Packed columns dumped packings

Fig. 10 Axial profile of the void fiuction in a column dumped with Cascade Mini-Ring 1A with nominal size 25 mm versus the height of the packing.

FIG. 14-80 Cost of internal devices for columns containing dumped packings, a) Holddown plates and support plates, (h) Redistributors, (c) Liquid distributors. [Pikulik and Diaz, Cbem. Eng., 84(21), 106 (Oct. 10, 1977).]... 

Once packing heights are determined in other sections from HETP (distillation) or Koa (absorption), the height allowances for the internals (from Figure 1) can be added to determine the overall column height. Column diameter is determined in sections on capacity and pressure drop for the selected packing (random dumped or structured). 

Random packings rings, saddles and proprietary shapes, which are dumped into the column and take up a random arrangement. 

Ceramic and metal packings are normally dumped into the column wet , to ensure a truly random distribution and prevent damage to the packing. The column is partially filled with water and the packing dumped into the water. A height of water must be kept above the packing at all times. 

Random or dumped packings (Figs. 14-48 and 14-49) are discrete pieces of packing, of a specific geometric shape, that are dumped or randomly packed into the column shell. 

Column packing is as much art as it is science. Even the professionals in the held cannot routinely prepare columns that will give the same plate count column to column. They quality control the columns with a set of standards, and columns that deviate by more than a set amount are either dumped and repacked (not cost effective) or are sold as specialty columns. Columns that exceed QC specifications are almost as bad as poor efficiency columns ... 

You may find that for teaching purposes that packing your own columns may be cost effective. An analytical column holds about 3 g of packing and the column itself can be dumped, cleaned, and reused. However, I would recommend not packing your own research columns. I will show you ways of extending the lifetimes of your columns enough that commercial columns could be cost effective. 

As an alternative to trays, especially at low volumetric liquid-to-vapor ratios, packing can be used to promote vapor-liquid contact. One approach is to dump specially shaped pieces of metal, glass, or ceramic material into the column, wherein they are supported on a grid. An example of dumped or random packing is shown in Fig. 7. 

A 20-mL sample was preconcentrated on a 3-cm column containing Ct reverse-phase material and eluted and chromatographed with a mobile phase o/ 30 70 methanol.O.lM ammonium acetate, pH 6.2 on a 15 cm x 4.6 mm analytical column packed with Ct material electrochemical detector operated at +500 mV vs. Ag/AgCI—(A) standard aqueous solution (B) ground water sample collected near an industrial chemical dumping area. 

R. Billet, M. Schultes, Prediction of mass transfer columns with dumped and arranged packings, Trans. Inst. Chem. Engrs., 1999, 77... 

As long as dumped packing in commercial columns is properly wetted [more than 1000 lb/(h)(ft2) or 5000 kg/(h)(m2)], the following HETP values will result in a workable column ... 

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