Date of Award

8-1-1984

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Abstract

The rheological behavior of coal-water slurries was stud ied, using a Brookfield Rheolog viscometer with a thermosel system to maintain constant temperature. The coal used for making up the slurries was Sarpy Creek subbituminous coal from Montana. The effect of particle size, slurry concen tration and hot water drying process on the rheology was in vestigated. The particle size used ranged from 0.223 mm to 0.044 mm mean particle diameter, and the solids concentra tion in the slurry varied from 15 to 70 weight %. Tempera ture was maintained at 28 C (82 F).

Coal-water slurries exhibited a pseudoplastic behavior. The behavior of coal-water slurries was described accurately by a power law model of the form t = a(R)b where 1t ' is the shear stress, 'R' is the shear rate and 'a' and 'b' are experimentally determined constants. It was seen that apparent viscosity increased with an increase in solids concentration. It was also observed that the coeffi cient 'a' increased with an increase in solids concentra tion, while the exponent ’b' did not show any definite pat tern in its variation.

The moisture content of the hot water dried coal was de termined to be 13%, as compared to 25% for the unprocessed coal (as received coal). The slurry made with hot water dried coal showed a pseudoplastic or shear thinning behav ior, and it was seen that the apparent viscosity of hot wa ter dried coal-water slurries was lower than the apparent viscosity of unprocessed coal-water slurries.

Sedimentation characteristics of coal-water slurries were also studied by using a specially designed sedimentation ap paratus. The settling rates of coal particles were found to vary inversely with increase in slurry concentration, and directly with particle size. The particle sizes used were the same as those used for obtaining the rheology data. Hot water dried coal-water slurries exhibited negligible set tling.

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