Selective catalytic reduction of NOx by NH3 in an adiabatic reverse flow reactor

The selective catalytic reduction (SCR) of nitrogen-oxides by ammonia to nitrogen and water vapours is widely used for decontamination of both technological, quite concentrated tail gases and industrial boilers with nitrogen oxides content not more than 1g/m(3). For treatment of low-temperature gases traditional SCR now-sheet includes heat-exchanger for heat transfer between inlet and reacted gases. In the flow reversal catalytic processes the catalyst bed of an adiabatic reactor acts as a catalyst and as a regenerative heat exchanger, simultaneously. An experimental reactor has been constructed, which almost completely reached the goal of an adiabatically operating system. The influence of several operating parameters such as gas flowrate, cycle period, chemical composition of inlet gases (space velocity of 10,000-30,000 h(-1), temperature: 200-600 degrees C, inlet molar ratio of NOx:NH3=1:1, inlet concentration of NOx: 2000 ppm, catalyst. V2O5/gamma-Al2O3 spheres with a diameter of 6 mm) is studied. In conclusion from our experimental results, the reverse flow SCR process under autothermal operation is a very efficient method in the removal of nitrogen oxides. The conversion rate of nitrogen oxides is relatively high even if the chemical composition of inlet gas mixture changed in a wide range and it slightly depends on the max. temperature of the unsteady-state catalyst bed. The selectivity of the traditional SCR denoxation process highly decreases above the optimal temperature of catalyst bed, but in a reverse flow one the selectivity of catalyst bed remains at a high level in a wide range of bed temperature (max. 280-460 degrees C).