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Kinetics of noncatalytic, nonisothermal, gas‐solid reactions: Hydrofluorination of uranium dioxide
Author(s) -
Costa Eduardo C.,
Smith J. M.
Publication year - 1971
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690170431
Subject(s) - chemistry , thermal diffusivity , thermodynamics , reaction rate , activation energy , reaction rate constant , pellet , mass transfer , thermal conductivity , heat transfer , chemical kinetics , order of reaction , kinetics , materials science , chromatography , organic chemistry , catalysis , physics , quantum mechanics , composite material
A single‐pellet, stirred‐tank reactor was used to measure temperatures, compositions, and rates of reaction for the hydrofluorination of UO 2.14 at atmospheric pressure. By correlating the rate with conditions at the reacting surface, the activation energy of the first‐order reaction was found to be 6,070 cal./g.‐mole. Since the product forms an unreactive layer around the core of UO 2.14 , and since the heat of reaction is high, significant concentration and temperature differences develop between the gas phase and the reaction surface. The temperature and rate data were used to calculate the effective diffusivity and thermal conductivity of the product layer under reaction conditions. An adaptation of a pseudosteady state method was developed for predicting the conversion and temperature history of a pellet. Using rate constants for reaction and mass and energy transfer derived from the experimental data, this method gave good results. Predictions with estimated rate constants were poor, indicating that an accurate value was necessary for the effective diffusivity in the product layer.