Page 207 - Design of Simple and Robust Process Plants

192 Chapter 5 Process Simplification and Intensification Techniques
5.7.1.1 Homogeneous reaction; G and L
Tubular reactor The most simple form of a reactor design is a tubular reactor. Here,
the only provision that needs to be added is the heat transfer.

Tubular reactor

The heat transfer alternatives are included at an increasing level of complexity. An
adiabatic design for endothermal, as well as exothermal reactions, is ± in its simplest
form ± an empty tube.

. The way that the adiabatic condition is realized is also ordered in terms of
simplicity, and in order to discuss this more fully we need to refer to exother-
mal reactions:
± Increase in process flow by either one of the reactants.
± Increase in solvent flow, although this will result in lower concentrations of
the reactants.
± Decrease in inlet temperature of the feed stream; this might be limited by
the start temperature of the reaction. In the reactor presented in Figure 4.7 in
Chapter 4, this was elegantly solved by creating an adiabatic CSTR in front of
the tubular reactor, all in one embodiment. In this way the temperature in
the CSTR is maintained well above the start temperature while the inlet tem-
perature can be lower.
± Injection of cold feed is an other option (see Figure 5.26, which describes a
tubular reactor for the peroxide production using the anthraquinone route).
This latter option is more difficult to operate, and requires a sophisticated
automated control design, (Tururen et al., 1999).
± A combination of the above-mentioned options.
. Heat exchange with the reactor: here, different designs are available, and al-
though the application depends heavily on the specific reaction, the designs
include:
± jacket pipe, for tubes;
± a staged, inter-cooled reactor system; and
± a shell and tube-type of reactor.