Plastic vitrinite

Previous work hod shown that low temperature coke is formed from cools hooted to between 450° and 500° C. by a process of nudeation and growth of spherical bodies in the plastic vitrinite. An essentially similar process has now been found to occur with coke-oven and petroleum pitches, with polyvinyl chloride, and with some polynuclear hydrocarbons, all of which yield carbons which grophitize readily at high temperatures. The process is probably general for the initial stages of formation of such carbons from the liquid phase. Some control of the solidification process has been achieved on the laboratory scale, and the physical and chemical structure of the spherulites has been investigated. 

The process of development of a mosaic texture was observed by Taylor (2) first in thermally metamorphosed coals and then in partially carbonized vitrinite. He noted the appearance of spherical bodies in the plastic vitrinite, their growth, and the final development of the mosaic texture which is characteristic of the walls of the vesicular coke structure. From their appearance and behavior in polarized light it was deduced that the spherical bodies probably had a single plane of preferred orientation—i.e., a lamellar structure. 

Ralph J. Gray. Dr. Taylor states that the transformation of plastic vitrinite or coal-tar pitch into low temperature coke has some of the characteristics of a crystallization process. The authors place much emphasis on the development of spherical bodies in lx>th vitrinite and pitch. My question concerns the type of pitch, the method of its production, and the method of pitch coke production. 

The circular black region is a resin filled devolatilization pore surrounded by bitumen semicoke. Fused vitrinite is the bright region with very little texture. The photomicrograph suggests that neither the bitumen or the plastic coal are mutually soluble and the presence of bitumen does not interfere strongly with the fusion of vitrinite macerals. 

Recent work in this Division has shown that various substances other than vitrinites, such as pitches from coal tars and petroleum tars, polyvinyl chloride, and polynuclear hydrocarbons, develop similar mosaic structures on heating. In fact this effect occurs with most high carbon materials which pass through a plastic stage during carbonization. 

Binder phase continuous solid carbon matrix formed during the thermoplastic deformation of those coal macerals that become plastic during carbonization formed from the thermoplastic deformation of reactive (vitrinite and liptinite) and semi-inert (semi-fusinite) coal macerals of metallurgical bituminous coals (ASTM D-5061). 

The distribution of the inertinite and liptinite within vitrinite of the coal particle—a particle composed of only a pure maceral or distinctive gains of macerals will have different plastic properties (and therefore coke/char morphology) than a particle where the inertinite and/or liptinite is distributed throughout the vitrinite. 

On the other hand, thermal treatment of bituminous coal that contains a substantial amount of reactive macerals (such as vitrinite and exinite) shows an exothermic reaction accompanied by softening or plastic behavior followed by solidification (Biirkiit et al., 1994). 

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