Ismail, Lukman
(2007)
An Experimental Investigation.ofParaffin Wax Deposition in
a Batch Oscillatory Baffled Column.
PhD thesis, Heriot-Watt University.
Abstract
Problems related to crystallisation and deposition of paraffin waxes on oil pipelines
during production and transportation of crude oil caused huge operational and financial
losses to petroleum industry. This study is focused on the fundamental understanding of
the mechanisms of wax deposition and investigates the effect of several major
parameters on such deposition in a batch oscillatory baffled column (OBC). The OBC is
a relatively new mixing technology and offers more uniform mixing and particle
suspension than traditional reactors. It is the intention of this work to characterise the
effect of oscillatory mixing on the wax deposition process perhaps as an alternative way
for mitigation of wax deposition problems. Experiments have been carried out to
examine the effects of OBC's operational parameters, wax-oil volume, paraffin wax
content, carbon number of the solvents, baffles materials and structure on the wax
deposition. Analyses conducted to evaluate and characterise the wax deposition are: the
percentage of wax deposition (0, wt.%); the Avrami exponent (n) which corresponds to
the type of wax crystals; and the half time of deposition (tll2) which is associated with
the rate of deposition. On the study of the effect of OBC' s parameters, it was found that
increasing the oscillation frequency and amplitude reduced the overall deposition;
baffles oscillation altered the type of wax crystal formed from needle type to clustered
plate-like shapes; and accelerated the rates of deposition. On the effect of wax-oil
volume, it was observed that increasing the volume reduced the deposition, increased n
values and t112 hence reduced the deposition rates. The study on the effect of paraffin
wax content revealed that increasing the wax content increased the deposition, reduced
n values and caused higher crystallisation rates. On the effect of solvent carbon
numbers, it was found that the higher the carbon numbers, the more the deposition,lower nand trn. Lastly on the study of baffles materials and structure, it can be deduced
that using different baffle materials had no significant impact on the deposition in the
OBC. In summary, oscillatory baffled flow can be an effective means of mitigation of
wax deposition problems. This work may also lead to a screening test for wax
deposition inhibitors. Since the deposition of viscous materials is common to other
sectors of the process industries, the results of this study will provide essential
information for understanding and perhaps later implementation of the OBC technology
in the related fields.
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