Coal deposits of Turkey: properties and importance on energy demand

Κατά τις τελευταίες δυο δεκαετίες η παραγωγή και η κατανάλωση ηλεκτρικής ενέργειας στην Τουρκία αυξήθηκε με γρήγορους ρυθμούς. Περίπου 80% της παραγόμενης ηλεκτρικής ενέργειας προέρχεται από συμβατικά καύσιμα, όπως εισαγόμενο φυσικό αέριο και πετρέλαιο, αλλά και εγχώριους γαιάνθρακες. Καθώς όμως η σύγχρονη ενεργειακή πολιτική προσανατολίζεται σε μείωση της εξάρτησης από εισαγωγές καυσίμων, ο εγχώριος γαιάνθρακας, ιδιαίτερα ο χαμηλού βαθμού ενανθράκωσης, αποκτά σημασία για τη χώρα. Οι τελευταίες έρευνες ανεβάζουν τα αποθέματα σε ~13 Gt, με τον λιγνίτη και τον υποβιτουμενιούχο γαιάνθρακα να κυριαρχούν. Κοιτάσματα γαιανθράκων, που σχηματίστηκαν κάτω από διάφορες συνθήκες και σε διάφορες γεωλογικές περιόδους, υπάρχουν σε όλη τη χώρα. Τα σημαντικότερα είναι Τριτογενούς ηλικίας, με αυτά του Νεογενούς να είναι τα καταλληλότερα για ηλεκτροπαραγωγή εξαιτίας των μεγάλων αποθεμάτων παρά την υψηλή τέφρα και τη χαμηλή θερμαντική ικανότητα. Με την εφαρμογή ορθολογικής εκμετάλλευσης και καταλλήλων μεθόδων εμπλουτισμού ο γαιάνθρακας θα διαδραματίσει στο μέλλον σημαντικό ρόλο στην ενεργειακή τροφοδοσία της Τουρκίας.In the last two decades electricity generation and consumption in Turkey was increasing steadily. Around 80% of the electricity generated is derived from fossil fuels such as imported natural gas and oil, and domestic coal. As the energy policy now is focusing on reducing the dependency on imported fuels, coal, particularly this of low-rank, is becoming important for the country. Latest explorations showed that total coal reserves of Turkey reach to 13 Gt with low-rank coals (i.e. lignite and sub-bituminous) being dominant. Coal deposits, formed under various conditions and in various geological times, are widely spread over the territory. The most significant deposits are of Tertiary, especially Neogene age. Neogene coals are most appropriate for combustion in the thermal power plants due to the high total reserves despite the high ash yields and the low calorific values. We imply that applying reasonable exploitation planning and appropriate washing techniques, coal will play a key role in future energy supply of the country

Element behaviour during combustion in coal-fired Orhaneli power plant, Bursa-Turkey

This study focuses on element behaviour during combustion in the Orhaneli thermal power plant (a 210 MW unit, Bursa-Turkey). A total of 51 samples, feed coals (FCs), fly ashes (FAs) and bottom ashes (BAs), which were systematically collected over an eight-week period, have been analysed for major, minor and trace elements (Al, Ca, Fe, K, Mg, Na, S, As, B, Ba, Be, Bi, Cd, Co, Cr, Cs, Cu, Ga, Ge, Hf, Hg, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Y, Zn, Zr and REEs). This study shows that FCs on an airdried basis have high moisture (av. 9%), high volatile matter (av. 33%), very high ash yield (av. 53%), relatively high sulfur content (av. 2.14%) and low gross calorific value (av. 1775 kcal/kg). Proximate analyses of combustion residues imply that BAs have higher contents of unburned carbonaceous matter than FAs. Mean values of trace element concentrations in FCs fall within the ranges of most world coals, except for Cr, Cs, Ni and U which occur in concentrations slightly higher than those determined for most of world coals. Some elements such as S, Hg, As, B, Bi, Cd, Cs, Ge, K, Pb, Rb, Sb, Se, Sn, Tl, and Zn are indicating enrichments in FAs. The remaining elements investigated in this study have no clear segregation between FAs and BAs. The mass balance calculations point to Ca content of feed coal controlling the partitioning of elements in this power plant, producing a high removal efficiency for highly volatile elements such as Hg, B and Se, and a high retention of As, Bi, Cd, Cs, Ge, Pb, Rb, Sb, Sn, Tl and Zn in FAs. However, the high enrichment in trace elements of FAs can increase the hazardous potential of this coal by-product

Coal resource estimation in the Bayir field, Yatagan-Mugla, SW Turkey

This study focuses on some coal properties and calculation of coal resources with two classical (isopach and polygon) methods in the Bayir field, Yatagan-Mugla, which is located in southwestern Anatolia. This field has not been mined because it is still in the exploration stage. A productive coal seam of Early (?)-Middle Miocene age has a mineable coal thickness of 1.25 m to 18.01 m. Proximate analysis results indicated that this coal seam contains high moisture, ash, volatile matter, total sulphur content, and net calorific values. The weighted average mineable coal thickness calculated from the isopachs is 7.52 m and 7.82 m from polygonal methods. The in situ tonnages with isopach and polygonal methods were calculated to be 122.8 Mt and 130 Mt, respectively. The average value of the two methods shows 126.4 Mt in situ coal tonnages. Total amount of the in situ mineable coal resources is 77.7 Mt, which indicates an important coal potential in the Bayir field. The overburden thickness ranges from 72 m to 493 m in the Bayir field, averaging 257 m, indicating a deep coal mine. The overburden ratio averages 37 m3/ton, indicating an underground coal mine to feed a power plant in near future

Properties and reserves of lignite in the Aydin-Sahinali field, Turkey

This study focuses on some lignite properties and calculation of lignite reserves with two classical (isopach and polygon) methods in the Aydin-Sahinali field, Turkey, which is located in the western Turkey. This field has been mined by a private coal company since 1960 by open-cast and mainly underground mining methods. The producing lignites are consumed in domestic heating and industrial factories around Aydin. The metamorphic rocks of Palaezoic age form the basement of the coal field. The lignite-bearing unit of Miocene age, from bottom to the top, consists mainly of pebblestone, lignite and clayey lignite, siltstone with sandstone lenses, white colored claystone, clayey limestone and silisified limestone lenses. This unit in the lignite field was unconformably overlain by Pliocene unconsolidated sands and gravels. Three hundred seventy-three borehole data have been evaluated, and this study shows that a relatively thick and lateral extensive lignite seam has a mineable thickness of 1.6-14.4 m. The core samples from boreholes in panels in the lignite field indicate that the coal seam, on an as-received basis, contains high moisture contents (17.95-23.45%, average), high ash yields (16.30-26.03%, average), relatively high net calorific values (3,281-3,854 kcal/kg, average), and low total sulfur contents (1.00-1.22%, average). The remaining lignite potential in the Aydin-Sahinali lignite field was calculated as a 4.7 Mt of measured and a 2.9 Mt of mineable lignite-reserves

The geology, mineralogy, petrography, and geochemistry of the Miocene Dursunbey coal within fluvio-lacustrine deposits, Balıkesir (Western Turkey)

The Dursunbey coalfield, a typical example of coalfields in the western Anatolia, hosts a mineable coal seam (about 9.0-m coal thickness) with altered tuff layers within early Miocene fluvio-lacustrine sequences. The aim of this study is to identify peat-accumulation conditions and factors controlling the mineralogy and geochemistry of this seam. The standard coal features and petrographical, mineralogical, and elemental compositions display changes throughout the seam. Ash yields display decreasing trends towards to the upper parts of seam, while total C contents and gross calorific values are increasing. Furthermore, the coal-facies patterns evidence changes of depositional conditions and vegetation in the palaeomires. During initial stages of peat accumulation, the contribution of herbaceous peat-forming plants were more common and palaeomires were open to detrital inputs, whereas woody peat-forming were becoming predominant, and the water table was stable and high, which caused development of anoxic conditions, during late stages. Therefore, the content of detrital minerals, such as quartz and clay minerals (illite, smectite, and chlorite) increases in the lower parts of seam, while that of pyrite increases in the upper parts. In addition, the SEM-EDX data show that matrices of clay mineral aggregates are illitic in composition in the lower parts of seam, while those of smectite prevalence are more common below and above altered tuff layers. Interestingly, authigenic rhomboid K-feldspar grains are observed within smectite clay aggregates in the samples from the upper parts of seam. Framboidal pyrite grains and clusters were also commonly identified from these samples as well. This data shows that synchronous volcanic inputs were altered within a hydrologically closed system under slight acidic to neutral conditions during late syngenetic stages. The enriched elements, such as Cr, Ni, Cs, and V, display moderate to strong positive correlations with ash yields while AlO, and KO indicate an aluminosilicate affinity (clay mineral and feldspar). Considering the presence of metamorphic and ophiolitic rocks in the basement and the adjacent areas, clastic inputs into the palaeomire seems to be controlling aluminosilicate-affiliated elements. Additionally, the SEM-EDX analyses denoted that Ni and As are associated with pyrite. The Ni and As-bearing epigenetic pyrite infillings are mostly identified in coal samples below altered tuff layers; hence, As and Ni enrichments are controlled by precipitation of leached pore waters from altered tuff layers. Nevertheless, As- and Ni-bearing syngenetic pyrite grains and clusters are related with the development of anoxic conditions within palaeomires. This could also favour a Mo and U enrichment, which is another testimony for synchronous volcanic inputs altered under anoxic conditions. Overall, high detrital-input ratios from adjacent areas during initial stages of peat-accumulation in the study area controlled by enrichments of aluminosilicate affiliated elements, whereas during late stages of peat-accumulation, the development of a hydrologically closed system and redox conditions within the palaeomire caused As, Ni, Mo, and U enrichments and the formation of smectite and authigenic K-feldspars.A part of this (geological setting and sedimentological descriptions) was produced from the second author's PhD thesis, which was done under Dr. İ. Türkmen's supervision at the Department of Geological Engineering, Balıkesir University. A.I. Karayigit and R.G. Oskay performed standard coal analysis, petrographic, SEM, and mineralogical examinations; sampling collecting, field studies and sedimentary facies analysis were done by A. Bircan and İ. Türkmen; ICP-AES and ICP-MS analyses of raw coal samples were conducted by X. Querol. The manuscript was written through contributions of all authors. The authors would thank to mining companies in the study area for their support during field studies, Dr. Ebru Kavukçu (MTA, Ankara) for her helps during lab studies, and Caner Diker (Hacettepe University) for his assistance in preparing a digital-elevation-model map. Special thanks to Dr. Jim Hower, for his contributions and editing the revised version of the manuscript, and Drs. Carley Johnson and M. Sezgül Kayseri-Özer for their suggestions for improving the revised manuscript. Finally, the authors would like to thank Dr. Shifeng Dai, Editor-in-Chief of the Journal, for positive contributions and the anonymous reviewers for their comments and suggestions

Variations in elemental and mineralogical compositions of Late Oligocene, Early and Middle Miocene coal seams in the Kale-Tavas Molasse sub-basin, SW Turkey

The Kale-Tavas sub-basin, which is the south-western part of the Lycian Molasse Basin, SW Turkey, hosts several coal seams of Late Oligocene, Early and Middle Miocene age within, respectively, the Mortuma, Yenidere, and Sekköy Formations. This study aims to determine coal rank, mineralogical, and geochemical features of the coal seams, and to ascertain factors controlling the mineralogical distribution and elemental enrichment. The distinct differences among the studied coal seams refer to mean random huminite/vitrinite reflectance (Rr). The highest Rr values (0.63–0.69%) are measured on the Late Oligocene Tavas coal, whereas the lowest Rr values (0.26–0.27%) were recorded in the Middle Miocene Narlı coal. Similar mineralogical assemblages were found in all the studied coal seams; however, aluminosilicate minerals are dominant to abundant phases in the coal from the Mortuma and Yenidere Formations, while carbonate minerals are the dominant phases in the coal from the Sekköy Formation. Accordingly, aluminosilicate-related elements (e.g. Al, K, Ti, and Li) display relatively higher concentrations in the studied coal seams from the Mortuma and Yenidere Formations, whereas relatively high-Ca concentrations and depletion of aluminosilicate-affiliated elements were recorded in the coal of the Sekköy Formation. Furthermore, Ni, Mo, and U are relatively enriched in all the studied seams, while relative B-enrichment is identified in the coal seams of the Mortuma and Yenidere Formations, and these seem to be related to possible marine influence of the palaeomires during Late Oligocene and Early Miocene and/or the occurrence of specific B-bearing aluminosilicate minerals. Also, U and Mo enrichments in the Narlı coal may be related with the development of anoxic conditions within the palaeomires during the Middle Miocene. Other indicators for anoxic conditions are framboidal pyrite grains and accessory Ni-bearing iron sulphides in all the studied samples. Although coal-bearing formations in the Kale-Tavas sub-basin deposited under different sedimentary environment, as the source areas for sediment supply of the coal seams remained the same during the Late Oligocene to Early Miocene, the mineralogical composition and elemental enrichment of the coal were mainly controlled by clastic inputs and redox conditions within the palaeomires; to a lesser extent a possible marine influence might have contributed to elemental enrichment.This study was partially supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK) under a project (YDABCAG-117Y377) entitled “A multidisciplinary approach on palaeoenvironmental and palaeoclimate reconstruction of Kale-Kurbalık (Denizli) paralic coal basin” and by Hacettepe University, the Scientific Research Coordination Unit under the project number 05-01-602-002. The authors would like to thank Prof. Dr. Jim Hower for positive contributions, to Assoc. Prof. Dr. Mine Sezgül Kayseri-Özer for her contribuitons on geological age, and mining companies such as Azora, Bol, Özberil, As, and Emre for their permission for sampling and support during field studies. Special thanks go to mining engineer Mr. Ayhan Bircan for his assistance and support during sampling. Finally, the authors would like to thank Dr. Shifeng Dai, Editor-in-Chief of the Journal, and the anonymous reviewers for their comments and suggestions

Development of a petrographic classification system for organic particles affected by self-heating in coal waste. (An ICCP Classification System, Self-heating Working Group - Commission III)

Self-heating of coal waste is a major problem in the leading coal-producing and consuming countries, independent of the recent or past coal exploitation history. The phenomenon of self-heating is dependent on many factors such as the properties of organic matter (maceral composition and rank), moisture and pyrite content, climate effects, and storage conditions (shape of the dump or compaction of the coal waste). Once deposited, coal waste undergoes oxidation, which can lead to self-heating with the overall temperatures exceeding 1000 degrees C. During these self-heating processes, both organic and mineral matter undergo oxidative and thermal alterations, being influenced, among others, by the rate of heating as well as by the access of air and moisture. The morphological features of organic matter in coal waste at microscopic scale reflect the thermal conditions within the waste dump. Since 2008, several exercises designed to establish a petrographic classification system of oxidatively- and thermally-altered morphological forms of organic particles present in self-heated coal waste dumps have been carried out within the Self-heating of Coal and Coal Waste Working Group (Self-Heating WG), in Commission III of the International Committee for Coal and Organic Petrology (ICCP). Based on the degree of oxidative and thermal alteration, all assessed organic particles were divided into unaltered particles (huminite, vitrinite, liptinite, and inertinite macerals), altered particles, and newly formed particles (pyrolytic carbon, bitumen, chars, graphite, and coke). Altered particles were further divided according to their optical properties (porous, massive; isotropic, anisotropic). For altered particles the following specific features were distinguished: fractures, fissures, cracks; brighter rims; darker rims; plasticised edges; bands; devolatilisation pores; paler in colour particles. The final petrographic classification of oxidatively- and thermally-altered morphological forms of organic particles in coal waste dumps was established as a result of the successively performed Round Robin Exercises 2008-2017. The selected criteria and categories proved the high performance of the analysts characterised by a minor bias. The proposed petrographic classification system based on petrographic methods represents a useful way to characterize the undesirable phenomena occurring in coal waste dumps. Microscopic analyses and application of the petrographic classification system for organic particles affected by self-heating in coal waste offers the identification, documentation and monitoring of coal waste oxidation, self-ignition and combustion processes. It also enables a selection and application of appropriate measures to delay or even prevent undesired environmental impacts. The established classification system may assist in the air quality monitoring and assessment of burning waste dump sites and, thus, provide a relevant support in the environmental management of the disposal sites related to coal mining. The classification system can provide an important instrument for environmental protection agencies to increase the effectiveness of measures applied in fire hazard combating. The proposed classification of oxidatively- and thermally-altered morphological forms of organic particles in coal waste dumps can be applied on self-heating coal waste or mining dumps research, being a useful tool for coal waste managements performed by environmental agencies responsible for the landfill managements and monitoring of waste dumps