Co-firing in the Greek power sector, which is heavily dependent on lignite-fired power plants, is one of the most promising options for GHG emissions reduction. However, it is expected that the most available and economically attractive co-firing fuels will pose technical challenges due to high alkali and chlorine content. The purpose of the current work is to present a demonstration activity of Cynara Cardunculus (cardoon) / lignite co-firing ina 300 MWe lignite-fired unit at Kardia power plant in Northern Greece. Cardoon was added to the fuel mixture over a period of 3 ½ days and constituted about 10% of the overall thermal share. During the demonstration, an extensive measurement campaign that included fuel and ash sampling, particle sampling from the boiler, fouling / slagging and corrosion probes, as well as the impact on gaseous emissions and ESP performance,was performed. Results indicate that, although cardoon has high percentages of chlorine and alkali content and low ash melting temperatures, co-firing has no major impact in the operational and environmental performance of the plant for such thermal shares, while indications of positive trends such as an enhancement of burning conditions in the furnace and a reduction of NOx emissions were identified. The high sulfur and calcium content of the lignite appear to have a positive impact during co-firing due to the sulfation of alkalis and the possible capture of chlorine by lime. Overall, co-firing biomass in Greek lignite-fired power plants at low thermal shares appears to be a technologically viable alternative for GHG emissions reduction.
Keywords:co-firing, lignite, cardoon, corrosion, chlorine