Determination of Changes in Rheological Properties of Coal Slurries in Process Streams

Document Type

Article

Publication Date

1-1-1995

Abstract

A new technique involving a rotational (coaxial cylinder) viscometer and a vibrating sphere viscometer was developed for the rheological characterization of coal slurry process streams as either Newtonian or non- Newtonian. Both viscometers were able to measure apparent viscosity as low as one centipoise, and special precautions were taken to allow measurement of rapidly settling coal suspensions. In this technique, the vibrating sphere viscometer was used to measure the apparent viscosity at a high shear rate, while the rotational viscometer was used to measure the apparent viscosity at a low shear rate. Together, the two instruments could determine the shear-rate dependency of the viscosity, and thus provide an estimate of the total slurry rheology. The technique was first verified using two types of fluid with known rheological properties; sucrose solutions ranging from 10 to 60% by weight (Newtonian fluids), and solutions of Dow Methocel A4M ranging from 0.5 to 2% by weight (Pseudoplastic fluids). Following verification with the known fluids, a high-ash Pittsburgh seam bituminous coal was ground to 80% passing 34 micrometers, and was used to prepare slurries ranging from 10 to 45% solids by weight in distilled water. Apparent viscosity of each slurry sample was measured simultaneously by both viscometers and the results were then compared. With this technique, the onset of non- Newtonian flow behavior was clearly observed for slurries of this particular coal when the solids loading exceeded 20% solids by weight. © 1995, Taylor & Francis Group, LLC. All rights reserved.

Publication Title

Coal Preparation

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