Investigations of CH∗ chemiluminescence and blackbody radiation in opposed impinging coal-water slurry flames based on an entrained-flow gasifier

Abstract

The characteristics of excited CH radical (CH∗) chemiluminescence and blackbody radiation in opposed impinging coal-water slurry (CWS) flames were investigated in this paper based on a bench-scale opposed multi-burner (OMB) gasifier. CH∗ chemiluminescence is a significant radical species in flame spectral diagnostics, and blackbody radiation can reflect the spatial distribution of solid particles produced in flame. A fiber-optic spectrometer and a CCD camera coupled with multiple bandpass filters are used to obtain the spectral emission lines and two-dimensional spectral distributions, respectively. The results show that CH∗ emission peak at 431 nm and continuous blackbody radiation can be detected in CWS flames. The differences of spectral distributions between diesel and CWS impinging flame are analyzed. Impinging zone is the core chemical reaction region, and solid particles are also concentrated in impinging zone, indicating that four-burner impinging can well restrict the reactants and flames in the impinging zone, thereby greatly reduce the damage to the refractory walls. Moreover, according to the time-averaged distributions, the intensity and area of CH∗ emission and blackbody radiation are enhanced with the increase of oxygen and carbon molar ratio (O/C), demonstrating that improving O2 velocity promotes the chemical reactions, and flame temperature plays more dominant role than solid particle quantity in blackbody radiation. The time-dependent blackbody radiation evolution presents periodical change. Besides, it is found that O/C or syngas concentration can be feasibly estimated using CH∗ chemiluminescence in OMB gasifier.