Chemical and Biomolecular Engineering - Theses
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ItemYielding of waxy crude oil and numerical simulation of gelled oil pipeline start-up( 1998)As a main resource of energy, crude oil has been produced for many decades around the world. Pipeline system has been considered as the only feasible and most economical means for transporting large quantities of crude oil due to its big and reliable transportation capacity. The oil flow in pipelines may be shut down regularly for operational reasons and occasionally for emergency reasons, although it is desirable to maintain a steady and continuous flow rate without any interruption for an efficient operation of a pipeline system. After the flow is shut down, the warm crude oil in pipelines may be statically cooled to a considerably low temperature) depending on the ambient temperature and the duration of the shutdown. The declining production of conventional oil and increasing market demand for petroleum have resulted in more and more waxy crudes being produced. Waxy crude oils have relatively large proportions of high-molecular-weight paraffins and therefore high pour points. Statically cooling a waxy crude oil below its pour point may lead to a strong interlocking network of waxy crystals forming in the oil, which imparts various complex non-Newtonian and nonlinear characteristics to the flow properties of the oil including its particular yielding behaviour. To restart a pipeline fiI1ed with the structured oil, a pressure higher than that required for the normal operation must be applied to make the oil yield. The yielding properties of the waxy crude oil, which will be studied in this work, are directly related to the start-up and restart operations of pipeline transportation systems, and are a key for the successful design and operation of a pipeline system. (From Summary)