An Overview of Gas Phase Separation and the Role of Pressurised Vessels in Its Completion

June 8, 2021

Phase separation is a core part of well stream division in a crude oil environment, but we also find the term used at the end point of the fuel distillation chain where it's perceived as a drawback. This somewhat ironic situation occurs when water damage causes a chemical reaction in an ethanol-based fuel and the blended hydrocarbon breaks down. Still, in the context of initial refinement, phase separation is an essential stage in creating the many fractions we depend on for powering the fossil fuel civilisation we live in today.

Robustly engineered 2 and 3-stage separators are placed early in the oil refinement process. They're the horizontal and vertically-mounted vessels built to withstand extreme pressures and sudden temperature changes. They're constructed in spherical configurations clustered around heat exchangers and debutaniser columns, ushering in sublime solutions for splitting streams of raw gas and oil. The 3-stage configurations go further yet, removing water from the flow before moving the phase separated fluids and gases onward for additional separation, storage, or delivery to market.

Two-Phase Separation

Deals in the division of oil and gas emulsions by delivering the gas/oil mix into a series of perpendicular plates or baffles. The physical properties of the emulsion are such that the liquid component remains at the bottom of the pressurised vessel while the gaseous component is separated, whereupon it rises to the top of the container to be streamed into the gas stage of the refinement process.

Three-Phase Separation

Generally speaking, crude oil comes to the ground as an emulsion with three components. Those components are as follows, oil, gas, and water. There's also likely to be trace contaminants in the form of sulphur, but let's keep our focus on the three main constituents. It's the ratio of these three fractions that defines the many possible process configurations. For example, an excess of water would logically divert the flow to a free-water knockout stream, but the presence of large volumes of gas and oil send the mix to three-phase separation vessels. Ratios is a major factor in crude oil refinement.

Products constructed to deal with these scenarios vary greatly, but it's generally accepted that low gas-to-oil ratios are processed within vertically constructed pressure vessels while horizontal variants are tasked with separating high gas-to-oil mixes. A combination of baffles, cyclonic action, and mist extraction then combines with the assorted pressurised vessels established within the Gas-Oil Separator Plant (GOSP) to successively split the three key components.

Categorisation of each separator product depends on its location in the two and three-stage separation cycle. Other factors that affect the attributes of the vessels include pressure ratings and physical construction (vertical or horizontal vessel) and the mechanical assembly within the container.

Contact Details

Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619

1865 Frankston Flinders Road,
Hastings, VIC 3915

Ph: (03) 5909 8218

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