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were not designed to be cleaned in place. However, process designers and glasslined
vessel manufacturers have made great strides in increasing the cleanability
of these systems. Many of the strategies employed on reactor systems can be
used to clean other pieces of equipment common to API production. Therefore,
this chapter will address these systems in detail and then discuss other systems
(isolation, drying, etc.).
It is instructive to compare a traditional design of a glass-lined reactor
system not designed for CIP with the one incorporating features that will
enhance CIP effectiveness. Examination of atypical glass-lined reactor system,
as illustrated in Figure 1, will permit identification of those areas that are difficult
to clean/wet using aboil-up or simple flushing approach. While the examples
shown are of glass-lined systems, the findings can also be applied to alloy
reactor systems.
Most readers will recognize this illustration as asimplified diagram of aglasslined
vessel system. There are provisions for liquid and solids charges, nitrogen
inertion, reflux/distillation, emergency relief, and process transfer. Those areas in
this example that constitute potential cleaning challenges, or that need to be
properly designed for CIP, include the reactor vessel (A), the condenser (B), the
emergency vent line and relief device (C), the vapor riser and instrumentation (D),
the baffle and unflushed nozzles (E), the solids charge port (F), the dip tube (G), the
agitator (H), and the bottom outlet (I).
This traditional glass-lined reactor system was never intended or designed to
be cleaned in place. Some of the major deficiencies of this system are asfollows:
& Condensers mounted horizontally or with aslight pitch are difficult to clean
efficiently. Condensing boil-up vapors will not uniformly clean the tubes, and
little cleaning action will be directed to any soil located on the bonnets and
tube sheets. Flushing with solvent would be an effective way to clean, but
this would require hundreds or thousands of gallons per minute to achieve.
One approach that has been used for this condenser orientation is aliquid
fill-and-soak with an effective cleaning solution, but the lack of solution
movement will lead to inconsistent results. Analternative (not shown) is the
addition of arecirculation pump to maintain alow rate of recycle through the
flooded tubes.
& Another area of concern is the vapor riser, emergency vent piping, and all the
instrumentation incorporated in this system. In operation, these lines become
soiled due to a reactor foam-over and the carryover of dust from solids
charging operations. As was pointed out previously, boil-ups produce only
small amounts of condensing liquids. In the case of the emergency vent line,
it is improbable that vapor will rise into this space, effectively displace the
inert atmosphere, and efficiently wet the surface uniformly at arate sufficient
to remove all soil consistently.
& Nozzles designed for liquid charges can be cleaned easily, but those that are
not externally flushed, such as the baffle, level transmitter, dip tube, and
solids charge port, may be difficult to clean effectively and consistently with a
solvent boil-up method.
The reactor vessel itself has much to do with the ultimate success of cleaning.
Older style glass-lined vessels were designed for simplicity of fabrication and ease
of maintenance with little thought to cleaning. These vessels are often characterized