Investigation On Slurry Transportation Performance Of Coal-Water Mixture At High Concentrations

Abstract

The present study on the coal-water slurry rheology and its transportation performance was conducted at the Mechanical Engineering Department, Thapar University, Patiala. The rheological behaviour of five Indian coal samples were investigated by using Anton Paar RheolabQC rheometer to generate extensive rheological data with a perspective to study the effect of solids concentration, particle size distribution, fraction of coal fines and use of a natural additive as dispersant on the slurry rheology. The rheological data so obtained were utilized to numerically evaluate the pressure drop characteristics of coal water slurry flowing in straight pipe and 90o pipe bend using ANSYS FLUENT 14.0 computational fluid dynamics code. The rheological results revealed that the coal water slurry exhibited non-Newtonian behaviour at solids loading greater than 30 % by weight. The coal water slurry flow behaviour was described by the Power-Law and Herschel-Bulkley models. The apparent viscosities of coal water slurry increased with solids loading. The Particle Size Distribution affected the slurry rheology which was investigated by correlating Rosin-Rammler distribution modulus with the apparent viscosities. The coal water slurry showed a decrease in apparent viscosity values by adding fraction of finer coal particles in a relatively coarse size range until an optimum coarse/fine ratio was reached. The dispersant chosen was Shikakai powder; a natural product available in India. The dispersant was effective in reducing the apparent viscosity of slurry with a dosage of 0.5 % by weight. The pressure drop predictions were obtained by utilizing the rheological data and the results revealed that in both straight pipe and 90o pipe bend, with increase in solids loading and mean flow velocities, the pressure drop increased. However, by utilizing additive ar a dosage of 0.5 % by weight the pressure drop decreased for the same solids concentration.