Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 2007 SPE Annual Technical Conference and Exhibition held in Anaheim, California, U.S.A., 11–14 November 2007. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, Texas 75083-3836 U.S.A., fax 01-972-952-9435. Abstract Conventional separators in the oil industry use a feed of oil and gas in two-phase multi-component equilibrium. Recently a new concept of separators has been introduced which can be fed with a single-phase gaseous mixture. The separator combines a quasi-isentropic expansion of the gas during which liquid droplets are formed by the nucleation process and a gas- liquid cyclonic separator. The performance predictions of such a separator depend critically on an adequate description of nucleation phenomena. For a large number of practical cases the Classical Nucleation Theory is very inaccurate. The recently proposed Mean-field Kinetic Nucleation Theory yields quantitatively accurate predictions of nucleation behavior of various microscopically diverse substances. An important advantage of non-equilibrium separation is the minimal use of chemicals and absence of regeneration systems, as opposed to conventional separation methods such as glycol contactors or silica gel towers. Introduction A separator is used to separate gas, oil and water from the fluids produced in oil fields. The focus of this paper is on a new concept for natural gas separators. Conventionally the industry used vessel-type separators, in which gas is separated from the oil by gravity forces. Vessel separators are large, heavy and expensive in terms of the space that they occupy on offshore platforms. One attractive alternative appears to be the use of Gas-Liquid Cylindrical Cyclone (GLCC). For this device the oil and gas phases are also already in equilibrium before entering the separator. It is essentially a cylindrical pipe in which a mixture of gas and liquid in thermodynamic equilibrium are injected tangentially, thereby causing a vortex. The gas-oil mixture is thus separated by centrifugal and buoyancy forces. The cylinder has two outlets, at the bottom and at the top, used for gas and oil respectively. The introduction of GLCC technology started only in the early 1990’s [1]-[3] when economic and operational pressures encouraged the use of less expensive and more efficient separators, especially for offshore applications. However, in 1996 only 45 GLCC’s were used world-wide in oil production facilities, mainly because the theory from which the design criteria could be computed was not well established, and LCO (liquid carry over) and GCU (gas carry under) were unpredictable. Since then the hydrodynamic theory for GLCC’s has gradually been established [4]-[5]. As the mechanistic model was improved, a design code [6] could be formulated and the number of field applications increased considerably. The optimal performance is, however, constrained because the feed stream in conventional GLCC’s is typically a two-phase mixture at equilibrium conditions. The dispersed phase (being liquid droplets, bubbles or solid particles) is separated using the inertia of the heavier phase, but generally no phase transition occurs. Note that the separation of water in conventional devices frequently requires the use of chemicals [7]. In the present paper we are not aiming at optimizing GLCC but at introducing a completely new concept of a gas-liquid separator. Instead of the conventional scheme operating under equilibrium conditions, one can think of a device based on a very different physical mechanism, namely, nonequilibrium phase transitions [8]. In such a device, the feed stream is generally a single-phase multi-component gaseous mixture containing condensable vapors. The gas flows through a separation section, representing a Laval nozzle, at supersonic velocity. Three main physical processes are: • A near isentropic expansion of the gas in the nozzle resulting in a drop of temperature and pressure due to the high (supersonic) velocity SPE-110736-PP New developments in nucleation theory and their impact on natural gas separation Vitaly Kalikmanov, Marco Betting / Twister Supersonic Gas Solutions BV Johannes Bruining, David Smeulders/ Delft University of Technology