Staged columns stripping

The rectifying or stripping section of a column must operate somewhere between total reflux and minimum reflux conditions. The range of feasible operation of a column section can thus be defined for a given product composition. It can be seen in Figure 12.19 that these section profiles are bounded for a stage column by the distillation line and the pinch point curve. As noted previously, the pinch point curve provides a minimum reflux boundary for both staged and packed columns,... 

Fig. 4.12. Design diagrams for isopropyl acetate (IPOAc) reactive distillation column and comparison with simulation results (solid curves simulated column profile markers = stage composition for column rectifying section + = stage composition for column stripping section).

The feed flow rate is lOOkmol/h, and the feed is fed on Stage 32 of a 52-stage column. A hquid sidestream is withdrawn from Stage 12 and is fed into a small 6-stage stripping column. The flowsheet is given in Figure 10.15. The bottoms from the stripper is the MeOH product. The vapor from the stripper is fed back to the main column. 

The solution procedure reported by Mahajani and Kolah (1996) for packed columns is quite similar to that described by Buzad and Doherty (1994) for staged columns ( ) expressions 3.12-3.14 are solved simultaneously for various values of Da, determining the range where the stripping and rectifying profiles intersect (ii) the satisfaction of the second necessary condition is then evaluated and ( ) the sizing of the RD column is performed. 

There are a number of additional modes of operating a distillation column. These include partial condenser open steam introduced at the column bottom without a reboiler enriching distillation column stripping distillation column operation with a side stream, etc. We will briefly describe each one of these in the context of equilibrium stages/ plates and constant molal overflow. 

Above the feed a typical equiUbrium stage is designated as n the stage above n is n - - 1 and the stage below n is n — 1. The section of column above the feed is called the rectification section and the section below the feed is referred to as the stripping section. 

FIG. 22-43 Graphical determination of theoretical stages for a foam-fractionation stripping column. 

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