Page 183 - Design of Simple and Robust Process Plants

168 Chapter 5 Process Simplification and Intensification Techniques
. Distillation equipment requires low velocities, to achieve a gravity separation
between vapor and liquid and this results in large diameters; relatively low
velocities do not enhance mass transfer.
. Shell and tube heat exchangers have a relative low surface area per volume.
While these background points were seen as starting points for process intensifica-
tion, the efforts taken can be divided into the following categories:

. Building more compactly: mass and heat transfer exchangers increase the
2
3
effective surface area per unit volume M /M .
. Increase heat, mass, and impulse transfer.
. Benefit from centrifugal forces (ªHigeeº).
. Overall process improvements (see Section 5.6).
These categories have been selected to emphasize the technique of process intensifi-
cation, rather than focus on the unit's operation and its applications.

5.5.1
Building More Compact Units

The concept here is to create more separation area per unit volume. The develop-
ments in this field were not among the first to be evaluated, but were an intensified
continuation of ongoing developments.

5.5.1.1 Phase separation
The technology for phase separation provided more separation area in gravity
separators by the installation of tilted plates in the separator, thus reducing the verti-
cal distance that the particles/droplets must pass before separation (Figure 5.24).
These improvements were greatly appreciated by the offshore oil industry to reduce
the oily water separator sizes. The onshore industry also improved the performance
of these separators by increasing the separation area within the existing units. The
same principle was applied in centrifuges, where tilting plates were introduced to
shorten the separation distance and so increase the separation capacity of the unit.

Fig. 5.24. Tilted plate separator.