Design and CFD Studies of Multiphase Separators—a Review Ali Pourahmadi Laleh, 1 * William Y. Svrcek 1 and Wayne D. Monnery 2 1. Chemical & Petroleum Engineering, The University of Calgary, Calgary, Alberta, Canada, T2N 1N4 2. Chem-Pet Process Tech Ltd., Calgary, Alberta, Canada The multiphase separators are generally the first and largest process equipment in an oil production platform. This primary separation step is a key element in the oil and gas production facilities in that downstream equipment, such as compressors, are completely dependent on the efficient performance of these multiphase separators. The literature on this critical unit operation, multiphase separators, abounds with macro studies and design methodologies for two- and three-phase vertical and horizontal separators. There are very few studies that provide the micro details of the actual separation process. In fact, the popular classic methods for separator design, mostly due to a lack of a usable mathematical model for estimation of droplet ‘separation velocities’, do result in a conservative design and would specify extremely oversized separators. In order to reflect the current situation and address recent findings, this study will review the important literature on design and CFD simulation of multiphase separators. This review will show the benefits that CFD analyses can provide in optimising the design of new separators and solving problems with existing designs. Keywords: CFD simulation, phase separation, multiphase flows, design INTRODUCTION O n production platforms, a multiphase separator is usually the first equipment through which the well fluid flows fol- lowed by other equipment such as heaters, exchangers and distillation columns, etc. Therefore, multiphase separators and their performance are key issues to economical and stable hydrocarbon fluid processing. As illustrated in Figure 1, the phase separation process is typically accomplished in three zones: The first zone, primary separation, separates the bulk of the liquid phase. In this zone, an inlet diverter is used so that an abrupt change in flow direction and velocity causes the largest liquid droplets to impinge on the diverter and then drop by gravity. In the next zone, gravity separation zone, the vapour and liquid phases flow through the main section of the separator at relatively low velocities and little turbulence. This leads to gravity separation of fine droplets out of the gas stream. This zone also includes the liquid collection section in which entrained gas bubbles or other liquid droplets join their corresponding phases because of gravity and buoyancy. This section also provides the holdup and surge volumes for safe and smooth operation of the separator. In the last zone, mist elimination zone, very fine droplets that could not be separated in the gravity separation zone are separated by passing the gas stream through a demister. Vanes, wire mesh pad or coalescing plates may be used in this zone to provide an impingement surface for very fine droplets to coalesce and form larger droplets which can be separated out of gas stream by gravity. Computational fluid dynamic (CFD) simulation is routinely used to modify the design and to improve the operation of most types of chemical process equipment, combustion systems, flow measurement and control systems, material handling equipment and pollution control systems (Shelley, 2007). For implementa- tion of a CFD simulation using a commercial software package, the geometry of the object of interest is specified (with a computer aided design drawing of the object) and the corresponding discre- tised grid system is created using a mesh-generation tool. For mesh generation, present software tools provide some predefined build- ing units in a variety of forms, such as tetrahedral, pyramidal, hexahedral, and recently, polyhedral blocks. However, generating a high quality mesh for the system is still one of the most techni- cal and time-consuming phases in any CFD-based analysis. After ∗ Author to whom correspondence may be addressed. E-mail address: apourahm@ucalgary.ca Can. J. Chem. Eng. 9999:1–14, 2011 © 2011 Canadian Society for Chemical Engineering DOI 10.1002/cjce.20665 Published online in Wiley Online Library (wileyonlinelibrary.com). | VOLUME 9999, 2011 | | THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING | 1 |