CO 2 mineral sequestration in oil-shale wastes from Estonian power production

Abstract

In the Republic of Estonia, local low-grade carbonaceous fossil fuel – Estonian oil-shale – is used as a primary energy source. Combustion of oil-shale is characterized by a high specific carbon emission factor (CEF). In Estonia, the power sector is the largest CO 2 emitter and is also a source of huge amounts of waste ash. Oil-shale has been burned by pulverized firing (PF) since 1959 and in circulating fluidized-bed combustors (CFBCs) since 2004–2005. Depending on the combustion technology, the ash contains a total of up to 30% free Ca–Mg oxides. In consequence, some amount of emitted CO 2 is bound by alkaline transportation water and by the ash during hydraulic transportation and open-air deposition. The goal of this study was to investigate the possibility of improving the extent of CO 2 capture using additional chemical and technological means, in particular the treatment of aqueous ash suspensions with model flue gases containing 10–15% CO 2. The results indicated that both types of ash (PF and CFBC) could be used as sorbents for CO 2 mineral sequestration. The amount of CO 2 captured averaged 60–65% of the carbonaceous CO 2 and 10–11% of the total CO 2 emissions.