The Influence of Swirl and O2 Addition On Flame Stability, NO Formation, Carbon Burnout, and Flame Temperature In a High Oxygen Participation Pulverized Coal Burner

To be submitted to AIChE 2011 Annual Meeting, October 16-21, 2011, Minneapolis, MN

The Influence of Swirl and O₂ Addition on Flame Stability, NO Formation, Carbon Burnout, and Flame Temperature in a High Oxygen Participation Pulverized Coal Burner

Darrel Zeltner, Teri S. Draper, and Dale R. Tree

Brigham Young University

Chendhil Periasamy, Taekyu Kang, Yuan Xue, and Remi Tsiava

Air Liquide

Air Liquide has developed a high oxygen participation burner for coal combustion. For successful operation of such burners for different applications, selection of burner design variables and appropriate oxygen injection schemes are important.  In order to provide insights into the use of higher oxygen concentration for coal burners, NO emissions, coal burnout, flame temperature, and flame emissivity were  measured on a 150 kW_th, pipe-in-pipe version of the burner for three swirl ratios and varying primary and secondary O₂ concentrations. Swirl was varied by a swirl plate with angles of 0, 15 and 40 degrees. Oxygen concentration injected into the center of the coal stream was varied from 4 to 50% and CO₂ was added to the secondary stream in increments from 0 to 72%. With no swirl, the coal flame was attached only when CO₂ concentrations in the secondary stream was less than 24%. At 15 degree swirl angle, the flame was stable over a broad range of operating conditions. NO was lowest with 96% of the O₂ in the secondary annulus. Burnout and NO increased with increasing CO₂ concentration in the secondary annulus. With 40 degree swirl angle, images showed large regions of unburned coal being transported through the flame. Flame temperature increased and emissivity decreased with increasing O₂ flow to the primary. Further, the data show an increase of O₂ to the primary center tube increases NO without improving burnout.