- Email: [email protected]
Chemical investigation of lignite samples and their ashing products from Kardia lignite field of Ptolemais, Northern Greece
Fuel 86 (2007) 2502–2508 www.fuelfirst.com
Chemical investigation of lignite samples and their ashing products from Kardia lignite field of Ptolemais, Northern Greece K. Adamidou a, A. Kassoli-Fournaraki b,*, A. Filippidis b, K. Christanis c, E. Amanatidou d, L. Tsikritzis d, O. Patrikaki a b
a Environmental Centre of Kozani, 1st Km Ptolemais-Kozani, 50200 Ptolemais, Greece Department of Mineralogy–Petrology–Economic Geology, School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece c Department of Geology, Section of Earth Materials, University of Patras, 26500 Rio-Patras, Greece d Technological Educational Institute of Western, Macedonia, Koila, Kozani 50100, Greece
Received 19 January 2007; received in revised form 5 February 2007; accepted 6 February 2007 Available online 16 March 2007
Abstract Twenty-six lignite samples were collected from the Kardia lignite field (Ptolemais, Greece). Ash content, moisture and CO2 were determined. The lignite samples were heated at 900 °C producing 26 ash samples. The chemical composition (major and trace elements) both of the lignite samples and ash products was determined using INAA, ICP-OES and ICP-MS. CaO, SiO2 and Al2O3 are the dominant oxides both in lignite and ash samples. A relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper lignite samples. Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. Sr displays a relative increase while Ni and Cr decrease with depth in the lignite samples. In the ash samples, Ni shows the most obvious decrease with depth. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Ptolemais; Lignite; Ash content; Heating procedure; Greece
1. Introduction More than 73% of the electrical power requirements of Greece are generated in coal-fired power plants which combust lignite to produce power generation. The Greek power plants consume more than 65 million tons of lignite per year producing about 13 million tons of total ash. The main coal mining area in Greece is the Lignite Centre of Western Macedonia, in the area of Ptolemais–Florina, where four big mines (Southern, Kardia, Main and Amyntaion lignite fields) of lignite exploitation are operating (total power 4438 MW). The lignite production in 2003 reached 54.58 million tons in the Lignite Centre of Western
*
Corresponding author. Tel.: +30 2310998457; fax: +30 2310998463. E-mail address: [email protected] (A. Kassoli-Fournaraki).
0016-2361/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.02.008
Macedonia. The mean lower calorific value of the Ptolemais lignite reaches 1300 kcal/kg. The exploitation and combustion of lignite in the above mentioned coal-fired power plants are of environmental concern for the broader area of Kozani–Ptolemais–Florina. Hence, the chemical determination of the lignite used and its ash contributes to the control of the environmental quality in the area. Lignite combustion in Greece and environmental impact has been the subject of several studies (e.g. [1–8]). This study concerns the investigation of the chemical composition (major and trace elements) of lignite and its ashing products from Kardia lignite field (Sector 6). This lignite field is active since 1990 and constitutes the main supplier for the Kardia power plant (power 1200 MW), having an annual production of more than 21 million tons. The lignite of the Kardia lignite field has low energy fuel with upper calorific value 4094 kcal kg 1 and lower calorific value 1469 kcal kg 1.
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
1.1. Geological features The Kardia lignite field is situated approximately in the central part of the Neogene lignite basin of Ptolemais (Fig. 1). The sediments of the basin are divided into the lower (Upper Miocene to Lower Pliocene) formation, the Pliocene middle formation and the Quaternary upper formation (e.g. [9,10]). The Pliocene middle formation contains the upper and lower lignite seams. The lignite seams alternate with clays, marls, sandy marls and sands. The thickness both of the lignite seams and the intermediate steriles is variable. In this study, all seams were sampled for chemical investigation. 2. Materials and methods 2.1. Sampling For the purposes of this investigation 26 samples of lignite were used. The sampling was carried out during
2503
November and December 2005 in Kardia (Sector-6) lignite mine. The samples were collected according to ASTM D 4596 standards perpendicular to the bedding and covering the whole stratigraphic series. The sampling column was 126.5 m long. The thickness of the lignite seams ranges from 0.4 m to 4.5 m. 2.2. Analytical techniques The samples were homogenized, dried in room temperature for three days and crushed to <5 mm grain size. Afterwards, the samples underwent dry sieving to pass 2 mm sieve. A quantity of 300–500 g was taken from the treated material of each sample. The ash content, total moisture and CO2 were determined for the 26 lignite samples using a LECO TGA 701 apparatus for ash and moisture determination. Each sample was heated in 106 °C till stabilization of its weight, for the determination of total moisture, and in 550 °C for the determination of CO2. Heating in 850 °C followed for the ash content determination.
Fig. 1. Simplified geological map of Ptolemais area.
2504
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
A quantity of each lignite sample was ground and 0.2 g of it were heated for ash production. Heating took place in laboratory furnaces, in gradually increasing temperature up to 900 °C. The ashing procedure for each sample lasted 25–40 h of continuous heating, according to the quantity of each lignite sample. The heating procedure was repeated till the production of 5 g of ash from each sample. Both the 26 lignite samples and the produced 26 ash samples were chemically analyzed for their major and trace elements, using INAA, ICP-OES and ICP-MS analytical techniques at the Actlabs – Activation Laboratories Ltd of Canada. 3. Results and discussion 3.1. General features It is well known that coals contain organic and inorganic constituents, hence, the related trace element concentrations may vary considerably. This relation has been discussed in various previous works (e.g. [3,11–16]). The elemental composition (major and trace elements) of a coal deposit is related to many things: the nature of the plant communities, the environment of deposition, the age and rank of the coal, the activity of ground water, the weathering of coal, the geological setting, the composition of the country rocks and mineralizations, as well as their weathering and transportation conditions [11,14,15, 17–20]. The Neogene sediments which host the lignite beds in the Kardia lignite field, are of lacustrine origin while the superimposed Quaternary sediments derive from the erosion of the surrounding limestones and metamorphic rocks. 3.2. Ash content, moisture and CO2 The lignite of Kardia lignite field is characterized by low energy fuel and high percentage of moisture and ash (Table 1). The ash content ranges considerably, depending on the lignite quality as well as on the moisture which displays differences even for lignites of the same quality. A characteristic feature of the Kardia lignite is the high content in carbonates which decompose during combustion releasing CO2. From the results of Table 1, it is observed that the ash content ranges between 13.26% and 30.07%. No relation of ash content with depth was noticed. Total moisture ranges between 9.11% and 25.96% and CO2 between 1.08% and 15.98%. 3.3. Chemical composition of lignite The chemical composition of the lignite samples is presented in Tables 2 and 3. Ten major elements and 51 trace elements (16 of which are presented in Table 3) were measured. Among the main oxides, CaO, SiO2 and Al2O3 appear with higher concentrations due to calcite, quartz and feld-
Table 1 Total moisture, ash content and CO2 of the Kardia lignite samples Sample
Lignite seam no.
Seam thickness (m)
Moisture (%)
Ash (%)
CO2 (%)
L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
2.5 0.6 1.4 3.0 0.7 1.0 0.7 0.6 0.8 0.5 0.6 2.5 0.7 2.5 1.9 1.9 1.4 4.5 0.7 3.0 1.4 3.0 1.7 2.2 1.4 0.4
11.27 13.74 14.9 14.7 12.24 12.03 13.34 13.7 13.05 21.46 14.77 13.1 16.73 10.49 12.39 12.18 9.11 11.78 11.66 11.38 12.85 12.64 12.79 13.16 25.96 12.83
24.6 21.61 19.61 16.31 18.65 27.17 27.6 25.4 24.73 29.21 25.32 17.99 17.12 29.36 27.33 23.46 30.07 22.21 21.26 23.5 14.65 13.26 13.48 16.74 13.29 18.13
6.46 1.36 1.74 1.19 2.57 3.59 1.08 1.31 1.19 2.57 4.44 2.15 1.16 10.01 2.29 6.06 15.98 8.38 8.22 12.28 3.38 2.13 2.33 6.52 2.05 7.56
Ash and CO2 on dry basis.
spars which constitute the main mineral phases of the lignite samples. The rest oxides display low concentrations. CaO ranges between 2.89% and 19.04% with the sample L38 displaying the highest value. SiO2 ranges between 0.91% and 21.95%, while Al2O3 shows values of 0.54–10.17%. Loss on ignition shows high values, as well. A relative increase of Fe2O3 is observed only for some samples. No systematic change of the major element concentrations with depth is observed, however, a relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper samples. Among the trace elements, the most abundant is Ni with an average concentration of 127 lg/g. Sr, Cr, Ba and V follow with average values of 99 lg/g, 77 lg/g, 71 lg/g and 40 lg/g, correspondingly. The trace elements As, Br, Cu, Zn, Pb, Co, Rb, Zr, La, Ce and U display average mean values between 5 lg/g and 14 lg/g with the concentrations of Pb, Co and Zr being below detection limits in some samples. Determinations were also made for Sc, Sb, S, Ga, Y, Nb, Cs, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Tl and Th, all of which gave values <5lg/g and in some samples were not detectable, thus they were not included in Table 3. Finally, the trace elements Au, Ir, Se, Cd, Ag, Be, Ge, Mo, In, Sn and Bi gave all concentrations below detection limits. Correlation of the trace element concentrations with depth showed that the lignite samples of the deeper seams contain lower concentrations of all the trace elements
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
2505
Table 2 Major elements (wt%) of the Kardia lignite samples Samples
SiO2
Al2O3
Fe2O3(T)
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
4.86 4.79 21.95 8.66 3.08 4.46 3.75 17.67 8.37 9.81 8.45 5.33 3.47 5.71 3.46 9.59 1.27 1.44 2.10 1.73 1.95 3.19 2.37 0.91 4.4 1.2
2.23 2.29 10.17 4.15 1.34 1.96 1.99 7.88 4.03 4.35 3.32 2.77 1.93 2.66 1.76 4.49 0.73 0.70 1.14 0.75 0.97 1.61 1.06 0.54 2.16 0.59
1.41 1.79 4.54 2.95 0.89 1.36 3.56 4.24 0.90 1.09 3.06 1.35 0.97 1.70 1.86 4.21 0.82 0.70 1.12 0.71 0.83 0.90 0.79 0.61 0.84 0.54
0.02 0.01 0.02 0.02 0.00 0.01 0.02 0.02 0.00 0.00 0.00 0.01 0.00 0.01 0.01 0.03 0.01 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00
0.67 0.76 1.80 1.16 0.64 0.82 0.85 1.42 0.76 0.84 0.97 0.98 0.89 0.75 0.86 1.04 0.96 0.81 1.04 0.80 0.82 0.87 0.87 0.85 0.78 0.86
9.59 4.66 4.88 8.29 3.33 5.73 7.47 2.89 3.39 3.63 7.68 8.28 3.84 3.53 13.22 4.91 14.45 19.04 11.93 9.41 15.52 4.62 4.36 9.41 4.35 8.65
0.06 0.06 0.12 0.07 0.07 0.06 0.07 0.13 0.25 0.24 0.12 0.05 0.04 0.06 0.04 0.05 0.03 0.04 0.06 0.08 0.07 0.04 0.04 0.04 0.20 0.09
0.20 0.10 0.69 0.18 0.17 0.17 0.13 0.45 0.29 0.39 0.24 0.09 0.09 0.20 0.16 0.27 <0.01 0.07 0.14 0.06 <0.01 0.13 0.05 0.03 0.24 0.03
0.11 0.10 0.40 0.16 0.06 0.09 0.09 0.34 0.16 0.19 0.15 0.09 0.06 0.13 0.08 0.21 0.03 0.03 0.05 0.03 0.04 0.07 0.05 0.02 0.08 0.02
0.08 0.05 0.18 0.17 0.04 0.05 0.17 0.13 0.08 0.09 0.05 0.09 0.06 0.04 0.10 0.09 0.07 0.05 0.04 0.05 0.06 0.05 0.06 0.05 0.11 0.07
79.25 84.18 54.20 72.69 88.92 83.93 80.42 63.59 81.19 78.91 74.70 80.23 87.28 84.32 76.93 74.86 81.60 75.62 81.02 85.49 78.78 87.07 88.71 86.11 85.25 86.69
Table 3 Trace elements (lg/g) of the Kardia lignite samples
Detection limit L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
As
Br
Cr
Cu
Ni
Zn
Pb
V
Co
Rb
Sr
Zr
Ba
La
Ce
U
0.5 11 16 27 21 14 20 34 20 11 6 10 11 10 7 14 7 5 5 8 5 5 7 7 4 9 5
0.5 8 9 10 9 9 10 13 9 7 7 8 12 14 11 9 12 8 7 7 8 8 11 10 9 12 8
5 39 61 423 189 25 44 162 243 26 24 38 117 99 60 54 77 28 16 53 29 22 38 40 25 40 21
1 6 7 38 16 4 6 11 25 7 9 7 11 9 8 7 14 4 3 7 3 3 7 11 4 9 3
1 34 110 664 266 75 229 294 396 28 30 57 210 147 70 95 85 34 24 65 32 32 73 65 49 78 52
1 7 14 64 24 8 11 13 39 15 18 12 14 20 11 8 22 3 1 5 6 3 8 10 3 9 1
5 6 5 22 9 <5 5 6 19 19 15 5 <5 7 6 6 8 <5 <5 <5 <5 <5 <5 <5 <5 9 <5
5 33 44 170 79 22 36 114 87 34 36 29 36 38 28 35 38 13 8 32 14 16 29 23 11 36 11
1 2 7 32 13 5 8 14 16 3 4 4 14 6 4 5 6 <1 <1 7 2 1 3 2 1 4 1
1 10 12 48 20 8 10 6 28 20 20 16 10 8 10 7 14 4 3 5 4 4 8 6 2 9 2
2 105 88 82 85 67 84 76 71 120 124 87 81 65 64 101 74 132 119 115 116 129 98 97 125 139 130
4 12 12 55 22 9 12 19 43 33 31 15 7 6 17 12 24 <4 <4 7 <4 12 6 5 <4 9 <4
3 93 64 191 99 49 61 63 169 178 168 61 40 27 45 57 66 32 36 34 32 38 34 31 31 92 45
0.05 5 6 23 11 3 4 7 16 11 11 7 4 3 6 5 10 2 2 2 2 3 4 4 1 6 1
0.05 11 11 42 21 5 8 12 31 22 22 14 7 6 11 9 20 3 4 4 4 6 8 9 2 12 2
0.01 7 8 10 6 3 9 9 9 6 6 6 6 5 5 7 6 3 2 6 3 3 4 4 1 5 1
(except Sr) compared to the samples of the upper and intermediate lignite seams. Sr seems to display a relative
increase with depth. Especially, Ni and Cr show a distinguished increase in the samples of the upper lignite seams.
2506
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
Table 4 Major elements (wt%) of the ash samples from the Kardia lignite samples Samples
SiO2
Al2O3
Fe2O3(T)
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
A3 A5 A7 A9 A11 A13 A15 A17 A19 A21 A23 A26 A28 A30 A32 A34 A36 A38 A40 A42 A44 A46 A48 A50 A52 A54
21.79 29.99 44.66 31.60 27.12 26.75 19.80 46.69 43.23 44.74 32.50 26.96 26.06 35.15 13.85 38.46 5.60 4.85 9.63 9.52 7.84 25.15 5.67 22.07 33.17 6.21
10.39 15.23 20.95 15.51 14.82 13.50 10.99 21.11 21.61 20.55 13.07 14.73 17.50 18.44 7.56 17.05 3.69 2.48 5.66 4.93 3.95 13.59 4.08 10.45 15.48 4.22
6.28 11.73 9.34 11.23 8.56 8.86 18.92 11.54 4.60 5.02 11.60 6.72 7.92 10.13 7.68 16.25 3.84 2.35 5.19 4.18 3.33 7.16 4.04 7.14 5.23 3.41
0.07 0.03 0.04 0.10 0.02 0.04 0.12 0.05 0.02 0.02 0.02 0.07 0.02 0.04 0.06 0.12 0.05 0.04 0.05 0.05 0.04 0.03 0.03 0.02 0.02 0.02
3.09 4.98 3.60 4.13 8.16 6.16 4.42 3.85 3.97 3.86 4.15 5.26 8.15 6.04 3.65 4.04 4.70 2.89 5.36 5.37 3.83 8.06 6.48 9.10 5.62 6.12
47.06 30.15 10.57 31.11 36.08 38.75 41.64 8.50 16.40 15.70 31.90 38.60 34.62 24.28 54.80 18.06 67.30 66.36 65.71 64.01 65.47 38.95 67.40 41.82 30.42 64.92
0.24 0.23 0.23 0.19 0.27 0.20 0.21 0.27 1.30 1.11 0.28 0.20 0.15 0.20 0.18 0.23 0.10 0.10 0.12 0.14 0.11 0.25 0.16 0.32 1.32 0.25
0.67 0.92 1.34 0.88 0.74 0.66 0.49 1.18 1.85 1.66 0.92 0.57 0.59 1.01 0.42 0.99 0.14 0.10 0.17 0.14 0.20 0.81 0.14 0.75 1.26 0.26
0.50 0.65 0.83 0.58 0.62 0.59 0.42 0.92 0.84 0.90 0.63 0.46 0.52 0.88 0.33 0.87 0.14 0.11 0.26 0.21 0.18 0.55 0.14 0.56 0.53 0.14
0.28 0.24 0.33 0.53 0.23 0.24 0.71 0.32 0.41 0.40 0.21 0.42 0.45 0.27 0.33 0.33 0.29 0.16 0.18 0.29 0.21 0.32 0.30 0.49 0.65 0.24
8.91 4.46 7.56 3.50 3.45 3.44 1.78 4.80 5.07 6.20 3.96 5.60 2.99 4.00 9.96 3.26 13.02 19.44 7.49 11.51 13.35 3.88 11.65 6.02 6.44 14.21
Table 5 Trace elements (lg/g) of the ash samples from the Kardia lignite samples
Detection limit A3 A5 A7 A9 A11 A13 A15 A17 A19 A21 A23 A26 A28 A30 A32 A34 A36 A38 A40 A42 A44 A46 A48 A50 A52 A54
As
Cr
Cu
Ni
Zn
V
Co
Rb
Sr
Y
Zr
Ba
La
Ce
Nd
U
0.5 48 83 55 69 110 127 14 54 44 25 45 53 71 45 53 25 22 11 41 29 22 52 29 52 46 26
5 180 440 950 680 250 340 800 700 130 140 160 620 880 380 240 320 150 60 280 170 120 330 160 340 230 130
1 26 51 82 61 81 44 76 64 30 39 30 53 59 35 33 44 27 10 45 39 41 59 30 47 54 37
1 131 566 1380 813 517 1290 1120 975 110 113 202 819 891 313 293 260 125 65 262 153 107 494 252 412 367 246
1 19 22 131 32 5 47 33 82 29 38 36 26 71 36 7 27 <1 <1 5 <1 1 8 <1 36 12 <1
5 148 269 340 277 231 256 496 240 176 158 121 187 284 198 147 156 70 42 180 95 68 257 86 204 238 68
1 13 44 67 45 51 58 65 43 15 18 18 69 48 24 22 27 4 3 37 11 5 26 10 21 25 10
1 44 61 91 61 44 37 26 71 99 87 56 45 57 56 23 60 8 12 20 15 14 66 11 60 60 9
2 474 501 167 291 623 517 364 195 639 584 331 389 486 411 405 300 660 459 602 700 550 771 828 861 924 833
0.5 19 26 36 35 22 21 30 35 28 26 21 18 24 30 19 32 8 6 14 11 9 24 5 33 19 4
4 105 136 160 124 146 139 143 181 353 259 133 80 86 183 78 175 36 32 69 47 42 120 35 153 149 46
3 413 378 389 334 418 362 291 431 953 803 223 187 178 253 231 260 162 120 163 176 153 266 198 270 614 258
0.05 25 36 46 41 29 28 35 45 60 52 29 20 24 40 23 41 9 8 14 13 12 32 7 40 41 10
0.05 50 67 85 75 56 54 59 85 120 103 57 38 45 79 42 81 17 15 27 27 24 63 14 89 80 17
0.05 21 29 37 33 24 24 24 36 48 42 24 17 21 33 17 34 7 6 12 11 10 27 6 38 30 6
0.01 33 58 21 21 48 75 45 29 36 31 21 31 49 46 30 27 18 10 38 21 15 40 14 47 36 11
3.4. Chemical composition of ash Concerning the most important elements, the ash of the Kardia lignite belongs to C category and to the calcic mode
(ASTM C618-92), since it displays high Ca content [6,21,22]. Major elements appear considerably enriched in the ash samples compared to the initial lignite samples (Table 4).
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
Equally to the lignite samples, CaO, SiO2 and Al2O3 are the dominant oxides compared to the rest oxides in ash samples, while Fe2O3 and MgO display a relative increase. The most abundant oxide is CaO ranging between 8.50% and 67.40% and having a value of more than 30% in the majority of the samples. This value displays an increase in the samples of the deeper lignite seams. SiO2 appears with values 4.85–46.69% while Al2O3 with values 2.48– 21.61%. Both of them increase in the samples of the upper lignite seams. Concerning the trace elements, the most abundant is Sr with a mean value of 533 lg/g (Table 5). Increased values are observed (especially for some samples) for Cr with a mean value of 353 lg/g, Ni with 472 lg/g, V with 192 lg/g, Zr with 123 lg/g and Ba with a mean value of 326 lg/g. The mean values of As, Cu, Zn, Co, Rb, Y, La, Ce, Nd and U range between 21 and 56 lg/g. Sc, Pb, Ga, Nb, Mo and Th gave concentrations with mean values of 10–18 lg/g, while Au, Br, Sb, S, Ag, Be, Ge, Sn, Cs, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Hf, Ta, W, Tl, and Bi display concentrations <10 lg/g, being below detection limits in some samples. Ir, Se, Cd and In were not detected. Some trace elements display decreasing concentrations in the samples derived from the deeper lignite seams. This variation with depth is more obvious for Ni. The trace elements Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. 4. Conclusions The 26 lignite samples collected perpendicular to the bedding of the Kardia lignite field, display high percentages of moisture (9.11–25.96%) and ash content (13.26–30.07%) with CO2 ranging from 1.08% to 15.98%. CaO, SiO2 and Al2O3 are the dominant oxides among the major elements. No systematic change of the major element concentrations with depth was observed, however, a relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper samples. Concerning the trace elements of the lignite samples, Ni was found to be the most abundant while Sr, Cr, Ba and V follow. The rest trace elements contribute with low values with some of them being below their detection limit. The lignite samples of the deeper seams contain lower concentrations of all the trace elements (except Sr) compared to the samples of the upper and intermediate lignite seams. Sr seems to display a relative increase with depth while Ni and Cr show a distinguished increase in the samples of the upper lignite seams. The chemical composition of the ashing products of the 26 lignite samples classify them in the C category and to the calcic mode. Major elements appear considerably enriched in the ash samples compared to the initial lignite samples with CaO, SiO2 and Al2O3 being the dominant oxides. CaO is the most abundant oxide displaying an increase in the samples of the deeper lignite seams while SiO2 and Al2O3 increase in the ash samples of the upper lignite
2507
seams. Concerning the trace elements, Sr is the most abundant with Cr, Ni, V, Zr and Ba following. Some trace elements display decreasing concentrations in the samples derived from the deeper lignite seams. This variation with depth is more obvious for Ni. The trace elements Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. Acknowledgement The cost of the chemical analyses was financed by the ‘ARHIMIDES II’ project – Support of research groups in ecology and environment. References [1] Georgakopoulos A, Kassoli-Fournaraki A, Filippidis A. Morphology, mineralogy and chemistry of the fly ash form the Ptolemais lignite basin (Greece) in relation to some problems in human health. Trends Mineral 1992;1:301–5. [2] Kassoli-Fournaraki A, Georgakopoulos A, Michailidis K, Filippidis A. Morphology, mineralogy and chemistry of the respirable-size (<5 lm), fly-ash fraction from the Main and Northern lignite fields in Ptolemais, Macedonia, Greece. In: Fenoll Hach-Ali P, Torres-Ruiz J, Gervilla F, editors. Current Research in Geology Applied to Ore deposits. Granada: La Gionconda; 1993. p. 727–30. [3] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A. Morphology and trace element contents of the fly ash from Main and Northern lignite fields, Ptolemais, Greece. Fuel 1994;73:1802–4. [4] Georgakopoulos A, Fernandez-Turiel JL, Filippidis A, Llorens JF, Kassoli-Fournaraki A, Querol X, et al. Trace element contents of the Lava xylite/lignite and Ptolemais lignite deposits, Macedonia County, Greece. In: Pajares JA, and Tascon JMD, editors. Coal science and technology 24, Coal Science, 1995. p. 163–6. [5] Filippidis A, Kassoli-Fournaraki A, Georgakopoulos A. Mineralogy, major and trace element contents of fly ashes from the Electric Power Stations of the Ptolemais-Amynteo Lignite Center. In: Proceedings of the national symposium on fly ash uses in constructions, Kozani, Tome B, 1997. p. 159–68. [6] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, Iordanidis A, Fernandez-Turiel JL, Llorens JF, et al. Environmentally important elements in fly ashes and their leachates of the power stations of Greece. Energy Source 2002;4(1):83–91. [7] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, FernandezTuriel JL, Llorens JF, Mousty F. Leachability of major and trace elements of fly ash from Ptolemais power station, Northern Greece. Energy Source 2002;24(2):103–13. [8] Tsikritzis IL, Ganatsios SS, Duliu OG, Sawidis TD. Heavy metals distribution in some lichens, mosses and trees in the vicinity of lignite power plants from Western Macedonia, Greece. J Trace Microprobe Tech 2002;20(3):395–413. [9] Pavlides S. Neotectonic evolution of the Florina-Vegoritis-Ptolemais basin (W. Macedonia, Greece). Aristotle University of Thessaloniki, PhD Thesis 1985; 265 pp. [10] Koufos G, Pavlides B. Correlation between the continental deposits of the lower Axios valley and Ptolemais basin. Bull Geol Soc Greece 1988;20:9–19. [11] Gluskoter HJ, Ruch RR, Miller WG, Cahill RA, Dreher GB, Kuhn JK. Trace elements in coal: Occurrence and distribution, III. State Geol Surv Circ 1977;499:154 pp. [12] Valkonic V. Trace Elements in Coal, vol. 1. Boca Raton, Fla: CRC Press; 1983. 210 pp. [13] Eskenazy G. Rare elements in a sampled coal from the Pirin deposit. Bulgaria Int J Coal Geol 1987;7:301–14.
2508
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
[14] Swaine DJ. Trace Elements in Coal. London: Butterworth; 1990. 278 pp. [15] Finkelman RB. Trace and minor elements in coal. In: Engel MH, Macko SA, editors. Organic Geochemistry. New York: Plenum Press; 1993. p. 593–607. [16] Finkelman RB. Models of occurrence of potentially hazardous elements in coal: levels of confidence. Fuel Process Technol 1994;39:21–34. [17] Goodarzi F. Trace element concentrations in Canadian coals, II. Byron Creek collieries, British Columbia. Fuel 1987;66:250–4. [18] Goodarzi F. Concentration of elements in lacustrine coals from zone A, Hat Creek deposit No. 1, British Columbia, Canada. Int J Coal Geol 1987;8:247–68.
[19] Goodarzi F. Comparison of elemental distribution in fresh and weathered samples of selected coals in Jurassic-Cretaceous Kootenay Group, British Columbia. Chem Geol 1987;63:21–8. [20] Goodarzi F, Van Der Flier-Keller E. Geological controls and constraints on the concentration of elements in western Canadiam coals. Geol Surv Can 1992;39889:389–412. [21] Suloway JJ, Roy WR, Skelly TM, Dickerson TR, Schuller RM, Griffin RA. Chemical and toxicological properties of coal fly ash. Environ Geol Notes 1983;105:1–70. [22] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, Iordanidis A, Fernandez-Turiel JL, Llorens JF, et al. Leachability of major and trace elements of fly ash form Ptolemais station, Northern Greece. Energy Source 2002;24(2):103–13.
Chemical investigation of lignite samples and their ashing products from Kardia lignite field of Ptolemais, Northern Greece K. Adamidou a, A. Kassoli-Fournaraki b,*, A. Filippidis b, K. Christanis c, E. Amanatidou d, L. Tsikritzis d, O. Patrikaki a b
a Environmental Centre of Kozani, 1st Km Ptolemais-Kozani, 50200 Ptolemais, Greece Department of Mineralogy–Petrology–Economic Geology, School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece c Department of Geology, Section of Earth Materials, University of Patras, 26500 Rio-Patras, Greece d Technological Educational Institute of Western, Macedonia, Koila, Kozani 50100, Greece
Received 19 January 2007; received in revised form 5 February 2007; accepted 6 February 2007 Available online 16 March 2007
Abstract Twenty-six lignite samples were collected from the Kardia lignite field (Ptolemais, Greece). Ash content, moisture and CO2 were determined. The lignite samples were heated at 900 °C producing 26 ash samples. The chemical composition (major and trace elements) both of the lignite samples and ash products was determined using INAA, ICP-OES and ICP-MS. CaO, SiO2 and Al2O3 are the dominant oxides both in lignite and ash samples. A relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper lignite samples. Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. Sr displays a relative increase while Ni and Cr decrease with depth in the lignite samples. In the ash samples, Ni shows the most obvious decrease with depth. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Ptolemais; Lignite; Ash content; Heating procedure; Greece
1. Introduction More than 73% of the electrical power requirements of Greece are generated in coal-fired power plants which combust lignite to produce power generation. The Greek power plants consume more than 65 million tons of lignite per year producing about 13 million tons of total ash. The main coal mining area in Greece is the Lignite Centre of Western Macedonia, in the area of Ptolemais–Florina, where four big mines (Southern, Kardia, Main and Amyntaion lignite fields) of lignite exploitation are operating (total power 4438 MW). The lignite production in 2003 reached 54.58 million tons in the Lignite Centre of Western
*
Corresponding author. Tel.: +30 2310998457; fax: +30 2310998463. E-mail address: [email protected] (A. Kassoli-Fournaraki).
0016-2361/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.02.008
Macedonia. The mean lower calorific value of the Ptolemais lignite reaches 1300 kcal/kg. The exploitation and combustion of lignite in the above mentioned coal-fired power plants are of environmental concern for the broader area of Kozani–Ptolemais–Florina. Hence, the chemical determination of the lignite used and its ash contributes to the control of the environmental quality in the area. Lignite combustion in Greece and environmental impact has been the subject of several studies (e.g. [1–8]). This study concerns the investigation of the chemical composition (major and trace elements) of lignite and its ashing products from Kardia lignite field (Sector 6). This lignite field is active since 1990 and constitutes the main supplier for the Kardia power plant (power 1200 MW), having an annual production of more than 21 million tons. The lignite of the Kardia lignite field has low energy fuel with upper calorific value 4094 kcal kg 1 and lower calorific value 1469 kcal kg 1.
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
1.1. Geological features The Kardia lignite field is situated approximately in the central part of the Neogene lignite basin of Ptolemais (Fig. 1). The sediments of the basin are divided into the lower (Upper Miocene to Lower Pliocene) formation, the Pliocene middle formation and the Quaternary upper formation (e.g. [9,10]). The Pliocene middle formation contains the upper and lower lignite seams. The lignite seams alternate with clays, marls, sandy marls and sands. The thickness both of the lignite seams and the intermediate steriles is variable. In this study, all seams were sampled for chemical investigation. 2. Materials and methods 2.1. Sampling For the purposes of this investigation 26 samples of lignite were used. The sampling was carried out during
2503
November and December 2005 in Kardia (Sector-6) lignite mine. The samples were collected according to ASTM D 4596 standards perpendicular to the bedding and covering the whole stratigraphic series. The sampling column was 126.5 m long. The thickness of the lignite seams ranges from 0.4 m to 4.5 m. 2.2. Analytical techniques The samples were homogenized, dried in room temperature for three days and crushed to <5 mm grain size. Afterwards, the samples underwent dry sieving to pass 2 mm sieve. A quantity of 300–500 g was taken from the treated material of each sample. The ash content, total moisture and CO2 were determined for the 26 lignite samples using a LECO TGA 701 apparatus for ash and moisture determination. Each sample was heated in 106 °C till stabilization of its weight, for the determination of total moisture, and in 550 °C for the determination of CO2. Heating in 850 °C followed for the ash content determination.
Fig. 1. Simplified geological map of Ptolemais area.
2504
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
A quantity of each lignite sample was ground and 0.2 g of it were heated for ash production. Heating took place in laboratory furnaces, in gradually increasing temperature up to 900 °C. The ashing procedure for each sample lasted 25–40 h of continuous heating, according to the quantity of each lignite sample. The heating procedure was repeated till the production of 5 g of ash from each sample. Both the 26 lignite samples and the produced 26 ash samples were chemically analyzed for their major and trace elements, using INAA, ICP-OES and ICP-MS analytical techniques at the Actlabs – Activation Laboratories Ltd of Canada. 3. Results and discussion 3.1. General features It is well known that coals contain organic and inorganic constituents, hence, the related trace element concentrations may vary considerably. This relation has been discussed in various previous works (e.g. [3,11–16]). The elemental composition (major and trace elements) of a coal deposit is related to many things: the nature of the plant communities, the environment of deposition, the age and rank of the coal, the activity of ground water, the weathering of coal, the geological setting, the composition of the country rocks and mineralizations, as well as their weathering and transportation conditions [11,14,15, 17–20]. The Neogene sediments which host the lignite beds in the Kardia lignite field, are of lacustrine origin while the superimposed Quaternary sediments derive from the erosion of the surrounding limestones and metamorphic rocks. 3.2. Ash content, moisture and CO2 The lignite of Kardia lignite field is characterized by low energy fuel and high percentage of moisture and ash (Table 1). The ash content ranges considerably, depending on the lignite quality as well as on the moisture which displays differences even for lignites of the same quality. A characteristic feature of the Kardia lignite is the high content in carbonates which decompose during combustion releasing CO2. From the results of Table 1, it is observed that the ash content ranges between 13.26% and 30.07%. No relation of ash content with depth was noticed. Total moisture ranges between 9.11% and 25.96% and CO2 between 1.08% and 15.98%. 3.3. Chemical composition of lignite The chemical composition of the lignite samples is presented in Tables 2 and 3. Ten major elements and 51 trace elements (16 of which are presented in Table 3) were measured. Among the main oxides, CaO, SiO2 and Al2O3 appear with higher concentrations due to calcite, quartz and feld-
Table 1 Total moisture, ash content and CO2 of the Kardia lignite samples Sample
Lignite seam no.
Seam thickness (m)
Moisture (%)
Ash (%)
CO2 (%)
L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
2.5 0.6 1.4 3.0 0.7 1.0 0.7 0.6 0.8 0.5 0.6 2.5 0.7 2.5 1.9 1.9 1.4 4.5 0.7 3.0 1.4 3.0 1.7 2.2 1.4 0.4
11.27 13.74 14.9 14.7 12.24 12.03 13.34 13.7 13.05 21.46 14.77 13.1 16.73 10.49 12.39 12.18 9.11 11.78 11.66 11.38 12.85 12.64 12.79 13.16 25.96 12.83
24.6 21.61 19.61 16.31 18.65 27.17 27.6 25.4 24.73 29.21 25.32 17.99 17.12 29.36 27.33 23.46 30.07 22.21 21.26 23.5 14.65 13.26 13.48 16.74 13.29 18.13
6.46 1.36 1.74 1.19 2.57 3.59 1.08 1.31 1.19 2.57 4.44 2.15 1.16 10.01 2.29 6.06 15.98 8.38 8.22 12.28 3.38 2.13 2.33 6.52 2.05 7.56
Ash and CO2 on dry basis.
spars which constitute the main mineral phases of the lignite samples. The rest oxides display low concentrations. CaO ranges between 2.89% and 19.04% with the sample L38 displaying the highest value. SiO2 ranges between 0.91% and 21.95%, while Al2O3 shows values of 0.54–10.17%. Loss on ignition shows high values, as well. A relative increase of Fe2O3 is observed only for some samples. No systematic change of the major element concentrations with depth is observed, however, a relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper samples. Among the trace elements, the most abundant is Ni with an average concentration of 127 lg/g. Sr, Cr, Ba and V follow with average values of 99 lg/g, 77 lg/g, 71 lg/g and 40 lg/g, correspondingly. The trace elements As, Br, Cu, Zn, Pb, Co, Rb, Zr, La, Ce and U display average mean values between 5 lg/g and 14 lg/g with the concentrations of Pb, Co and Zr being below detection limits in some samples. Determinations were also made for Sc, Sb, S, Ga, Y, Nb, Cs, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Tl and Th, all of which gave values <5lg/g and in some samples were not detectable, thus they were not included in Table 3. Finally, the trace elements Au, Ir, Se, Cd, Ag, Be, Ge, Mo, In, Sn and Bi gave all concentrations below detection limits. Correlation of the trace element concentrations with depth showed that the lignite samples of the deeper seams contain lower concentrations of all the trace elements
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
2505
Table 2 Major elements (wt%) of the Kardia lignite samples Samples
SiO2
Al2O3
Fe2O3(T)
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
4.86 4.79 21.95 8.66 3.08 4.46 3.75 17.67 8.37 9.81 8.45 5.33 3.47 5.71 3.46 9.59 1.27 1.44 2.10 1.73 1.95 3.19 2.37 0.91 4.4 1.2
2.23 2.29 10.17 4.15 1.34 1.96 1.99 7.88 4.03 4.35 3.32 2.77 1.93 2.66 1.76 4.49 0.73 0.70 1.14 0.75 0.97 1.61 1.06 0.54 2.16 0.59
1.41 1.79 4.54 2.95 0.89 1.36 3.56 4.24 0.90 1.09 3.06 1.35 0.97 1.70 1.86 4.21 0.82 0.70 1.12 0.71 0.83 0.90 0.79 0.61 0.84 0.54
0.02 0.01 0.02 0.02 0.00 0.01 0.02 0.02 0.00 0.00 0.00 0.01 0.00 0.01 0.01 0.03 0.01 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00
0.67 0.76 1.80 1.16 0.64 0.82 0.85 1.42 0.76 0.84 0.97 0.98 0.89 0.75 0.86 1.04 0.96 0.81 1.04 0.80 0.82 0.87 0.87 0.85 0.78 0.86
9.59 4.66 4.88 8.29 3.33 5.73 7.47 2.89 3.39 3.63 7.68 8.28 3.84 3.53 13.22 4.91 14.45 19.04 11.93 9.41 15.52 4.62 4.36 9.41 4.35 8.65
0.06 0.06 0.12 0.07 0.07 0.06 0.07 0.13 0.25 0.24 0.12 0.05 0.04 0.06 0.04 0.05 0.03 0.04 0.06 0.08 0.07 0.04 0.04 0.04 0.20 0.09
0.20 0.10 0.69 0.18 0.17 0.17 0.13 0.45 0.29 0.39 0.24 0.09 0.09 0.20 0.16 0.27 <0.01 0.07 0.14 0.06 <0.01 0.13 0.05 0.03 0.24 0.03
0.11 0.10 0.40 0.16 0.06 0.09 0.09 0.34 0.16 0.19 0.15 0.09 0.06 0.13 0.08 0.21 0.03 0.03 0.05 0.03 0.04 0.07 0.05 0.02 0.08 0.02
0.08 0.05 0.18 0.17 0.04 0.05 0.17 0.13 0.08 0.09 0.05 0.09 0.06 0.04 0.10 0.09 0.07 0.05 0.04 0.05 0.06 0.05 0.06 0.05 0.11 0.07
79.25 84.18 54.20 72.69 88.92 83.93 80.42 63.59 81.19 78.91 74.70 80.23 87.28 84.32 76.93 74.86 81.60 75.62 81.02 85.49 78.78 87.07 88.71 86.11 85.25 86.69
Table 3 Trace elements (lg/g) of the Kardia lignite samples
Detection limit L3 L5 L7 L9 L11 L13 L15 L17 L19 L21 L23 L26 L28 L30 L32 L34 L36 L38 L40 L42 L44 L46 L48 L50 L52 L54
As
Br
Cr
Cu
Ni
Zn
Pb
V
Co
Rb
Sr
Zr
Ba
La
Ce
U
0.5 11 16 27 21 14 20 34 20 11 6 10 11 10 7 14 7 5 5 8 5 5 7 7 4 9 5
0.5 8 9 10 9 9 10 13 9 7 7 8 12 14 11 9 12 8 7 7 8 8 11 10 9 12 8
5 39 61 423 189 25 44 162 243 26 24 38 117 99 60 54 77 28 16 53 29 22 38 40 25 40 21
1 6 7 38 16 4 6 11 25 7 9 7 11 9 8 7 14 4 3 7 3 3 7 11 4 9 3
1 34 110 664 266 75 229 294 396 28 30 57 210 147 70 95 85 34 24 65 32 32 73 65 49 78 52
1 7 14 64 24 8 11 13 39 15 18 12 14 20 11 8 22 3 1 5 6 3 8 10 3 9 1
5 6 5 22 9 <5 5 6 19 19 15 5 <5 7 6 6 8 <5 <5 <5 <5 <5 <5 <5 <5 9 <5
5 33 44 170 79 22 36 114 87 34 36 29 36 38 28 35 38 13 8 32 14 16 29 23 11 36 11
1 2 7 32 13 5 8 14 16 3 4 4 14 6 4 5 6 <1 <1 7 2 1 3 2 1 4 1
1 10 12 48 20 8 10 6 28 20 20 16 10 8 10 7 14 4 3 5 4 4 8 6 2 9 2
2 105 88 82 85 67 84 76 71 120 124 87 81 65 64 101 74 132 119 115 116 129 98 97 125 139 130
4 12 12 55 22 9 12 19 43 33 31 15 7 6 17 12 24 <4 <4 7 <4 12 6 5 <4 9 <4
3 93 64 191 99 49 61 63 169 178 168 61 40 27 45 57 66 32 36 34 32 38 34 31 31 92 45
0.05 5 6 23 11 3 4 7 16 11 11 7 4 3 6 5 10 2 2 2 2 3 4 4 1 6 1
0.05 11 11 42 21 5 8 12 31 22 22 14 7 6 11 9 20 3 4 4 4 6 8 9 2 12 2
0.01 7 8 10 6 3 9 9 9 6 6 6 6 5 5 7 6 3 2 6 3 3 4 4 1 5 1
(except Sr) compared to the samples of the upper and intermediate lignite seams. Sr seems to display a relative
increase with depth. Especially, Ni and Cr show a distinguished increase in the samples of the upper lignite seams.
2506
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
Table 4 Major elements (wt%) of the ash samples from the Kardia lignite samples Samples
SiO2
Al2O3
Fe2O3(T)
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
A3 A5 A7 A9 A11 A13 A15 A17 A19 A21 A23 A26 A28 A30 A32 A34 A36 A38 A40 A42 A44 A46 A48 A50 A52 A54
21.79 29.99 44.66 31.60 27.12 26.75 19.80 46.69 43.23 44.74 32.50 26.96 26.06 35.15 13.85 38.46 5.60 4.85 9.63 9.52 7.84 25.15 5.67 22.07 33.17 6.21
10.39 15.23 20.95 15.51 14.82 13.50 10.99 21.11 21.61 20.55 13.07 14.73 17.50 18.44 7.56 17.05 3.69 2.48 5.66 4.93 3.95 13.59 4.08 10.45 15.48 4.22
6.28 11.73 9.34 11.23 8.56 8.86 18.92 11.54 4.60 5.02 11.60 6.72 7.92 10.13 7.68 16.25 3.84 2.35 5.19 4.18 3.33 7.16 4.04 7.14 5.23 3.41
0.07 0.03 0.04 0.10 0.02 0.04 0.12 0.05 0.02 0.02 0.02 0.07 0.02 0.04 0.06 0.12 0.05 0.04 0.05 0.05 0.04 0.03 0.03 0.02 0.02 0.02
3.09 4.98 3.60 4.13 8.16 6.16 4.42 3.85 3.97 3.86 4.15 5.26 8.15 6.04 3.65 4.04 4.70 2.89 5.36 5.37 3.83 8.06 6.48 9.10 5.62 6.12
47.06 30.15 10.57 31.11 36.08 38.75 41.64 8.50 16.40 15.70 31.90 38.60 34.62 24.28 54.80 18.06 67.30 66.36 65.71 64.01 65.47 38.95 67.40 41.82 30.42 64.92
0.24 0.23 0.23 0.19 0.27 0.20 0.21 0.27 1.30 1.11 0.28 0.20 0.15 0.20 0.18 0.23 0.10 0.10 0.12 0.14 0.11 0.25 0.16 0.32 1.32 0.25
0.67 0.92 1.34 0.88 0.74 0.66 0.49 1.18 1.85 1.66 0.92 0.57 0.59 1.01 0.42 0.99 0.14 0.10 0.17 0.14 0.20 0.81 0.14 0.75 1.26 0.26
0.50 0.65 0.83 0.58 0.62 0.59 0.42 0.92 0.84 0.90 0.63 0.46 0.52 0.88 0.33 0.87 0.14 0.11 0.26 0.21 0.18 0.55 0.14 0.56 0.53 0.14
0.28 0.24 0.33 0.53 0.23 0.24 0.71 0.32 0.41 0.40 0.21 0.42 0.45 0.27 0.33 0.33 0.29 0.16 0.18 0.29 0.21 0.32 0.30 0.49 0.65 0.24
8.91 4.46 7.56 3.50 3.45 3.44 1.78 4.80 5.07 6.20 3.96 5.60 2.99 4.00 9.96 3.26 13.02 19.44 7.49 11.51 13.35 3.88 11.65 6.02 6.44 14.21
Table 5 Trace elements (lg/g) of the ash samples from the Kardia lignite samples
Detection limit A3 A5 A7 A9 A11 A13 A15 A17 A19 A21 A23 A26 A28 A30 A32 A34 A36 A38 A40 A42 A44 A46 A48 A50 A52 A54
As
Cr
Cu
Ni
Zn
V
Co
Rb
Sr
Y
Zr
Ba
La
Ce
Nd
U
0.5 48 83 55 69 110 127 14 54 44 25 45 53 71 45 53 25 22 11 41 29 22 52 29 52 46 26
5 180 440 950 680 250 340 800 700 130 140 160 620 880 380 240 320 150 60 280 170 120 330 160 340 230 130
1 26 51 82 61 81 44 76 64 30 39 30 53 59 35 33 44 27 10 45 39 41 59 30 47 54 37
1 131 566 1380 813 517 1290 1120 975 110 113 202 819 891 313 293 260 125 65 262 153 107 494 252 412 367 246
1 19 22 131 32 5 47 33 82 29 38 36 26 71 36 7 27 <1 <1 5 <1 1 8 <1 36 12 <1
5 148 269 340 277 231 256 496 240 176 158 121 187 284 198 147 156 70 42 180 95 68 257 86 204 238 68
1 13 44 67 45 51 58 65 43 15 18 18 69 48 24 22 27 4 3 37 11 5 26 10 21 25 10
1 44 61 91 61 44 37 26 71 99 87 56 45 57 56 23 60 8 12 20 15 14 66 11 60 60 9
2 474 501 167 291 623 517 364 195 639 584 331 389 486 411 405 300 660 459 602 700 550 771 828 861 924 833
0.5 19 26 36 35 22 21 30 35 28 26 21 18 24 30 19 32 8 6 14 11 9 24 5 33 19 4
4 105 136 160 124 146 139 143 181 353 259 133 80 86 183 78 175 36 32 69 47 42 120 35 153 149 46
3 413 378 389 334 418 362 291 431 953 803 223 187 178 253 231 260 162 120 163 176 153 266 198 270 614 258
0.05 25 36 46 41 29 28 35 45 60 52 29 20 24 40 23 41 9 8 14 13 12 32 7 40 41 10
0.05 50 67 85 75 56 54 59 85 120 103 57 38 45 79 42 81 17 15 27 27 24 63 14 89 80 17
0.05 21 29 37 33 24 24 24 36 48 42 24 17 21 33 17 34 7 6 12 11 10 27 6 38 30 6
0.01 33 58 21 21 48 75 45 29 36 31 21 31 49 46 30 27 18 10 38 21 15 40 14 47 36 11
3.4. Chemical composition of ash Concerning the most important elements, the ash of the Kardia lignite belongs to C category and to the calcic mode
(ASTM C618-92), since it displays high Ca content [6,21,22]. Major elements appear considerably enriched in the ash samples compared to the initial lignite samples (Table 4).
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
Equally to the lignite samples, CaO, SiO2 and Al2O3 are the dominant oxides compared to the rest oxides in ash samples, while Fe2O3 and MgO display a relative increase. The most abundant oxide is CaO ranging between 8.50% and 67.40% and having a value of more than 30% in the majority of the samples. This value displays an increase in the samples of the deeper lignite seams. SiO2 appears with values 4.85–46.69% while Al2O3 with values 2.48– 21.61%. Both of them increase in the samples of the upper lignite seams. Concerning the trace elements, the most abundant is Sr with a mean value of 533 lg/g (Table 5). Increased values are observed (especially for some samples) for Cr with a mean value of 353 lg/g, Ni with 472 lg/g, V with 192 lg/g, Zr with 123 lg/g and Ba with a mean value of 326 lg/g. The mean values of As, Cu, Zn, Co, Rb, Y, La, Ce, Nd and U range between 21 and 56 lg/g. Sc, Pb, Ga, Nb, Mo and Th gave concentrations with mean values of 10–18 lg/g, while Au, Br, Sb, S, Ag, Be, Ge, Sn, Cs, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Hf, Ta, W, Tl, and Bi display concentrations <10 lg/g, being below detection limits in some samples. Ir, Se, Cd and In were not detected. Some trace elements display decreasing concentrations in the samples derived from the deeper lignite seams. This variation with depth is more obvious for Ni. The trace elements Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. 4. Conclusions The 26 lignite samples collected perpendicular to the bedding of the Kardia lignite field, display high percentages of moisture (9.11–25.96%) and ash content (13.26–30.07%) with CO2 ranging from 1.08% to 15.98%. CaO, SiO2 and Al2O3 are the dominant oxides among the major elements. No systematic change of the major element concentrations with depth was observed, however, a relative decrease of SiO2 and Al2O3 as well as an increase of CaO was noticed in the deeper samples. Concerning the trace elements of the lignite samples, Ni was found to be the most abundant while Sr, Cr, Ba and V follow. The rest trace elements contribute with low values with some of them being below their detection limit. The lignite samples of the deeper seams contain lower concentrations of all the trace elements (except Sr) compared to the samples of the upper and intermediate lignite seams. Sr seems to display a relative increase with depth while Ni and Cr show a distinguished increase in the samples of the upper lignite seams. The chemical composition of the ashing products of the 26 lignite samples classify them in the C category and to the calcic mode. Major elements appear considerably enriched in the ash samples compared to the initial lignite samples with CaO, SiO2 and Al2O3 being the dominant oxides. CaO is the most abundant oxide displaying an increase in the samples of the deeper lignite seams while SiO2 and Al2O3 increase in the ash samples of the upper lignite
2507
seams. Concerning the trace elements, Sr is the most abundant with Cr, Ni, V, Zr and Ba following. Some trace elements display decreasing concentrations in the samples derived from the deeper lignite seams. This variation with depth is more obvious for Ni. The trace elements Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. Acknowledgement The cost of the chemical analyses was financed by the ‘ARHIMIDES II’ project – Support of research groups in ecology and environment. References [1] Georgakopoulos A, Kassoli-Fournaraki A, Filippidis A. Morphology, mineralogy and chemistry of the fly ash form the Ptolemais lignite basin (Greece) in relation to some problems in human health. Trends Mineral 1992;1:301–5. [2] Kassoli-Fournaraki A, Georgakopoulos A, Michailidis K, Filippidis A. Morphology, mineralogy and chemistry of the respirable-size (<5 lm), fly-ash fraction from the Main and Northern lignite fields in Ptolemais, Macedonia, Greece. In: Fenoll Hach-Ali P, Torres-Ruiz J, Gervilla F, editors. Current Research in Geology Applied to Ore deposits. Granada: La Gionconda; 1993. p. 727–30. [3] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A. Morphology and trace element contents of the fly ash from Main and Northern lignite fields, Ptolemais, Greece. Fuel 1994;73:1802–4. [4] Georgakopoulos A, Fernandez-Turiel JL, Filippidis A, Llorens JF, Kassoli-Fournaraki A, Querol X, et al. Trace element contents of the Lava xylite/lignite and Ptolemais lignite deposits, Macedonia County, Greece. In: Pajares JA, and Tascon JMD, editors. Coal science and technology 24, Coal Science, 1995. p. 163–6. [5] Filippidis A, Kassoli-Fournaraki A, Georgakopoulos A. Mineralogy, major and trace element contents of fly ashes from the Electric Power Stations of the Ptolemais-Amynteo Lignite Center. In: Proceedings of the national symposium on fly ash uses in constructions, Kozani, Tome B, 1997. p. 159–68. [6] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, Iordanidis A, Fernandez-Turiel JL, Llorens JF, et al. Environmentally important elements in fly ashes and their leachates of the power stations of Greece. Energy Source 2002;4(1):83–91. [7] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, FernandezTuriel JL, Llorens JF, Mousty F. Leachability of major and trace elements of fly ash from Ptolemais power station, Northern Greece. Energy Source 2002;24(2):103–13. [8] Tsikritzis IL, Ganatsios SS, Duliu OG, Sawidis TD. Heavy metals distribution in some lichens, mosses and trees in the vicinity of lignite power plants from Western Macedonia, Greece. J Trace Microprobe Tech 2002;20(3):395–413. [9] Pavlides S. Neotectonic evolution of the Florina-Vegoritis-Ptolemais basin (W. Macedonia, Greece). Aristotle University of Thessaloniki, PhD Thesis 1985; 265 pp. [10] Koufos G, Pavlides B. Correlation between the continental deposits of the lower Axios valley and Ptolemais basin. Bull Geol Soc Greece 1988;20:9–19. [11] Gluskoter HJ, Ruch RR, Miller WG, Cahill RA, Dreher GB, Kuhn JK. Trace elements in coal: Occurrence and distribution, III. State Geol Surv Circ 1977;499:154 pp. [12] Valkonic V. Trace Elements in Coal, vol. 1. Boca Raton, Fla: CRC Press; 1983. 210 pp. [13] Eskenazy G. Rare elements in a sampled coal from the Pirin deposit. Bulgaria Int J Coal Geol 1987;7:301–14.
2508
K. Adamidou et al. / Fuel 86 (2007) 2502–2508
[14] Swaine DJ. Trace Elements in Coal. London: Butterworth; 1990. 278 pp. [15] Finkelman RB. Trace and minor elements in coal. In: Engel MH, Macko SA, editors. Organic Geochemistry. New York: Plenum Press; 1993. p. 593–607. [16] Finkelman RB. Models of occurrence of potentially hazardous elements in coal: levels of confidence. Fuel Process Technol 1994;39:21–34. [17] Goodarzi F. Trace element concentrations in Canadian coals, II. Byron Creek collieries, British Columbia. Fuel 1987;66:250–4. [18] Goodarzi F. Concentration of elements in lacustrine coals from zone A, Hat Creek deposit No. 1, British Columbia, Canada. Int J Coal Geol 1987;8:247–68.
[19] Goodarzi F. Comparison of elemental distribution in fresh and weathered samples of selected coals in Jurassic-Cretaceous Kootenay Group, British Columbia. Chem Geol 1987;63:21–8. [20] Goodarzi F, Van Der Flier-Keller E. Geological controls and constraints on the concentration of elements in western Canadiam coals. Geol Surv Can 1992;39889:389–412. [21] Suloway JJ, Roy WR, Skelly TM, Dickerson TR, Schuller RM, Griffin RA. Chemical and toxicological properties of coal fly ash. Environ Geol Notes 1983;105:1–70. [22] Georgakopoulos A, Filippidis A, Kassoli-Fournaraki A, Iordanidis A, Fernandez-Turiel JL, Llorens JF, et al. Leachability of major and trace elements of fly ash form Ptolemais station, Northern Greece. Energy Source 2002;24(2):103–13.