No abstract

The rheological behavior of power plant ash samples collected from JSPL (M=s Jindal Steel & Power Limited, Raigarh), India, was carried out using a HAAKE rotational rheometer (Model: RheoStress 1, Thermo Fisher Scientific). The ash slurry indicated non-Newtonian behavior in the solids concentration range of 50-60% by mass. The rheological data were best fitted by Bingham plastic model in the studied ranges of concentrations and shear rates. Two selective additives, namely sodium silicate and Ghadi detergent, were applied in small quantities (0-0.6% of total solids) and their effects on rheological parameters were evaluated. It was indicated that the small dosage of sodium silicate substantially influenced the Bingham parameters of the ash slurry than the Ghadi detergent. The percentage reduction in Yield stress at a slurry concentration of 60% by weight were found to be 59.3% and 46.23% for sodium silicate and Ghadi detergent, respectively, at a maximum dosage of 0.6% additives. More importantly, the plastic viscosity reduced by 37.6% and 16.3%, respectively, with the same dosage of sodium silicate and Ghadi detergent at same slurry concentration.

The huge quantity of coal ash produced in Indian thermal power plants is disposed of in ash landfills or ash ponds. The deposition of ash in ash ponds through conventional lean slurry form is viewed as a major potential release of many environmentally sensitive heavy metals due to possible contamination with ground water. An attempt has been made in this paper to assess the leachability of the heavy metals such as Cu, Pb, Ni, Co, Zn, Cd, Hg and As from two Indian power plant ash samples in the presence of some selective low-cost additives. The additives used for the study were sodium silicate (Na 2-SiO 3 Á5H 2 O), Reetha fruit (botanical name: Sapindus Mukorossi) extract, banana leaf extract, Aloe vera juice and active carbon. By adopting short duration (7 days) batch leaching test and toxicity characteristics leaching procedure (TCLP), the behaviour of various heavy metal ions released in water influenced by small dosage of these selective additives has been analysed. By introducing the same additives, the rheological behaviour of the two fly ash samples at high solids concentration (C W = 55-67.5 % by weight) was carried out using a HAAKE rotational rheometer (model: RheoStress 1, Thermo Fisher Scientific). The influence of small dosage of these additives on rheological parameters of the ash-water slurry has been discussed.