Hypothesis for an agglomeration mechanism in concentrated coal-water slurries

Abstract

Coal-water slurries (CWS) with an anionic type of additive have a “critical dynamic stress” above which their rheological properties (stability and viscosity) preclude their technological utilization (e.g. pipeline transportation). This degradation is accompanied by a large decrease in concentration of the fluidizing additive in the aqueous solution used for CWS preparation. This rheological degradation could be attributed to aspects of the solid-liquid interphase, since slurries can be considered as disperse systems of large surface extension. Ultraviolet spectra obtained on samples of degraded and undegraded suspension indicate that the main effect in this phenomenon is the modification of coal surface by mechanical energy supplied. The surface modification involves ions and prevents efficient dispersing action of the additive.