Development and validation of rare earth modified Fe-BEA SCR catalyst for mitigation of NOx from NH3 gas turbine

Abstract

This study investigated NH3-SCR of NOx from the exhaust of 300 kW NH3 gas turbine using Fe-zeolite and rare earth modified Fe-zeolite catalyst. As part of greenhouse gas reduction program, a gas turbine for power generation using NH3 and/or natural gas as fuel is developed where the challenge was to develop a catalyst that reduces NOx with high efficiency with minimum NH3 consumption as well as small SCR unit size. From laboratory bench scale evaluations Fe-BEA catalyst was identified to show desired NOx conversion, however upon aging in presence of steam at 800 °C the performance degraded. The Gd modified Fe-BEA catalyst showed high NOx reduction >98% at 600 °C and remained durable even after aging at 800 °C. The characterization results of XRD, UV and NH3-TPD revealed that addition of rare earth cations to Fe-BEA decreased the agglomeration of active iron species and stabilized the zeolite structure leading to minimal decrease in NH3 storage sites all of which are responsible for increased NOx conversion. The Gd/Fe-BEA catalyst was scaled up and tested behind a 300 kW NH3 gas turbine and it was demonstrated that the reduction of NOx from 477 ppm to 4.3 ppm, which is below the set target of 70 ppm in the exhaust was achieved.