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r L = axial coordinate in adsorber in the direction of liquid flow, = length of carbon bed, m m Greek Letter9 C B CL cp = particle porosity p = liquid viscosity, kg/(m)(s) p = liquid density. kg/m3 T 71 = void fraction in the bed = dynamic liquid holdup, (volume of liquid)/(volume of empty tube) = retention time in the bed, ~L l / u , . , s = total average retention time from injection point to detector, s LITERATURE CITED Coto, S., and J. M. Smith. Trickle-Bed Reactor Performance: Part 1. phases was measured and correlated using the data of previous investigators. The correlation is for a flat bladed turbine operating within the turbulent regime in fully baffled vessels. The accuracy of the predictions and the range of geometrical Department d Chemlcal Englneerlng Unlvmny d Rhode Island variations and equipment sizes support the use of the correlation for scaleup o p erations. Kingston, RI 02881 SCOPE The power consumption of impellers used for agitating gasliquid systems is a widely used parameter for determining gas ISSN ~I -I M I -R~-S~I~-O I % -~~ 00 : Q he Amencan inrtituie d Chemical h g i m r s . 1882holdup, interfacial area and mass transfer rates in baffled vessels. The use of this parameter leads to complications since to date, there appears to be no general working equations for the prediction of power consumption.

Three-phase contacting is often carried out in gas-slurry stirred vessels. The influence of the solids concentration on the gas-liquid interfacial area has to date always been determined by chemical methods. This method has many drawbacks, including the fact that the mass transfer coefficient kL itself is dependent on the bubble diameter and interfacial area. Therefore a mass-transfer-independent means was used to evaluate the gas-liquid interfacial area. Also the solids concentration and sizes were varied and a coalescence frequency determined to evaluate the influence of the size of the solids on bubble coalescence. Experimental ProcedureThe experimental apparatus, shown in Figure 1, consisted of a 0.44 m dia. by 0.46 m high fully baffled stirred tank agitated with a single six-blade, flat-disk impeller. Two impellers having diameters of 0.23 and 0.15 m, respectively, and an impeller width-to-diameter ratio of 1/5 were used at an impeller location of one impeller diameter off of the bank bottom.Dispersions of air in water slurries of glass beads, having average sizes of 25,70, and 200 pm, were studied at various concentrations. The method of light scattering (Calderbank, 1958) was used to determine the gas-liquid interfacial area. Details of the equipment can be found elsewhere (Nagaraj, 1984). In each case the gas rate was maintained at a constant rate of 0.0283 m'/min and the light intensity readings were taken at an optical path length of 0.0508 m. Measurements in liquid, gas-liquid, solid-liquid and gas-liquid-solid systems were made for calibration purposes.The concentrations of solids were kept low to limit the effect of multiple scattering. McLaughlin and Rushton (1973) and Weinstein and Treybal ( 1973) have discussed conditions under which multiple scattering is negligible, and McLaughlin and Rushton have considered that when less than 10% of the inciThe prcsent address of N. Nagaraj is Ames Research Center. Moffett Field, CA 94035 dent intensity is received by the photocell, multiple scattering becomes important. This was further confirmed by two methods.1. Since the solids are much smaller than the gas bubbles, it could be expected that any multiple scattering, if present, would largely be due to the solids. Absence of multiple scattering in a solid-liquid system was confirmed by the method of Van de Hulst (1957), whereby a linear relationship was obtained between light attenuation and solids concentration.2. The effect of multiple scattering on the data obtained was found to be negligible by comparing the results obtained for the cases where the photocell received less than 10% of the incident light, using the linear correlation of Mclaughlin and Rushton (1973), and also using the multiple scattering calculations of Langlois et al. (1954). The work of Langlois et al. does not cover a gas-liquid-solid system, but does cover a liquid-solid system (glass beads in liquid) and a gas-liquid (air-glucose) system. By extrapolating these results, a value of , f 3 = 1.4 was used for the present system. This va...