Effect of additive on the permeability of coal-tar pitch infiltrating through qi filter cake

Particles packing bed composed of quinoline insoluble (QI) always forms on the surface of the preform during impregnation of coal tar pitch. The permeability of coal-tar pitch through the cake is one of the most critical factors to determine the impregnation efficiency. Additive, mixture of an anodic mineral and a nonionic organic compound, was added in the coal-tar pitch to discover its effect on the permeability of the coal tar pitch. The viscosity and compositions of pitch changed little, but the permeability was improved obviously by comparing with the parent coal tar pitch. On the basis of Darcy's Law, the mechanism of the additive was thought as dual-flocculant, which can agglomerate QI particles to bigger aggregations. As a result, the mean size of the particles and porosity of the cake were improved, so the permeability the pitch was enhanced. The permeability increased to a maximum and then decreased with increasing concentration of the flocculants. It was found that the additive could increase the densification efficiency when the high-density 2D carbon preform was impregnated and carbonized, though it seems the carbon yield maybe decrease to some degree.