Correlation of viscosity of coal liquids

Applicability of viscosity correlations for predicting viscosities of coal liquids was tested against experimental viscosity data of seven coal liquids. The data considered in this work were at ambient pressure and moderate temperatures (294−360 K). The predicted viscosities were much lower than the experimental viscosities with an average absolute deviation of about 30% at best and 70% maximum. It appears that the association effects owing to hydrogen bonding in coal liquids are responsible for this deviation since the petroleum correlations for viscosity predictions were developed for nonpolar, nonassociating fluids. A simple correction is suggested which helps in predicting coal liquid viscosities more accurately to within an average absolute deviation of 12%.