MASS TRANSFER IN LIQUID FLUIDIZED BEDS AT LOW REYNOLDS NUMBERS

Abstract

Mass transfer coefficients between fluidized ion exchange resins (Dowex 2 × 8) and dilute solutions of hydrochloric acid and of benzoic were measured in the low Reynolds number range (Re < 1.0). In the case of benzoic acid, the experimental mass transfer coefficients are in agreement with the values predicted by standard correlation Sh = (0.81 ± 0.05) ε−1 Re 0.5 Sc 1/3 in the range 0.1 < Re < 1, but below this value of Re the measured mass transfer coefficients are much lower. With hydrochloric acid the experimental mass transfer data are well correlated by the equation Sh = 1.1 ε−1 Re Sc 1/3 in the range Re < 1. The observed decrease of the mass transfer coefficients in the low range of Reynolds numbers is most probably related to the effects which are considered in Nelson and Galloway's theory and in Rowe's modification of the same theory. The theoretical results were found useful in the interpretation of experimental data. The least squares analysis of the experimental data showed that the value of parameter α, with which the best fit between experimental and theoretical results was obtained, was α = 0.62 with benzoic acid and α = 0.7 with hydrochloric acid, in good agreement with the value value proposed by Rowe and established earlier with an NaOH system. Qualitatively, the theory predicts the correct dependence of Sh on Sc as Re → 0.