Page 127 - Design of Simple and Robust Process Plants

112 Chapter 4 Process Synthesis and Design Optimization

Extraction of two components from product stream
The lightest component has a low partition coefficient
The second component has a high partition coefficient and
formed an azeotrope with the main product

Original solution; extract both components followed
by a distillation
The result was a large extraction column with a high
solvent flow
Low cost solution; extraction of second component
followed by three component distillation
The result is a small extraction column with lower (1/3)
solvent flow, a low cost solution

Fig. 4.25. Summary of extraction example.

Fig. 4.26. Integration of dephlegmator in the overhead condenser.

condenser of the tower and detailed in Figure 4.25, The combination of a condenser
and a dephlegmator or vent condensor an example of a combination of equipment
is also applied for other applications as reactor venting, see Figure 5.7. A summary
of the above extraction example is given in Figure 4.26.
Note that the simplification examples given here relate only to distillation applica-
tions; a more detailed discussion on simplification is provided in Chapter 5.
It is advocated that preliminary sequence selection be exercised during separation
step 1. However, careful studies need to be carried out on the integration of separa-
tions to simplify the flowsheet before extensive work is performed on final sequence
selection and energy integration during synthesis step 2. The simplest solution is