Characteristics of Soot Collected in Industrial Diffusion Flames

Abstract

The Study Group of Natural Gas Flames (G.E.F.G.N.) makes trials on industrial diffusion flames in the Research Station of TOULOUSE. During these investigations some results about soot particles sampled in flames were collected. These soot particles make up the main source of luminosity of flames

Sampling of gas and soot particles in the flame are done with a cooled I.F.R.F. type probe

In the case of a diffusion flame of natural gas one can observe the formation and subsequently the burning out of certain products: carbon monoxide, hydrogen and unsaturated hydrocarbons. At the same time the production of soot in the flame is noticed

The same phenomenons take place in a heavy fuel oil flame. The soot particles, sampled at different points in a flame have been observed with an electron microscope. The mean size of particles is about 250 Å, both for heavy fuel oil and natural gas

Electron microdiffraction reveals that soot has an amorphous structure in the two cases

The chemical nature is different: the atomic ratio H/C is lower for soot produced by natural gas than for soot produced by heavy fuel oil

The extinction coefficient of particles, calculated from the emissivity of flames, is about 3000 m²/kg for soot sampled in a natural gas flame and 2000 m²/kg for soot sampled in heavy fuel oil flames

The chemical nature seems the only possible explanation of the differences observed in the optical properties of particles.