Annex 40 Complementary information to source category 4f Oil Shale Processing
Overview of recent revisions
No revisions of emission factors have been made. Additional guidance has been introduced on classifying sources within this category, estimating activity rates, and on data quality aspects.
Derivation of emission factors
Release to Air
From an Estonian plant, two sets of emission data were reported – 0.40-4.8 pg TEQ/m³ (at 6% O2) and 0.23-4.2 pg TEQ/m³ (at 6% O2). The corresponding emission factors were calculated to be from 0.2 to 3.5 ng TEQ/t of oil shale. For the purpose of this Toolkit, a preliminary emission factor of 0.003 μg TEQ/t oil shale was chosen (Schleicher et al. 2004b).
According to Schleicher et al. (2004b), incoming oil shale is heated with hot flue gas, separated in cyclones and mixed with hot ash to attain the reaction temperature of at least 480°C. Kerogen is fractionated into gas, condensable oil, and a solid residue. The decomposition of the kerogen starts at around 300°C and proceeds more rapidly at higher temperatures (480-520°C). The vapor phase is cooled to result in an oil fraction and a gaseous phase. The gas is typically burned in a power plant and the oil fraction is further fractionated into heavy oil, light oil, diesel, and gasoline. A substantial part of the oil is used to heat up the Estonian power plant. The solid residue is subsequently burned with excess air in a special furnace at 750-800°C.
Release to Water
No release to water is expected. If effluents are released, their source in the process should be noted.
Release to Land
No release to land is expected. All solids are covered in the section on Release in Residues.
Release in Products
Estonia has analyzed two samples of oil shale that was mined in the northeastern part of this country and pyrolyzed to fuel. The concentrations measured in these oil shale samples were 0.61 and 0.75 ng TEQ/kg shale oil (Roots 2001).
Release in Residues
Schleicher et al. (2004b) report PCDD/PCDF concentrations between 1.9 and 2.9 ng TEQ/kg ash. An emission factor based on tons of oil shale produced cannot be calculated and thus, the annual release has to be calculated by using the mass of solid residues from all plants to be multiplied by the concentration in ash.