Characterizing potassium release under turbulent conditions during biomass stream combustion: A comparative analysis of different pretreatments

Abstract

The release rate of potassium during biomass combustion significantly influences slagging, fouling, and corrosion in industrial equipment. Given that dispersed biomass stream combustion predominantly occurs under turbulent ambient conditions, we investigate the combustion characteristics and potassium release behavior of rice husk and its derived fuels (water-washed, torrefied, and char) under high-turbulent conditions in a tubular flame burner (TFB). Tunable diode laser absorption spectroscopy (TDLAS) technology, combined with high-speed imaging, was employed to online monitor the release of atomic potassium (K(g)) and the ignition characteristics of biomass stream combustion. The results showed that the rice husk stream followed a joint hetero-homogeneous ignition mechanism, whereas the biochar stream underwent heterogeneous ignition in the TFB. The K(g) peak, occurring ahead of the maximum spontaneous radiation position, was observed at approximately 25 mm from the injectors, with a concentration of 0.067 ppmv during rice husk stream combustion. In contrast, the peak K(g) concentrations for biochar and torrefied rice husk were delayed, reaching 0.026 ppmv and 0.021 ppmv, respectively, compared to the raw biomass samples combusted in the TFB. Distinct differences in activation energy for K(g) release were identified, with pulverized rice husk exhibiting the lowest activation energy (75.53 kJ/mol) and rice husk-char showing the highest (94.20 kJ/mol).