Rheological characteristics of indian coal ash slurries in relevance to high concentration slurry disposal systems

Fly ash is generated in thermal power plants at different locations namely ESP hoppers, economizer and mechanical dust collector, whereas bottom ash is collected from the bottom of the furnace. Present study is focused on the fly ash collected from ESP hoppers. The properties namely PSD, Specific gravity, settling characteristics and pH of fly ash samples collected from different fields of ESP hoppers (Fields 1 to 5) have been evaluated. The rheological properties of the samples have also been evaluated at solid concentrations by weight (Cw) of 60%,62%,65% and 70%. Fly ash samples collected from different fields have been analyzed in terms of variation in physical & rheological properties. The particle size (dwm) of fly ash samples decreases from Field-1 to Field-5, whereas the static settled concentration and specific density increase. The pH values of all samples are almost constant and non-reactive in nature. The rheological properties at any given concentration namely viscosity and yield stress increase from Field-1 to Field-5.The increase is non-linear and is very steep at higher concentrations .