4.+The+problem+with+Paraffin+Wax+Deposition

=**The Problem **=

Today's petroleum products fall into one of three categories: light distillates (liquified petroleum gas, gasoline, and naphtha), middle distillates (kerosene and diesel), or heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, and asphalt) (Wikipedia: Oil Refinery... [updated 2010]).

As the supply of the more favorable light and middle distillates are depleted, the energy industry is forced to look into the conversion of the heavier fraction of the crude to meet the increasing energy demand around the world. These heavier fractions of crude, however, contain a significant concentration of paraffin waxes, asphaltenes as well as numerous other macromolecules that require treatment before going to market. These petroleum macromolecules have the ability to cause severe, if not hazardous, problems if left untreated.

As we become more and more dependent on heavy and extra heavy crude oils for energy, the control of these macromolecules becomes a challenge for engineers. One of the most common problems in the production of heavy crude involves the formation of paraffin wax deposition in pipelines. The inner surface of the pipeline becomes fouled with these paraffin deposits, which reduces flow diameter, decreases overall throughput, and results in a higher pressure drop when crude is pumped through the pipeline.

The transportation of heavy crude from its production location to the refinery can require a substantial network of pipelines. These pipeline networks become even more important when it comes to the success of newly developing undersea, off shore energy projects. The colder conditions under water promotes deposition and presents challenges for maintainence and replacement. Hence, the build-up of paraffin waxes in these pipelines can cause great losses in profit and efficiency.

The presence of asphaltene adds another level of difficulty for wax treatment because these structures are almost always found in association with waxes when they are retrieved from wells, storage tanks or pipelines (Becker 1997). Paraffin wax deposition could be reduced by increasing the flow velocity of crude through pipelines since less time in the pipeline means less time for the deposits to form. However, increasing the fluid velocity increases the likelihood of asphaltene deposition. To resolve paraffin wax deposition, sometimes it is also necessary to consider emulsions, dispersed solids, and inorganic scales (Becker 1997). Thus, it can be very difficult and costly to maximize production by only treating one but not the other influencing factors. It is up to the engineers and scientists to seek an economically viable solution that reduces the formation of paraffin wax without increasing the concentration of other macromolecules.

Effects of Paraffin Deposition
Some of the general effects include:
 * 1) A decrease in pipeline cross-sectional area due to the presence of deposits, which then limits throughout and operating capacity.
 * 2) An increase in capital investment due to higher maintenance cost, the cost for remedial action, and prevention.
 * 3) Placing additional strain on pumps, consuming more energy, and requiring additional investment for replacing pumps.
 * 4) A loss of production due to complete blockage of pipes, which lead too costly periodic production shutdowns for maintenance and replacement.

Costs of Paraffin Deposition
The cost for preventing and removing paraffin deposits are substantial. Studies from the early 1990s have shown that this cost accounted for as much as 0.25% of global GPD (Mokhatab et. al. 2009). Those numbers have only increased since then.

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