Fig volatile components

Raisin and Dried Fig Volatile Components Possible Insect Attractants... 

Consider the sequence of simple columns shown in Fig. 5.12. In the direct sequence shown in Fig. 5.12, the composition of component B in the first column increases below the feed as the more volatile component A decreases. However, moving further down the column, the composition of component B decreases again as the composition of the less volatile component C increases. Thus the composition of component B reaches a peak only to be remixed. ... 

Batch distillation (see Fig. 3) typically is used for small amounts of solvent wastes that are concentrated and consist of very volatile components that are easily separated from the nonvolatile fraction. Batch distillation is amenable to small quantities of spent solvents which allows these wastes to be recovered onsite. With batch distillation, the waste is placed in the unit and volatile components are vaporized by applying heat through a steam jacket or boiler. The vapor stream is collected overhead, cooled, and condensed. As the waste s more volatile, high vapor pressure components are driven off, the boiling point temperature of the remaining material increases. Less volatile components begin to vaporize and once their concentration in the overhead vapors becomes excessive, the batch process is terrninated. Alternatively, the process can be terrninated when the boiling point temperature reaches a certain level. The residual materials that are not vaporized are called still bottoms. 

If a waste contains a mixture of volatile components that have similar vapor pressures, it is more difficult to separate these components and continuous fractional distillation is required. In this type of distillation unit (Fig. 4), a packed tower or tray column is used. Steam is introduced at the bottom of the column while the waste stream is introduced above and flows downward, countercurrent to the steam. As the steam vaporizes the volatile components and rises, it passes through a rectification section above the waste feed. In this section, vapors that have been condensed from the process are refluxed to the column, contacting the rising vapors and enriching them with the more volatile components. The vapors are then collected and condensed. Organics in the condensate may be separated from the aqueous stream after which the aqueous stream can be recycled to the stripper. 

Pressures can be specified at any level below the safe working pressure of the column. The condenser pressure will be set at 275.8 kPa (40 psia), and all pressure drops within the column will be neglected. The eqnihbrinm curve in Fig. 13-35 represents data at that pressure. AU heat leaks will be assumed to be zero. The feed composition is 40 mole percent of the more volatile component 1, and the feed rate is 0.126 (kg-mol)/s [1000 (lb-mol)/h] of saturated liquid (q = 1). The feed-stage location is fixed at stage 4 and the total number of stages at eight. 

For dilute solutions, the technical literature contains some direct (dilato-metric) measurements of v2, the partial molar volume of the more volatile component, but the accuracy of these measurements is usually not high. A survey was made by Lyckman and Eckert (L6) and they established the rough correlation shown in Fig. 5. On the ordinate, the partial molar volume is... 

FIGURE 8.39 A schematic illustration of the process of fractional distillation. The temperature in the fractionating column decreases with height. The condensations and reboilings illustrated in Fig. 8.38 occur at increasing heights in the column. The less volatile component returns to the flask beneath the fractionating column, and the more volatile component escapes from the top, to be condensed and collected. 

The reason for this is subtle and subject to verification in specific cases but related to the more fundamental nature of relative concentrations than component particle densities in mixtures. If we use this tanh( , x) scheme then we find, for example, that the volatile component will naturally show adsorption to the interface. This is illustrated in Fig. 2. 

FIG. 2 The tanh(w, x) profiles for a liquid-gas interface in a binary mixture are illustrated. The full and dashed lines correspond to mole fractions Xi(z) and X2(z), while dash-dotted and dotted lines correspond to particle densities i(z) and 112(2) of a nonvolatile (1) and volatile (2) component. Note that there is adsorption of the volatile component to the interface. 

Skunks deter predators by release of a liquid spray containing seven major volatile components classified as thiols (compounds containing the -SH functional group) and acetate derivatives of thiols (characterized by the SC(0)CH3 functionality). In particular, two of the more odiferous components responsible for the strongly repellent odor of the skunk s secretion are 2-butene-1-thiol (Fig. 13.2.1) and 3-... 

The ability of the new precursors to decompose thermally to yield singlephase CIS was investigated by powder XRD analysis and EDS on the nonvolatile solids from the TGA experiments of selected compounds. Furthermore, using TGA-evolved gas analysis (EGA), the volatile components from the degradation of the SSPs could be analyzed via real-time fourier transform infrared (FTIR) and mass spectrometry (MS), thus providing information for the decomposition mechanism.3 The real-time FTIR spectrum for 7 and 8 shows absorptions at approximately 3000,1460,1390,1300, and 1250 cm-1 (see Fig. 6.7). 

Fig. 4.22. Complementary thermogravimetric and DSC thermograms, showing loss of a volatile component and solid-solid conversion of some of the sample from the amorphous to the crystalline phase.

Selecting an approach Off-flavors are typically due to volatile compounds present at extremely low levels. (Flavor is sensed more by the olfactory system than the tongue, which senses only 5 flavors, sweet, sour, bitter, salty, and umami). GC is ideal for detecting low levels of volatile components. In this case, headspace GC will allow you to treat the plastic directly. Since the off-flavor is suspected to be derived from the polypropylene packaging material, you decide to compare different samples ( good vs. bad ) of the material using headspace GC with both a flame ionization detector (FID) and a sniff port. These chromatograms are shown in Fig. 21.9. 

The engineering analysis and design of these operations addresses questions which are different than those addressed in connection with the shaping operations. This is illustrated in Fig. 1 which is a flow sheet, cited by Nichols and Kheradi (1982), for the continuous conversion of latex in the manufacture of acrylonitrile-butadiene-styrene (ABS). In this process three of the nonshaping operations are shown (1) a chemical reaction (coagulation) (2) a liquid-liquid extraction operation which involves a molten polymer and water and (3) a vapor-liquid stripping operation which involves the removal of a volatile component from the molten polymer. The analysis and design around the devolatilization section, for example, would deal with such questions as how the exit concentration of... 

When devolatilization processes are conducted in screw extruders, the screw channels are only partially filled with the polymeric solution to be stripped of the volatile component (see Fig. 5) while the unoccupied portion of the screw channel serves to carry away the evaporated liquid. Because the barrel has a component of motion Vbz in the down channel direction, the solution is caused to flow from the extruder inlet to the outlet, which, in this case, is out of the plane of the paper. The crosschannel component of the barrel motion, Vtx, has two effects. First, it causes a circulation of the fluid in the nip and because of the continual... 

Fig. 7. Variation of the dimensionless exit concentration of the volatile component as a function of screw speed, liquid flow rate, and Peclet number. Curves were computed using...

Fig. 15. Comparison of the measured and predicted exit concentrations obtained by Todd for a polystyrene polymer containing ethylbenzene as the volatile component. Data were obtained in a twin-screw extruder. From Todd (1974).

One of the earliest published studies on extraction in twin-screw extruders was conducted by Todd (1974). In this work devolatilization was conducted under vacuum using two different polymeric systems, polystyrene in one and polyethylene in the other. In the case of polystyrene, styrene was not used as the volatUe component so as to avoid problems associated with further polymerization or depolymerization instead, use was made of mixtures of thiophene and toluene or ethylbenzene. Todd found good agreement between the measured exit concentrations of the volatile component and the predicted values using Pe = 40 in the solution to Eq. (38) (see Fig. 15). The value of 5 in Eq. (39) was not reported and it is not known whether a value was chosen to provide a fit with the data or whether it was known a priori. In any event, what is clear is that the exit concentration varies with IVwhich suggests that mass transfer is occur-... 

In the case of polyethylene, the volatile component was cyclohexane and here, too, good agreement was obtained between the measured exit concentration and the predicted values using Pe = 40 in the solution of Eq. (38) (see Fig. 16). Tliese data also suggest that mass transfer is occurring by molecular diffusion through a wiped film since the exit concentration varies with N in accordance with the theory. It is somewhat disconcerting, however, that the value of B used in the theoretical expression was not reported, and the question naturally arises as to whether realistic values were used to obtain the fit with the data. 

The decrease in the exit concentration with decreases in the extraction pressure seen in Figs. 17 and 18 is a consequence of the fact that the driving force for mass transfer is directly related to the partial pressure of the volatile component in the vapor phase, which, in this case, is constant and equal to the extraction pressure. In fact, reasonably good agreement between the data in Fig. 17 and the predictions of Eq. (38) can be obtained provided it is assumed that the dimensionless group (ki ATlk y p/L) is independent of pressure. This point is illustrated in Fig. 19, which is a plot of Eq. (38) for Pe =. The value used for (ki Aj/k v(kp/L) was chosen so as to obtain the asymptotic value of wi in Fig. 17. 

Fig. 19. Theoretical prediction (—) of the variation of the exit concentration of a volatile component with extraction pressure. The prediction is based on Eq. (38) with [ kia)iy pVL = 0.115. The circles are selected experimental (MMA/PMMA) data points taken from Fig. 17.

Figure 21 is a plot of Eq. (74), whereas Figure 22 shows the variation of bubble radius and extraction efficiency with time for specific values for the dimensionless parameters, j8, Rq, and P. Initially, the amount of volatile component remaining in the solution decreases sharply with time, but after about 80% of the material is extracted, further changes are insignificant. Thus, efforts to increase the lifetime of the bubble beyond this point would not be beneficial. The effect of pressure on extraction efficiency is shown in Fig. 23. 

A single feed stream is fed as saturated liquid (at its bubblepoint) onto the feed tray N,. See Fig. 3.12. Feed flow rate is F (mol/min) and composition is z (mole fraction more volatile component). The overhead vapor is totally condensed in a condenser and flows into the reflux drum, whose holdup of hquid is Mj) (moles). The contents of the drum is assumed to be perfectly mixed with composition Xo The liquid in the drum is at its bubblepoint Reflux is pumped back to the top tray (iVj-) of the column at a rate R. Overhead distillate product is removed at a rate D. 

Female mice have volatile components in their urine that are depressed after adrenalectomy. Six components have been detected, of which three (2-heptanone, trans-5-h. ptea-l-one., and tra 5-4-hepten-2-one) have no apparent effects either as a group or when added to the other three components. The active three components are w-pentyl acetate, m-2-penten-l-yl acetate, and 2,5-dimethylpyrazine (Fig. 8.3). If 2,5-dimethylpyrazine is painted daily on the external nares of young female mice from day 21 on, the time of the first vaginal estrus is delayed. These three compoimds act in redimdant fashion the two acetate esters delay vaginal estrus by 1.5 days, on average 2,5-dimethylpyrazine alone delays it by 2.4 days, and a mixture of all three delays it by 1.7 days. (Novotny et a /., 1986a). 

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