The Influence of Solid Particles in Pitch on the Preparation and Baking of the Carbon Blocks

Abstract

The solid particles in pitch are determined by filtration from pitch dissolved in very good solvents (quinoline, pyridine, anthracene oil). They comprise particles of different origin: carbonaceous particles formed by cracking of tar vapors, entrained coal and coke and insoluble particles formed from the liquid phase by heat soaking during the production of pitch. All these different species can be identified by microscopy and usually semiquantitatively determined by chemical methods. The concentration of the pyrolytic solid particles is a sensitive indicator of the degree of dehydrogenation of tar vapors during carbonization. C/H ratio of isolated solid particles might be an indicator of heat soaking during the pitch fabrication but only microscopy gives the definite answer. Solid pyrolytic particles influence the determination of the softening point and viscosity to a different degree. Nevertheless, within a narrow range of concentration of pyrolytic solid particles, there is a definite correlation between the viscosity and softening point. During heat soaking or carbonization of pitch the pyrolytic particles are pushed together by spherical bodies of mesophase and reinforce the plastic liquid which does not penetrate readily into the porous structure of the filler.