Ind. Eng. Chem. Process Des. Dev. 1900, 19, 328
320 QL -rA
= volumetric liquid flowrate, cm3/s = rate of conversion of A, mol of A/(s) (cm3 of liquid
holdup) V = volume of reactor bed, cm3 X A = conversion fraction of A a, = wetted area of catalyst particles per unit volume of bed, cm2/cm3 a, = total area of catalyst particle per unit volume of bed, cm2/cm3 e = catalyst bed void fraction 7 = catalyst effectiveness factor c(L = viscosity of liquid, g/(cm)(s) uL = kinematic viscosity of liquid, cmz/s pL = density of liquid, g/cm3 T
= 3.1415.-
Sir: In our opinion Marangozis (1980) has not only confused the purpose of our paper (Montagna et al., 1977) but has also misunderstood the aim of our other papers on the same subject (Paraskos et al., 1975; Montagna and Shah, 1975). Our reasons are as follows. (1)The purpose of the paper by Montagna et al. (1977) was to discriminate between holdup and effective wetting models in pilot plant reactors. These two correlating models predict different dependence of conversion (or more specifically In (CAi/CAq),where CAiand CAoare the reactor inlet and outlet concentrations) on the catalyst particle diameter. We cannot derive the relationship In (CAi/CAo)0: dp-4/3(where d, is the catalyst particle diameter) suggested by Marangozis (1977). Even if the holdup model suggests In (CAi/CAo)a di4I3,this relationship will not be satisfied by the data of Montagna et al. (1977). Also, as pointed out by Mears (1974), the use of eq 2 of Marangozis for correlating trickle-bed data is questionable. Thus, the data of Montagna et al. (1977) show the effective wetting model to be a better correlating model than the holdup model. (2) Equation 5 of Marangozis (1977) is simply the plug-flow model for a trickle-bed reactor. With the help of data obtained at various liquid hourly space velocity and length of catalyst beds, Paraskos et al. (1975) and Mon-
0196-4305/80/1119-0328$01 .OO/O
u = surface tension of liquid, dyn/cm uc = critical surface tension of bed packing,
dyn/cm
Literature Cited Henry, H. C., Gilbert, J. E., Ind. Eng. Chem. Process Des. Dev., 12, 328-334
(1973). Mears. D. E., Adv. Chem. Ser., No. 133, 218-227 (1974). Montagna, A. A.. Shah, Y. T I Paraskos, J. A,, Id.Eng. Chem. Process Des. Dev.. 16, 152-155 (1977). Puranik, S. S., Vogelpohl, A., Chern. Eng. Sci., 29, 501-507 (1974). Onda, K., Takeuchi, H. Koyama, Y., Kagaku Kogaku, 31, 126 (1967). Satterfield, C. N., Pelossof. A. A,. "herwood, T. K.. AIChEJ., 15, 226-234
(1989).
School of Chemical Engineering National Technical Uniuersity Athens, Greece
John Marangozis
tagna and Shah (1975) showed that this equation does not satisfactorily correlate small pilot scale data. This equation should be used only in the absence of significant wetting, dispersion, etc. effects. Thus, this equation cannot be used to correlate the effect of particle size on the conversion in pilot scale operation. Equation 5 of Marangozis predicts In (CAi/CAo)a 7 (where '7 is the catalyst effectiveness factor) whereas eq 9 of Marangozis predicts In (CAi/CAo) 0: d,0.17*. These two proportionalities are close. However, they cannot be compared because eq 5 is not applicable to the dat, of Montagna et al. (1977). Literature Cited Marangozis, J., Ind. Eng. Chem. Process Des. Dev., preceding paper in this Issue (1980). Montagna, A. A., Shah, Y . T.. Paraskos, J. A,, Ind. Eng. Chem. Process Des. Dev.. 16. 152 (1977). Paraskos. J.' A,, F;ayer,'J. A,, Shah, Y. T., Ind. Eng. Chem. Process Des. Dev., 14, 315 (1975). Montagna, A. A., Shah, Y. T., Ind. Eng. Chem. Process Des. Dev., 14, 479
(1975). Mears. D. E., Adv. Chem. Ser., No. 133, 218 (1974).
Department of Chemical and Petroleum Engineering University o f Pittsburgh Pittsburgh, Pennsylvania 15261
Q 1980 American Chemical Society
Yatish T. Shah
