(267c) Application of Photo-Imaging Techniques to Quantify Flame STABILITY Characteristics DURING Oxy-Coal Combustion

The purpose of this research is to better understand and to scale the effect of partial pressures of O2 and CO2, two additional degrees of freedom for oxy-coal combustion, on coal jet ignition and flame stability in the near burner zone. A novel methodology is developed to quantify the flame stability and flame length by introducing an image processing technique. Ultimately the experiment is designed to provide data for simulation validation studies that can be used to predict how air fired combustors may be retrofitted to oxy-coal.

Specifically the objective is to explore effects of the partial pressure of O2 and CO2 on coal jet flame stability, which is here quantified by stand-off distance, the distance between burner tip and the base of the detached flame. The experiments are carried on in a 100 kW pilot-scale laboratory furnace outfitted with a coaxial burner (primary jet in the center pipe and secondary stream in the annular sleeve, no swirl, Type 0 turbulent flames) and arrays of electrically-heated panels in the burner zone in order to control variations in near-burner heat loss. Currently fresh, one-through CO2 (instead of flue gas recycle) and O2 streams are introduced to the burner. The furnace also has visual access to the burner zone through quartz windows, which allows for optical measurements. A special CMOS sensor based camera, which is more sensitive to the near infrared wavelength (responsivity: 1.4 V/lux-sec (550nm)), is applied to capture Type 0 axial turbulent diffusion flame shapes for the use of statistical studies of stand-off distance under the influence of changes in various operational parameters, including systematic variations of partial oxygen pressure in both transport and secondary oxidant stream. Statistical analysis is used to scale the effect of oxygen partial pressure in both transport and secondary stream on coal jet ignition and flame stability. Ultimately the statistics from the photo images help to generate probability density functions (PDF's), which can be used to evaluate the experimental accuracy, reproducibility and allow more precise model validation.

Keywords: oxy-coal combustion, flame stability, oxygen partial pressure (PO2), stand-off distance, near burner phenomena, coal jet, type 0 axial turbulent flames, probability density function (PDF), image processing, statistical analysis