Evaluation of the k_La_e of Structured Packings in Small Diameter Columns - The Key Role of Wall-Wipers

Abstract

Wall wipers are commonly used in columns filled with structured packings in order to reduce the liquid flow along the column walls. In small diameter columns wall regions are prominent and wall flow, if not well tended to, can adversely affect measured mass transfer parameters, particularly the liquid side mass transfer coefficient kLae. Wire gauze wall wipers provided by some manufacturers do not properly prevent wall liquid flow. In this work, specific wall wipers designed to re-direct liquid wall flow onto packing surfaces were tested against standard wall wipers that do not always properly reduce wall flow. Tests were run on two distinct facilities each with a column diameter of about 150 mm and with bed heights from 0.42 to 1.68 m of Mellapak™ 250.Y packing. The results demonstrate that with the more effective wall wipers it is possible to measure intrinsic height independent values of kLae that match those obtained in a 300 mm diameter column with standard wall wipers.