An experimental study on the spectroscopic characteristics in coal-water slurry diffusion flames based on hot-oxygen burner technology

The characteristics of spectral emissions in coal-water slurry (CWS) diffusion flames are investigated in this paper. Using Praxair's improved hot-oxygen burner (HOB) technology, CWS can be ignited directly in the ambient atmosphere. Moreover, the spectral emissions in methane and CWS diffusion flames are obtained by a fiber-optic spectrometer and a high-spatial-resolution ultraviolet imaging system, respectively. The results indicate that the spectral emission lines of the excited radicals in CWS flames can be used to evaluate whether the coal has been ignited. Besides, the peak intensity evolutions of several main radicals under different conditions were analyzed. Based on the two-dimensional OH* distributions, the axial and radial OH* intensity distribution in CH4 and CWS flames were discussed. Moreover, the areas of the flames and reaction regions show the proportions of the reaction region in the flame. Additionally, for the CWS diffusion flames, the OH* radicals can be considered as a good indicator of heat release rate. The OH*/CH* and OH*/C2* intensity ratios can be used to estimate the O/C or CWS flow rate.