Comprehensive Characterization of Pond Ash and Pond Ash Slurries for Hydraulic Stowing in Underground Coal Mines

In this study, the physicochemical and self-heating characteristics of pond ashes from Talcher Thermal Power Station (TTPS), located in the Angul district of the Indian state of Odisha are studied. The study revealed that the TTPS pond ashes belong to Class F fly ash category consisting mainly of SiO₂, Al₂O₃, and Fe₂O₃, with a small amount of CaO. The presence of mineral phases, namely, quartz, mullite, magnetite, and hematite in the pond ash are confirmed by x-ray diffraction. Based on the pond ash properties, various properties of the slurries of one representative pond ash, namely, density, volume concentration, and viscosity are determined by varying the ash concentration from 45% to 65% with an increment of 5%. As well, the critical deposition velocities of slurries as a function of slurry concentration and pipe diameter are determined. The results showed that the slurry viscosity increases exponentially with increase in solid content and the critical velocity increases linearly with increase in slurry concentration and pipe diameter. The relationships generated through regression analysis can be used to quickly predict the critical velocity of similar types of ash slurries for any known slurry concentrations and pipe sizes.