Applicability of viscosity correlations for predicting viscosities of
coal liquids was tested against experimental viscosity data of seven c
oal 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 a
ssociation effects owing to hydrogen bonding in coal liquids are respo
nsible for this deviation since the petroleum correlations far-viscosi
ty predictions were developed for nonpolar, nonassociating fluids. A s
imple correction is suggested which helps in predicting coal liquid vi
scosities more accurately to within an average absolute deviation of 1
2%.