Page 123 - Design of Simple and Robust Process Plants

108 Chapter 4 Process Synthesis and Design Optimization
. The first generation scheme converts the first separation after the reactor
into a side draw column which removes unconverted reactant and tars in one
column; the side draw had to be removed as a vapor to reduce the tar content.
In this case the flowsheet is reduced to four columns.
. The second generation flowsheet combines the first column with the one
after the reactor by installing a three-component distillation (a divided wall
column; Kaibel, 1987).
. The last two columns are also replaced by a divided wall column; now, the
flowsheet is reduced to three columns.

Lights from reaction
Lights from
feed

Feed
Water
Reactor

Tars/heavies By-product Product
Unconverted reactant

Fig. 4.17. Conventional distillation scheme: 1st generation.

Lights
Lights

Feed Water
Reactor

Unconverted
reactant
Heavies
Tars By-product Product
Fig. 4.18. Distillation scheme: 2nd generation.