Experimental Investigation and Comparison of Pulverized Coal Combustion in CO2/O2− and N2/O2−Atmospheres

This paper presents results from measurements of flue gas components and spontaneous emission originated from excited OH-molecules of pulverized coal combustion in air- and CO2/O2−atmospheres. Measurements were conducted for various local oxygen-fuel ratios and O2 contents of the CO2/O2−atmosphere. For this purpose a swirl burner (60kWth) specially designed for oxy-fuel combustion was used. In the present study, measurements in the flame of the swirl burner were performed in a vertical downward fired test furnace. A CCD-camera system was used to capture spontaneous emission of excited OH-molecules. Furthermore, the global flue gas emissions were measured in the stack to gain data for a general description of the combustion process. The measurements were performed for combustion with air and with a premixed oxy-fuel atmosphere. Two different oxy-fuel atmospheres were tested (21 vol.-% O2/ 79 vol.-% CO2 and 25 vol.-% O2/ 75 vol.-% CO2). In addition the oxygen-fuel ratio in the proximity of the burner was varied between 1.0 and 0.6 while the global oxygen-fuel ratio was fixed at 1.3. Global concentrations of CO and NO in the flue gas as well as profiles of the spontaneous emission of OH-molecules are presented and discussed within this paper. Based on these measurements flame structures and flame characteristics are identified.