Gravity Separation - FMC Technologies

The majority of separators in the oil and gas industry are gravity separator vessels. These have one thing in common; they all rely on the gravity force to achieve separation. By installing internals that ensures good flow distribution and enhanced separation in the gravity section, the gravity separator vessels will perform at high efficiency. Enhanced gravity separation of gas, oil, water and solids results in a maximum overall performance of the separator while its dimensions are minimized.

CDS Drained Meshpad Agglomerator™

A mesh agglomerator can be used

•if a very high degree of gas-liquid separation is required
•if the separation duty is demanding due to the presence of small droplets
•if a high turndown of the separator or scrubber is required

It can be positioned either vertically or horizontally within a vessel.

The overall liquid handling capacity and separation efficiency of a separator or scrubber can be significantly increased with the drained meshpad agglomerator. It captures and agglomerates the droplets prior to the liquid entering the downstream mist elimination device using a patented drain system integrated into the agglomerator. It can also improve the turndown of the separator or scrubber. It is mounted upstream of the mist eliminating assembly and differs from the mesh type demister as it is designed to operate in a flooded condition. This has the effect of enlarging the sizes of the upstream droplets thus increasing the amount of liquid removal within the downstream device. The result is a substantially improved efficiency of the vessel. Furthermore since it provides a pressure drop prior to the mist eliminator any slight misdistribution present on the face of the mesh will be evened out prior to the gas entering it.

Distribution Baffles

In horizontal vessels fluids can shortcut through the vessel and the actual residence time for separation will be much shorter than with a perfect distributed flow. In order to achieve an efficient gas-liquid and liquid-liquid separation it is important to have a quiescent flow regime along the length of the vessel. This is achieved through the use of perforated baffles. It has been demonstrated in tests and CFD models and, more importantly, in the field that without these internals the separation process can be adversely affected.

Plate Pack Coalescer

Gravity separation of oil and water is accomplished by droplets settling. A certain retention time is required to allow for a droplet to settle and be united to its bulk phase. A plate pack coalescer is used in the liquid section of a separator or scrubber to optimize the degree of liquid-liquid separation. The flow through the narrowly spaced plates is laminar and smaller droplets are separated since the distance the dispersed phases have to travel to the interface is greatly reduced. The plates are bundled in small compartment which fit through the man way. The operating principle of parallel plate separators relies on the density difference between the oil and water phase: Oil droplets in the water phase will rise to the oil/water interface and water droplets in the oil phase will settle. Parallel plates are fitted in the separation chamber for two reasons:

1.The flow through the narrowly spaced plates will be less turbulent; therefore separation of much smaller droplets can be expected
2.The distance the dispersed phases have to pass through to reach the interface is much shorter; therefore the residence time can be much quicker