Emission factors and annual emissions of bulk and trace elements from oil shale fueled power plants

Measurements were carried out to investigate the emission factors and annual emissions of bulk and trace elements from two large oil shale fueled power plants in northeastern Estonia. The samples from fuel and different ash fractions were collected at the same time as the SO₂, NO_x and fly ash concentrations in the stack gases were measured at the power plants. The elemental concentrations of 30 elements in the fuel, bottom ash, ash from super heater and economizer, cyclone and electrostatic precipitator ash, and fly ash were analysed by ICP-AES, ICP-MS or INAA. According to the balance studies, based on analyses of the fuel and different ash fractions, 40–50% of sulphur and selenium, and 25–35% of arsenic, cadmium and thallium are released in the gas phase. Other elements, except for chlorine, bromine and iodine, are retained in the ash fraction by over 90%. The emission factor for SO₂ in oil shale fueled power plants is on the same level and the emission factor for NO_x one third of that in coal fueled power plants. The fly ash emission factor of oil shale fueled power plants, 1100 mg/MJ, is about 20 times higher than in coal fueled power plants. Due to the large size of these oil shale fueled power plants (electricity output 1390 and 1610 MW) and high fly ash emission factors, the total annual emissions of many elements, both toxic and non-toxic, are very high. For example, the arsenic and lead emissions are 12 and 36 tons per year, respectively, and calcium emissions 36 000 tons/year.