Ind. Eng. Chem. Fundam., Vol. 18, No. 1, 1979
rates. Equation 2 specifies the flow rate of gas which passes through the bed in form of bubbles alone (visible bubble flow rate). This expression was derived by Partridge and Rowe (1966,a),and their analysis produced the result in agreement with one of the basic postulates of the simple two-phase theory regarding the bubble flow rate. However, in the simple two-phase theory one doesn’t take into account the existence of bubble clouds as is done in Partridge and Rowe’s model (1966a,b). There are no logical contradictions in this development, and Partridge and Rowe are not using two distinctly different pictures of the bed. However, there is some evidence, both theoretical and experimental, that eq 2 tends to overestimate the visible bubble flow rate. A theoretical analysis of Lockett et al. (1967) predicts smal1e.r values of GB than eq 2 . Experimental measurements of Grace and Harrison (1969), Geldart (1971), and Chavarie and Grace (1975a,b) indicate that the visible bubble flow rate is smaller than eq 2 predicts. Equation 20 of my paper, which is proposed for
79
the visible bubble flow rate, is in qualitative agreement with these experimental results. It seems that Professor Levenspiel is not familiar with Potter’s analysis (1971) of Partridge and Rowe’s model, which was cited in my paper. Potter obtained eq 9 of my paper, with f , being substituted by eq 10 without introducing concepts of bubble wake and solid circulation.
Literature Cited Chavarie, C., Grace, J. R., Ind. Eng. Chem. Fundam., 14, 75 (1975a). Chavarie, C., Grace, J. R., Ind. Eng. Chem. Fundarn., 14, 79 (1975b). Geldart, D., Ph.D. Dissertation, University of Bradford, U.K., 1971. Grace, J. R., Harrison, D., Chem. Eng. Sci., 24, 497 (1969). Lockett, J. J., Davidson, J. F., Harrison, D., Chem. Eng. Sci.. 22 1059 (1967). Partridge, B. A., Rowe, P. N., Trans. Inst. Chem. Eng., 44, T349 (1966a). Partridge, B. A., Rowe, P. N., Trans. Inst. Chem. Eng., 44, T335 (1966b). Potter, 0. E., “Fluidization”, J. F. Davidson and D. Harrison, Ed., 332-333, Academic Press, London, 1971
Faculty of Technology University of Novi Sad 21000 Novi Sad, Yugoslavia
CORRECTION
In the Correspondence, “Catalytic Oxidation of Phenol in Aqueous Solution over Copper Oxide”, by A. I. Njiribeako, R. R. Hudgins, and P. L. Silveston [Ind.Eng. Chem. Fundam., 17, 234 (1978)], the reply by Professor Katzer is correct: the value of 148 g/L is a thousandfold too high. It should be 148 mg/L.
Dragomir B. Bukur
