Gas–solid flow and numerical simulation of novel deep peak–shaving swirl burner burning faulty coal

Existing swirl burners faced issues such as bluff body wear, insufficient understanding of concentration ring, and limitations of numerical simulation conditions, making it difficult to support stable combustion under deep peak–shaving. To address this issue in boilers firing faulty coal, the novel swirl stable combustion technology was developed. It was applied to prototype swirl burners used in a 700 MW utility boiler. Cold–state gas–particle experiments using phase doppler anemometry (PDA) and full–scale numerical simulations were conducted on the novel burner. With three–stage CR, the recirculation zone (RZ) was annular, measuring 2.5d in length and 0.50d in diameter, where d denoted the burner outlet inner diameter. With two–stage CR, it shortened to 1.5d and 0.46d, respectively. Without CR, the RZ became a heart–shaped central zone, 2.5d long and 0.70d in diameter, originating 1.0d downstream of burner outlet. Burner with three–stage CR exhibited a higher recirculation ratio, stronger turbulence kinetic energy, and better particle confinement near centerline compared to the two–stage CR case. r denoted the radial distance measured from a given point to the centerline. Compared to the two–stage CR case, the three–stage CR case also produced a broader and stronger region of negative particle volumetric flux at r/d = 0.2–0.4. Numerical simulations showed that the new burner could raise the gas temperature to 1000 °C within 0.25 m. Compared to the original design, the retrofitted boiler, where the middle and lower burner layers were replaced with new burners, showed an overall increase in furnace temperature, about 25 % reduction in fly ash unburned carbon and 70 mg/m³@6%O₂ reduction in NO_x emissions. Even at 30 % load, the new burners alone maintained temperatures above 1300 °C at the main combustion zone.