THERMOPHORETIC SAMPLING OF COAL-DERIVED SOOT PARTICLES DURING DEVOLATILIZATION

Thermophoretic sampling of soot particles formed during high-temperatu re coal devolatilization is performed in order to examine soot particl e sizes and shapes. Coal particles are injected along the centerline o f a laminar flow flat flame burner, where a fuel-rich methane-air flam e is used as a heat source, Volatiles released from the coal particles form a cloud of soot particles at high temperatures in the absence of oxygen. A carbon-coated microscope grid is briefly inserted into the soot cloud, where the temperature gradient between the soot particles and the cold grid surface causes the migration of soot particles and r esults in deposition. Soot particles are analyzed using transmission e lectron microscopy.; Distinct primary soot particles with approximate diameters of 25-60 nm are observed, along with agglomerates composed o f multiple primary particles. Condensed, highly volatile, liquid-like deposits are observed in some cases, which are thought to be tar at so me stage of secondary reaction. Coal-derived soot is also compared to thermophoretically collected butane soot.