Eight poly-aromatic hydrocarbons as model compounds of coal extract were added to coal blends, in order to clarify the mechanism on the effect of coal extract (HyperCoal) on coke strength. The addition of large aromatic-ring compounds (coronene, perylene and naphtho[2,3-a]pyrene) greatly enhanced the coke strength, while, the three ring aromatics did not have a significant effect on the coke strength. Since large poly-aromatic compounds have better affinity to coal molecules, they co-fused with coal particles. As a result, formation of large pores during coking was suppressed, leading to the increased coke strength.
