Sedimentation of coal particles in lower aliphatic alcohols and the stability of alcohol–coal suspensions

The sedimentation of coal particles in lower aliphatic alcohols from the methanol–pentanol series was studied. It was demonstrated that, in the metamorphism series, the alcohol–coal suspensions based on brown coal and anthracite are the most and least stable, respectively. It was found that the stability of the coal suspensions increases with the length of a hydrocarbon radical in the alcohol molecules. It was established that the sedimentation of coal particles in dilute alcohol–coal suspensions obeys Stokes’ law. The sedimentation of coal particles in concentrated alcohol–coal suspensions is of structural nature and strongly depends on interactions between the particles through a liquid layer. In this case, the most stable suspensions are those in which the surface tension of a dispersion medium approaches the surface tension of coal and a difference between the polarities of a dispersed phase and a dispersion medium decreases.