Abstract:
The present study investigates concentrated coal ash slurries' rheological and pipe flow characteristics. Our results reveal coal ash slurries' shear thinning flow behavior regardless of solid volume fraction (phi) = 0.17-0.6. Rheo-microscopy study explains the thixotropy, yielding where slurry microstructure varies with time and applied shear. Experimental viscosity data fit with Dabak and Yucel model with a maximum coal ash packing fraction (phi(m)) = 0.63. The yield stress (tau(y)) determined using the creep test, stress sweep, Herschel-Bulkley model, and oscillatory sweep tests indicate the exponential relationship of tau(y) with phi = 0.43-0.6. The head loss (hL) during pipeline transportation of slurries increases with coal ash concentration (phi = 0.272-0.349) and slurry velocity (v(m) = 0.5-3 m/s). h(L) estimated from the rheological data is comparable with the experimental pipe-loop data with pipe length, L = 12 m, and pipe diameters, D = 25 and 50 mm at higher v(m) (similar to 2-3 m/s).