Effect of co-combustion of coal with biomass on the morphology of soot

This study performed an experimental investigation to explore the effect of co-combustion of coal with biomass on the morphological parameters and nanostructure of soot. Three types of soot, namely Shenghua coal (SH) soot, Pinewood biomass (PW) soot, and Co-combustion of SH and PW (CC) soot, were collected from the combustion flames of Shenhua coal, Pinewood biomass, and a mixture of coal and biomass. Thereafter, the soot samples were observed and analyzed by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) to obtain their morphological parameters and nanostructure characteristics. The TEM results showed that the size of nascent soot particles generated in co-combustion flame is the largest, rather than between the sizes of PW and SH soot. The nanostructure of the three types of soot primary particles is mainly composed of straight parallel crystal stripes. The separation distance of crystal stripes in SH soot was measured to be larger than that in PW soot, indicating that the crystal structure of soot generated in Pine biomass combustion flame is more compact. It was also observed that both coal-derived primary soot particles and biomass-derived primary soot particles were formed in the co-combustion flame. SEM results indicated that PW soot agglomerates have stronger aggregation performance and more compact structure then SH soot and CC soot. The primary particle size of SH and CC soot agglomerates was mainly concentrated between 50 and 70 nm, while that of PW soot agglomerates was relatively uniform. Furthermore, the number of primary particles in SH soot and CC soot was distributed over a wide range compared to PW soot.