592
Ind. Eng. Chem. Process Des. Dev. 1980, 19, 592-599
TB,P , TRG= absolute temperature at blast condition, exit reduction zone and raw gas, respectively X = Nn o fNn1o: 6Y = ~&1fNH20 Literature Cited Anthony, D. B., Howard, J. B., AIChE J., 22, 1625 (1976). Amundson, N. R., Arri, L. E., AIChE J., 24, 87 (1978). Arri, L. E., Amundson, N. R., AIChE J., 24, 72 (1978). Arthur, J. R., Trans. Faraday Soc., 47, 164 (1951). Bgmford, C. H., Tipper, C. F. H., Compr. Chem. Kinet., 17, 207 (1977). Biba, V., Macak, J., Klose, E.,Malecha, J., fnd. Eng. Chem. Process Des. Dev., 17, 92 (1978). Denn, M. M., "Moving bed gasifier modeling", EPRI Workshop on Coal Gasification Reactor Modeling, Asilomar, Calif., June 21-23, 1978. Denn, M. M., Yu, W. C., Wei, J., Ind. Eng. Chem. Fundam., 18, 286 (1979). Desai, P. R., Wen, C. Y., US. DOE Rept. MERC/CR-78/3 (1978). Elgin, D. C., Perks, H. R., Proc. 6th Synth. Pipeline Gas Symp., 247 (1974). Ergun, S.,Mentser, M., Chem. fhys. Carbon, 1, 203 (1965). Friedman, L. D., Rau, E., Eddinger, R . T., Fuel, 47, 149 (1968). Gumz, W., "Gas Producers and Blast Furnaces", Chapter 6, Wiley, New York, 1950. Hebden, D., Proc. 7th Synth. Pipeline Gas Symp., 387 (1975).
Hibbrand, F. B., "Introduction to Numerlcal Analysis". p 451, Waw-HI!. New York, 1956. Juntgen, H., van Heek, K. H., Fuel, 47, 103 (1968). Kosky, P. G., "Some limltatkns on Um mathematbl modeling of coal gsitiers", EPRI Workshop in Coal Oasificatkn Reactor Modeling, Asilomar, Calif., June 21-23, 1978. Kydd, P. H., Chem. Eng. frog., 71, 62 (1975). Lacey, J. A., Adv. Chem. Ser., No. 89, 31 (1967). Loison, B., Chauvin, R., Chem. I d . , 91, 269 (1964). Von Fredersdorff, C. G., Elliot, M. A., "Chemistry of Coal Utilization, 3", H. H. Lowry, Ed., "Coal gasification", p 960, Wiiey, New York, 1963. Walker, W. H., Lewis, W. K.. McAdams, W. H., Gilliland, E. R., "Principles of Chemical Engineering", 3rd ed, p 239, McGraw-Hill, New York, 1937. Waiters, J. G., Ortugllo, C., Glaenzer, J., U . S . Bur. Mines Bull. 643 (1967). WccdaiDuckham Ltd, "Trials of American Coals in a Lurgl Gasifier at Westfield, Scotland", NTIS Fe-105 (1974). Woodmansee, D. E., Palmer, P. M., ACS Symp. Ser., 22(1), 159 (1977). Yoon, H., Wei, J., Denn, M. M., "Slmulation of a Lurgi Gasification Reactor", preprint, 69th Annual AIChE Meetlng. Chicago, Nov 28-Dec 2, 1976. Yoon, H., Wei, J., Denn, M. M., AIChE J., 24, 885 (1978).
Received for review October 12, 1979 Accepted May 21, 1980
Behavior of Gas Bubbles in Bubble Columns Korekaru Ueyama Department of Chemical Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113, Japan
Shlgeharu Morooka Department of Applied Chemistry, Kyushu University#Higashi-ku Fukuoka, 8 12, Japan
Koro Kolde Department of Chemical Engineering, Shizuoka University. Johoku, Hamamatsuahi, Shizuoka, 432, Japan
Hlsatsugu Kajl Nishiki Research Laboratory, Kureha Chemical Industry Company, Ltd., Nishlki-machi, Iwaki-shi, Fukushima, 974, Japan
Terukatsu Mlyauchl' Department of Chemical Engineering, University of Tokyo, Bunkyo-ku, Tokyo, 113, Japan
The behavior of gas bubbles in a bubble column of 0.6 m i.d. was experimentally studied by changing gas velocity, liquid depth, and the gas distributor used. The resutts were compared with those obtained using a large-scale bubble column of 5.5 m i.d. There was no clear effect of column diameter on the average gas holdup corresponding to bubbling bed height. However, the axial and lateral distribution of local gas holdup which was detected by an electric resistivity probe showed strong dependence on the absolute value of liquid depth and the type of gas distributor used. The axial and lateral distributions of bubble velocity and bubble size were also obtained using twin electric resistivity probes. When the superficial gas velocity was 0.02-0.04 m s-', the mean diameter of bubbles for 5.5 m i.d. was almost twice as large as that for 0.6 m i.d. On the basis of these data, the flow characteristics of the bubble column were discussed.
Introduction
The bubble column is a typical reactor used for gasliquid systems as it can be easily constructed owing to simplicity of design and an absence of moving parts. To date, many studies have been undertaken on the flow characteristics of the bubble column (Maeda, 1963; Kato, 1963; Ptergaard, 1968; Sada, 1969; Akita, 1973). Most of these studies, however, are confined to the bubble-flow
regime where the gas flow rate is small and individual bubbles ascend homogeneously after uniform generation by a gas sparger. Recently, special interest has been directed toward operating a bubble column in the higher gas feed regime where the majority of bubbles concentrate in the central region of the column and ascend by alternately coalescing and breaking up (Pavlov, 1965; Towel1 et al., 1965; Yosh-
0196-4305/80/1119-0592$01.00/00 1980 American Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 4, 1980 593 ,Column wall of conicoi
tube
'Air
Figure 2. Details of gas inlet of the multi-nozzle type gas injector. Figures are in units of millimeters. or ric
Multi-nozzles
Air
electrode
Figure 1. Experimental apparatus. Figures are in units of millimeters.
itome, 1967; Yamagoshi, 1969; Miyauchi and Shyu, 1970; Hills, 1974; Ueyama, 1978). For example, a recent application t~ high-temperature steam cracking of petroleum asphalt, a process named EUREKA utilizes this type of reactor (Gomi et al., 1975; Takahashi and Washimi, 1976). Flow and mass transfeir properties of the bubble-columntype reactor used in the process were studied by the research team on large-scale bubble columns (Koide et al., 1979; Kataoka et al., 1979; Kojima et al., 1980). Flow properties of the column, however, showed interesting but puzzling behavior as a result of the bottom section of the column being a conic,al shape and of the aspect ratio thereof (i.e., liquid depth/column diameter) being close to unity. To elucidate these effects, a series of experimental studies has been perforined by using a medium-size bubble column. The column is transparent and its geometrical shape is similar to the one utilized in the EUREKA Process. This paper reports a part of the studies, and is especially concerned with the behavior of bubbles. Experimental Apparatus a n d Procedure Experimental Apparatus. Figure 1 shows the dimensions of the bubblie column used in this experiment. It consists of a conical lower section with a cone angle of 0.5 a rad and a cylindrical upper section with a diameter of 0.60 m. Both sections are made of transparent PVC plate. Air with a ternperature of 288-291 K was fed through gas injectors installed in the lower part of the conical section. Two types of gas injectors were used and details thereof are shown in Figures 2 and 3. The liquid used was tap water at a temperature of about 283 K. The height of liquid was kept a t 0.35, 1.3, and 1.8 m above the level where the conical and the cylindrical section were welded together (level A in Figure 1). During a run, the liquid was neither fed nor discharged. Axial distribution of Z, the cross-sectional average of gas holdup, was obtained by measuring static pressures at different heights in the column. Twenty-two pressure taps with a diameter of 0.0101 m were installed in the wall of
1
Air
Figure 3. Details of gas inlet of the single-nozzle type gas injector. Figures are in units of millimeters.
0 25Rrad
t
7
ss steel pipe
s Connecting wire
T
