Minimum reflux side rectifiers

To redistribute the stages in the remaining sections, a shortcut simulation is used to find out the required number of trays, the feed tray location and the minimum reflux ratio for each column in the sequence. To make use of the existing column with the same number of trays (24 trays) iterations are required to adjust the sum of the rectifying sections in each column equal to 24 (number of trays in the main column). Finally, the sequence of the simple columns is merged into a complex column. The main column is not changed, but the side strippers and pump arounds need to be relocated or adjusted. 

With a normal equilibrium curve it is seen from Fig. 18.19 that at minimum reflux ratio the intersection of the q line and the equilibrium curve gives the concentrations of liquid and vapor at the feed plate (and at an infinite number of plates on either side of that plate). So an invariant zone forms at the bottom of the rectifying section and a second one at the top of the stripping sec tion. The two zones differ only in that the liquid-vapor ratio is LjV in one and LjV in the other. 

FIGURE 6.34 Tlie two CSs across die feed stage operating at minimum reflux for die (a) side stripper and (b) side rectifier. 

Interestingly, since is always negative in the side rectifier, the feed quali is always pseudo superheated. Conversely, the feed to the thermally coupled junction in the side stripp is pseudo subcooled because is always positive. Everything in the pseudo column has been specified and we can proceed with the minimum reflux calculations in the same manner as shown previously for mple columns. For the same arbitrarily chosen product specifications as Hgure 6.34, the minimum reflux of the thermally coupled CSs can be represented using the TTs technique, as depicted in Figure 6.36. 

Leading to the heat demand of the column being Qss 1.554AHv /> for the side stripper, where the subscript SS indicates the side stripper. Following the same procedure, we are able to calculate the minimum reflux conditions for the side rectifier noting that in this case [0, 0.03, 0.97]. The design with all relevant... 

FIGURE 6.42 A side rectifier for the [benzene, p xylene, toluene] system at minimum reflux using the TT technique. 

Taking into consideration the symmetry of these sphts, we confine the discussion to the direct split. In the mode of minimum reflux, point x/ should coincide with the stable node A +, and point x/ i should belong to rectifying minimum reflux bundle 5 - Nf (Fig. 5.30). Along with that, Eq. (5.18) should be valid. The search for the value (L/ F) is carried out in the following way at different values (L/V)r, he coordinates of point X/ = Nf are determined by means of the method tray by tray for bottom section and then the coordinates of point x/ i are determined by Eq. (5.18). At(L/F), < (L/F) , points X/-1 and xd are located on different sides from the plane or hyperplane - Nf and, at (L/ V)r > (L/ y)f", these points are located on one side. That finds approximate values (L/ F) (not taking into consideration curvature of bundle 5 - Nf) and approximate coordinates of points X/ i and x/. To determine exact values (L/ F) and coordinates X/-1 and Xf, one varies the values of (LjVjr in the vicinity of found approximate value (L/V)f. Then one realizes trial calculations of top section trajectories by means of the method tray by tray from feed cross-section to the product. If at... 

We now turn to the columns with side strippings (for the colunms with side rectifiers, the calculation of minimum reflux mode is carried out the same way). 

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