CARBONIZATION RATE OF SOOT PRECURSOR PARTICLES

The presence of soot precursor particles in hydrocarbon diffusion flam es is made clearly evident by means of contemporary sampling technique s in combination with transmission electron microscopy (TEM). These pa rticles are the immediate predecessors of mature, partially dehydrogen ated carbonaceous soot aggregates, and recent analytical tests indicat e they contain a mixture of polycyclic aromatic hydrocarbons. In this work, the conversion rate of precursor particles to carbonaceous soot aggregates is investigated. In one method the time interval for the mo rphological conversion of precursor particles to aggregates is observe d in diluted diffusion flames. Temperature profiles are measured by ra pid insertion thermocouple thermometry. This information is supplement ed by the observation of the sudden decrease of the hydrogen mole frac tion of soot precursor particles as measured by laser microprobe mass spectrometry. The Arrhenius rate constants for the carbonization of pr ecursor particles are derived from these measurements. Illustrations o f the use of this data in achieving high combustion efficiencies and r educed soot formation in combustion devices are discussed.