Abstract
The first combined mineralogical and geochemical investigation of coal ashes from the Northwest Thrace Coal Basin, Turkey, was performed as a case study. The coal ash samples were obtained at 525 °C (group I), 750 °C (group II), and 1000 °C (group III) ashing temperatures from coal samples from the basin and were studied in terms of their mineralogical and geochemical composition using XRD and ICP-MS methods. The determination of the mineralogical composition was done for all of the groups; the geochemical analysis was carried out only for group II. In accordance with the high SiO2, Fe2O3, CaO, and SO3 content of the ash, quartz (SiO2), hematite (Fe2O3), and anhydrite (CaSO4) are the major crystalline phases for all of the ash groups. The other minerals are muscovite, thenardite, tridymite, calcite, wollastonite, anorthite, cristobalite, gibbsite, ternesite, mullite, nahcolite, and nacrite. High-temperature phases such as mullite, wollastonite, and anorthite were observed at 750 and 1000 °C. According to the (Fe2O3 + CaO + MgO+ K2O+ Na2O)/(SiO2 + Al2O3+ TiO2) ratios varying from 0.19 to 5.65, the ashes are highly prone to slagging. Compared to average values of low-rank coal ashes, the contents of V, Cr, Co, Ni, Zn, As, Rb, Sr, Mo, Cs, W, and U of the ash are higher, whereas the total content of rare earth elements (REEs) (Σ 163.7 ppm) are lower. Based on upper continental crust normalization, As, Se, Th, and U are enriched in all of the samples. The higher trace element contents in the ashes might be considered as a possible health hazard. The correlation analyses indicated that Ca is associated with anhydrite and As with hematite. The correlation analyses also showed that newly formed Al and Ca silicates may contain the elements such as Ti, K, Na, Cr, Sn, and Pb.
Original language | English |
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Article number | 221 |
Journal | Arabian Journal of Geosciences |
Volume | 10 |
Issue number | 10 |
DOIs | |
Publication status | Published - 1 May 2017 |
Bibliographical note
Publisher Copyright:© 2017, Saudi Society for Geosciences.
Funding
This research was supported by the Scientific Research Projects Unit of Istanbul Technical University (project number 37013), the Scientific and Technological Research Council of Turkey (TÜBİTAK) (project number 115Y095) and General Directorate of Turkish Coal Enterprises (TKİ). The authors would like to specially thank the associated editor Dr. S. Dai and anonymous reviewers for critical reviews and suggestions to improve the manuscript.
Funders | Funder number |
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General Directorate of Turkish Coal Enterprises | |
TÜBİTAK | 115Y095 |
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu | |
Istanbul Teknik Üniversitesi | 37013 |
Keywords
- Ashing temperature
- Coal ash
- Environment
- Mineral composition
- Trace element