The world energy consumption will increase in the next decades. However, many aging oil fields are showing a steady decline in oil production. And they are producing increasing amounts of water, making the separation of the oil from the oil-water mixture an important processing step. In-line separation equipment using swirling flow can provide a light-weight, compact solution for offshore platforms and deepsea production sites, for which the use of large gravity-based separation vessels is very costly. In a collaborative project such an in-line separator has been investigated. The separator consists of a pipe, in which the internal swirl element (ISE) is placed. The ISE is equipped with vanes, which generate the swirling flow. Downstream of the ISE, the oil is extracted by a concentrically placed pick-up tube. In the pipe, the radial distribution of the axial velocity is W-shaped with an annular region of reversed flow and positive axial velocity in the center of the pipe and near the wall. The distribution of the azimuthal velocity shows a solid-body rotation in the center and a potential-flow vortex type of distribution at larger radius. A parameter study has demonstrated that the flow pattern in the separator is complex and that its dependence on the input parameters is complicated. For two-phase flow, the simulations predict good separation performance. However, the numerical results overpredict the separation efficiency, in some extreme cases by 50 %. The differences in results between experimental and numerical work decreases substantially when for the simulations an inlet droplet size is used, which corresponds more closely to the one in the flow loop at Delft University. Moreover, the inclusion of an anisotropic turbulent dispersion model in the computation may improve the numerical predictions. The result for poly-dispersed two-phase flow show only a modest increase in the Sauter mean diameter from 50 to about 80 µm in the center of the pipe. Although much progress has been made, further research is required to achieve a better prediction of the two-phase flow in a centrifugal separator.
|Award date||22 May 2013|
|Place of Publication||Enschede|
|Publication status||Published - 22 May 2013|