Kinds of Packings

The broad classes of packings for vapor-liquid contacting are either random or structured. The former are small, hollow structures with 

Whenever possible, the ratio of tower and packing diameters should exceed 15. As a rough guide, 1 in. packing is used for gas rates of about 500 cfm and 2 in. for gas rates of 2000 cfm or more. 

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Packung, /. packing seizing, seizure. Packungs-art, /. kind of packing (Cryat.) structure, -erscheimmg, /. packing phenomenon. 

If it is desired to evaluate a change in performance on an existing tower, knowing the required conditions and numbers of decks and kind of packing, calculate KaV/L for we assumed values of L /G. ... 

As usual, this can be due both to thermodynamic and kinetic reasons. In fact, the presence of comonomeric units increases, in general, the energy content of all the crystalline forms, but, since the extent of increase may be different, it may destabilize some chain conformation or some kind of packing more than other ones. On the other hand, the influence of the comonomeric units on the polymorphic behavior of a polymer can be due to a change in the crystallization rates of the various forms. 

Corresponding to its inferior space filling, the body-centered cubic packing of spheres is less frequent among the element structures. None the less, 15 elements crystallize with this structure. As tungsten is one of them, the term tungsten type is sometimes used for this kind of packing. 

The solid complex of TV-methylbenzothiazol -2(3H)-selcnonc (mbts) with Te(Ph)Br contains two symmetry-independent molecules, both of which pack in a way that weak dimers through T-T contacts are formed (Figure 29). In molecule A the distance between the Te atom and the neighbouring conjugated ji-system is 365.6 pm, and the Te atom is positioned over the central carbon atom of selenoamide function (Te- Se 413.8 Te- -S 396.1 Te- -N 393.4 pm). In molecule B, the distance from Te to the rc-system is 370.5 pm, and the Te atom is shifted away from the central carbon atom towards the endocyclic sulfur atom (Te- -Se 422.7 Te- -S 390.6 Te- -N 450.2 pm). Related T-T contacts are a general kind of packing for Se and Te-centred T-structures. 

A number of siloxane-containing controlled release packs have been devised and used. Glaucoma, motion sickness, and diabetes have been treated using drugs dispersed in a silicon matrix. This kind of pack needs to be placed near the site of intended activity for greatest effectiveness. 

Polystyrene is a common polymer used to make Styrofoam containers, packing peanuts, and insulation. Another kind of packing peanut used is made of starch. Place about a cup of acetone in a glass container. Acetone is available wherever paint is sold. Do this in a well-ventilated area. Be careful with the acetone, it can remove paint and ruin finishes. Add a starch packing peanut to the acetone and then a Styrofoam packing peanut. The starch peanut will not dissolve, but the polystyrene peanut will. Dilute the acetone with ample amounts of water before disposing down the sink. 

Numerous investigations have been conducted of mass transfer coefficients in vessels with a variety of kinds of packings. Many of the mote acceptable results are cited in recent books on mass transfer, for instance, those of Sherwood et al. (Mass Transfer, McGraw-Hill, New York, 1975), Cussler (Diffusion, Cambridge, 1984), and Hines and Maddox (1985). A convenient correlation of mass transfer coefficients in granular beds covering both liquid and vapor films is that of Dwivedi and Upadhyay [Ind. Eng. Chem. Process Des. Dev. 16, 157 (1977)], namely,... 

HTUs vary with the kind of packing, the flow rates, the distribution of flow across the cross section, and sometimes with the packing height and column diameter. They are necessarily experimental data. Some of these data are discussed at the end of this chapter. 

Figure 13.40. Comparison of pressure drops through several kinds of packed beds, (a) 2 in. Raschig and pall rings fEckert et al., Chem. Eng. Prog. 54(1), 70 (1958)]. (b) 1 in. Tellerettes [Teller and Ford, Ind. Eng. Chem. 50, 1201 (1958)]. (c) 2 in. plastic Tripack and other 2 in. packings (Polymer Piping and Metals Co.).

A class of operations has been devised in which the process fluid is pumped through a particular kind of packed bed in one direction for a while, then in the reverse direction. Each flow direction is at a different level of an operating condition such as temperature, pressure, or pH to which the transfer process is sensitive. Such a periodic and synchronized variation of the flow direction and some operating parameter was given the name of parametric pumping by Wilhelm (1966). A difference in concentrations of an adsorbable-desorbable component, for instance, may develop at the two ends of the equipment as the number of cycles progresses. 

What kind of packing arrangement do these oranges have ... 

A summary of stacking patterns, coordination numbers, amount of space used, and unit cells for the four kinds of packing of spheres is given in Table 10.10. Hexagonal closest-packing is the only one of the four that has a noncubic unit cell. 

Which of the four kinds of packing used by metals makes the most efficient use of space, and which makes the least efficient use ... 

In principle, all powerful element-specific methods that are able to monitor continuously the effluents of separation processes commonly in the range of a few mimin-1 and in element concentrations of some Klpg liter-1. A well-suited method is based on modern element-specific quadrupole mass spectrometry (MS) with an inductively coupled plasma (ICP) interface to the separation unit [e.g., liquid chromatography (LC) or field-flow fractionation (FFF)].Tlie ICP-MS detection can also be used for continuously characterizing the effluent of any kind of packed column (Metreveli and Frimmel, 2007). By this, the transport and elution properties of... 

Various kinds of packing defects exist in the ionic crystals of NaCl type. A pair of cation and anion may be shifted from their stable positions toward the surface of the crystal, thus leaving behind a pair of vacancies. This is called the Schottky defect. The cation may leave its stable position and enter into an interstitial site. The formation of an interstitial cation and a vacancy is called the Frenkel defect. In addition to these two common kinds of defects, the presence of impurity atoms, atoms of varied valence, vacancies, and/or interstitial atoms is also possible. Some other important defects are discussed below. 

Unfortunately, Darcy s law says nothing about the microscopic flow profile in the packing. The most serious weakness of Darcy s law, however, is that K0 varies strongly with the kind of packing material with no hint on the nature of the dependence. This shortcoming is addressed below. 

Q A heat pack can be used to supply heat to injuries. One type of heat pack is re-usable. It contains a supersaturated solution of a salt and a disc of metal. When the metal disc is bent, the solute begins to crystallize and releases heat. The pack can be reset by heating it in boiling water, which causes the salt to dissolve again. How can you account for the heat that is released by this kind of pack ... 

Fig. 14a. Packed column Fig. 14b. Various kinds of packing (a) Raschig...

In the manufacture of sulfuric acid, the SO2 is first catalytically oxidized, to SO3 which is then absorbed into a H2SO4-H2O-SO3 solution (absorption directly into H2O is not feasible because a mist forms with SO3 that cannot be absorbed). An absorption tower is usually composed of various kinds of packing, but sometimes trays are used as in a distillation column. For sulfuric acid manufacture the steel tower is lined with acid proof masonry, and chemical stoneware is used for the packing. A tower might be 7 or 8 m in diameter and absorb 1,000 tons per day of SO3. Absorption towers are used to retrieve many other gases from the vapor phase into the liquid phase (not necessarily water). 

While the selection of a stationary phase to be used in the analytical column may appear complex, the decision can be greatly simplified by considering the three basic methods of separation currently in use. These are gel filtration or size-exclusion separation, reversed-phase or hydrophobic separation, and ion-exchange separation. In general, each type of separation uses a different kind of packing material, and since each type of separation exploits a different property of the molecules, the choice of packing really comes down to which property of the molecules would be most useful in achieving the separation. 

The number of transfer units is sensitive to the value of L/G, but the effect of k lkf, is more modest, at least over the high range used data for this ratio do not appear to be prominently recorded. Figure 9.16 shows a wide range of heights of transfer units for the different kinds of packings, here characterized by the surface a, (sqft/cuft) and substantial variation with L/G. The last line of the calculation summary shows variation of the tower height with L/G. 

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