COLLOIDAL AND ELECTROCHEMICAL ASPECTS
OF THE GENERATION OF SOOT AND COKE
The question why bitumen and varieties of ‘heavy’ oil do not atomize into aerosols in the same manner as paraffins do at the wick of a candle has been analyzed, see Oral “Electrolytic effects generated by thermolysis of non-volatile
organic liquids”. It showed that during thermolysis colloidal and electrochemical interactions occur. Experiments indicate that electrolytic parameters like electronegativity and electrical conductivity control a number of colloidal and physicochemical
Thermolytic generated mobile carbon atoms are prone to cluster. Such clusters grow by absorption of mobile carbon atoms and sterically fitting ions and molecules. When agglomerates accomplish electrical conductivity, surface charge develops
by charge transfer. Similarly charged carbon particles repel each other, but when dissimilarly charged attraction results. Brownian motion causes charge transfers of electrons that promote structural densification. The growth of soot and coke is controlled
by hydrodynamic and dielectric properties.
At interfaces between coexisting liquid phases and at surfaces of submerged particles electronegativities and electrical conductivities diverge. This divergence cause electrokinetic effects. The solid/liquid
and the solid/gas surfaces of partially submerged carbon particles, e.g. at the outside of wicks, are acted upon by traces gaseous oxygen and by the electrolytic condition of the liquid. These dualities induce charge transports, causing every kind of interface
to become charged electrically.
During thermolysis electrical interactions control physicochemical mechanics, like atomization of non volatile liquid organics at heated substrates and growth of carbon particles inside thermolyzing droplets. When partially
submerged particles are exposed to a trace of gaseous oxygen the agglomeration of carbon clusters inside droplets accelerates. The electrolytic condition of the liquid controls agglomeration as well. Substantial increases of the local conductivity induces
surfaces to discharge, weakens electrostatic repulsion between carbon particles and accelerates agglomeration.
Thermolytic reactions proceed according to quite different time scales. The release of electrochemically active species, like hydrogen and
hydrogen activated compounds lower the electronegativity in seconds or less, whereas the conductivity increases in minutes. The difference between these time scales can be understood as being due to their primary and secondary natures. The disintegration of
molecules releases components that instantly boost charge transfer processes at interfaces, where the concentration of mobile carriers of electrical charge develops more slowly as a result of reactions between fragments of molecules.
that contribute to atomization of non-volatile fuel and the generation of soot, seem also be in control of the generation of carbon agglomerates, that grow on walls inside “cokers” and more generally on walls inside reaction vessels where organic
processes proceed. Electronic sensors that locally record on line electronegativity and conductivity simultaneously are of value to optimize process engineering.
The electrochemical conditions of charge transfer during the growth of soot and the deposition
of coke indicate that when cooled down both substances are wetted and remain at all times contacted by dissolved polyquinones. These substances are well known for their reactivity. The molecular structure of polyquinones produced during thermolysis and agglomeration
of carbon clusters will reflect the molecular structure of thermolyzing originals. Such relations are of value to document health hazards of soot.