Cold experimental investigations into gas/particle flow characteristics of a low-NOx axial swirl burner in a 600-MWe wall-fired pulverized-coal utility boiler

With the use of a three-dimensional particle-dynamics anemometer in conjunction with a gas/particle two-phase test facility, we measured the flow characteristics in the near-burner region of a low-NOx axial swirl burner (LNASB). Mean velocities, root mean square (RMS) velocities and particle volume flux profiles were obtained. The data shows that the central recirculation zone exists only in the region x/d = 0.1-0.3 between r/d = 0.25-0.4. The central recirculation zone has maximum size at cross-section x/d = 0.1 located between the primary and secondary air flow zones. Moreover, with a maximum recirculating velocity of 4 m/s, the recirculation zone has a high particle volume flux that can easily result in the slagging and deformation in the burner nozzle. Oxygen concentrations are also high in this zone which can easily lead to NOx formation. In the region x/d = 0.1-0.5, the primary and secondary air flow zones exhibit two peaks in both axial and radial velocity profiles while a single peak appears in the tangential velocity profiles in the secondary air flow zone.