One distillation field

Both pure products A and B belong to the same distillation field since there is no distillation boundary (one distillation field). 

The pure products A and B are separated by a distillation boundary and belong to different distillation fields. In this case, the distillation boundary must be sufficiently curved, such that one split can cross it and gives opportunities for separating the other pure component. 

A general rule in split assessment can be formulated as follows pure components only as nodes, while entrainer and azeotropes are saddles since they are recycled. 

Figu re 3.12 Separation of an azeotropic mixture in one distillation region. 

High boiler Yes (extractive distillation) Medium-boiler min azeo with B 

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Figure 3.10 shows typical RCM for nonideal mixtures involving azeotropes. For the mixture ace tone/heptane /benzene (plot a) there is only one distillation field. The problem seems similar to a zeotropic system, except for the fact that the minimum boiler is a binary azeotrope and not a pure component. With the mixture acetone/chloroform/toluene (plot b) there is one distillation boundary linking the high-boiler with the low-boiler azeotrope. Consequently, there are two distillation regions. Similar behavior shows the plot c, with two azeotropes. The mixture acetone/chloroform/methanol (plotd) has four azeotropes (3 binaries and 1 ternary) displaying a behavior with four distillation regions. 

Table 3.16 Criteria for entrainer selection for separations in one distillation field.

In addition, for a minimum AB azeotrope the entrainer may be 1) low boiler that forms medium-boiling maximum azeotrope with A, and 2) maximum boiler. The last case is quite special, and it is known as extractive distillation. For maximum AB azeotrope, the entrainer may be high-boiler that forms medium-boiling minimum azeotrope with B. It should be noted that is difficult to find entrainers giving opposite azeotropes with A or B with respect to the original AB azeotrope. Hence, the choice of an entrainer generating separations in one distillation field is in practice limited. 

There has been only one major use for ozone today in the field of chemical synthesis the ozonation of oleic acid to produce azelaic acid. Oleic acid is obtained from either tallow, a by-product of meat-packing plants, or from tall oil, a byproduct of making paper from wood. Oleic acid is dissolved in about half its weight of pelargonic acid and is ozonized continuously in a reactor with approximately 2 percent ozone in oxygen it is oxidized for several hours. The pelargonic and azelaic acids are recovered by vacuum distillation. The acids are then esterified to yield a plasticizer for vinyl compounds or for the production of lubricants. Azelaic acid is also a starting material in the production of a nylon type of polymer. 

Field Tests. Recently we conducted a field test at a site contaminated with fuel oil. Our measurements were 0.0625 0.0212 mA for the well water and 0.0189 0.0119 mA for distilled water (showing errors of one standard deviation). From calibration curves, these numbers can be reported as equivalent to 50 ppb phenol or 34 ppb xylenes. Nine-month-old laboratory results (EPA method 624 and GC/FID) for this site indicated concentrations of 25 ppb for benzene, toluene, and xylenes combined and 100 ppb for fuel oil. The important result is the significant difference between the distilled-water and well-water measurements. We are very encouraged by these results and are planning future field tests. 

As might be expected, the vapour phase may offer the controlling resistance to mass transfer in high pressure distillations. Values for tray efficiencies at elevated pressure are scarce [23, 24]. The prediction of tray efficiency may be approached in several ways. One way is to utilize field performance data taken for the same system in very similar equipment. Unfortunately such data are seldom available. When they are available, and can be judged as accurate and representative, they should be used as a basis for efficiency specification [25], Another way is to utilize laboratory-or pilot-plant efficiency data. For example a small laboratory-Oldershaw tray-column can be used with the same system. Of course, the results must be corrected for vapour-and liquid mixing effects to obtain overall tray efficiencies for large-scale design [26], Another approach is the use of empirical or fundamental mass-transfer models [27-30],... 

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