eesti teaduste
akadeemia kirjastus
SINCE 1984
Oil Shale cover
Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2022): 1.9


Ash reactivation technology using the Szego MillTM for grinding ashes with water, previously presented** at the Clearwater Clean Energy Conference in Florida, USA, June 2018, is now being applied to the activation of ashes from oil shale combustion.    For coal ashes, typically from fluidized bed combustion (FBC), limestone has been added as a source of calcium. In typical oil shales, there is a great deal of calcium carbonate present naturally. In an FBC boiler, there is enough time for sulfur adsorption, but with pulverized firing, that is not the case. Thus, it is necessary to remove the sulfur dioxide from the flue gases.    At the Eesti Power Plant in Narva, Estonia, the Alstom-developed Novel Integrated Desulfurization (NID) reactor system is used and some additional lime is added since much of the original calcium has been encapsulated at the high combustion temperature in the furnaces. Several tests using cyclone ash from that plant, activated with the Szego Mill, have been carried out with good results. The initial publication has compared the characteristics of activated ash and commercial lime and established their importance for sulfur capture. The performance results indicate that, per unit free CaO, well-activated ash is at least as good as the purchased lime, but three times more is needed due to the lower CaO content.    Further testing is planned, both in the laboratory and, it is hoped, also at the Power Plant in Narva. As use of oil shale is increasing in various countries, the results anticipated should find broader utilization.

TM Szego MillTM is a trademark of General Comminution Inc. for its planetary ring-roller mills.

**             Presented by the Corresponding Author of the current article.


1.      Ots, A. Oil Shale Fuel Combustion Technology. SC Estonian Energy, Tallinn, 2006.

2.      Kaljuvee, T., Trass, O., Pihu, T., Konist, A., Kuusik, R. Activation and reactivity of Estonian oil shale cyclone ash towards SO2 binding. J. Therm. Anal. Calorim., 2015, 121(1), 19‒28.

3.      Harvie, B. A. Historical review paper. The shale-oil industry in Scotland 1858‒1962. I: Geology and history. Oil Shale, 2010, 27(4), 354‒358.

4.      Urov, K., Sumberg, A. Characteristics of oil shales and shale-like rocks of known deposits and outcrops. Monograph. Oil Shale, 1999, 16(3), 1‒64.

5.      Raukas, A., Punning, J.-M. Environmental problems in the Estonian oil shale industry. Energy Environ. Sci., 2009, 2(2), 723‒728.

6.      Trass, O. Characterization and preparation of biomass, oil shale and coal-based feedstocks. In: Advances in Clean Hydrocarbon Fuel Processing (Rashid Khan, M., ed), Ch. 1, Woodhead Publ., Oxford, UK, 2011.

7.      Anthony, E. J., Granatstein, D. L. Sulfation phenomena in fluidized bed com­bustion systems. Prog. Energ. Combust. Sci., 2001, 27(2), 215‒236.

8.      Trass, O., Delibas, C., Anthony, E. J. Efficient reactivation of fluidized bed combustor ashes: Test results from a 35 MWt utility boiler. In: Proc. 9th Inter­national Conference on Circulating Fluidized Beds, CFB-9, Hamburg, Germany, May 13‒16, 2008, 869‒874.

9.      Anthony, E. J., MacKenzie, A., Trass, O., Gandolfi, E., Iribarne, A. P., Iribarne, J. V., Burwell, S. M. Advanced fluidized bed combustion sorbent reactivation technology. Ind. Eng. Chem. Res., 2003, 42(6), 1162‒1173.

10. Trass, O., Gandolfi, E., Anthony, E. J. Ash Reactivation, U.S. Patent No. 7, 323, 021 B2, 2008.

11. Trass, O. Efficient reactivation of fluidized bed combustor ashes: A simplified procedure. 41st International Technical Conference on Clean Coal & Fuel Systems, June 6, 2016, Clearwater, FL.

12. Trass, O., Papachristodoulou, G. L., Gandolfi, E. A. J. Wet grinding of coal in the Szego mill: Limiting predictions and experimental results. Coal Prep., 1995, 16(3‒4), 179‒201.

13. Trass, O. Reactivation of Fluidized Bed Combustor Ashes – Economic Evalua­tion and Implementation. Proc. 29th Intl. Techn. Conf. on Clean Coal & Fuel Systems, April 18–22, 2004, Clearwater, FL.

Back to Issue