paraffin wax deposition and fouling

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9. CONCLUSIONS
The nature and properties of solutions containing wax foulants have
been studies in the oil industry where extensive work has been done
on paraffin deposition at laminar flow conditions.
In the present work the effects of flowrate, temperature, concentra
tion and. time were investigated.
The experimental flow conditions were
turbulent and solution bulk temperatures were kept well above the cloud
points.
I; was found that paraffin wax deposition increased asymtotic—
ally to some
critical value and then broke dom to build up again, giving
rise to random fluctuations.
The amount of wax depositing and the
magnitude of the fluctuations, resulting from the buildup and removal
process, were found to decrease with fiowrate and temperature, but
increase with concentration.
3y calcuiathng temperature distributions the raraffin wax was found
to come out of solution inside the boundary layer at a temperature inter
face eaual to the cloud Doint.
From the interface to the deposition
surface there existed a suspension of wax particles in kerosene.
The
temperature of the deposition surface was at or below the solution rour
point.
The breakdown and removal of derosits is considered to be due to
crystal transformation at the tube wall giving rise to planes of weakness
resulting in failure.
The deposition mechanism is thought to be controlled
by the cohesive prorer;es of tne wax partcles in tne bounary iayer
suspension.
Low shear stresses and high concentrations both increase
the rrobabili;y of cohesion.