Packed columns, packing random packings

The design of packed columns using random packings is covered in books by Strigle (1994) and Billet (1995). 

Figure 8.7 provides fractionation column internal trays that are to be added to the overall pressure vessel cost. A packed-column internal (random packing) cost is also given as cost per cubic foot of column-packed volume. 

Fig. 7.2 Counter-current vapor-liquid contact in packed columns, either randomly packed (e. g., Raschig rings) or A/ith structured packing (e.g., Sulzer BX)...

TABLE M Maximum Prasaura Drops Racommandad lor Packed Columns with Random Packings ComftwwC) ... 

FIG. 14-81 Cost of internal devices for columns containing random packings, (a) Holddown plates and support plates, (b) Redistributors. [Pikulik and Diaz, Chem. Eng., 84(21), 106 (Oct, 10, 1977).]... 

Choose between the tray column, the randomly packed column, and the systematically packed column. It is unlikely that a single 300-ft tray column or a 400-ft randomly packed column would be installed for this system. In addition, multiple-column operation, by its nature, is expensive. So it is reasonable to opt for the 131 -ft column containing systematically packed corrugated-wire-gauze... 

Verify the packing size and diameter of the column. Column diameter should be a minimum of 10 times the packing size for random packing. Column diameters smaller than this criterion have a significant risk of excessive liquid and vapor channeling. Select a new packing size as needed. 

Orts, P. 1995. Petformance and Scale-up of a Laboratory-Scale Distillation Column Containing Random Packing, diploma thesis, Universite de Liege, May. 

As in distillation columns, a packed column contains small packing elements dumped into the column in a random fashion, and these elements can provide the needed intimate contacting of the descending liquid and the rising gas or vapor. Packings of an ordered, or structured, form are rarely if ever used for absorption or stripping. 

Belles and Fair evaluated a large data bese of published tests ou the performance of columns containing random packing and developed a mass transfer mode) that appeals to be superior to those previously... 

In distinction to plate columns, in which the various parts are permanently built in, and packed columns, which contain packing in a random arrangement, the columns to be described now are provided with some loose, regularly-arranged form of solid or perforated contact element. 

When only the upper sections of a column contain random packings. The expense of filling the entire column with water in order to wet-pack the upper sections is rarely justified. 

To obtain the most effective exposed wet-table surface in a column with random packing (Fig. 2-71), the liquid should be... 

Column with random packing (see Table 2-27) or tower with random packed tubes (heat exchange possible to a cooling agent on the shell side). Specific surface 50-300 mVm diameter up to 2.5 m vapor load factor 1-2.5 Pa trickle density 2-100 m / (m h) specific pressure drop 20-120 mm water gauge gas and liquid phase are both continous. 

It is assumed that the mass tiansfer occurs in the layers on both sides of the phase boundary. According to the model, the mass transfer is caused by molecular diffusion. Therefore, a linear concentration profile is built up in the boundary layers. At the phase boundary itself, thermodynamic equilibrium is reached. More or less empirical correlations for the mass transfer coefficients /I and for the effective phase interface area are usually provided by the simulation program for different column internals (random packings, structured packings, and trays). The necessary diffusion coefficients can again be calculated according to Section 3.3.6. 

Figure 6-21 Distillation column—Packed random saddle design...

The work of Brauer [3, 4] and Reichelt [1, 2] as well as [6,19-24] show that it make sense to take into account the influence of the column wall on the hydraulic diameter dh of packed columns with random and stacked packing elements. 

Some of the simplest designs are spray columns without internals and packed columns containing randomly filled and stacked packing elements, tube columns or columns with structured packing, see Fig. l-2a. 

Dispersed Phase Hold-Up in Packed Columns Containing Random and Structured Packings... 

Fig. 2. Packing materials for packed columns, (a)—(f) Typical packing elements generally used for random packing (g) example of stmctured packing.

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