Page 169 - Design of Simple and Robust Process Plants

154 Chapter 5 Process Simplification and Intensification Techniques

PRODUCT A PRODUCT A

FEED FEED
STEAM
STEAM
STEAM STEAM
PRODUCT B
PRODUCT B
PRODUCT C PRODUCT C

Fig. 5.4. Side stripper installed external or internal (Emmrich et
al., with permission of Krupp Uhde).

PRODUCT A
PRODUCT A

PRODUCT B PRODUCT B
FEED
FEED
STEAM
STEAM

PRODUCT C
PRODUCT C

Fig. 5.5. Side rectifier installed external and internal (Emmrich
et al., with permission of Krupp Uhde).

5.3.2.2 Divided wall columns (DWC)
Divided wall columns are used to separate three to four purified product streams
from a feed mixture. This technology, although having been known for decades as
the Petlyuk column (Petlyuk et al., 1965), now enjoys only limited application at the
industrial scale. The original concept emphasized the thermal coupling between a
pre-fractionator and the main column (Figure 5.6). The concept was revitalized by
Kaibel (1987, at BASF) through introduction of the divided wall column at industrial
scale which emphasized a one-column configuration, resulting in a much cheaper
design (Figure 5.7).
The advantage compared with a conventional side draw application is that the
system can be designed for any purity requirement. Studies carried out at UMIST in
Manchester, UK, have resulted in an improved design and control understanding of
this (in principle) rather simple configuration (Triantafafyllou and Smith, 1992;
Lestak and Smith, 1993; Mutalib, 1995). In particular, the design of a control config-