TEM Study of soot aggregates from pulverized-coal combustor

摘要

Soot from pulverized-coal flames received renewed attention due to its health effects on human beings as well as its environmental effect on NO{sub}x formation. In this paper, the soot generated from a pilot-scale 25 kW down-fired combustor was extensively investigated by using a nitrogen-aspirated, water-cooling isokinetic probe with two-stage dilution. A 13-stage Electric Low Pressure Impactor (ELPI) was used to deposit particles, in which the last six stages are selected for the further analysis by the high-resolution transmission electron microscopy (HRTEM). The soot aggregate typically has a structure of chainlike branches with size of 100 nm to 2000 nm, whereas the size of primary particle ranges from 10nm to 100 nm. The onion-like, capsule-like and grapheme-fibre nanostructures of soot were observed. The complexity of fuel property, the flame condition and the existing catalytic effect of mineral matters results the complex structure of soot particles.