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Energy & Fuels 2005, 19, 230-239
Quality Characteristics of Greek Brown Coals and Their Relation to the Applied Exploitation and Utilization Methods C. Papanicolaou,† M. Galetakis,*,‡ and A. E. Foscolos‡ Institute of Geology and Mineral Exploration, Messoghion 70, Athens 11527, Greece, and Department of Mineral Resources Engineering, Technical University of Crete, AkrotirisHania 73 100, Greece Received October 6, 2003. Revised Manuscript Received September 21, 2004
Brown coal exploitation in Greece is of primary interest because it is an abundant domestic energy resource that contributes more than 70% in total electricity production. Greek brown coals present challenging and diverse technological characteristics, which should be studied to design and manage efficiently the mining, as well as, the operation of nearby power stations. The present study focuses on the organic and inorganic properties, as well as the mineralogy of the most-prominent Greek coal basins and their importance to mine planning, as well as to power station design and a productive working operation.
Introduction Brown coals in Greece are located in 68 coal basins of various sizes.1 The major coal basins that supply feedcoals (and will supply feedcoals for the next 50-60 years) are presented in Figure 1.2 Coal exploitation in Greece has increased drastically over the last 50 years, from 900 thousand tons per year to over 72 million tons per year. The progress made in the last 10 years is presented in Figure 2. Mineable coal deposits amount to 4.6 billion tons and are exclusively exploited by the Public Power Corporation of Greece S. A. for power generation, to satisfy ∼68% of Greece’s power needs. In 2003, to supply a new 365 MW power plant, production was increased to 72 million tons, using 2.5 million tons of brown coal. This output ranks Greece as one of the largest brown coal producers in the world and places it second in the use of lignite for power generation.3 Continuous surface mining methods are mainly used for the exploitation of lignite deposits. The applied method uses high-capacity bucket wheel excavators, conveyors belts, and stackers. Also, conventional mining equipment (including trucks, front-end loaders, electric rope and hydraulic shovels, and dozers) are used for specific mining operations. These large-scale mining operations have been selected to achieve the required production and cost targets. Almost all of the output is burned in power stations, which are all, more or less, * Author to whom correspondence should be addressed. Fax: +302821069554. E-mail address:
[email protected]. † Institute of Geology and Mineral Exploration. ‡ Technical University of Crete. (1) Papanicolaou, C. Coal Petrographic Parameters. Quality-Biomarkers. In Atlas of Greek Coals (in Greek); Institute of Geology and Mineral Exploration: Athens, Greece, 2001; 418 pp. (2) Koukouzas, C.; Foscolos, A. E.; Kotis, T. Research and Exploration of Coal in Greece. A View to the Future. Energy Sources 1997, 19, 335-347. (3) World Energy Statistics 2001. World Coal Institute, 2001 (http:// www.wci-coal.com).
Figure 1. Lignite-bearing basins of Greece. Major coal basins are (1) Ptolemais, (2) Florina, (3) Drama, (4) Elassona, and (5) Megalopolis. (From Koukouzas et al.2)
mine mouth plants, whereas ∼1% is used to produce dry lignite and briquettes. The total electric generating capacity is 5155 MWe.4 (4) Public Power Corporation of Greece, 2003 (http://www.dei.gr).
10.1021/ef030164b CCC: $30.25 © 2005 American Chemical Society Published on Web 12/08/2004
Quality Characteristics of Greek Brown Coals
Figure 2. Brown coal production (in millions of tons) from 1993 to 2003.
Greek brown coals are divided into different types: lignites and xylites. Lignites are derived from marsh reeds, whereas xylites are derived from woody remnants.1 Both types have diverse quality characteristics that cause technological challenges in mining and power plant operations, as well as problems that are related to environmental pollution.5 Therefore, an integral study of coal properties is essential. Such study involves determination of the critical quality characteristics, such as proximate and ultimate analysis, calorific values, and maceral composition, because these characteristics will affect ignition, flame stability, reactivity, burnout, and finally heat distribution. The latter, in turn, influences the steam temperature and, hence, the steam turbine efficiency.6 Also, the determination of ash content and its mineralogical and chemical composition is important, because it affects slagging and fouling deposits, as well as the corrosion and erosion of boilers.7 These detailed studies assist mechanical and electrical engineers in designing more-efficient boilers and allow mining engineers to exploit coal seams more wisely and enable environmental engineers to reduce pollution and improve reclamation planning. Properties of Greek Brown Coals Proximate and Ultimate Analyses. The results concerning the characteristics of the organic portion of the Greek coals are based on the existing literature.1,8-27 (5) Papanicolaou, C.; Kotis, T.; Foscolos, A.; Goodarzi, F. Coals of Greece: A Review of Properties, Uses and Future Perspectives. Int. J. Coal Geol. 2004, 58, 147-169. (6) Carpenter, A. M. Coal Blending for Power Stations, IEACR/81; IEA Coal Research: London, 1995; 83 pp. (7) Skorpuska, N. M. Coal SpecificationssImpact on Power Station Performance, IEACR/52; IEA Coal Research: London, 1993; 120 pp. (8) Anastopoulos, J.; Koukouzas, C, N. Economic Geology of the Southern Part of Ptolemais Lignite Basin (Macedonia-Greece). In Geological and Geophysical Research, Vol. 16, No. 1 (in Greek with an English abstract); Institute of Geology and Mineral Exploration: Athens, Greece, 1972; 189 pp. (9) Antoniadis, P.; Kaouras, G.; Khanaqa, P. A.; Riegel, W. Petrographishe Untersuchungen an der Neogene Braunkohle in Becken von Chomatero-Koroni, S. W. Peloponnes, Griechenland. Acta Palaeobotanica 1992, 32 (1), 27-31. (10) Broussoulis, J.; Economou-Mimidis, E.; Kolovos, G. Geology of the Ioannina Basin (in Greek); Institute of Geology and Mineral Exploration: Athens, Greece, 1979; p 12. (11) Broussoulis, J.; Yakkoupis, P.; Arapogiannis, E.; Anastassiadis, J. Drama Lignite Deposit. In Geology, Exploration, Resources, Vol. 2 (in Greek with English abstract); Institute of Geology and Mineral Exploration: Athens, Greece, 1991; p 19. (12) Cameron, A. R.; Kalkreuth, W. D.; Koukouzas, C. N. The Petrology of Greek Brown Coals. Int. J. Coal Geol. 1984, 4, 173-207. (13) Foscolos, A. E.; Goodarzi, F.; Koukouzas, C. N.; Hatziyannis, G. Reconnaissance Study of Mineral Matter and Trace Elements in Greek Lignites. Chem. Geol. 1989, 76, 107-130.
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The data from the representative proximate and ultimate analyses, on an “as-received” basis, for coal samples from the 14 most important coal basins of Greece are presented in Table 1. The relatively large variations between the basins, as well as within the basins, are attributed to the age, nature of occurrence (multilayer deposits), environment of deposition, and the geological settings.24 An average typical coal composition, which includes water, ash, volatile matter, and fixed carbon content, as well as the total carbon, hydrogen, oxygen, nitrogen, and sulfur content of the feedcoals from the most important coal basins (Megalopoli, Ptolemais/Amynteon, and Florina) is presented in Figure 3. Calorific Values. Calorific values are variable. The lowest values of 3.9 and 4.0 MJ/kg are observed in the Ioannina and Megalopolis coal basins, respectively. Midrange values of 5.9 and 9.2 MJ/kg are determined for the Ptolemais and Florina coals, respectively, whereas the Moschopotamos basin coals show the highest values, 15.0 MJ/kg (see Table 1). The distribution of minable coal deposits (with a ratio of overburden to lignite of ∼7), based on the calorific value, is shown in Figure 4.24 A comparison of the moisture content, ash content, and calorific values of the mineable Greek brown coals, comparable to those of other mineable brown coals in the world, is presented in Figure 5. (14) Foscolos, A. E.; Goodarzi, F.; Koukouzas C. N.; Hatziyannis, G. Assessment of Environmental Impact of Coal Exploration and Exploitation in the Drama Basin, Northeastern Greek-Macedonia. Energy Sources 1998, 20, 795-820. (15) Georgakopoulos, A.; Valceva, S. Petrographic Characteristics of Neogene Lignites from the Ptolemais and Servia Basins, Northern Greece. Energy Sources 2000, 22 (7), 587-602. (16) Gentzis, T.; Goodarzi, F.; Koukouzas, C. N.; Foscolos, A. E. Petrology, Mineralogy and Geochemistry of Lignites from Crete, Greece. Int. J. Coal Geol. 1996, 30, 131-150. (17) Gentzis, T.; Goodarzi, F.; Foscolos, A. E. Geochemistry and Mineralogy of Greek Lignites from the Ioannina Basin. Energy Sources 1997, 19, 111-128. (18) Kalkreuth, W.; Kotis, T.; Papanicolaou, C.; Kokkinakis, P. The Geology and Coal Petrology of a Miocene Lignite Profile at Meliadi Mine, Katerini, Greece. Int. J. Coal Geol. 1991, 17, 51-67. (19) Kavouridis, K. Lignite and Energy Balance. Present and Future Status of the Coal Mines in the Wider Area of Ptolemais and Amynteo. Presented at the Meeting on the “Future of Lignite in Greece. Its Relation into the Ever-increasing Demands of Electric Power”, Ptolemais, Greece, April 1-2, 1995; 25 pp. (20) Kaouras, G.; Antoniadis, P.; Blickwede, H.; Riegel, W. Petrographische und Palynologische Untersuchungen an Braunkohlen in Becken von Drama, Ostmakedonien (Griechenland). Neues Jahrb. Geol. Palaeontol. Monatsh. 1991, H3, 145-162. (21) Kotis, T. The Lignite Formation of the Neogene Basin of Moschopotamos, Katerini, in Relation to the Geotectonics Units of Pieria. Economic Geology, Exploration and Evaluation, Ph.D. Thesis, University of Patras, Greece, 1997, 268 pp (and Supplement, 188 pp). (22) Kotis, T.; Ploumidis, M.; Metaxas, A.; Varvaroussis, G. Coal Exploration of Vevi Sub-area: Florina District, Western GreekMacedonia (in Greek with English abstract); Institute of Geology and Mineral Exploration: Athens, Greece, 1992; 97 pp. (23) Koukouzas, N. Distribution of Lignite Deposits in Greece Based on Age, Type and the Reserves (in Greek with English abstract). Miner. Wealth 1998, 106, 53-68. (24) Koukouzas, C.; Koukouzas, N. Coals of Greece. Distribution, Quality, Reserves. Eur. Coal Geol. Assoc., Spec. Publ. 1995, 82, 171180. (25) Papanicolaou, C.; Dehmer, J.; Fowler, M. Petrological and Organic Geochemical Characteristics of Coal Samples from Florina, Lava, Moschopotamos and Kalavryta Coal Fields, Greece. Int. J. Coal Geol. 2000, 44, 267-292. (26) Papanicolaou, C. Quality of Greek Lignites Based upon Methods of Organic Petrology and Geochemistry (in Greek with abstracts in English, German, and French), Ph.D. Thesis, Technical University of Crete, Chania, Crete, Greece, 1994, 300 pp. (27) Papanicolaou, C.; Demetriou, D. Geology, Organic Petrology and Organic Geochemistry of Elassona Coal Basin, Western Macedonia, Greece. Miner. Wealth 2002, 127, 37-58.
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Table 1. Range and Mean Weighted Average Concentration of Moisture Content, Ash Content, Proximate and Ultimate Analyses, and Calorific Values, on an As-Received Basis, from Representative Coal Basins of Greece
age
moisture
Proximate Analysis (%) VM FC
Upper Oligocene
2.3-18.6 (9)
19.8-29.9 (24.4)
Upper Oligocene
25.6-31.4 (26)
13.5-27.6 (19.7)
Pleistocene
56.2-62.3 (59)
12.1-22.2 (16.4)
Lower Pliocene
38.1-43.8 (40)
15.4-44.0 (26.0)
Upoer Pliocene
43.4-60.6 (56)
8.9-33.1 (17.2)
Pliocene
49.3-58.1 (54)
10.3-35.7 (19.2)
Upper Miocene
13.3-24.2 (18)
25.7-31.0 (27.1)
Pleistocene
43.6-74.8 (66)
6.6-32.3 (16.2)
Pliocene
28.7-31.5 (29)
18.3-38.0 (26.6)
Pliocene
16.7-25.4 (21)
26.0-41.7 (32.9)
Pleistocene
57.5-65.0 (60)
13.3-25.2 (16.1)
Pleistocene
31.9-51.3 (46)
13.4-39.2 (22.90)
Upper Miocene
29.8-35.6 (32)
24.1-37.3 (31.1)
Middle Miocene
7.1-20.4 (15)
17.3-23.3 (20.1)
ash
C
Ultimate Analysis (%) H N ST
Alexandroupolis Coal Basin 20.1-30.3 11.2-61.9 21.3-32.2 3.9-2.6 (24.7) (41.9) (26.2) (3.2) Orestiada Coal Basin 11.4-23.2 22.5-32.2 16.3-33.2 1.4-2.9 (16.6) (37.7) (22.8) (3.0) Drama Coal Basin 6.2-11.1 11.7-21.8 11.9-21.6 1.0-1.9 (8.2) (16.4) (16.1) (1.4) Florina Coal Basin 10.2-29.1 9.9-0.28.4 16.0-45.9 1.3-3.7 (17.2) (16.8) (27.1) (2.2) Ptolemais Coal Basin 7.3-26.9 6.7-24.6 9.4-36.0 0.8-3.1 (14.0) (12.8) (18.7) (1.6) Kozani Coal Basin 8.0-27.7 6.4-22.2 11.9-41.3 1.0-3.5 (14.9) (11.9) (22.2) (1.9) Moschopotamos Coal Basin 17.6-32.9 27.7-42.4 32.6-49.5 0.4-2.7 (27.7) (27.2) (40.2) (3.0) Ioannina Coal Basin 3.3 -19.6 4.0-24.0 5.8-34.6 0.4-2.7 (8.0) (9.8) (14.1) (1.1) Zeli Coal Basin 14.9-30.5 18.2-29.3 21.5-42.1 1.6-3.3 (21.3) (23.1) (29.4) (2.3) Kalavryta Coal Basin 15.1-24.2 17.1-47.5 25.3-40.5 1.9-3.0 (19.1) (27.0) (32.0) (2.4) Megalopolis Coal Basin 7.38-13.5 12.3-23.5 12.2-22.8 0.9-1.8 (9.0) (14.9) (15.2) (1.2) Olympia Coal Basin 8.8-25.0 26.7-32.4 14.4-42.3 1.8-4.1 (15.1) (16.0) (24.7) (2.8) Koroni Coal Basin 14.1-24.7 13.9-22.8 27.5-38.4 1.8-3.2 (19.5) (17.4) (31.6) (2.5) Plakias Coal Basin 18.6-25.1 6.2-64.5 24.8-33.4 2.0-2.7 (21.6) (43.3) (28.8) (2.3)
Organic Petrology. Differences in the calorific values are reflected by the variable rank of Greek coals. Vitrinite reflectance (VRo) values range from 0.21%, for the coals from the Ioannina basin, to 0.42%, for the sub-
Figure 3. Average percentage of moisture, coal, and ash content (proximate and ultimate analyses) in the feedcoals of Florina, Ptolemais, and Megalopolis.
O
calorific value (MJ/kg)
0.6-0.9 (0.7)
3.5-5.3 (4.3)
12.9-17.5 (14.7)
11.4-14.3 (13.1)
0.3-0.5 (0.4)
1.4-2.8 (1.9)
6.6-13.4 (9.2)
6.4-9.7 (7.5)
0.3-0.5 (0.4)
0.08-0.12 (0.1)
4.8-8.7 (6.5)
3.7-4.8 (4.3)
0.1-0.3 (0.2)
0.4-1.2 (0.7)
7.7-22.0 (13.0)
8.4-9.8 (9.2)
0.1-0.4 (0.2)
0.2-0.8 (0.4)
5.4-19.8 (10.3)
4.6-6.5 (5.9)
0.3-0.9 (0.5)
0.2-0.7 (0.4)
5.0 17.3 (9.1)
3.8-4.4 (4.0)
0.8-1.2 (1.0)
1.1-1.7 (1.4)
7.5-11.4 (9.3)
13.4-17.6 (15.0)
0.2-1.0 (0.4)
0.6-3.4 (1.4)
2.9-17.6 (7.2)
2.2-4.6 (3.9)
0.6-1.1 (0.8)
0.5-1.0 (0.7)
10.2-20.9 (14.6)
8.3-11.3 (10.8)
0.7-1.1 (0.9)
1.2-1.9 (1.5)
9.0-22.3 (14.7)
8.8-14.1 (11.1)
0.2-0.5 (0.3)
0.9-1.8 (1.2)
5.8-10.2 (7.1)
3.6-4.6 (4.0)
0.2-0.4 (0.3)
1.1-2.4 (1.6)
6.1-11.8 (8.6)
5.15-8.6 (7.3)
0.2-0.4 (0.3)
0.8-1.4 (1.1)
11.2-22.4 (15.1)
11.4-13.6 (12.6)
0.3-0.4 (0.3)
0.2-0.5 (90.4)
8.5-11.5 (9.9)
9.0-11.8 (10.3)
bituminous coals from the Alexandroupoli basin, which correspond to calorific values of 3.9 MJ/kg for the coals
Figure 4. Distribution of economically recoverable lignite reserves, based on their calorific value.24
Quality Characteristics of Greek Brown Coals
Energy & Fuels, Vol. 19, No. 1, 2005 233
Figure 5. Relation of moisture content (percentage) to ash content (percentage) and calorific values, on an as-received basis, from various coal basins in the world. (From Kavouridis.19)
of the Ioannina basin and 13.1 MJ/kg for the coal of the Alexandroupoli basin. Substantial differences are also encountered in the maceral composition (Table 2).1 These variations are exemplified in the composition of the feedcoals from the coal basins of Ptolemais/Amynteon and Megalopolis, as well as coals from the Florina and Elassona basins, which will supply feedstock for two new 365-MWe power
Figure 6. Average huminite composition of Greek coal samples from the coal basins of Megalopoli, PtolemaisAmynteon, Florina, and Elassona.
plants. An additional factor that differentiates the Greek brown coals from each other is the presence and the sum of fluorescent tissue that is the concentration of liptinites and resinous textinites and textoulminites in the coals (Figures 6 and 7). The concentration of fluorescent tissues in the Greek brown coals ranges from 3% for the feedcoals from Ptolemais/Amynteon basins to 66% for the xylitic coals from the Florina basin. Liptinites, resinous textinites, and textoulminites affect the amount and type of volatile matter, because it includes not only the sum of H2O and CO2 but also the
Table 2. Maceral Composition of Greek Coals from Ptolemais-Amynteon, Megalopolis, Florina, and Elassona Coal Basins Composition (vol %) maceral huminite textinite A textinite B textoulminite A textoulminite B eulminite A eulminite B attrinite densinite corpohuminite porigelinite levigelinite total huminite liptinite sporinite cutinite resinite suberinite alginite chlorophyllinite fluorinite bitumenite liptodetrinite total liptinite semifusinite fusinite macrinite micrinite inertodetrinite sclerotinite total inertinite
Ptolemais-Amynteon
Megalopolis 2
20 25 27 7 1 80
25 1 7 1 24 25 5 90
1 3 2 1
Florina
Elassona
25 1 12 3 1 8 11 7 5 0 1 74
6 2 11 9 14 9 17 15 2 0 3 88
1 6 10 5
2 2 2 1
1 1
1 3
2 8
2 24
2 10
13
1
2
1
3 1 17
1 2
1 2
2
total organic matter
100
100
100
100
VRO (%)
0.32
0.28
0.32
0.31
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Energy & Fuels, Vol. 19, No. 1, 2005
Figure 7. Average liptinite composition of Greek coal samples from the coal basins of Megalopoli, Ptolemais-Amynteon, Florina, and Elassona.
highly flammable resinous compounds that contain substantial heat flux, which is released at much lower temperatures.28 This affects the heating profile of the combustible material. Finally, the concentration of inertinite is another important factor that affects not only the quality of the ash but also the efficient operation of the boiler. Brown coals from Ptolemais/ Amynteon have an average concentration of inertinite of 17%, and because the combustion temperature is ∼850 °C, inertinite is unburned. As a result, inertinite either concentrates in the fly ash or can be entrapped with SO2 in the flue gases and when combined with alkalis, which are vaporized when the coal is burned. This forms an insulating sleeve around the boiler tube surfaces, which reduces the thermal conductivity and, therefore, the heat transfer of the boiler. In certain coal samples obtained from boreholes of the Ptolemais/ Amynteon basins, the inertinite concentration reaches values as high as 50%.1 On the other hand, fly ash rich in inertinite, from the Ptolemais area, is an excellent fertilizer for acid soils, because it has a high amount of CaO (as shown in Table 5, presented later in this work), which increases the pH values, thus immobilizing any toxic elements which might be present in soils and adds organic matter (organic carbon, 4%-5% as inertinite) which is common practice. Mineralogy. The mineralogy of Greek brown coals has been studied by several scientists.13,16,17,29-34 The (28) Vamvuka, D.; Kastanaki, E.; Lasithiotakis, M. Devolatilization and Combustion Kinetics of Low-Rank Coal Blends from Dynamic Measurements. Ind. Eng. Chem. Res. 2003, 42 (20), 4732-4740. (29) Foscolos, A. E.; Kostakis, G. A. On the Nature of Lignites in the Wider Ptolemais Basin. In Organic Petrology, Proximate and Ultimate Analysis, Pyrolysis of Organic Matter, Inorganic Geochemistry, Particle Size Analysis and Electron Microscopy of Ashes, Partings and Interbedded Sediments; Public Power Corporation of Greece: Athens, Greece, 1990; 190 pp. (30) Filippidis, A.; Georgakopoulos, A. Mineralogical and Chemical Investigation of Fly Ash from the Main and Northern Lignite Fields in Ptolemais, Greece. Fuel 1992, 71, 373-376. (31) Filippidis, A.; Georgakopoulos, A.; Kassoli-Fournaraki, A. Mineralogical Components from Ashing at 600 °C to 1000 °C of the Ptolemais Lignite, Greece. Trends Mineral. 1992, 1, 295-300. (32) Georgakopoulos, A.; Kassoli-Fournaraki, A.; Filippidi, A. Morphology, Mineralogy and Chemistry of the Fly Ash from the Ptolemais Lignite Basin, Greece, in Relation to Some Problems in Human Health. Trends Mineral. 1992, 1, 301-305.
Papanicolaou et al.
mineral composition of coals is important, because of its impact on the wearing of mining equipment, the boiler’s performance, and the environment. Minerals with a hardness of more than 6 (such as quartz, feldspars, and pyrite) are abrasive. They destroy the metallic parts of the boiler.35-37 In addition, because fly ash is used in various industrial products, it is important to know their mineral composition and their concentrations. Mineral Matter in Coal. Several minerals have been identified in low-temperature ashes. Ubiquitous are quartz, feldspars, mixed layer silicates, illite, kaolinite, chlorite, calcite, gypsum, anhydrite, bassanite, and pyrite (Table 3). Less-common minerals are dolomite, siderite, meta-aluminite, and amphiboles, whereas epsomite, jaroisite, anatase, hercynite, jacobsite, and witherite are rare. Newly Formed Minerals. New minerals are created during the combustion of calcium-rich feedcoals. The type of new minerals is dependent on the original mineral content and composition and the temperature of combustion, which, in the Greek power stations, does not exceed 850 °C. Although newly formed gehlenite, lime, portlandite, calcite, ettringite, thaumasite, aphithitalite, wollastonite, and Ca2SiO4 are only encountered in calcium-rich feedcoals, hematite and anhydrite are present in all fly ashes. Chemistry. Major Elements in Fly Ashes. Data for the concentration of major elements in coal ash are summarized in Table 4.13,17,29-32,34 The results imply variations of values, reflecting the different paleodepositional environments and mineralogies of the coals. The average chemical composition of major elements in coal from the six main power stations is presented in Table 5. Effects of Brown Coal Properties on Mining and Power Plant Performance One of the most vital considerations in the exploitation of multiseam, low-rank coal deposits, which represent the majority of Greek brown coal deposits, is the identification/selection of mineable seams. Although the optimum mined section may be readily apparent on the basis of coal quality, from a “ply-by-ply” analysis of drill cores, this may not necessarily be the more favorable interval to be excavated, from a mining engineering point of view. Thin layers of lignite or waste material within seams can be taken separately only when its thickness is greater than the minimum thickness that can be handled by the excavating equipment. If an intraseam waste layer cannot be removed by selective mining, the waste is co-excavated with the lignite layers. These thin waste layers, which have highly varying (33) Papagianakis, S.; Vallindras, N. Hydration, Microstructure and Properties of Milled Fly Ash from Ptolemais Power Station. In Proceedings on Applications of Fly Ashes in Construction (two-day workshop organized by The Centre of Technology and Application of Solid Fuels, Kozani, Greece, October 3 and 4, 1997); Vol. 2, pp 43-62. (34) Sakorafa, V.; Michailidis, K.; Burragato, F. Mineralogy, Geochemistry and Physical Properties of Fly Ash from the Megalopolis Lignite Fields, Peloponnese, Southern, Greece. Fuel 1996, 75, 419-423. (35) Raask, E. Erosion Wear in Coal Utilization; Hemisphere Publishing Company: Washington, DC, 1988; 621 pp. (36) Scott, D. S. Coal PulverizerssPerformance and Safety, IEACR/ 79; IEA Coal Research: London, 1995; 83 pp. (37) Sligar, J. Component Wear in Coal Utilization. Int. J. Miner. Process. 1996, 44-45, 569-581.
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Energy & Fuels, Vol. 19, No. 1, 2005 235
Table 3. Minerals Encountered in Low- and High-Temperature Ashes in Greek Coals Low-Temperature Ash ubiquitous quartz feldspars pyrite
a
High-Temperature Ash rare
illite kaolinite chlorite 2:1 layer silicate gypsum anhydrite bassanite calcite dolomite magnesite siderite
ubiquitous
diaspore amphiboles anatase ammonium iron sulfate jarosite jacobsite meta-aluminite epsomite illmenite rutile hexahydrite barite apatite witherite kiezerite stromayerite hercynite
quartz feldspars
rare
anhydrite limea gehlenitea portlanditea ettringitea thaumasitea aphithitalitea hematite
diaspore amphiboles anatase rutile illmenite magnetite maghemite apatite barite witherite
In calcium-rich lignite when combusted to 855 °C.
Table 4. Concentration Range of Major Elements Encountered in Coal Ashes from 15 Representative Coal Basins of Greece Concentration Range (%) coal basin
Age
SiO2
Alexandroupoli Orestiada Drama Serres Florina Ptolemais Kozani Moschopotamos Ioannina Elassona Zeli Kalavryta Megalopolis Olympia Plakias
Upper Oligocene Upper Oligocene Pleistocene Miocene Lower Pliocene Upper Pliocene Pliocen Upper Miocene Pleistocene Upper Miocene Pliocene Pliocene Pleistocene Pleistocene Middle Miocene
32.8-51.9 31.2-32.0 19.6-55.4 11.9-32.8 26.0-48.2 9.1-55.3 15.4-24.5 32.0-52.7 11.6-56.0 30.4-51.4 47.3-57.4 42.1-50.9 51.8-57.5 49.3-50.9 33.4-46.5
Al2O3
TiO2
Fe2O3
12.3-24.1 0.1-0.6 16.2-23.0
