Simultaneous removal of nitrogen oxides and fly-ash from coal-based power-plant flue gases

Abstract

Catalytic filters are, in principle, capable of performing shallow-bed dust filtration plus a catalytic reaction, promoted by a catalyst deposited in their inner structure. Such a feature may allow potential cost reduction in several environmental applications and particularly in flue-gas treatment of pressurised fluidised-bed coal combustors (e.g. fly-ash removal+selective catalytic reduction of NO x with NH 3). Lab-scale V 2O 5·TiO 2(anatase)-deposited filters were prepared, characterised and tested for their activity towards the SCR reaction. The effect on NO conversion of operating temperature, superficial feed velocity and amount of deposited catalyst was determined. Results were interpreted on the grounds of a specific model, taking into account the mass transfer and reaction kinetics taking place inside the filter. Wide operating margins were found in which nearly complete NO abatement was achieved with negligible by-product release (N 2O, unreacted ammonia) for superficial velocities typical of the industrial practice (5–65 m h −1).