Packing selection, initial

Because the volume of aqueous feed solution is much greater than the volume of solvent, the water phase will be dispersed into the solvent phase in order to generate the maximum interfacial area for mass transfer. The packing selected will be 40IMTP packing, which will be wetted initially with solvent. From Table 11-4, this packing has a surface area of 46 ft /ft, and the void fraction is 0.972. 

Using the thin layer initial condition the lower layer increases in height due to mass transfer from the upper to lower layer. Thus the initial mass of solids in the upper layer must be sufficient to form the lower layer. In order to achieve this the volume fraction of the gas in the upper layer must be reduced, otherwise the model will fail when the gas volume fraction in the upper layer reaches unity. Using the thick layer option there is no need to do this since the mass transfer is in the opposite direction. As a result selecting initial conditions using the thick layer option is more straightforward. This corresponds with the almost foil-bore flow of densely packed material may be observed at the discharge from a blow tank (pressure vessel) feeder. 

Table 3 compares packings as an aid to initial selection. For simple applications use Pall Rings for studies as a tried and true packing. This will give conservative results when compared w ith more recent random packings. 

Filter life varies with make and type, and may be limited by the ability of the fan to operate against pressure drop. It is a function of the dirtiness of the air and the amount of material packed into the filter bank. Life may be quoted in terms of dust held in g/m face area. For fan selection knowledge of pressure drop is required. Typically, a panel filter might be quoted as operating from, say, 75 Pa initially at 2.5 m/s face velocity to 250 Pa when loaded and a HEPA might operate up to 700 Pa. The pressure drop... 

In subsequent work the same supported catalysts were used in different reactor setups [20] (Figure 3.3). A vapour-phase reactor in which the supported catalyst was mounted on a bed was used for the hydroformylation of volatile alkenes such as cis-2-butene and trifluoropropene. The initial activities and selectivity s were similar to those of the homogeneous solutions, i.e. a TOF of 114 and 90% ee in the hydroformylation of trifluoropropene was reported. No rhodium was detected in the product phase, which means less then 0.8% of the loaded rhodium had leached. The results were, however, very sensitive to the conditions applied and, especially at longer reaction times, the catalyst decomposed. In a second approach the polymer supported complex was packed in a stainless steal column and installed in a continuous flow set-up. 

Note A mixture of two organic liquids is used for this study. The specific liquids will be selected by your instructor. They should be available in a vial equipped with a rubber septum. Your instructor has also selected the initial column packing and length. The two liquids should be in a ratio of approximately 1 1 by volume. 

In the first example, a broad distribution sample of polystyrene was analyzed on a set of high efficiency Ultrastyragel GPC columns (lO. lO jlO A) with which It was determined that Mw = 214,000 and Mn = 87,000. In the Ideal case, a similar set of three (10, 10, lO A) preparative Styragel columns (each 57 mm I.D. X 4 ft) could have been used to fractionate the polystyrene sample. However, we Initially chose to demonstrate the extent of fractionation possible with only one preparative column and selected the lO A column packing material so as not to exclude any of the higher molecular weight fractions. 

Other important parameters in providing successful GC are the column packing, temperature conditions, and selection of a detector as specific to the analyte as possible. Maximum resolution of the halocar-bons is achieved with an 8-ft X 0.1-in. i.d. column of Carbopack-B coated with 1% SP-1000. The initial temperature of 45 °C is held for 3 min and then programmed at 8 °C/min to 220 °C. An organohalogen detector (OHD) is used. The aromatics are best resolved with a 6-ft X 0.085-in. i.d. column of Supelcoport coated with 5% SP-1200 plus 1.75 Bentone-34. They are measured with a photoionization detector. The temperature conditions are as follows 50 °C for 2 min then programmed at 6 °C/min to 90 °C. A 10-ft X 2-mm i.d. Porapak-QS (80-100 mesh) column at a temperature of 110 °C for 1.5 min and rapidly heated to 150 °C is now used for acrolein and acrylonitrile. This method employs a flame ionization detector (FID). 

Relative sizes of reactors based on the two models are given in Figure 17.2 for second- and half-order reactions at several conversions. For first order reactions the ratio is unity. At small values of the parameter n and high conversions, the spread in reactor sizes is very large. In many packed bed operations, however, with proper initial distribution and redistribution the value of the parameter n is of the order of 20 or so, and the corresponding spread in reactor sizes is modest near conversions of about 90%. In such cases the larger predicted vessel size can be selected without undue economic hardship. 

Photographs taken of distribution decks, tower packing, nozzles, waterfall patterns, sumps, etc. can be useful but are almost never taken, either during an initial survey or during the implementation of any subsequent water treatment contract. Both vendors and operators tend to rely on memories, which are notoriously selective and not quantifiable. 

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