Numerical Investigation of the Effects of Swirl-Vane Angle and Particle Size on Combustion and Flow Characteristics in a Vertical Cyclone Barrel

The cyclone-fired boiler has become a very competitive boiler type for utilizing coal with a low ash melting point and high alkali. Because of the higher combustion intensity in the cyclone barrel, good flow and combustion performances are of great significance to the safe and efficient operation of the cyclone-fired boiler. The flow and combustion characteristics in a vertical cyclone barrel were numerically investigated, which has never been done before to the author's knowledge. The results showed that the pulverized coal particles are spun forward in the cyclone barrel driven by the tangentially rotating airflow, and the maximum velocity in the cyclone barrel is in the annular zone near the barrel wall. With the decrease in the swirl-vane angle of the primary air inlet or the increase in the particle diameter, the location where the particles collided with the barrel wall moves up along the axial direction of the cyclone barrel and the colliding chance increases. For the vertical cyclone barrel, the optimum particle diameter range is 70-110 mu m, so the capture ratio of particles is greater than 99.4%.