Online measurement of soot formation distribution along time and axial in the volatile flames of coal and biomass using light scattering

In this paper, the online light scattering method, combined with the offline thermophoretic sampling particle diagnostic method, was used to measure the formation and evolution of soot during coal and biomass combustion along the time and axial. A light scattering measurement system that can accurately move vertically was constructed to measure the light scattering intensity along axial. The particle size distribution was obtained by the thermophoretic sampling particle diagnostic method. The results show that the scattered light intensity of sesame stalk flame is divided into three stages over time, namely the slow rising zone (zone I), the rapid rising zone (zone II), and the rapid decreasing zone (zone III). The rising zone of sesame stalk is long and the decreasing zone is extremely short. The scattered light intensity of Shenhua coal flame is divided into two stages over time, namely the rising zone (zone I) and the decreasing zone (zone II). The rising zone and the decreasing zone of Shenhua coal are almost symmetrical. When the flame burns stably, a large amount of soot is formed at the height of H = 10 mm, and the soot mass of Shenhua coal is about twice that of sesame stalk, which is mainly due to the large difference in volatile components between the two. As the flame height rises, the soot mass drops rapidly at H = 10-30 mm. In the range of 10-20 mm, the soot mass has been decreased by 76.07% for Shenhua coal, and 51.71% for sesame stalk. When H > 30 mm, the soot mass of sesame stalk and Shenhua coal slowly decreases. It is due to the change in the total surface area of soot particles during the combustion process.

Automated summary

In this paper, the formation and evolution of soot during coal and biomass combustion were investigated using the online light scattering method combined with the offline thermophoretic sampling particle diagnostic method. The results showed that there were differences in the formation and reduction of soot under different combustion conditions and fuels.