Untersuchungen zur Freisetzung und Einbindung von Alkalimetallen bei der reduzierenden Druckwirbelschichtverbrennung

Modern 2nd Generation Pressurized Fluidized Bed Combustion (PFBC) Combined Cycle Power Systems are a sufficient way to increase the efficiency of coal combustion. However, Combined Cycle Power Systems require a reliable hot gas cleanup. Especially alkalimetals, such as Sodium and Potassium, can lead to severe damage of the gasturbine blading due to hot corrosion. The investigations described in this thesis were performed to determine the potential of alkalimetal reduction from hot gases by alumosilicate sorbents unter reducing atmospheres at 750 °C. Using a flow channel reactor, an alkalichloride laden gas stream was passed through a bed of alumosilicate sorbent. Both, qualitative and quantitative analysis of the hot gas downstream the sorbent bed was achieved using High Pressure Mass Spectrometry (HPMS). Thus, the influence of several different gas atmospheres on the alkalisorption behaviour could be observed and conclusions be drawn concerning the chemical reactions occuring inside the sorbent bed. Several annealing experiments were performed to determine the maximum loading capacity of the sorbent, subsequent REM and XRD analysis showed the phases formed inside the tested sorbent materials. Finally, thermodynamic calculations were done to upscale the results of the laboratory experiments to conditions prevailing in 2nd Gen. PFBC systems. The investigations revealed the possibility of reducing the overall alkali concentration in the hot gas under 2nd Gen. PFBC conditions to values < 25 ppbvol by alumosilicate sorbents