(58c) Evaluation of Structured Packing Hydraulic Performance Using X-Ray Computed Tomography

Existing models used to predict hydraulic and mass-transfer performance of packed columns are semi-empirical and rely on column-average properties for parameters such as liquid holdup. These models do not accurately describe the performance observed in operating packed columns, particularly for hydraulic studies. X-ray Computed Tomography (CT) is a non-invasive, non-intrusive imaging technique that was used to provide insight into the liquid distribution and other flow properties within an operating air-water contactor utilizing structured packing. Several commercial stainless steel structured packings, including Sulzer Mellapak 250Y, were installed in a 6-inch air-water column and imaged under irrigated and static conditions using X-ray CT. Liquid rates varied from 0-20 GPM/ft2, and vapor rates ranged from F-factor 0 to 2. Programs to analyze the resulting CT images were written using IDL, a commercial image processing code. Liquid holdup was calculated at several elevations within the packed section through analysis of CT slices. Holdup measurements from slices obtained at evenly spaced intervals were integrated over the height of the column and compared to both experimental data and existing hydraulic performance models. Hydraulic behavior at packing element joints was further investigated by taking several CT slices at close intervals around the joints. Liquid holdup profiles of the packed section showed local peaks at or slightly above packing element joints. Three-dimensional models up to 6? in height of both dry and irrigated packing were obtained by taking a series of CT slices at close intervals and reconstructing using 3-D imaging software. Use of 3-D modeling aims to provide detailed images of liquid location within a volume of the packing, yielding insight to liquid flow path, film thickness and behavior, and wetted and interfacial areas. Data from the CT experiments is to be incorporated in the development of a new predictive model for packed column hydraulic performance.