temperature. Furthermore, for the demetallization reactions, severe intraparticle diffusional effects appear t o make k' insensitive to the temperature change in case of 22% KVTB. The liquid flow used in this study is about 0.05 kg/m2-s. At such a flow rate,'Figure 4 of Satterfield (1975) indicates that the catalysts are most likely incompletely wetted. Thus, relation 2 may be the most adequate representation of the physical situation for the present experiments. It should be noted that the accuracy of the power 0.82 on d, in relation 3 depends upon the validity of Puranik and Vogelpohl(l974) correlation for the present case. Within the accuracy of the present data, this power on d, appears to be reasonable. T h e power on d, in relation 1 is obtained from the holdup correlation of Satterfield et al. (1969). This correlation is obtained for flow of liquid down a string of spheres and its applicability to the present experimental system may be questionable. I t is clear from this study that relation 1cannot correlate the present data. Relation 2 predicts more realistic dependence of In (CA~,CAJon d, than that predicted by relation 1. Based on this study the effective catalyst wetting model appears to be more realistic than the holdup model. Nomenclature CA, = the reactor inlet concentration of A, g/cm3 C A= ~ the reactor outlet concentration of A, g/cm? d, = catalyst diameter, cm D ~ ~= f effective f diffusivity of A in the catalyst, cm2/s k = intrinsic rate constant for the reaction, l./s k' = a quantity proportional to,fcm
L = length of the catalyst bed, cm LHSV = liquid hourly space velocity, h-' u = kinematic viscosity of the liquid feedstock, cm2/s u = surface tension of the liquid feedstock, dyn/cm
Subscripts A = refers to sulfur, nickel, vanadium, or asphaltenes i = reactor inlet condition o = reactor outlet condition L i t e r a t u r e Cited Aris, R., Chern. Eng. Sci., 17, 167 (1962). Henry, H. C., Gilbert, J. B., Ind. Eng. Chem., Process Des. Dev., 12, 328 (1973). Mears, D. E., Adv. Cbem. Ser., No. 133, 218 (1974). Montagna, A., Shah, Y. T.. Ind. Eng. Cbem., Process Des. Dev., 14, 479 (1975). Paraskos, J. A., Frayer, J. A., Shah, Y . T., Ind. Eng. Cbem., Process Des. Dev., 14, 315 (1975). Puranik, S. S..Vogelpohl, A., Cbern. Eng. Sci., 29, 501 (1974). Satterfield, C. N. Pelossof, A. A., Sherwood, T. K., AIChE J., 15, 226 (1969). Satterfield. C. N., AIChEJ., 21, 209 (1975).
Gulf Research a n d Development Company Angelo A. Montagna Pittsburgh, Pennsylvania 15250 Yatish.T. Shah*' John A. Paraskos Received /or review March 26, 1976 Accepted July 26,1976
Author to whom correspondence should be sent at the Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pa., 15261.
LETTER T O THE EDITOR
Mass Transfer and Power Consumption in a Reciprocating Plate Extraction Column Sir: I t was brought to my attention by Dr. A. Karr that the word stroke (meaning twice the amplitude) should be used in the text to agree with the meaning of a in eq 2 and the values in Table I of Ioannu et al. (1976). Further, Dr. Karr suggested Table I Large holes and free area, Karr and Lo (1971) Methyl Isobutyl Ketone Dispersed, Water a (rnP 0.0125b 0.0125 f (s-')u 4.75 4.63 Power (W/m") 226.0 210.0
Small holes and free area, present investigation Extractant 0.009 0.009 2.0 1.6 166.0 42.0
Methyl Isobutyl Ketone Continuous, Water Extractant a (m) 0.0125 0.010 f (s-1) 4.75 1.68 Power (W/m3) 226.0 108. Values corresponding to the minimum HETS. 3-in. column diameter based on earlier results by Karr (1959).
comparing the power consumption a t the minimum values of "HETS". We were reluctant to estimate point values of the power because of the approximate nature of eq 2. However, such comparison gives the results in the present Table I. It is also worthwhile to add that presence of solids in the system and/or ease of construction of plates (which favor plates with large holes and free area) should be considered together with the power consumption in comparing the two plate designs.
L i t e r a t u r e Cited loannou, J., Hafez, M.,Hartland. S.,Ind. Eng. Cbern., Process Des. Dev., 15, 469 (1976).
Department of Industrial and Engineering Chemistry Swiss Federal Institute o f Technology Zurich, Switzerland
Joachim Ioannou Mahmoud Hafez*' Stanley Hartland
Address correspondence to this author at the Chemical Engineering Department, McMaster University, Hamilton, Ontario, Canada L8S 4L7. Ind. Eng. Chem., Process Des. Dev., Vol. 16, No. 1, 1977
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