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Countercurrent Extraction with Extract Reflux

In the triangular diagram in Fig. 6-25 the state point U of / lies on the connecting line between the state points and Lq of the flows and Lo and according to Eq. (6-90) also on the line LoEq. [Pg.422]

A mass balance over the extract enrichment section of the column (Fig. 6-24) at any cross section gives [Pg.422]

RS Raffinate stripping section, below feed point ES Extract enriching section, above feed point [Pg.422]

A mass balance over the extract separation unit gives [Pg.422]

Therefore, the state points of the extract and raffinate phases E and in a common column cross section lie on the binodal curve and connecting line E, R,U (lines through the pol U) (Fig. 6-25). The state points of the phases leaving a theoretical extraction stage ( jy, E, R2 , etc.) lie on [Pg.422]


Example 7.6 Countercurrent Extraction with Extract Reflux... [Pg.449]

The extract is pumped from the bottom of D-l to a stripper D-2 with 35 trays. The stripped solvent is cooled with water and returned to D-l. An isoprene-acetonitrile azeotrope goes overhead, condenses, and is partly returned as top tray reflux. The net overhead proceeds to an extract wash column D-3 with 20 trays where the solvent is recovered by countercurrent washing with water. The overhead from D-3 is the finished product isoprene. The bottoms is combined with the bottoms from the raffinate wash column D-4 (20 trays) and sent to the solvent recovery column D-5 with 15 trays. [Pg.37]

A reflux arrangement is now added at the lower end of the column. The extract is sent to a solvent removal unit, and the solvent-free extract is split into an extract product and an extract reflux which is sent back to the bottom of the column. Without the solvent, the extract reflux is now composed of the raffinate component and the solute (components R and E), so that this reflux is actually on the raffinate side of the equilibrium curve (Section 11.2 and Figure 11.2) flowing countercurrent to the extract phase. The extract phase is thus interacting with a raffinate phase which is richer in the solute than the feed. As a result, the extract enrichment with the solute is greater than it would be if the extract were interacting directly with the external feed in the absence of the extractor section below the feed. A higher-purity extract product can therefore be expected. [Pg.359]

Since the binodal curves intersect the TMB-methane axis, it is possible to obtain pure TMB using a countercurrent extraction process with reflux. If the system pressure were increased above the TMB-methane critical pressure at 35°C, a closed-dome, two-phase region would exist and it would not be possible to obtain pure TMB with a countercurrent process. [Pg.185]

FIGURE 7.3 8 Countercurrent extraction with reflux as in Fig. 7.3-7, showing location of A, and A2. [Pg.424]

COUNTERCURRENT EXTRACTION OF TYPE II SYSTEMS USING REFLUX. Just as in distillation, reflux can be used in countercurrent extraction to improve the separation of the components in the feed, This method is especially effective in treating type II systems, because with a center-feed cascade and the use of reflux, the two feed components can be separated into nearly pure products. [Pg.638]

A flow diagram for countercurrent extraction with reflux is shown in Fig. 20.14. To emphasize the analogy between this method and fractionation, it is assumed that the cascade is a plate column. Any other kind of cascade, however, may be used. The method requires that sufficient solvent be removed from the extract leaving the cascade to form a raffinate, part of which is returned to the cascade as reflux, the remainder being withdrawn from the plant as a product. Raffinate is withdrawn from the cascade as bottoms product, and fresh solvent is admitted directly to the bottom of the cascade. None of the bottom raffinate needs to be returned as reflux, for the number of stages required is the same whether or not any of the raffinate is recycled to the bottom of the cascade. The situation is not the same as in continuous distillation, in which part of the bottoms must be vaporized to supply heat to the column. [Pg.638]

PRACTICAL EXAMPLES OF EXTRACTION WITH REFLUX. There are few, if any, practical examples of reflux in the simple manner shown in Fig. 20.14. For systems such as aniline-heptane-methylcyclohexane (Fig. 20.11), the ratio of MCH to heptane in the extract is only modestly greater than in the raffinate, so a great many stages would he needed for high-purity products. Furthermore, the low solubility of both solutes in aniline would mean a very large flow of solvent to be handled. However, a modification of the reflux concept has been applied in several industrial processes for extraetive separation. Enrichment of the extract is accomplished by countercurrent washing with another liquid, chosen so that the small amounts of this liquid that dissolve in the extract can be easily removed. The Sulfolane process for extraction of aromatics is an example of this type. [Pg.639]

Analyze countercurrent extraction cascades with reflux combining... [Pg.431]

Figure 7.17 Countercurrent multistage extraction with extract reflux. Figure 7.17 Countercurrent multistage extraction with extract reflux.
Figure 7.18 Use of Janecke diagram with auxiliary distribution curve for countercurrent extraction with reflux. Figure 7.18 Use of Janecke diagram with auxiliary distribution curve for countercurrent extraction with reflux.
Example 10.3. As shown in Fig. 10.22, a countercurrent extraction cascade equipped with a solvent separator to provide extract reflux is used to separate methylcyclopentane A and n-hexane C into a final extract and raffinate containing 95wt% and 5wt% A, respectively. The feed rate is 1000 kg/hr with 55 wt% A, and the mass ratio of aniline, the solvent S, to feed is 4.0. The feed contains no aniline and the fresh solvent is pure. Recycle solvent is also assumed pure. Determine the reflux ratio and number of stages. Equilibrium data at column temperature and pressure are shown in Fig. 10.23. Feed is to enter at the optimum stage. [Pg.212]

A feed stream containing 35 wt% acetone in water is to be extracted at 25°C in a countercurrent column with extract and raffinate reflux to give a raffinate containing 12% acetone and an extract containing 55% acetone. Pure 1,1,2,-trichloroethane, which is to be the solvent, is removed in the solvent separator, leaving solvent-free product. Raffinate reflux is saturated. Determine... [Pg.594]

As multistage extraction with phase countercurrent flow and extract reflux... [Pg.400]

Fig. 6-25. Graphical determination of number of theoretical stages, countercurrent extraction column with reflux. Fig. 6-25. Graphical determination of number of theoretical stages, countercurrent extraction column with reflux.
Fig. 6.63. Countercurrent extraction with reflux on distribution coordinates. Fig. 6.63. Countercurrent extraction with reflux on distribution coordinates.

See other pages where Countercurrent Extraction with Extract Reflux is mentioned: [Pg.472]    [Pg.473]    [Pg.225]    [Pg.421]    [Pg.421]    [Pg.422]    [Pg.194]    [Pg.195]    [Pg.193]    [Pg.288]    [Pg.251]    [Pg.140]    [Pg.142]    [Pg.639]    [Pg.251]    [Pg.445]    [Pg.445]    [Pg.472]    [Pg.473]    [Pg.225]    [Pg.225]    [Pg.225]    [Pg.604]    [Pg.32]    [Pg.421]    [Pg.421]    [Pg.422]    [Pg.178]    [Pg.184]    [Pg.194]    [Pg.194]    [Pg.195]   


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