Analysis of hydrophobicity of carbonaceous solids and their effect on the slurry viscosity

Carbonaceous solid-water slurry rheology is greatly affected by the surface properties of the solids used. Surface interaction energies of the three carbonaceous solids-petcoke, semi-anthracite and Illinois#6 coal were calculated. It was observed that hydrophobic interaction energy (calculated on the basis of contact angle measurements) is 2-3 orders of magnitude higher than the electrostatic interaction energy (calculated on the basis of zeta potential) and the Van der Waal interaction energy. Therefore in cases of petcoke, semi-anthracite and Illinois#6 coal water slurries, attractive hydrophobic interaction energy plays the dominant role in determining slurry rheology and the other interaction energies can be safely ignored. Petcoke having the maximum inter-particle hydrophobic interaction energy demonstrates maximum yield stress and viscosity when in suspension with water. Illinois#6 coal water slurry has higher yield stress and viscosity value as compared to semi-anthracite coal water slurry because of higher oxygen content.