Page 179 - Design of Simple and Robust Process Plants

164 Chapter 5 Process Simplification and Intensification Techniques
5.4
Integration of Process Equipment

In this section, we will concentrate on the integration of equipment. The difference
between integration and the combination of process function is explained by the
heat recovery in the following example. The integration of a vent condenser with
another condenser represents integration of equipment, but modification of the
vent condenser to a dephlegmator (where rectification and cooling are combined) is
a combination of functionality (see Figure 5.9). Some examples of integration of
equipment are described below, though the list is far from complete, there being
many opportunities within the different processes.
Reactors often have integrated equipment, such as:

. Internal cyclones in fluidized bed reactors.
. Jacket or coils in kettle reactors
. Reflux condensers on top of kettle reactors; this solution is cheaper than
recycle cooling (Figure 5.19).
. Integration of adiabatic beds, such as radial reactors, in one shell, and occa-
sionally integrated with an inter-stage exchanger (an example is an NH 3 reac-
tor).
. Integration of horizontal adiabatic beds with inter-stage tubular reactor (Fig-
ure 5.20). This example shows a flue-gas-heated system for a styrene reactor
(other systems exist with molten salt heating, for a similar application).
Exergy-wise, the molten salt system is more efficient as the molten salt can
be recycled at a higher temperature level, and this resulted in less generation.
(Pumping can be carried out higher temperature compared with compres-
sion of gases).
. Integration of three isothermal CSTRs in series by an adiabatic CSTR, and
an adiabatic plug flow reactor all in one vessel (Figures 4.7). This was
achieved by lowering the feed inlet temperature and slightly increasing one
of a reactant flow.

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Fig. 5.19. Reactor with recycle loop versus a reflux condenser.