Key components in multicomponent

Stupin, W. J., and F. J. Lockhart, The Distribution of Non-Key Components in Multicomponent Distillation, paper presented at the 61st Annual Meeting of AIChE, Los Angeles, California, December 1-5, 1968. 

Yaws [124] et al. provide an estimating technique for recovery of each component in the distillate and bottoms from multicomponent distillation using short-cut equations and involving the specification of the recovery of each component in the distillate, the recovery of the heavy key component in the bottoms, and the relative volatility of the light key component. The results compare very well with plate-to-plate calculations. Figure 8-46, for a wide range of recoveries of 0.05 to 99.93% in the distillate. 

The Underwood and Fenske equations may be used to find the minimum number of plates and the minimum reflux ratio for a binary system. For a multicomponent system nm may be found by using the two key components in place of the binary system and the relative volatility between those components in equation 11.56 enables the minimum reflux ratio Rm to be found. Using the feed and top compositions of component A ... 

The FUG method, which applies to binary and multicomponent feeds, is described in detail by Seader and Henley (1998) and in Perry s Chemical Engineers Handbook (1997). Only the procedure is discussed here. The method involves five steps based on the desired separation of two key components in the feed. It includes an estimation of the separation of the nonkey components. 

Later, these columns were independently rediscovered (Petlyuk, Platonov, Slavinskii, 1965 Platonov, Petlyuk, Zhvanetskiy, 1970) on the basis of theoretical analysis of thermodynamically reversible distillation because this distillation complex by its configuration coincides with the sequence of thermodynamically reversible distillation of three-component mixture (see Chapter 4), but in contrast to this sequence it contains regular adiabatic columns. The peculiarities of Petlyuk columns for multicomponent mixtures are (1) total number of sections is n(n - 1) instead of 2(n - 1) in regular separation sequences (2) it is sufficient to have one reboiler and one condenser (3) the lightest and the heaviest components are the key components in each two-section constituent of the complex and (4) n components of a set purity are products. 

But that s only for a binary feed composition. In multicomponent distillation, the ratio of the key components in the feed will typically not coincide with the ratio of the key components in the liquid on the tray, even though the tray temperature is the same as the feed at its bubble point temperature. 

Simple analytical methods are available for determining minimum stages and minimum reflux ratio. Although developed for binary mixtures, they can often be applied to multicomponent mixtures if the two key components are used. These are the components between which the specification separation must be made frequendy the heavy key is the component with a maximum allowable composition in the distillate and the light key is the component with a maximum allowable specification in the bottoms. On this basis, minimum stages may be calculated by means of the Fenske relationship (34) ... 

Determine the height of an overall transfer unit Hog using methods given in Sec. 5, Table 5-28. For a multicomponent mixture, the key components are often used in determining Hog-... 

Assume a multicomponent distillation operation has a feed whose component concentration and component relative volatilities (at the average column conditions) are as shown in Table 8-3. The desired recovery of the light key component O in the distillate is to be 94.84%. The recovery of the heavy key component P in the bottoms is to be 95.39%. 

To aid in solving the tedious Underwood equation to ultimately arrive at (L/D)niin, Frank [100] has developed Figure 8-47, which applies for liquid feed at its bubble point and whether the system is binary or multicomponent, but does require that the key components are adjacent. Otherwise, the system must be solved for two values of 0 [74]. To obtain the necessary parameters for Figure 8-47, Frank recommends using the same overhead con-... 

Although this method has not found as much wide acceptance when referenced to use by designers or controversial discussion in the literature, it nevertheless allows a direct approximate solution of the average multicomponent system with accuracy of 1-8% average. If the key components are less than 10% of the feed, the accuracy is probably considerably less than indicated. If a split key system is considered, Scheibel reports fair accuracy when the split components going overhead are estimated and combined with the light key, the badance considered with the heavy key in the L/D relation. 

Temperature is often used as an indication of composition. The temperature sensor should be located at the position in the column where the rate of change of temperature with change in composition of the key component is a maximum see Parkins (1959). Near the top and bottom of the column the change is usually small. With multicomponent systems, temperature is not a unique function of composition. 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such solute molecules. When dilute 2% phospholipid in alkane is used in the artificial membrane [25,556], the effect of hydrogen bonding and electrostatic effects may be underestimated. We thus explored the effects of higher phospholipid content in alkane solutions. Egg and soy lecithins were selected for this purpose, since multicomponent mixtures such as model 11.0 are very costly, even at levels of 2% wt/vol in dodecane. The costs of components in 74% wt/vol (see below) levels would have been prohibitive. 

Figure 9.15 Pinch location (zones of constant composition) for binary and multicomponent systems. Brackets indicate key components remaining in a product stream due to incomplete recovery.

For multicomponent systems, components A and B refer to the light and heavy keys respectively. In this problem, o-cresol is the light key and m-cresol is the heavy key. A mass balance may be carried out in order to determine the bottom composition. Taking as a basis, 100 kmol of feed, then ... 

In multicomponent distillation, A and B are the light and heavy key components respectively. In this problem, the only data given for both top and bottom products are for m-and p-xylene and these will be used with the mean relative volatility calculated in the previous problem. Thus ... 

The articles of this book have been grouped into 3 parts. Part I focuses on the relationships between molecular structure and properties. Tailoring molecular structure for an intended apphcation is a principal component in product design. Part II describes the design and manufacture of various structured / multicomponent products. A key feature for consumer products is the assessment of qualitative product qualities that are required to satisfy the consumers wants and needs. Part III contains student design projects as well as views for the further development of product design. 

In the fractionation of multicomponent mixtures, the essential requirement is often the separation of two components. Such components are called the key components and by concentrating attention on these it is possible to simplify the handling of complex mixtures. If a four-component mixture A-B-C-D, in which A is the most volatile and D the least volatile, is to be separated as shown in Table 11.3, then B is the lightest component appearing in the bottoms and is termed the light key component. C is the... 

Many of the recent advances in synthetic applications of allylic boron reagents have focused on the use of these reagents as key components of tandem reactions and one-pot sequential processes, including multicomponent reactions. The following examples briefly illustrate the range of possibilities. Most cases involve masked allylboronates as substrates, and the tandem process is usually terminated by the allylboration step. 

The simplified design calculations presented in this section are intended to reveal the Key features of gas absorption involving multi-component systems. It is expected that rigorous computations, based upon the methods presented in Sec. 13, will be used in design practice. Nevertheless, it is valuable to study these simplified design methods and examples since they provide insight into the key elements of multicomponent absorption. 

The first objective of a shortcut method is selection of two key components and then setting all conditions around these components. Call the light key component LK and the heavy key HK. The fractionation objective is to separate these two key components per a given specification. The distribution (distillate product analysis and bottoms product analysis) of a multicomponent system is also accomplished in this proposed shortcut fractionator program, Hdist. 

Usually separation specifications in multicomponent mixtures are imposed on a particular (key) component of the cut, e.g. on component 1 in main-cut 1, on component 2 in main-cut 2 and likewise. Of course, it is possible to set intuitively some of the heavier component compositions to zero during lighter cuts and some of the lighter component compositions to zero during heavier cuts. But it is really difficult to specify independently the compositions of the preceding and few successive component compositions in a particular cut. 

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