| Crude petroleum unlike many other
industrial raw materials is a natural product, and
will carry with it the characteristics and impurities
depending on its origin. The refinery, therefore,
except for choosing amongst crudes available has
little control over the composition of the crude
namely, Sulphurous matter, acidic asphaltic/Napthenic
matter, salts, Fe-S compounds etc.
Added to this, there could exist problems related
to presence of chemicals used in the drilling
and transport operations, such as pour point depressants,
demulsifiers etc.
These extraneous matters can present problems
such as fouling, corrosion etc. arising out of
the tendencies of the impurities to interact,
decompose, polymerise etc.
The fouling problem can be severe in the reboiler/exchanger
areas of crude distillation operation especially
since the operating temperatures are high in this
zone and the flow/heat transfer requirements are
stringent for stable operations of the crude distillation,
whereas all the impurities mentioned are high
boilers presenting the maximum activity of polymerisation/decompostion/reaction
in this zone. This leads to frequent shutdown/steaming
out requirements to maintain satisfactory heat
transfer rates.
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