Analogy of absorption and distillation processes. Wetted-wall column study

In this paper we present results of the distillation experiments in the form of the HETP data and mass-transfer coefficients evaluated by the profile method. The experimental data are compared with those predicted on the basis of the absorption experiments results. The experimental HETP data acquired on the methanol-n-propanol and ethanol-n-propanol systems agree within 10-20% with the data predicted. The distillation mass-transfer coefficients evaluated by the profile method were correlated in the dimensionless form ShL=0.25ReL−0.12ScL0.47andShG=2.3⋅10−3ReLG1.07ScG0.61. The distillation kL values have been found to be 24% lower and the kG values 13% lower than the ones predicted according to absorption correlations. The gas-phase mass-transfer coefficient, kG, exhibits higher dependence on the vapor velocity than it was found in standard absorption measurements. Similar difference was found also for packed columns in previous works. Apparently, there is at least one unaccounted phenomenon which affects differently the mass-transfer performance of absorption and distillation packed columns. Poor results of the present diffusion models have been noticed in this work preventing deeper study of these differences. Improvement of these models is found to be inevitable for the further research in this area as well as for the reliable rate-based modeling of the industrial absorption and distillation columns.