Packed columns random dumped packings

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). 

The internals of a distillation column or an absorber need not be, and increasingly are not, a series of trays. The packings shown in figure 6.13 can be randomly dumped into a column upon a vapour distributor. The upward-flowing gas or vapour passes through the distributor and follows a meandering path to the top of the packing. This... 

Figure 2-5 illustrates a typical section of Intalox packing 2T for use in a small diameter column. As with random dumped packings, pressure drop is determined for structured packings using an air/water system at atmospheric pressure and ambient temperature. Figure 2-6 is a plot of the pressure drop for Intalox Structured packing 2T. These curves have... 

Later experiments in small diameter columns have shown that a bed of random dumped packing develops a definite number of preferred paths of internal liquid flow [8]. If liquid is distributed onto the packed bed with a greater number of streams per square foot than number of preferred liquid paths, the liquid streams within the bed coalesce until the number of preferred liquid paths is reached. If liquid is distributed onto the packed bed with a smaller number of streams per square foot than the number of preferred liquid paths, the packing redistributes the liquid until the number of preferred liquid paths is established. In this latter case, the upper portion of the packed bed has a lower-than-nor-mal separating efficiency. Figure 10-8 shows the performance of such a packed bed in a binary distillation. Curve I represents the separation obtained with a high-performance liquid distribution system. Curve II shows the effect of inadequate liquid distribution to the top surface of the 10-ft deep packed bed. 

The Crawford-Wilke flooding correlation for liquid-liquid contactors is shown as Figure 11-7. The values for surface area and void fraction for commonly used random dumped packings are given in Tables 11-4, 11-5, and 11-6. The correlations to predict maximum capacity of liquid-liquid contactors do not provide the same degree of reliability as offered by correlations for gas-liquid columns. 

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. 

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. 

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