Gas-particle flow, low-load combustion and anti-slagging characteristics of prototype and improved burners for Zhundong coal boiler: From laboratory to industrial scale

Against the background of deep peak shaving requirements and severe slagging and burnout issues of swirl burners in Zhundong coal-fired boilers, an improved Inner-Pulverized-Coal-Concentration (IIPCC) burner is proposed in this study. The flow and combustion characteristics of the original Outer-Pulverized-Coal-Concentration (OPCC) burner and the IIPCC burner are systematically investigated via a 1:6 cold-state gas-solid two-phase test and 600 MW industrial experiments. The results show that central air significantly suppresses the recirculation zone and delays ignition of the OPCC burner; reducing central air opening advances ignition only slightly, and the minimum stable combustion load remains as high as 60% rated load. Compared with the OPCC burner, the IIPCC burner removes central air, adds swirling slit air and three-stage concentration rings, and optimizes the secondary air nozzle. It forms a larger recirculation zone (max height from 0.22d to 0.33d), weakens the near-nozzle recirculation intensity (recirculation ratio from 24.10% to 18.36%), and achieves obvious internal-rich and external-lean pulverized coal distribution. Based on these cold model gas/particle experiments and flow field analysis, the IIPCC burner is projected to achieve stable combustion at a 20% rated load, and reduce the risk of burner slagging and burnout. This new technology exhibits a high engineering value, with simple modification and low cost, providing a feasible technical solution for deep peak shaving and anti-slagging retrofit of Zhundong coal-fired boilers.