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.
Distillation of Bulk Chemicals
This chapter discusses various aspects of the distillation of bulk chemical processes—that is, distillation columns with diameters of 6 ft (2 m) and larger. These large columns form the basis of all separations in state-of-the-art industrial (petro-) chemical plants. Competitive world-scale plants require hydraulically balanced (high-capacity) column internals that can be reliably scaled over several orders of magnitude in capacity. The design of such industrial columns requires attention to negative performance factors that are less well defined, such as foaming, wetting, polymerization/fouling, scaling, or entrainment. These factors often change over time and relate to catalyst aging or the handling of different feed-stocks. Chemical distillation processes must account for high turndown or complicated chemical interactions stemming from the nonideality of the components to separate, such as the presence of salts. The removal of trace components to produce high-purity products also requires nonstraightforward distillation process configurations. These topics are illustrated by means of distillation column internals layouts in actual industrial process plants. The first part of this chapter describes generic issues related to the design of distillation column internals in chemical process plants. In the second part, it will be shown how these translate to specific design aspects for the column internals of existing industrial processes; issues relating to unit operation lineup, column operation, configuration, integration, and design will be considered.
Influence of corrugation geometry on the performance of structured packings: an experimental study
Abstract While the utilisation of corrugated sheet structured packings is well established, these gas–liquid-contacting devices are still not well understood. A contributing reason is the rather limited publicly available performance data, most of which have been obtained from relatively small columns. A recent comparison of data from the 1.2 m Fractionation Research, Incorporated (FRI) and from the 0.43 m Separations Research Program (SRP) columns show excellent agreement based on equivalent packings. This is significant since the FRI column is considered to be of industrial scale. As a result, we sought to create an expanded data base emphasising packing geometric variations, using packings from a single manufacturer (J. Montz). Hydraulic characteristics of the same packings had been studied previously using air–water simulators at TU Delft. Total reflux distillation experiments were carried out at SRP using a bed height of 3.3 m for all packings. The cyclohexane– n -heptane system was utilized because of the availability of comparative data. The operating pressure was varied from 0.33 to 4.14 bar, to determine the effect of physical properties. The resulting data provided insight into the nature and effect of corrugation angle, specific surface area, and surface texture on pressure drop, capacity and efficiency. In this paper we report the results and also discuss the implications of the observations on model development and design.