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Chemical and petrographical characterization of representative samples of vitrinite and exinite concentrates
Fuel Processing Technology, 36 (1993) 33-39
33
Elsevier Science Publishers B.V., Amsterdam
Chemical and petrographical characterization of representative samples of vitrinite and exinite concentrates W.J.Z Fermont 2 J. Joziasse3,K.A. Naterl,A.M.H. van der Veen it
1European Centre for Coal Specimens SBN, P.O.Box 151, 6470 El) Eygelshoven, the Netherlands 2 Geological Survey of the Netherlands RGD 3 Netherlands Organization forApplied Scientific Research TNO
Summary The chemical and petrographical properties of maceral concentrates are described. 7 vitrinites, ran~ng in rank from high volatile bitnminous to anthractie, and 3 exinites of high volatile bit-minons coals have been prepared and characterized. The preparation of vitrinite concentrates and exinite concentrates with use of inorganic salt solutions have yielded maceral groups with a purity of 95% (vitrinite concentrates) and 85% (exinite concentrates) respectively. The ash content in the vitrinite concentrates is lower than that in the exiniite concentrates. The main "contamination"in the e~dniteconcentrates is vitrinite.
Introduction The relative amounts of microscopic constituents of coals, macerals, determine the chemical and physical prperties of coal. For various experiments, standardization and interlaboratory research large amounts of purified macerals are necessary. The preparative conditions as well as a discussion of the method have been published elsewhere [1]. F r o m the concentrates, representative subsamples have been prepared. The sample preparation of the concentrates is described elsewhere [2]. The final analyses, both chemically and petrographically, have been carried out on these samples. The reason for representative subsampling is obvious: the figures, as presented here, should be valid for the entire batch of material, within the statistical uncertainties.
Sample selection The coals selected for the separation of vitrinite and of exinite are listed in tables 1 and 2 respectively. Only the completely processed coals are listed here. The selection procedure has b e e n described elsewhere [1,3]. The coals for the preparation of the vitrinite concentrates have been selected for their high vitrinite content on mineral matter free basis. All coals are from the Ruhr area (Germany), except for the French anthracite La t
Author to send correspondence to.
0378-3820/93/$06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved.
84
Mure (203FR03), which has been added for its high rank of coalification (table 1). For the exinite concentrates preparation, a series of coals over such a wide rank is not possible, since exinite macerals loose gradually their identity with increasing rank. Therefore, coals have been selected with a low rank, and with a high exinite concentration (table 2). Coals are referred to as XXXYY99 where the digits indicate the volatile matter content, XXX is a sequence number, and YY is the country code. Vitrinite concentrates have codes of the model XXXYYVT, and exitites XXXYYEX. If the last two characters of the code have been left out, the code refers to the material in an intermediate state. Table 1 :Selection of coals for vitrinite concentrate pr~ mration Country
Mine
France German)/ Germany Germany Germany German), Germany
La Mure Consul Haard Polsum Haard Niederberg Emil Mayrisch
Seam
B Albert Wellington Hasen Kreftenscheer Mausegatt E
Rank (%Rm) 6.08 1.07 1.29 1.65 1.79 2.62 1.43
Code (parent coals) 203FR03 312DE31 313DE25 314DE17 315DE14 316DE10 505DE24
Table 2 : Selection of coals for exinite concentrate pre ~aration Country
Mine
Seam
Rank (%Rm)
Poland Poland Poland
Janina Par,/z Siersza
116/2 819 210 Wall 109
0.46 0.57 0.49
Code (parent coals) 234PO35 236PO42 237PO39
Petrographic analysis
After the maceral separation process, the samples prepared in accordance to the procedures for reference materials have been analyzed. Table 3 lists the results of the vitrinite reflectance measurements of the vitrinite concentrates and their parent coals. The average ranks of the concentrates and their parent coals have been tested with Student's t-test with 50 degrees of freedeom and at a probability level of 0.01. For the sampies 314DE, 315DE, and 316DE there is no significant difference in rank between the parent coal and the concentrate. For all other samples, the rank of the concentrates is lower than that of the parent coal. The maceral compositions of the samples are compiled in table 4.
35
trent coals and vitrinite concentrates
Table 3 : Vitrinite reflectance data
Rank
203FR
312DE 313DE 314DE 315DE
316DE
%Rm (parent coals)
6.08
1.07
1.31
1.63
1.89
2.61
1.43
tr
0.51
0.04
0.04
0.06
0.06
0.14
0.04
S.E.
0.071
0.006
0.006
0.008
0.008
0.020
0.006
Variability
8.38
3.78
3.05
3.68
3.17
5.36
2.80
%Rm (concentrates)
5.67
1.02
1.26
1.64
1.91
2.55
1.34
a
0.64
0.05
0.06
0.10
0.12
0.23
0.08
S.E.
0.091
0.007
0.008
0.014
0.017
0.033
0.011
Variability
11.29
4.90
4.76
6.09
6.29
9.00
5.97
t-test
3.86
5.52
5.00
0.61
1.05
1.58
7.11
Table 4 : Maceral ~rou]
505DE
position parent coals and vitrinite concentrates [203FR [312DE [313DE [314DE [315DE [316DE ]505DE
Parent Coal Vitrinite
84.4
48.2
69.0
82.4
65.2
53.6
77.2
E~dnite
0.0
7.4
0.0
0.0
0.0
0.0
0.0
Inertinite
15.4
29.4
10.0
15.0
32.8
3.0
11.5
Minerals
0.2
15.0
21.0
1.6
2.0
43.3
11.3
Vitrinite
98.6
93.8
98.0
95.8
96.0
96.4
97.8
Exinite
0.0
2.2
0.0
0.4
0.2
0.0
0.0
Concentrate
Inertinite
1.4
4.0
2.0
!3.8
3.6
3.6
2.2
Minerals
0.0
0.0
0.0
0.0
0.2
0.0
0.0
The data in table 4 indicate an efficient removal of mineral matter; at least on microscopic scale no mineral matter could be detected. The main "contamination" in the vitrinite concentrates is inertinite, except for the concentrate of 312DE, which contains also exinite (2.2%). The average vitrinite concentration amounts over 96%. For the exinite concentrates, a discussion of the change in vitrinite reflectance is no use, since vitrinite should have been removed during the maceral separation process. The purity of the samples has been determined by means of maceral group analysis (table 5). Table 5 : Maceral ~rou] ~compositi on parent coals and exinite concentrates Vitrinito
234PO35 24
234POEX
236PO42
236POEX
237PO39
237POEX
5.8
49
38.4
33
17.0
Exinite
44
Inertinite
28
85.0 9.2
32 19
51.6 10.0
30 33
188.2 4.8
Minerals
4
0.0
0
0.0
4
I0.0
36
The purity of the exinite concentrates is considerably lower than that of the vitrinite concentrates. The separation of 236PO did not succeed completely; although an enrichment of exinite was obtained, the purity is poor (51.6%). A successive separation could have yielded a higher exinite content in the concentrate. The reason for a lower purity in general is, that the highest concentration of exinite is not found in the finest grains of the coal, but in an intermediate fraction. This implicates that the chance of having particles of one maceral group only is considerably smaller than in the case of vitrinite. Coal characterization analysis
The parent coals as well as the concentrates have undergone the standard coal characterization analyses. In table 6, the results of the proximate analyses on the vitrinite concentrates and their parent coals are shown. The proximate analysis shows a Table 6 : Proximate analysis of vitrinite concentrates significant decrease of the ash and their ~arent coals (dry) content (on dry base). Although Code Ash VM FC CV this fact is to be expected, the (%) (%) ash content in the vitrinite coni203FR03 7.10 2.37 90.53 31.92 centrates is rather high, although 203FRVT 2.94 4.20 92.86 32.31 mineral matter could not be de312DE31 21.76 24.53 53.71 27.40 tected under the microscope. 312DEVT 4.70 28.30 67.00 33.67 Since the decrease in ash is 313DE25 25.78 18.30 55.92 26.27 rather big, it is no use to com313DEVT 4.80 22.40 72.80 34.87 pare the parameters of other 314DE17 6.12 16.33 77.55 34.11 analyses on dry base. In table 6, 314DEVT 3.30 17.00 79.70 35.10 the results for volatile matter (VM), fixed carbon (FC) and the 315DE14 10.99 12.41 76.60 32.26 calorific value (CV) are given on 83.20 34.79 315DEVT 3.70 13.10 dry basis (dry). The change in 316DE10 17.75 8.19 74.06 29.16 VM is not very big for most 316DEVT 4.30 7.10 88.60 34.95 coals, but there are some tend505DE24 8.44 24.48 67.08 32.51 encies. The anthracite 203FR 505DEVT 0.80 22.00 77.20 36.07 shows an increase in VM, whereas most other coals show a decrease in VM. The CV of the vitrinite concentrates is about equal for most coals except for 203FR (decrease by 1.2 MJ/kg), 313DE, 316DE, and 505DE (increase by ca. 1.1 MJ/kg). The ultimate analysis of the vitrinite concentrates (table 7) shows some tendencies which could be expected. The carbon content does not differ much for most concentrates in comparison with their parent coals, except for 312DE, 313DE, and 505DE, which all show an increase in carbon content (daf). Hydrogen is increased for most coals, except for 312DE and 313DE which show a decrease of about 0.4% absolute (daf). The higher
37 CV of 313DE and 505DE can be explained by the increase in carbon content. The higher CV of 505DE and 316DE can be explained by the increased hydrogen content. For the decrease in CV for 203FR, there is no such explanation. 312DEVT, 315DEVT, and 505DEVT show some increase in nitrogen content (daf). Sulphur as well as chlorine are reduced in all coals. This reduction must be a consequence of the removal of mineral matter. Apparantly, both elements are more frequently found in the inorganic matrices in the coal. The data for the exinites (table 8) are different from those for the vitrinites. The ash content of the exinite concentrates is not that much reduced as in the case of the vitrinite concentrates. The VM of the exinite concentrates show for all coals a strong increase and the absolute value is typically greater than 50% (daf). The CV shows also an increase for all three coals, which is big for 234PO and 237PO, and rather small for 236PO (0.5 MJ/kg).
Table 7 : Ultimate analysis of vitrinite concentrates and their parent coals (weil %, daf) Code
C
H
S
CI
203FR03
94.0
1.66
N 1.99
0.85
0.05
Odin 1.47
203FRVT
94.0
1.97
0.82
0.56
0.04
2.55
312DE31
85.9
5.16
1.67
1.33
0.15
5.79
312DEVT
86.5
4.77
1.79 I
0.82
0.01
6.13
313DE25
87.1
4.89
11.66
1.63
0.04
4.68
313DEVT
89.5
4.57
1.69
0.92
0.01
3.31
314DE17
90.6
4.41
11.54
1.03
0.03
2.39
314DEVT
90.4
4.87
1.52
0.79
0.02
2.42
315DE14
90.7
4.07
1.62
1.36
!0.09
2.13
315DEVT
91.0
4.53
1.80
0.62
0.01
2.08
316DE10
91.6
3.54
11.59
0.84
0.06
2.35
316DEVT
91.7
4.49
1.59
0.67
0.02
1.56
505DE24
88.5
4.74
1.52
1.06
0.04
4.14
505DEVT
89.2
5.13
1.81
0.68
0.01
3.14
Table 8 : Proximate analysis of exinite concentrates and their parent coals (dl Ash
VM
FC
(%)
(%)
(%)
(MJ/kg)
234PO35
8.70
35.10
56.20
27.29
234POEX
6.68
53.65
39.67
30.39
236PO42
3.50
41.40
55.10
31.79
236POE×
2.69
49.74
37.57
32.56
237PO39
12.10
36.40
51.50
26.80
237POEX
9.80
52.23
37.97
39.59
Code
CV
For the exinites, the ultimate analysis (table 9) shows some differences with respect to the vitrinites. The carbon content for instance shows no tendency towards an increase or decrease. The hydrogen content is raised in both 234POEX and 237POEX with respect to their parent coals, but 236POEX shows a slight decrease. The nitrogen content is lower in all concentrates. The decrease of sulphur is not as striking as in the case of the vitrinites, which may be due to the mineral matter content, which was not reduced that much with the separation of the exinites.
38 Discussion and conclusions
Table 9 : Ultimate analysis of exinite concentrates and their parent coals (daf)
Code C H N S CI Odiff Possible explanations for the 75.0 4.87 1.48 1.10 0.02 17.5 change in rank of the vitrinite 234PO35 76.9 5.73 1.04 0.69 0.01 15.6 concentrates in comparison with 234POEX the parent coals may reflect the 236PO42 80.5 5.87 1.93 0.99 0.05 10.6 difficulties in measuring the re236POEX 78.9 5.74 1.50 0.81 0.Q3 13.0 flectance of samples with a very 237PO39 75.1 5.21 1.39 1.30 0.02 17.0 fine grain size. On the other 237POEX 76.7 15.52 1.00 •.54 0.01 15.2 hand, it could also indicate that the vitrinite concentrates are not representative anymore for the coal as a whole. Although the lower ash contents in both the vitrinite and the exinite concentrates is to be expected, the ash content is rather high in both cases, although the mineral matter could not be found under the microscope. I
The nitrogen content in the vitrinite concentrates is a very interesting parameter in this study, since some coals have been comminuted chemically by means of ammonia. If the ammonia would react with the coal or it would not be removed completely, an increase of nitrogen content (daf) can be expected. It is not possible to show a clear relationship between ammonia treatment and the nitrogen content. Remarkable is the decrease in nitrogen content of 203FR. The preparation of vitrinite concentrates and exinite concentrates with use of inorganic salt solutions have yielded maceral groups with a purity of 95% (vitrinite concentrates) and 85% (exinite concentrates) respectively. Acknowledgements
The European Communities (EC) and the Netherlands Organization for Energy and Environment (NOVEM) are acknowledged for their funds. Dr. H.A.G. Chermin is thanked for his innovative contributions in the early stages of this research.
1 2 3
W.J.J. Fermont, J. Joziasse, K.A. Nater, A.M.H. Van der Veen, "Analytical procedures for large-scale preparation of maceral concentrates", this volume A.M.H. van der Veen, D.A.G. Nater, "Sample preparation from bulk samples: an overview", this volume W.J.J. Fermont, J. Joziasse, K.A. Nater, A.M.H. Van der Veen, "A.fscheiden van maceraalgroepen op kilogram schaar', Final Report, SBN Eygelshoven 1992
89 Discussion Chemical and petrographical characterization of representative samples of vitrinite and exinite concentrates W.J.J. Ferment, J. Joziasse, K.A. Nater and A.M.H. van der Veen Question: M. Cloke 1. We have also noted that mineral matter observed optically on the block is much lower than that indicated by the ash analysis. We attribute this to 'wash-out' during polishing. Any comments? 2. In your paper you state that the vitrinite concentrate may not represent the coal as a whole. What then is the value of looking at vitrinite concentrates to assess coal properties as a whole? Answer 1. That is one out of more possibilities. I think that a fraction of the mineral matter is of submicroscopic size. Presumably, this can never be removed from maeerals. 2. We suppose that there may be marginal differences between parent coals vitrinites and concentrates. However, we are interested in the much larger differences between different maceral groups.
33
Elsevier Science Publishers B.V., Amsterdam
Chemical and petrographical characterization of representative samples of vitrinite and exinite concentrates W.J.Z Fermont 2 J. Joziasse3,K.A. Naterl,A.M.H. van der Veen it
1European Centre for Coal Specimens SBN, P.O.Box 151, 6470 El) Eygelshoven, the Netherlands 2 Geological Survey of the Netherlands RGD 3 Netherlands Organization forApplied Scientific Research TNO
Summary The chemical and petrographical properties of maceral concentrates are described. 7 vitrinites, ran~ng in rank from high volatile bitnminous to anthractie, and 3 exinites of high volatile bit-minons coals have been prepared and characterized. The preparation of vitrinite concentrates and exinite concentrates with use of inorganic salt solutions have yielded maceral groups with a purity of 95% (vitrinite concentrates) and 85% (exinite concentrates) respectively. The ash content in the vitrinite concentrates is lower than that in the exiniite concentrates. The main "contamination"in the e~dniteconcentrates is vitrinite.
Introduction The relative amounts of microscopic constituents of coals, macerals, determine the chemical and physical prperties of coal. For various experiments, standardization and interlaboratory research large amounts of purified macerals are necessary. The preparative conditions as well as a discussion of the method have been published elsewhere [1]. F r o m the concentrates, representative subsamples have been prepared. The sample preparation of the concentrates is described elsewhere [2]. The final analyses, both chemically and petrographically, have been carried out on these samples. The reason for representative subsampling is obvious: the figures, as presented here, should be valid for the entire batch of material, within the statistical uncertainties.
Sample selection The coals selected for the separation of vitrinite and of exinite are listed in tables 1 and 2 respectively. Only the completely processed coals are listed here. The selection procedure has b e e n described elsewhere [1,3]. The coals for the preparation of the vitrinite concentrates have been selected for their high vitrinite content on mineral matter free basis. All coals are from the Ruhr area (Germany), except for the French anthracite La t
Author to send correspondence to.
0378-3820/93/$06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved.
84
Mure (203FR03), which has been added for its high rank of coalification (table 1). For the exinite concentrates preparation, a series of coals over such a wide rank is not possible, since exinite macerals loose gradually their identity with increasing rank. Therefore, coals have been selected with a low rank, and with a high exinite concentration (table 2). Coals are referred to as XXXYY99 where the digits indicate the volatile matter content, XXX is a sequence number, and YY is the country code. Vitrinite concentrates have codes of the model XXXYYVT, and exitites XXXYYEX. If the last two characters of the code have been left out, the code refers to the material in an intermediate state. Table 1 :Selection of coals for vitrinite concentrate pr~ mration Country
Mine
France German)/ Germany Germany Germany German), Germany
La Mure Consul Haard Polsum Haard Niederberg Emil Mayrisch
Seam
B Albert Wellington Hasen Kreftenscheer Mausegatt E
Rank (%Rm) 6.08 1.07 1.29 1.65 1.79 2.62 1.43
Code (parent coals) 203FR03 312DE31 313DE25 314DE17 315DE14 316DE10 505DE24
Table 2 : Selection of coals for exinite concentrate pre ~aration Country
Mine
Seam
Rank (%Rm)
Poland Poland Poland
Janina Par,/z Siersza
116/2 819 210 Wall 109
0.46 0.57 0.49
Code (parent coals) 234PO35 236PO42 237PO39
Petrographic analysis
After the maceral separation process, the samples prepared in accordance to the procedures for reference materials have been analyzed. Table 3 lists the results of the vitrinite reflectance measurements of the vitrinite concentrates and their parent coals. The average ranks of the concentrates and their parent coals have been tested with Student's t-test with 50 degrees of freedeom and at a probability level of 0.01. For the sampies 314DE, 315DE, and 316DE there is no significant difference in rank between the parent coal and the concentrate. For all other samples, the rank of the concentrates is lower than that of the parent coal. The maceral compositions of the samples are compiled in table 4.
35
trent coals and vitrinite concentrates
Table 3 : Vitrinite reflectance data
Rank
203FR
312DE 313DE 314DE 315DE
316DE
%Rm (parent coals)
6.08
1.07
1.31
1.63
1.89
2.61
1.43
tr
0.51
0.04
0.04
0.06
0.06
0.14
0.04
S.E.
0.071
0.006
0.006
0.008
0.008
0.020
0.006
Variability
8.38
3.78
3.05
3.68
3.17
5.36
2.80
%Rm (concentrates)
5.67
1.02
1.26
1.64
1.91
2.55
1.34
a
0.64
0.05
0.06
0.10
0.12
0.23
0.08
S.E.
0.091
0.007
0.008
0.014
0.017
0.033
0.011
Variability
11.29
4.90
4.76
6.09
6.29
9.00
5.97
t-test
3.86
5.52
5.00
0.61
1.05
1.58
7.11
Table 4 : Maceral ~rou]
505DE
position parent coals and vitrinite concentrates [203FR [312DE [313DE [314DE [315DE [316DE ]505DE
Parent Coal Vitrinite
84.4
48.2
69.0
82.4
65.2
53.6
77.2
E~dnite
0.0
7.4
0.0
0.0
0.0
0.0
0.0
Inertinite
15.4
29.4
10.0
15.0
32.8
3.0
11.5
Minerals
0.2
15.0
21.0
1.6
2.0
43.3
11.3
Vitrinite
98.6
93.8
98.0
95.8
96.0
96.4
97.8
Exinite
0.0
2.2
0.0
0.4
0.2
0.0
0.0
Concentrate
Inertinite
1.4
4.0
2.0
!3.8
3.6
3.6
2.2
Minerals
0.0
0.0
0.0
0.0
0.2
0.0
0.0
The data in table 4 indicate an efficient removal of mineral matter; at least on microscopic scale no mineral matter could be detected. The main "contamination" in the vitrinite concentrates is inertinite, except for the concentrate of 312DE, which contains also exinite (2.2%). The average vitrinite concentration amounts over 96%. For the exinite concentrates, a discussion of the change in vitrinite reflectance is no use, since vitrinite should have been removed during the maceral separation process. The purity of the samples has been determined by means of maceral group analysis (table 5). Table 5 : Maceral ~rou] ~compositi on parent coals and exinite concentrates Vitrinito
234PO35 24
234POEX
236PO42
236POEX
237PO39
237POEX
5.8
49
38.4
33
17.0
Exinite
44
Inertinite
28
85.0 9.2
32 19
51.6 10.0
30 33
188.2 4.8
Minerals
4
0.0
0
0.0
4
I0.0
36
The purity of the exinite concentrates is considerably lower than that of the vitrinite concentrates. The separation of 236PO did not succeed completely; although an enrichment of exinite was obtained, the purity is poor (51.6%). A successive separation could have yielded a higher exinite content in the concentrate. The reason for a lower purity in general is, that the highest concentration of exinite is not found in the finest grains of the coal, but in an intermediate fraction. This implicates that the chance of having particles of one maceral group only is considerably smaller than in the case of vitrinite. Coal characterization analysis
The parent coals as well as the concentrates have undergone the standard coal characterization analyses. In table 6, the results of the proximate analyses on the vitrinite concentrates and their parent coals are shown. The proximate analysis shows a Table 6 : Proximate analysis of vitrinite concentrates significant decrease of the ash and their ~arent coals (dry) content (on dry base). Although Code Ash VM FC CV this fact is to be expected, the (%) (%) ash content in the vitrinite coni203FR03 7.10 2.37 90.53 31.92 centrates is rather high, although 203FRVT 2.94 4.20 92.86 32.31 mineral matter could not be de312DE31 21.76 24.53 53.71 27.40 tected under the microscope. 312DEVT 4.70 28.30 67.00 33.67 Since the decrease in ash is 313DE25 25.78 18.30 55.92 26.27 rather big, it is no use to com313DEVT 4.80 22.40 72.80 34.87 pare the parameters of other 314DE17 6.12 16.33 77.55 34.11 analyses on dry base. In table 6, 314DEVT 3.30 17.00 79.70 35.10 the results for volatile matter (VM), fixed carbon (FC) and the 315DE14 10.99 12.41 76.60 32.26 calorific value (CV) are given on 83.20 34.79 315DEVT 3.70 13.10 dry basis (dry). The change in 316DE10 17.75 8.19 74.06 29.16 VM is not very big for most 316DEVT 4.30 7.10 88.60 34.95 coals, but there are some tend505DE24 8.44 24.48 67.08 32.51 encies. The anthracite 203FR 505DEVT 0.80 22.00 77.20 36.07 shows an increase in VM, whereas most other coals show a decrease in VM. The CV of the vitrinite concentrates is about equal for most coals except for 203FR (decrease by 1.2 MJ/kg), 313DE, 316DE, and 505DE (increase by ca. 1.1 MJ/kg). The ultimate analysis of the vitrinite concentrates (table 7) shows some tendencies which could be expected. The carbon content does not differ much for most concentrates in comparison with their parent coals, except for 312DE, 313DE, and 505DE, which all show an increase in carbon content (daf). Hydrogen is increased for most coals, except for 312DE and 313DE which show a decrease of about 0.4% absolute (daf). The higher
37 CV of 313DE and 505DE can be explained by the increase in carbon content. The higher CV of 505DE and 316DE can be explained by the increased hydrogen content. For the decrease in CV for 203FR, there is no such explanation. 312DEVT, 315DEVT, and 505DEVT show some increase in nitrogen content (daf). Sulphur as well as chlorine are reduced in all coals. This reduction must be a consequence of the removal of mineral matter. Apparantly, both elements are more frequently found in the inorganic matrices in the coal. The data for the exinites (table 8) are different from those for the vitrinites. The ash content of the exinite concentrates is not that much reduced as in the case of the vitrinite concentrates. The VM of the exinite concentrates show for all coals a strong increase and the absolute value is typically greater than 50% (daf). The CV shows also an increase for all three coals, which is big for 234PO and 237PO, and rather small for 236PO (0.5 MJ/kg).
Table 7 : Ultimate analysis of vitrinite concentrates and their parent coals (weil %, daf) Code
C
H
S
CI
203FR03
94.0
1.66
N 1.99
0.85
0.05
Odin 1.47
203FRVT
94.0
1.97
0.82
0.56
0.04
2.55
312DE31
85.9
5.16
1.67
1.33
0.15
5.79
312DEVT
86.5
4.77
1.79 I
0.82
0.01
6.13
313DE25
87.1
4.89
11.66
1.63
0.04
4.68
313DEVT
89.5
4.57
1.69
0.92
0.01
3.31
314DE17
90.6
4.41
11.54
1.03
0.03
2.39
314DEVT
90.4
4.87
1.52
0.79
0.02
2.42
315DE14
90.7
4.07
1.62
1.36
!0.09
2.13
315DEVT
91.0
4.53
1.80
0.62
0.01
2.08
316DE10
91.6
3.54
11.59
0.84
0.06
2.35
316DEVT
91.7
4.49
1.59
0.67
0.02
1.56
505DE24
88.5
4.74
1.52
1.06
0.04
4.14
505DEVT
89.2
5.13
1.81
0.68
0.01
3.14
Table 8 : Proximate analysis of exinite concentrates and their parent coals (dl Ash
VM
FC
(%)
(%)
(%)
(MJ/kg)
234PO35
8.70
35.10
56.20
27.29
234POEX
6.68
53.65
39.67
30.39
236PO42
3.50
41.40
55.10
31.79
236POE×
2.69
49.74
37.57
32.56
237PO39
12.10
36.40
51.50
26.80
237POEX
9.80
52.23
37.97
39.59
Code
CV
For the exinites, the ultimate analysis (table 9) shows some differences with respect to the vitrinites. The carbon content for instance shows no tendency towards an increase or decrease. The hydrogen content is raised in both 234POEX and 237POEX with respect to their parent coals, but 236POEX shows a slight decrease. The nitrogen content is lower in all concentrates. The decrease of sulphur is not as striking as in the case of the vitrinites, which may be due to the mineral matter content, which was not reduced that much with the separation of the exinites.
38 Discussion and conclusions
Table 9 : Ultimate analysis of exinite concentrates and their parent coals (daf)
Code C H N S CI Odiff Possible explanations for the 75.0 4.87 1.48 1.10 0.02 17.5 change in rank of the vitrinite 234PO35 76.9 5.73 1.04 0.69 0.01 15.6 concentrates in comparison with 234POEX the parent coals may reflect the 236PO42 80.5 5.87 1.93 0.99 0.05 10.6 difficulties in measuring the re236POEX 78.9 5.74 1.50 0.81 0.Q3 13.0 flectance of samples with a very 237PO39 75.1 5.21 1.39 1.30 0.02 17.0 fine grain size. On the other 237POEX 76.7 15.52 1.00 •.54 0.01 15.2 hand, it could also indicate that the vitrinite concentrates are not representative anymore for the coal as a whole. Although the lower ash contents in both the vitrinite and the exinite concentrates is to be expected, the ash content is rather high in both cases, although the mineral matter could not be found under the microscope. I
The nitrogen content in the vitrinite concentrates is a very interesting parameter in this study, since some coals have been comminuted chemically by means of ammonia. If the ammonia would react with the coal or it would not be removed completely, an increase of nitrogen content (daf) can be expected. It is not possible to show a clear relationship between ammonia treatment and the nitrogen content. Remarkable is the decrease in nitrogen content of 203FR. The preparation of vitrinite concentrates and exinite concentrates with use of inorganic salt solutions have yielded maceral groups with a purity of 95% (vitrinite concentrates) and 85% (exinite concentrates) respectively. Acknowledgements
The European Communities (EC) and the Netherlands Organization for Energy and Environment (NOVEM) are acknowledged for their funds. Dr. H.A.G. Chermin is thanked for his innovative contributions in the early stages of this research.
1 2 3
W.J.J. Fermont, J. Joziasse, K.A. Nater, A.M.H. Van der Veen, "Analytical procedures for large-scale preparation of maceral concentrates", this volume A.M.H. van der Veen, D.A.G. Nater, "Sample preparation from bulk samples: an overview", this volume W.J.J. Fermont, J. Joziasse, K.A. Nater, A.M.H. Van der Veen, "A.fscheiden van maceraalgroepen op kilogram schaar', Final Report, SBN Eygelshoven 1992
89 Discussion Chemical and petrographical characterization of representative samples of vitrinite and exinite concentrates W.J.J. Ferment, J. Joziasse, K.A. Nater and A.M.H. van der Veen Question: M. Cloke 1. We have also noted that mineral matter observed optically on the block is much lower than that indicated by the ash analysis. We attribute this to 'wash-out' during polishing. Any comments? 2. In your paper you state that the vitrinite concentrate may not represent the coal as a whole. What then is the value of looking at vitrinite concentrates to assess coal properties as a whole? Answer 1. That is one out of more possibilities. I think that a fraction of the mineral matter is of submicroscopic size. Presumably, this can never be removed from maeerals. 2. We suppose that there may be marginal differences between parent coals vitrinites and concentrates. However, we are interested in the much larger differences between different maceral groups.