Catalytic, hybrid lean combustion for gas turbines

In the CATHLEAN project (an EU Framework 5 project performed between 2003 and 2006) a consortium of researchers investigated the development of an advanced, ultra-low NOx, hybrid burner for heavy-duty gas turbines that combines catalytic and lean-premix combustion components. Catalytic elements were developed that preheat the incoming lean fuel/air mixture up to temperature of ca. 1100 K at the required high (20–30 m/s) operating velocities and inlet temperatures (670–690 K). High-pressure aging of a highly active Pd-based catalyst at 10 bars indicated that the catalyst activity decreases significantly in the first 200 h of operation, and that an optimal catalyst design should contain different regions (in the axial direction) to allow optimization of catalyst activity and material stability, e.g. higher activity at the flow entrance, greater thermal stability at the reactor outlet where temperatures are high. Full-scale burner investigations demonstrated the feasibility of the CATHLEAN hybrid catalytic burner concept, and provided an indication of performance enhancement due to catalytic conversion. Both NOx emissions and lean stability limit were improved (25% reduction in NOx emissions and reduction of lean blow-out limit of ca. 200 K).