KEPCO Journal on Electric Power and Energy

Korea Electric Power Corporation (한국전력공사)
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Leaching Kinetics of Yttrium Extraction from Coal Fly Ash using Sulfuric Acid

  • Kim, Jae-kwan (KEPCO Research Institute, Korea Electric Power Corporation) ;
  • Park, Seok-un (KEPCO Research Institute, Korea Electric Power Corporation) ;
  • Hong, Jun-seok (KEPCO Research Institute, Korea Electric Power Corporation) ;
  • Shin, Dong-ik (KEPCO Research Institute, Korea Electric Power Corporation) ;
  • Jeong, Jae-hyeok (KEPCO Research Institute, Korea Electric Power Corporation)
  • Received : 2017.01.02
  • Accepted : 2017.03.09
  • Published : 2017.06.30
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Abstract

Leaching kinetics for extracting yttrium from the coal fly ash was investigated in the presence of sulfuric acid during extraction. The leaching kinetics of yttrium were conducted at reactant densities of 5~1,000 g coal fly ash per L of $1.0{\sim}10.0N\;H_2SO_4$, agitation speed of 250 rpm and temperature ranging from 30 to $90^{\circ}C$. As a result, the leaching kinetic model was determined in a two-step model based on the shrinking core model with spherical particles. The first step was proceeded by chemical reaction at ash surface, and the second step was proceeded by ash layer diffusion because the leaching conversion of yttrium by the first chemical reaction increases with increased the time irrelevant to the temperature whereas it increases with increased the leaching temperature. The activation energy of the first chemical leaching step was determined to be $1.163kJmol^{-1}$. After the first chemical reaction, the activation energy of ash layer diffusion leaching was derived to be $41.540kJmol^{-1}$. The optimum conditions for leaching the yttrium metal of 60 % were found to be the slurry density of 250 g fly ash per L of $H_2SO_4$, solvent concentration of $2.0N\;H_2SO_4$, second step leaching of temperatures of $30^{\circ}C$ for 3 hours and then $90^{\circ}C$ for 3 hours at agitation rate of 250 rpm.

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