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Ind. Eng. Chem. Res. 1993.32, 652-656
Performance of Crossflow Cascade Packed Column at Gas Velocities above the Flooding Point of Countercurrent Beds Yoshishige Hayashi,' T a k u y a Kawanishi, T a k a s h i Uda: Yumi Akiyama) and Norihiko Kageyama* Department of Chemistry and Chemical Engineering, Kameaura Uniuersity, Kodatsuno, Kamrawa 920, Japan
Absorption experiments of COz and NH3 in water were performed using a crossflow cascade packed column with 4,8, and 12 stages. Packings used were 12-mm ceramic Raschig rings and 47-mm S - 0 Tellerettes. T h e flow behavior of the fluid in the cascade column was examined. The effect of baffle spacing arrangement on the absorption of COZand NH3 was investigated using the data on masstransfer coefficients, gas-phase pressure drops, and mean residence times of the aqueous phase. The optimum operating conditions and baffle arrangements were identified for the design of crossflow cascade columns that could achieve efficiencies equivalent t o those of conventional countercurrent packed beds. Introduction
t Liquid flow
A crossflow cascade packed column has several features in construction that are unique. The characteristics of both countercurrent and crossflow operations have been discussed by Thibodeaux et al. (1977). It can be operated atgasvelocitiesabovetheflocdingpointsofcountercurrent packed beds (Thibodeaux, 1980; Hayashi et al., 1988a,b). The gas-phase pressure drop in a crossflow cascade column is considerably less than that in countercurrent packed beds (Thibodeaux, 1979; Hayashi et al., 1988a,b). Good absorption capacityispmibleovera broadoperatingrange (Hayashi et al., 198813). Velaga et al. (1988) have investigated the stage efficiencies of chemical separation for stripping and distillation in crossflow cascade packed columns. In this study, the overall volumetric mass-transfer coefficientsfor the gas and liquid phases were determined in a crossflow cascade column packed with either 12-mm Raschig rings or 47-mm S - 0 Tellerettes. The absorption of Con and NH3 in water was studied. Gas-phasepressure drop and mean residence time of the aqueous phase were measured. The effects of the packed cross-sectional areas for the liquid and gas flows AL and Ao and the operating conditionsL and G on mass-transfer characteristics were investigated. The optimum design conditions for the crossflow cascade column were determined.
