. We are not satisfied, therefore, with low-temperature ashing as a method for deter-
48
FUEL, 1975, Vol 54, January
A corresponding simplification of a correction hydrogen due to the same authors gives: Ho, = H,
- (0.014 ash - O-0 17 S,,
to organic
- 0.02)
(4)
The constant 0.02 in equation (4) has been found to represent a good average for the algebraic sum of three terms present in the full Leighton-Tomlinson correction: -0.025 CO;! - 0.03 (Sati - Sso4), where Sso, represents the sulphatic sulphur content of the original coal. These various devices cannot be defended strongly; their principal justification is that they give better approximations than no corrections at all. Comparison of the mineral-matter content calculated by equation (1) with values determined by acid demineralization is available for 91 samples. The frequency distribution of differences, A = (calculated) - (direct), is as follows:
Range of A
No. of samples
Range of A
No. of samples
+0.5-0 1.oo-0.5 1 1.50-1.01 >+1.50
19 15 12 9
0 to 0.5 -0.51 to -1.00 -1.01 to -1.50 <-1.50
18 11 4 3
It will be noted that in 63 cases (69%) the difference is less than l%, and is more or less equally distributed between positive and negative values. The differences greater than 1.5% (range l-5-2.8%) all correspond to coals of high mineral-matter content (15-45%) and in these cases the formula tended to over-estimate more often than it underestimated.
p. H. Given, D. C. Cronauer, W. Spackman, H. L. Lovell, A. Davis and B. Biswas: Coal liquefaction behaviour (21
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9
4
Given, P. H., Cronauer, D. C., Spackman, W., Lovell, H. L., Davis, A. and Biswas, B. Fuel, Lond. 1975,54, 34 Van Krevelen,D. W. Coal, 2ndedn, Elsevier, Amsterdam, 1961 Fenton, ti. W. and Smith, A. H. V. Gas World (Coking Section) 1959, 149, (May), 81 Given, P. H., Peover, M. E. and Wyss, W. F. Fuel, Lond.
5
Given, P. H., Peover, M. E. and Wyss, W. F. Fuel, Lond.
6
Brown, J. K. BCURA Monthly Bull. 1959,23, 1 Oelert, H. H. Fuel, Lond. 1970,49, 119 Benedict, L. G., Thompson, R. R., Shigo, J. J. and
1960,39,
323
1965,44,425
8
10 11 12 13 14 15 16 17 18
Aikman, R. P. Fuel, Lond. 1968,47,125 Murchison, D. G. Coal Science, Adv. in Chem. Series No.55, Amer. Chem. Sot., 1964, p 307 Murchison, D. G. and Millais, R. Fuel, Land. 1969,48,247 Neavel, R. C. and Miller, L. V. Fuel, Lond. 1960.39, 217 King, J. G., Maries, M. B. and Crossley, H. E. J. Sot. them Ind. 1936, 55T, 277 Millott, J. O’N. Fuel, Lond 1958, 37, 71 Ward, D. L. and Millott, J. O’N. Fuel, Lond. 1960, 39, 293 Leighton, L. H. and Tomlinson, R. C. Fuel, Land. 1960, 39, 133 Brown. H. R.. Durie. R. A. and Shafer, H. N. S. Fuel, Lond. 1960,39,59 Bishop, M. and Ward, D. L. Fuel, Lond. 1958, 37, 191 Radmacher, W. and Mohrhauer Gliickauf 1953,89,503
FUEL, 1975, Vol 54, January
49