Transient response study of gas flowing through irrigated packing

The transient response of a gas phase as it flows through an irrigated packed column can be interpreted as a distribution of time spent by the elements of gas as they flow through the bed. A step function in helium concentration was introduced in the entering air stream of a column packed with Raschig rings, and the outlet concentration was recorded with time. Water was used as the liquid phase. Size of Raschig rings, depth of bed, water and gas flow rates were the main variables investigated. The response curve for the gas reveals an increasing departure from uniform flow of the gas stream as liquid and gas rates are increased to flooding. The first and second moments of the time distribution give directly the porosity and the axial dispersion of the gas. These quantities have been found to be mainly dependent on liquid flow rates. The skewness which characterizes the weight that the various gas elements have on the dispersion about the average residence time has been found to give a convenient measurement of the uniformity of gas flow through the bed.