ON THE PERFORMANCE OF A CASCADE CROSS-FLOW AIR STRIPPING COLUMN

The cascade crossflow packed column is an innovative design that offer s the separation advantages of countercurrent flow while avoiding floo ding limitations. Liquid and gas cross-sectional flow areas and path l ength in contact with packing may be controlled independently. These f eatures are illustrated by studying the air stripping of methylene chl oride (MeCl), 1,2-dichloroethane (1,2-DCA), and methyl ethyl ketone (M EK). Stripping efficiencies in the cascade crossflow column were gener ally slightly smaller than in countercurrent flow at equal liquid and gas flow rates. However larger gas-to-liquid ratios were possible in c rossflow, permitting larger maximum stripping efficiencies to be attai ned. The experimental mass transfer coefficients were smaller than pre dicted by the Onda correlation. Modifications to the gas-phase Onda co rrelation are proposed that reduce the magnitude of the average deviat ion between experiment and prediction for 40 tests to about 12%. Exper imental values of 38 of 40 tests were within +/-30% of modified Onda c orrelation predictions. Additional applications for the cascade crossf low concept are suggested, such as vacuum distillation columns and tri ckle-bed reactors, which require low pressure drop and/or large gas-to -liquid ratios.