Feasible designs simple columns

FIGURE 6 14 Feasible sharp split simple column designs at (a) minimum reflux and (b) above minimum reflux. 

This section has thus presented a quick synthesis and analysis method for two simplified infinite reflux cases. Just like simple columns, it can be generally stated that if a design is considered feasible at infinite reflux conditions, then a feasible design can be found at finite reflux too. This fact is particularly useful for nonideal systems. An illustration of a more complex infinite Petlyuk column example is given in the following example for the azeotropic acetone/benzene/chloroform system. 

There are several issues which need to be addressed when designing the basic control for the column. The first is one of pairing. We will see that on our simple column that there are five PVs that we must control - pressme, reflux drum level, column base level, distillate composition and bottoms composition. We normally have available five MVs - distillate flow, bottoms flow, reflux flow, reboiler duty and condenser duty. We need therefore to decide which MV is going to be used to control which PV. Theoretically there are 5 , or 120, possible combinations. While many of these are nonsensical, a large number of feasible schemes are possible. 

The procedure known as the list-processing method allows the designer to identify feasible sequences for separating ideal or slightly nonideal zeotropic mixtures by means of simple distillation columns. Table 3.13 presents a list of more specific heuristics for sequencing, supplementary to those in Table 3.7. The first one shows... 

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