Effects of the structure and primary air on the gas/particle flow, combustion and NOx emission characteristics of the swirl burner in a 350-MW supercritical Zhundong coal-fired boiler

The issue of burner burnout and slagging in power plant boilers is extremely common, particularly when using Zhundong coal. This study focuses on a 350 MW supercritical wall-fired boiler mainly fuelled by Zhundong coal. A 1:6 scale cold molding gas/particle experiment platform of swirl burner was established in the laboratory. The effects of the structure and primary air on the gas/particle flow characteristics were measured by particle dynamic analyzer (PDA) measurement. Additionally, industrial experiments measured flue gas temperature and composition concentrations at burner outlets. The results revealed that the primary air of both two burners is direct-flow, the swirl inner and outer secondary air is diffused to all around through the air cone and separated from the primary air. Moreover, there exists a large non-ventilated area between the primary air and inner secondary air of the two types of burners, thus forming an annular recirculation zone, and the starting point of the recirculation zone extends deep into the burner, which is exactly the direct cause of burnout and slagging of these two types burners. As the primary air mass flow increases, the ignition heat rises. This has a negative effect on coal ignition, causing the ignition distance to increase from 0.5 m to 0.8 m as the primary air mass flow increases. NOx did not peak within the measurement range of the equipment, with a maximum of less than 500 ppm at the field of the burner outlet.