Effects of hydrocarbon addition on increase in dilatation of coal

The addition of coal tar pitch mainly composed of polycyclic aromatic hydrocarbons (PAHs), increases the dilatation of coal. We investigated the effect of PAHs on the maximum dilatation (MD) of hard coking coals and semi-soft coking coals. Twenty-six kinds of PAHs and aliphatic hydrocarbon were used as additive agents. The use of a PAH with a molecular weight in the range 152.19-178.23 as an additive agent almost unchanged the MD. When a PAH with a molecular weight in the range 178.23-378.47 was added to the coal, the MD of the coal increased. The increase in MD achieved with the addition of 9,10-dihydrophen-anthrene was larger than that obtained with the addition of phenanthrene. This is likely because the hydrogen atoms in the ninth and tenth positions in 9,10-dihydrophenanthrene inhibit the polymerization of the coal structure. The MD was hardly affected by the addition of a linear aliphatic hydrocarbon (C₂₈H₅₈) but MD decreased due to the addition of anthraquinone with carbonyl carbon. When a PAH with non-planar structure was added to the coal, the increase in MD was smaller than when a PAH with planar structure was added.