Optical experimental study on the characteristics of impinging coal-water slurry flame in an opposed multi-burner gasifier

•Optical probe based on flame emission spectroscopy is shown to be capable for the monitoring of gasifier.•There are obvious radical emissions in the impinging area, including OH∗, H∗, NO∗, CO2∗, Na∗ and K∗ emissions.•The pathways of some radicals productions in gasifier have been explored.•With the increase of O/C, more reactions occur in the upward stream and OH∗ can clearly reflect the changes.•The change rules of OH∗ at the burner plane are similar to that of temperature and CO2 concentration.

Impinging flames have been used for a wide variety of industrial processes, especially for opposed entrained-flow gasification technology. The effective monitoring and controlling of flames are at the core of achieving high energy efficiency, reliable diagnosis for the gasification process and optimal gasification technology. Using an emission spectral analysis of an impinging area during coal-water slurry (CWS) gasification in a lab-scale opposed multi-burner (OMB) gasifier, the criterion for dominant reactions was identified. There were obvious radical emissions in the impinging area, including OH∗, H∗, NO∗, CO2∗, Na∗ and K∗ emissions. Intense black-body radiation appeared where the wavelength was longer than 400 nm. The radical emissions showed nonlinear variation with O/C, and there was a maximal value at the certain O/C, in accordance with the change of atmosphere, which could serve as a criterion for dominant reactions in gasification. The change tendency of OH∗ intensity on different conditions at the burner plane was similar to those of temperature and CO2 concentration. The temperature of the burner plane was the lowest in the reaction area. The change tendency of H∗ was similar to that of OH∗, and there was a linear correlation between OH∗/H∗ and O/C.