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Bhowmick S.,Chemical Engineering Division | Sharma V.K.,Isotope Production and Applications Division | Samantray J.S.,Isotope Production and Applications Division | Pant H.J.,Isotope Production and Applications Division | And 3 more authors.
Industrial and Engineering Chemistry Research | Year: 2015

The present paper describes measurements of time-averaged voidage distribution in a pilot-scale fluidized bed using γray transmission technique. The voidage profiles in absence of side gas injection showed that the tracks of bubble flow change from one side of the wall to the center of the bed with increasing superficial gas velocity. The side gas injection can drastically alter the shape of the bed voidage distribution. At incipient fluidization the jet bubbles and distributor bubbles were found to be moving without interacting with each other. At 1.5umf the jet bubbles and the distributor bubbles move from the wall to the central region of the bed with the increasing bed height above the nozzle plane. At 2umf the jet bubbles and distributor bubbles follow the same track from the nozzle plane. The void fraction measurement below the nozzle showed that there was no back mixing of gas injected through the nozzle. © 2015 American Chemical Society. Source


Keesari T.,Isotope Production and Applications Division | Sinha U.K.,Isotope Production and Applications Division | Deodhar A.,Isotope Production and Applications Division | Krishna S.H.,National Thermal Power Corporation | And 3 more authors.
Environmental Earth Sciences | Year: 2016

An assessment of fluoride distribution in groundwater of an industrialized area (Talchir), Odisha, India, was carried out to understand the potential sources and processes. This study is significant as the water resources are being endangered by the mining and other industrial activities in this region. High concentration of fluoride (4.4 mg/L) was observed in groundwater of this area, which was attributed mainly to mining activities. Additional source for high fluoride is the basement granitic rock containing fluoride bearing minerals like amphibole, biotite and fluorite. The dominant chemical types are found to be Na–Ca–HCO3, Na–Mg–HCO3, Ca–Mg–HCO3 and Ca–Na–HCO3. The groundwater facies variation was found in accordance with the local lithology. There was no marked difference in the fluoride concentration of groundwaters between near and far off mining zone. Geochemical modeling indicated precipitation of calcite and dolomite as the driving force for the release of fluoride from the formation. In addition to the precipitation of calcite and dolomite, evapotranspiration also contributes to high fluoride in groundwater. Environmental stable isotopes inferred that there was no clear isotopic distinction between high and low fluoride groundwater and the groundwater was found to be evaporated. Environmental tritium data suggested that the groundwater was modern and fluoride enrichment was facilitated by long residence time of groundwater. Statistical methods also corroborate the geochemical and isotopic inferences. The study highlights that natural geogenic source is the main cause for high fluoride in groundwater refuting earlier theories that attribute mining activities as the only source for high fluoride in this region. © 2016, Springer-Verlag Berlin Heidelberg. Source

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