Stripping McCabe-Thiele diagrams

An infinite reflux ratio v = 00 means no product is withdrawn at the head of the column (E = 0) all condensed overhead vapor is returned to the column. In the McCabe-Thiele diagram, stripping and enrichment lines coincide with the 45 diagonal and therefore the concentration of the feed Xp has no influence on the minimum number of stages... 

The test separation data are analyzed using a McCabe-Thiele diagram (Fig, 7.12a), with an equilibrium curve based on experimental data (average relative volatility of about 1,7), The analysis shows that the stripping section requires 12 theoretical stages. 

Temperature profile Pressure profile Flow profiles Mass transfer rates Stripping factors Key ratio profiles Relative volatilities McCabe-Thiele diagram Ponchon Savarit... 

The Murphree efficiency is defined using vapor concentrations as a matter of custom, but the measured efficiencies are rarely based on analysis of the vapor phase because of the difficulty in getting reliable samples. Instead, samples are taken of the liquid on the plates, and the vapor compositions are determined from a McCabe-Thiele diagram. A plate efficiency can be defined using liquid concentrations, but this is used only occasionally for desorption or stripping calculations. 

In order to correct the situation, it is proposed to add an intercondenser in the rectifying section to generate more reflux and an interreboiler in the stripping section to produce additional boilup. Show by use of a McCabe-Thiele diagram how such a proposed change can improve the operation. 

This is somewhat unusual, because it includes a bottoms concentration leaving the stripping column (column 2). The reflux for this top operating line is liquid of composition p. The McCabe-Thiele diagram for this system is shown in Figure 8-4B and is almost identical to Figure 8-3B. 

The point S is fixed by the intersection of the enrichment line and the locus of intersections line, and thus the second point of the stripping line is determined. This is the connection for C and S in the McCabe-Thiele diagram (Fig. 2-44). 

If the molar vaporization enthalpies of both of the components of the mixture are not equal, or if considerable enthalpy changes in the liquid fluxes appear, the fluxes are no longer constant in the column section of interest. The stripping and enrichment lines become curves that are determined from point to point in the McCabe-Thiele diagram. According to Hausen and... 

The minimum reflux ratio may also be determined graphically from the McCabe-Thiele diagram, from the requirement that the stripping and enrichment lines intersect at point S (Fig. 2-44). 

FIGURE 12J. McCabe-Thiele diagram for steady-state operation of a stripping unit with equilibrium shift. Note that enrichment is limited but stripping is unlimited. (From ref. 1, reprinted with permission of Martinus Nijhoff Publishers.)... 

The slope of this line is LJVS+ j. The line can be located as shown in Fig. 11.4-18 by the q line, which determines the intersection of the stripping line and Eq. (11.4-37), or it may be fixed by the specification of Xq, the side-stream composition. The step on the McCabe-Thiele diagram must actually be at the intersection of the two operating lines alx in an actual tower. If this does not occur, the reflux ratio can be altered slightly to change the steps. 

Figure 8.1.24. (a) Schematic for a partial condenser in a distillation column (feed and stripping section not shown), (b) McCabe-Thiele diagram for the partial condenser and the enriching section operating line. 

Figure 7.14 McCabe-Thiele diagrams for stripping and enriching sections of a continuous countercurrent adsorption plant (source Ruthven and Ching 1989).

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