Oil shale ash and semicoke, solid residues from the oil shale industry, are today disposed of separately in landfills which pose a considerable environmental hazard. In the current study, the possibility of co-depositing ash and semicoke was investigated in a small-scale field experiment. The purpose of the experiment was to elucidate which mineral changes in the landfilled material occurred and how these changes affected its permeability characteristics. For this purpose five mixtures with different ash-to-semicoke ratios were prepared and placed in the open air. Changes in the dry density, hydraulic conductivity and mineral composition of mixtures were recorded within a period of four months and after one year. During the experiment the mixtures expanded and showed increased permeability due to intensive secondary mineralization. The higher the ash content of a mixture, the more intensive the expansion and, consequently, the higher the permeability, which contributed to an increased infiltration of the leachate and toxic compounds through the landfilled material, thus leading to unfavourable environmental impacts. The above suggests the possibility of co-depositing ash and semicoke, but only if the ash content of their mixture is low enough.
1. Ots, A. Oil Shale Fuel Combustion. Tallinn, Tallinna Raamatutrükikoda, 2006.
2. Statistical Yearbook of Estonia. Tallinn, Statistics Estonia, 2010.
3. Kuusik, R., Uibu, M., Kirsimäe, K. Characterization of oil shale ashes formed at industrial-scale CFBC boilers. Oil Shale, 2005, 22(4S), 407–419.
4. Bityukova, L., Mõtlep, R., Kirsimäe, K. Composition of oil shale ashes from pulverized firing and circulating fluidized-bed boiler in Narva Thermal Power Plants, Estonia. Oil Shale, 2010, 27(4), 339–353.
5. Mõtlep, R., Sild, T., Puura, E., Kirsimäe, K. Composition, diagenetic transformation and alkalinity potential of oil shale ash sediments. J. Hazard. Mater., 2010, 184(1–3), 567–573.
6. Kann, J., Elenurm, A., Rohtla, I., Golubev, N., Kaidalov, A., Kindorkin, B. About thermal low-temperature processing of oil shale by solid heat carrier method. Oil Shale, 2004, 21(3), 195–203.
7. Koel, M. Estonian oil shale. Oil Shale Extra, 1999. Available at http://www.kirj.ee/public/oilshale/Est-OS.htm, last accessed 28.09.2011.
8. Soone, J., Doilov, S. Sustainable utilization of oil shale resources and comparison of contemporary technologies used for oil shale processing. Oil Shale, 2003, 20(3S), 311–323.
9. Külaots, I., Goldfarb, J. L., Suuberg, E. M. Characterization of Chinese, American and Estonian oil shale semicokes and their sorptive potential. Fuel, 2010, 89(11), 3300–3306.
10. Mõtlep, R., Kirsimäe, K., Talviste, P., Puura, E., Jürgenson, J. Mineral composition of Estonian oil shale semi-coke sediments. Oil Shale, 2007, 24(3), 405–422.
11. Kattai, V. Oil Shale – Source of Oil. Tallinn, Geological Survey of Estonia, 2003. (in Estonian).
12. List of Waste, Including Hazardous Waste. Regulation of the Government of the Republic of Estonia. Riigi Teataja RT I 2004, 23, 155 (in Estonian). Available at https://www.riigiteataja.ee/akt/1053350?leiaKehtiv, last accessed 22.08.2011.
13. Arro, H., Prikk, A., Pihu, T. Reducing the environmental impact of Baltic Power Plant ash fields. Oil Shale. 2003, 20(3S), 375–382.
14. Talviste, P. Geotechnical and filtration properties of oil shale ash on the basis of Kohtla-Järve Power Plant ash deposits. In: Proceedings of XIII Estonian Geotechnical Conference (P. Ilves, ed.). Tallinn, Estonian Geotechnical Society, 2008, 54–62 (in Estonian).
15. Taylor, J. C. Computer programs for standardless quantitative analysis of minerals using the full powder diffraction profile. Powder Diffr., 1991, 6(1), 2–9.
16. Anthony, E. J., Bulewicz, E. M., Dudek, K., Kozak, A. The long term behaviour of CFBC ash–water systems. Waste Manage, 2002, 22(1), 99–111.
17. Liira, M., Kirsimäe, K., Kuusik, R., Mõtlep, R. Transformation of calcareous oil-shale circulating fluidized-bed combustion boiler ashes under wet conditions. Fuel, 2009, 88(4), 712–718.
18. Myneni, S. C. B., Traina, S. J., Logan, T. J. Ettringite solubility and geochemistry of the Ca(OH)2-Al2(SO4)3-H2O system at 1 atm pressure and 298 K. Chem. Geol., 1998, 148(1–2), 1–19.
19. Taylor, H. F. W., Famy, C., Scrivener, K. L. Delayed ettringite formation. Cement Concrete Res., 2001. 31(5), 683–693.
20. Collepardi, M. A State-of-the-art review on delayed ettringite attack on concrete. Cement Concrete Comp., 2003, 25(4–5), 401–407.
21. Mehta, P. K. Effect of lime on hydration of pastes containing gypsum and calcium aluminates or calcium sulfoaluminate. J. Am. Ceram. Soc., 1973, 56(6), 315–319.
22. Stark, J., Bollmann, K. Delayed ettringite formation in concrete. In: Proceedings of XVII Symposium on Nordic Concrete Research, 1999, 4–28.
23. Chartschenko, I., Volke, K., Stark, J. Untersuchungen über den Einfluß des pH-Wertes auf die Ettringitbildung. Wissenschaftliche Zeitschrift der Hochschule für Architektur und Bauwesen Weimar, 1993, 39, 171–176 (in German).
24. Pihu, T., Arro, H., Prikk, A., Rootamm, R., Konist, A., Kirsimäe, K., Liira, M., Mõtlep, R. Oil shale CFBC ash cementation properties in ash fields. Fuel. 2012, 93, 172–180.