New 215 MW_el CFB Power Units for Estonian Oil Shale

Estonian basic power supply is over 90% covered by oil shale fired thermal power plants. Total installed thermal capacity of the boilers is 10.7 GW_th and every year about 11 millions tons of oil shale is fired. Two different combustion technologies, the old pulverized oil shale firing and the new CFB technology are used at the moment. The new CFB units totaling 430 MW_el delivered by Foster Wheeler Energia started operation in 2003–2004. The very first operational experience of CFB units are very promising and all basic problems of oil shale pulverized firing like high air emissions (SO₂ — 820–1360 mg/MJ; NO_x — 90–110 mg/MJ), fouling and corrosion of heating surfaces, low efficiency and low operational reliability seemed to be solved. Oil shale CFB firing at much lower temperatures (∼800°C) than pulverized firing (∼1400°C) results only partial decomposition of oil shale contained carbonates, meaning lower specific fuel consumption values and decreased CO₂ emissions. Also fly ash composition and properties has been changed, which results in different new prospectives of ash utilization possibilities, but also some additional ash land filling problems. The paper analyses the first data of Estonian oil shale industrial CFB firing in the light of almost 40 year experience of Estonian oil shale use in power production.