ELECTROCHEMICAL FLUE GAS DESULFURIZATION (PYROSULFATE, PEROVSKITE, SULFUR DIOXIDE, MOLTEN SALT)

Since the 1940's, increased use of fossil fuels in the industrialized nations has resulted in increased emissions of SO(,2) and NO(,x). These gases are transformed into acids when they are absorbed in cloud-water and rain-drops. The majority of the acid is due to sulfur dioxide pollution from power plants. Today the predominant power plant flue gas scrubbing process involves gas contact with an aqueous slurry of limestone, ultimately producing a disposable calcium sulfate sludge. The present investigation examines an alternative flue gas desulfurization method which removes and concentrates sulfur oxides in one continuous step without producing any waste sludge. This method utilizes a molten-salt electrochemical cell consuming electricity rather than expensive chemical reagents.;Various techniques were used to evaluate the candidate electrolytes. These experiments provided valuable information such as melting point, stability, reaction mechanism, and the reaction kinetics. Based on these data, potassium pyrosulfate containing small quantities of potassium sulfate and vanadium pentoxide was found to be the superior electrolyte choice.;Ceramic perovskite electrodes were manufactured and tested in a molten carbonate carbon dioxide concentrator. Their kinetic performance was similar to that of commercial nickel oxide electrodes. Improved fabrication procedures should render the perovskite an excellent choice for the electrode material in a flue gas desulfurization cell.;Design calculations were made for a system removing 80% of the sulfur dioxide from the flue gases of a 500 MW power plant burning 3.5% sulfur coal. It was determined that an electrode area of 1.74 x 10('4) m('2) would be required, and that the electrochemical flue gas desulfurization battery would consume 0.9% of plant power. A preliminary economic analysis revealed that the process is attractive compared to current desulfurization methods.;Previously, a device utilizing this principle was found to successfully remove sulfur dioxide from flue gas, but the high operating temperature (> 500(DEGREES)C) required for operation made application to conventional power plants difficult. In the present work, new electrolyte and electrode materials were tested for cell operation at significantly lower temperatures ((TURN) 350(DEGREES)C).