Abstract
An investigation has been carried out, on a pilot plant scale, into the factors affecting the hydrodynamic behaviour, mass transfer efficiency, liquid and gas residence times distribution functions and the extent of fluid mixing in a two sieve plate air-water distillation column simulator. The hydrodynamic behaviour was investigated as a function of the column operating conditions and wherever possible the results have been reported as correlation equation suitable for design purposes. The air-aqueous glycerol-oxygen system was chosen for the mass transfer study because the low solubility of oxygen in glycerol solutions means that the mass transfer may be regarded as being controlled by the liquid film. An accurate continuous sample and analysis technique was employed and the efficiency of both the tray alone and the tray plus downcomer was measured. The liquid phase residence time distribution functions were measured using an improved dye injection and photocell detection technique. The degree of mixing was determined using the variance of the residence time distribution function and the eddy diffusion model. The residence time and degree of liquid mixing were investigated as functions of the column operating conditions. The gas phase residence time distribution functions were measured using an ethane tracer with a double sample infra-red detection. The degree of mixing was interpreted using an eddy diffusion model and the Peclet number was successfully correlated with the liquid momentum. The mass transfer efficiency has been successfully related to the hydrodynamic behaviour, the liquid residence time and the extent of liquid mixing on the tray. The liquid momentum has been shown to be the major variable affecting the degree of mixing in both the gas and liquid phases.