Page 176 - Design of Simple and Robust Process Plants

5.3 Combination of Process Functions 161

Neutralized & Washed
product
Wash water

Neutralizer

Raw product
Effluent
Fig. 5.16. Wash column with two extraction functions and more
equilibrium stages.

5.3.3.1 Evaporators
These are used to concentrate a certain process stream by removal of a volatile compo-
nent. Applications are large energy consumers, and this is the reason why they are
often installed in series as multiple effect evaporators. Occasionally, these evaporators
are designed as crystallizers (evaporative crystallizers) and are provided with internals
to enforce a certain circulation. Such an integrated functionality requires a specific
design to achieve the correct balance between crystal nucleation and growth in order to
achieve the required particle size, the latter having a major impact on solids removal.
An evaporator as a concentrator might also be equipped with a light removal in the top
of a rectifier column, while the major vapor stream leaves as a side stream (Figure 5.17).

Not Integrated Integrated

LIGHTS
LIGHTS
FEED
FEED
VAPOR TO
NEXT EFFECT VAPOR TO
EVAPORATOR NEXT EFFECT
EVAPORATOR

CONCENTRATE

CONCENTRATE
Fig. 5.17. Evaporative concentrator integrated and not
integrated with lights removal.