Modifications to Structured Packings to Increase Their Capacity
The hydraulic performance of structured packed columns is characterized by parameters such as loading point, flooding point, and dry and wet pressure-drop. These parameters can be positively influenced by optimizing the transition areas between two adjacent packing layers. Tests have been done in a two-phase test rig with a rectangular column made of perspex. The test medium is a liquid hydrocarbon in counterflow to saturated nitrogen gas. The performance of different packing structures at the layer-to-layer transition zone and the addition of vane-type elements between two packing layers was evaluated. Several packing modifications were tested and the results were compared with those of a non-modified packing. The intentions of this work are: to rank the modifications of structured packings with respect to the achieved capacity increase; to determine whether flooding is initiated in the core of the corrugated packing or in the transition area in spite of the modifications made on the lower or top side of the packing sheets; and to find out how the loading point is influenced by the modifications.
Stretching the Capacity of Structured Packings
Comprehensive experimental and modeling studies conducted recently with various types and sizes of Montz structured packing have revealed most performance-related secrets of this gas−liquid contacting device. Compared with other established gas−liquid contacting devices, structured packings are generally known as having the lowest pressure drop per theoretical tray. Less known is the fact that only a small fraction of this low-pressure drop is used in mass-transfer processes. Knowing this and using a model capable of describing realistically the relationship between geometric features and fluid mechanics, we have manipulated the geometry of the packed bed to develop configurations that allow a substantial increase in capacity without affecting efficiency adversely. The resulting configurations were tested experimentally and a joint experimental and modeling effort by the Delft University of Technology and J. Montz GmbH has led to increased capacity of well-established 45° corrugated sheet packings.
Structured Packing PerformanceExperimental Evaluation of Two Predictive Models
A comprehensive total reflux distillation study of sheet metal structured packings was carried out with the cyclohexane/n-heptane test mixture. The experiments covered a wide range of pressures, two corrugation angles, two surface areas, and two surface designs. Experimental results include pressure drop, capacity, and mass-transfer efficiency. The database generated has been used to evaluate generalized performance models developed independently at The University of Texas Separations Research Program (SRP model)) and at Delft University of Technology (Delft model). This paper reports the experimental results and compares them with predictions from the two models. Deviations of predictions from measurements are discussed in terms of likely contacting mechanisms in the packed bed.