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


The paper presents analysis of data obtained from tests of oil shale (OS) and peat co-combustion in a full-scale 250 MWth (useful heat output) circulating fluidized bed (CFB) boiler. The tests were conducted at nominal boiler load, with peat thermal input up to 30%. During the experiments, gas analysis was performed and ash samples were collected. The specific con­sumption of the oil shale and peat blend per useful heat and gross electricity was calculated and other techno-economic characteristics were determined.
   It was found that the co-combustion of oil shale and wet peat increased the CO emission to the level of 60 mg/Nm3. The NOx concentration increased from 120 to 165 mg/Nm3. The SO2 and HCl emissions remained at a very low level – below 20 mg/Nm3. A significant ash reduction, approximately 4%, was measured in the case of a 30% peat content. Due to the high peat moisture, the flue gas volume increased 5–10%. As a result of addition of peat, the content of particulate matter (PM) 10/2.5 was also lower than that by conventional oil shale CFB firing. Oil shale and peat co-combustion can be considered as a viable option and near-term solution for reducing the environmental impact of oil shale power production.


1.       FE032: Capacity and production of power plants. Statistics Estonia, 2017. [Online]. Available: (accessed 10 Feb 2017).

2.       Roos, I., Soosaar, S., Volkova, A, Streimikene, D. Greenhouse gas emission reduction perspectives in the Baltic States in frames of EU energy and climate policy. Renew. Sustain. Energy Rev., 2012, 16(4), 2133–2146.

3.       Loo, L., Maaten, B., Siirde, A., Pihu, T., Konist, A, Experimental analysis of the combustion characteristics of Estonian oil shale in air and oxy-fuel atmospheres. Fuel Process. Technol., 2015, 134, 317–324.

4.       Konist, A., Valtsev, A., Loo, L., Pihu, T., Liira, M., Kirsimäe, K. Influence of oxy-fuel combustion of Ca-rich oil shale fuel on carbonate stability and ash composition. Fuel, 2015, 139, 671–677.

5.       Konist, A., Pihu, T., Neshumayev, D., Siirde, A. Oil shale pulverized firing: Boiler efficiency, ash balance and flue gas composition. Oil Shale, 2013, 30(1), 6–18.

6.       Konist, A., Maaten, B., Loo, L., Neshumayev, D., Pihu, T. Mineral sequestra­tion of CO2 by carbonation of Ca-rich oil shale ash in natural conditions. Oil Shale, 2016, 33(3), 248–259.

7.       Hotta, A., Parkkonen, R., Hiltunen, M., Arro, H., Loosaar, J., Parve, T., Pihu, T., Prikk, A., Tiikma, T. Experience of Estonian oil shale combustion based on CFB technology at Narva Power Plants. Oil Shale, 2005, 22(4), 381–397.

8.       Lüschen, A., Madlener, R. Economic viability of biomass cofiring in new hard-coal power plants in Germany. Biomass Bioenerg., 2013, 57, 33–47.

9.       Konist, A., Pihu, T., Neshumayev, D., Külaots, I. Low grade fuel – oil shale and biomass co-combustion in CFB boiler. Oil Shale, 2013, 30(2S), 294–304.

10.    Krzywanski, J., Rajczyk, R., Bednarek, M., Wesolowska, M., Nowak, W. Gas emissions from a large scale circulating fluidized bed boilers burning lignite and biomass. Fuel Process. Technol., 2013, 116, 27–34.

11.    Sahu, S. G., Chakraborty, N., Sarkar, P. Coal–biomass co-combustion: An overview. Renew. Sust. Energ. Rev., 2014, 39, 575–586.

12.    Hupa, M. Interaction of fuels in co-firing in FBC. Fuel, 2005, 84(10), 1312–1319.

13.    Hupa, M. Ash behavior in fluidized bed combustion – recent research high­lights. In: Proceedings of the 9th International Conference on Circulating Fluidized Beds, 13–16 May 2008, Hamburg, Germany, 845–856.

14.    Yrjas, P., Skrifvars, B.-J., Hupa, M., Roppo, J., Nylund, M., Vainikka, P. Chlorine in deposits during co-firing of biomass, peat, and coal in a full-scale CFBC boiler. From 18th International Conference on Fluidized Bed Combus­tion, Toronto, Ontario, Canada, May 22–26, 2005, 679–687. ASME Proceed­ings, 2005.

15.    Doshi, V., Vuthaluru, H. B., Korbee, R., Kiel, J. H. A. Development of a model­ing approach to predict ash formation during co-firing of coal and biomass. Fuel Process. Technol., 2009, 90(9), 1148–1156.

16.    Pronobis, M. The influence of biomass co-combustion on boiler fouling and efficiency. Fuel, 2006, 85(4), 474–480.

17.    Lu, G., Yan, Y., Cornwell, S., Whitehouse, M., Riley, G. Impact of co-firing coal and biomass on flame characteristics and stability. Fuel, 2008, 87(7), 1133–1140.

18.    Plamus, K., Ots, A., Pihu, T., Neshumayev, D. Firing Estonian oil shale in CFB boilers - ash balance and behaviour of carbonate minerals. Oil Shale, 2011, 28(1), 58–67.

19.    Kuusik, R., Uibu, M., Kirsimäe, K. Characterization of oil shale ashes formed at industrial-scale CFBC boilers. Oil Shale, 2005, 22(4S), 407–419.

20.    Pihu, T., Arro, H., Prikk, A., Rootamm, R., Konist, A. Corrosion of air preheater tubes of oil shale CFB boiler. Part I. Dew point of flue gas and low-temperature corrosion. Oil Shale, 2009, 26(1), 5–12.

21.    Shao, Y., Wang, J., Xu, C., Zhu, J., Preto, F., Tourigny, G., Badour, C., Li, H. An experimental and modeling study of ash deposition behaviour for co-firing peat with lignite. Appl. Energ., 2011, 88(8), 2635–2640.

22.    Baxter, L. L., Miles, T. R., Miles Jr.,  T. R., Jenkins, B. M., Milne, T., Dayton, D., Bryers, R. W., Oden, L. L. The behavior of inorganic material in biomass-fired power boilers: field and laboratory experiences. Fuel Process. Technol., 1998, 54(1–3), 47–78.

23.    Badour, C., Gilbert, A., Xu, C., Li, H., Shao, Y., Tourigny, G., Preto, F. Com­bustion and air emissions from co-firing a wood biomass, a Canadian peat and a Canadian lignite coal in a bubbling fluidised bed combustor. Can. J. Chem. Eng., 2012, 90(5), 1170–1177.

24.    Parve, T., Loosaar, J., Mahhov, M., Konist, A. Emission of fine particulates from oil shale fired large boilers. Oil Shale, 2011, 28(1S), 152–161.

 Plamus, K., Soosaar, S., Ots, A., Neshumayev, D. Firing Estonian oil shale of higher quality in CFB boilers – environmental and economic impact. Oil Shale, 2011, 28(1S), 113–126.

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