Application of Two-Color Pyrometry to Characterize the Two-Dimensional Temperature and Emissivity of Pulverized-Coal Oxy-Flames
Oxy-combustion is a developing technology that enables carbon dioxide (CO2) capture. Flame temperature and emissivity data were taken on a 150 kWth, pulverized-coal, burner flow reactor (BFR) that has been modified to run oxy-combustion with pure CO2 as simulated recycled flue gas. Data were taken at 78 conditions in which three parameters were varied, namely: the swirl angle of the fuel stream, the location of the oxidizer as it exited the burner, and the flow rate of diluent (pure CO2) added to the outer, secondary stream. At each condition, digital color images were obtained using a calibrated RGB camera. The images were used to determine lift-off length, temperature, and emissivity. The mathematical theory of two-color pyrometry and the calibration process used to measure the camera sensitivity is presented. The two most commonly used emissivity models in two-color pyrometry, the Hottel and Broughton and gray models, were investigated to determine which was the most appropriate for use in an oxy-coal flame. A significant difference of 7% in the temperature and 24% in the emissivity results were found when processing an image with the Hottel and Broughton and gray emissivity models. The Hottel and Broughton model was selected for processing, because the Hottel and Broughton model is more appropriate for soot which appeared to dominate flame emissions. Using the two-color data, several trends were documented. Flame temperature was seen to decrease with increasing CO2 flow rate. Within a given flame along the axial direction, temperature was seen to correlate with emissivity. As emissivity increased, flame temperature was seen to decrease. Many flames were lifted from the burner exit. Lift-off length was decreased and the flames became more attached by: 1) Increasing the amount of swirl given to the fuel stream, 2) Adding O2 to the center primary tube or 3) Decreasing the flow of secondary CO2. At higher center oxygen flow rates (above 8.5 kg/hr), the O2 jet velocity was large causing increased entrainment and mixing which degraded burner performance.
College and Department
Ira A. Fulton College of Engineering and Technology; Mechanical Engineering
BYU ScholarsArchive Citation
Draper, Teri Snow, "Application of Two-Color Pyrometry to Characterize the Two-Dimensional Temperature and Emissivity of Pulverized-Coal Oxy-Flames" (2012). Theses and Dissertations. 3206.
oxy-combustion, pulverized coal, flame, temperature, two-color pyrometry, emissivity, Hottel and Broughton, RGB, camera