Edson Yoshihito Nakagawa

A Modified Eulerian-Lagrangian Approach Applied to a Compact Down-Hole Sub-Sea Gas-Liquid Separator

This article presents a modified Eulerian-Lagrangian approach for solving multi-phase flow applied to a laboratory-scale gas-liquid separator designed for high gas content. The separator consists of two concentric pipes with a swirl tube in the annular space between the pipes. The gas-liquid mixture comes from a tangential side inlet and the system works with a combination of gravity and centrifugal forces to achieve a high-efficient gas-liquid separation. In the modified Eulerian-Lagrangian method, gas flow is coupled with the spray and wall film models. The spray model involves multi-phase flow phenomena and requires the numerical solution of conservation equations for the gas and the liquid phase simultaneously. With respect to the liquids phase, the discrete-droplet method (DDM) is used. The droplet-gas momentum exchange, droplet coalesces and breaks-up, and the droplet-wall interaction with wall-film generation and entrainment of the water droplet back into the gas stream are taken into account in this investigation. To be consistent with the experiments the experimental air water mixture on the liquid carry over (LCO) curve is used for the numerical investigation. The standard k-ϵ turbulence model is used for turbulence closure. The predicted results from the modified Eulerian-Lagrangian multi-phase model explain the complex flow behavior inside the separator and are in good agreement when compared with experiments.

Effect of pressure and salinity on the performance of a gas-liquid separator—a preliminary study

The separation of liquid from gas during the initial stages of separation process is very important to increase the well productivity. That’s why design of an efficient compact gas-liquid separator has received a lot of attention from academic researchers, as well as from field operators. All of them state the necessity of compact design to deploy separators offshore and potentially subsea in order to enhance the recovery of the gas wells. This current investigation describes an experimental and computational fluid dynamics (CFD) modelling of a laboratory scale compact gas-liquid separator designed by CSIRO. The separator consists of two concentric pipes with swirl tube in the annular space between the pipes. The gas-liquid mixture comes from the tangential side inlet and the system works with a combination of gravity and centrifugal forces to achieve a high-efficient gas-liquid separation. The effect of pressure and salinity on the performance of the gas-liquid CS-T (CSIRO’s Separation Technology) separator is investigated in this paper. The performance of the separator is visually established by observing the liquid carry over (LCO) regime in which liquid is carried out in the gas stream. The liquid and gas-flow rate at which the LCO is observed defines the upper operational range of the separator. Air-water mixture is used for both experimental and CFD investigations. The performance is evaluated at 1, 2, 5, 10 and 12 barg pressure. The upper operational range decreases with increases pressure. For higher pressure (10 and 12 barg) the LCO curve was nearly vertical which indicates no change in gas flow rate with the increase in water flow rate. The salinity does not affect the performance of the CS-T separator. The CFD results are used to visualize the constant LCO and to understand the physics and mechanism of LCO.