Study of gas/particle flow and low-load combustion stability of an improved swirl burner in a 350 MW Zhundong coal-fired boiler under different loads

To address the randomness and volatility of new energy sources, reducing the minimum stable combustion load of thermal power units is critical. We studied an improved swirl burner has the potential to achieve stable combustion without auxiliary combustion support under ultra-low load (20% rated load), which has been applied to a 350 MW boiler firing Zhundong coal. The novelty of this work lies in the systematic characterization of this new burner through a rigorous combination of laboratory-scale gas-solid two-phase flow measurements and full-scale industrial trials under different loads. A 1:6 scaled experimental platform utilizing Phase Doppler Anemometry (PDA) was established to measure three-dimensional velocity, turbulence intensity, and particle volume flux at varying loads. Industrial experiments revealed the distribution laws of flue gas temperature and component concentration of the improved burner under different loads. Results reveal that the improved burner forms an annular recirculation zone under all load conditions. As the load decreases, the reflux rate increases and the primary air mass flow decreases, demonstrating its potential for stable combustion at 20% rated load. When the load rates decrease from 246 MW to 165 MW, the ignition distance decreases from 0.9 m to 0.3 m. The distribution of flue gas composition concentrations shows a similar pattern. The ignition distance at 165 MW also shows an excellent low-load stable combustion ability of the improved burner.