Fractionation Packing

Packing used for fractionation can also reduce the pressure drop (Delta P) in a tower compared to trays. Tray designs are more limited in Delta P reduction. The packing surface allows intimate contact between vapor and liquid without having to have the vapor pass through the liquid. The liquid phase coats the packing surface as a film so the liquid phase movement is 

If the liquid flow to the packing is low and a spray distributor is used, the sprays can collapse so that the liquid contact with the vapor degrades causing low viscosity and poor volatility of the stream below. If the pumparound rate is too high, liquid may be atomized at the spray distributor and the small liquid droplets may be entrained upwards. If the liquid stream is from the pumparound, the product above the pumparound will be contaminated with heavy components. If there is leakage or overflow Ifom the sidestream draw off pan, the falling liquid does not contact the vapor and it will reduce the viscosity of the stream below and also result in poor volatility. 

---

Figure 9-43. Fraction packing wetted. Used by permission of Shul-man, H. L., Uiiich, C. F., Prouix, A. Z., etnd Zimmerman, J. O., A.I.Ch.E. Jour., V. 1, No. 2 (1955) p. 253 ail rights reserved.

Grohn and Vasiliu-Oprea (18,31,32,41) studied the grafting of several vinyl monomers on polyamide, mainly polycaprolactam. [Their work was summarized in the Simionescu and Vasiliu-Oprea book (73).] In each case, the polymer was first purified by extraction, dissolution and reprecipitation. The grinding was performed at 0.42 fraction packing and by using 16 mm diameter steel balls, at an amplitude of 1.75 mm and at 1420 rpm. With vinyl chloride the air was eliminated from the reaction jar and the monomer was introduced at up to two... 

Fig. 6 The release of ethinamate from capsules containing different particle size fractions packed to give different porosities.

Here cpmax is the maximum volume fraction (packing density) that the dispersed particles can have. At that value the viscosity becomes infinite (no flow possible). For random packing of monodisperse spheres, polydisperse systems, its value can be appreciably higher. Note that now particle size becomes a variable, though its spread (e.g., relative standard deviation) rather than its average is determinant. 

Name Material Nominal Size Surface Area (m m3) Void Fraction Packing Factor (m ) Vendor... 

Catalysts Ru loading (mass fraction) /% Packed density/ (g-cm ) Reaction rate Reaction conditions ... 

Figure 7. Various Types of Random Fractionation Packing (Drawing courtesy ExxonMobil Research and Engineering)...

---