Rheological behavior of coal-water slurries of Indian coals using carboxymethylcellulose as dispersant- a comparative study

ABSTRACT

The rheological nature of coal-water suspensions of two Indian coal samples (namely coal 1 and coal 2) was reported and compared in the shear rate range of 60–160 s⁻¹ at constant pH of 8. Proximate and ultimate analysis were used to characterize the coal, and zeta potential and turbidity measurements were carried out to test the suitability and selection of carboxymethylcellulose (CMC) as a dispersant for the Coal Water Slurry (CWS). The effects of percentage solid loading, dispersant dosage on the rheological nature were studied. The rheological data was fitted for the power law model to categorize the slurry flow nature with reference to the calculated flow behavior index of the model. At lower solid loadings (10%, 20%), the shear stress-shear rate relation did not alter with the dispersant dosage and the slurries exhibited shear thickening behavior. The effects of the slurry parameters were quite predominant at 30%, 40%, and 50% solid loadings as they exhibited the shear thinning behavior. The slurry with 30% solid loading showed transition from shear thickening to shear thinning with the increase in dispersant dosage. For a given percentage of solids, a lower magnitude of shear stress versus shear rate, a wider distribution of flow behavior index and favorable pumpable characteristics were seen for coal 1 in comparison to coal 2 owing to their chemical nature and amount of ash-bearing mineral constituents.

KEYWORDS:

• Coal water slurry (CWS)
• Indian coals
• Carboxymethylcellulose (CMC)
• rheology
• flow behavior index

Research highlights

• Rheological behavior of the two different Indian coal-water slurries was studied and compared at pH-8.

• Effect of Carboxymethyl Cellulose (CMC) as a dispersant, concentration of solids at pH-8 is studied and compared for two coal samples.

• Effect of flow behavior index on dispersant dosage, concentration of solids at pH-8 is studied and compared for two coal samples.

Acknowledgments

The authors express their sincere thanks to Director, CSIR-National Metallurgical Laboratory, Jamshedpur, for his valuable guidance, encouragement, and permission to publish this work.