Influence of division cone angles between the fuel-rich and the fuel-lean ducts on gas–particle flow and combustion near swirl burners

Abstract

Radial bias combustion pulverized coal swirl burners are used in boilers when burning low-grade coals, which are often low-volatility anthracite and lean coals that do not burn stably. In a gas–particle test facility, a three-dimensional particle-dynamics anemometer was used to measure gas–particle flows in the near-burner region. Division cones between the fuel-rich and the fuel-lean ducts of the burner were set at angles of 43.2° and 0°. Velocity and particle volume flux profiles were obtained and the influence of the cones on combustion was analyzed. Burners with a division cone angle of 43.2° were used in a lean-coal fired boiler (volatility 13.2% as received, ash 27.46% as received), rated at 670 t/h. Pulverized coal was conveyed by cold moisture-laden exhaust air from the pulverizer. In situ aerodynamic field measurements in cold state were made and combustion tests were carried out. Low NO x emission and high thermal efficiency resulted and the turn-down ratio was 50%.