Coalescer

A coalescer is a technological device performing coalescence. They are primarily used to separate emulsions into their components via various processes; operating in reverse to an emulsifier.

There are two types of coalescers. Mechanical coalescers use filters or baffles to make droplets coalesce while electrostatic coalescers use DC or AC electric fields (or combinations).

A coalescer which operates by method of physical alteration or involvement of a droplet is influenced by mechanical, or physical, means. A more common type of coalescer, mechanical coalescers are applied in oil and gas industries worldwide for removal of water or hydrocarbon condensate. While coalescers by definition function as a separation tool for liquids, they are commonly used, and mistakenly referred to, as filters.

In the area of compressed air purification, coalescing filters are used to separate liquid water and oil from compressed air using a coalescing effect. These filters additionally remove particles. The most commonly used media in this case is Borosilicate micro-fiber.

In the Oil and Gas, Petrochemical and Oil Refining industries, Liquid-Gas coalescers are widely used to remove water and hydrocarbon liquids to <0.011 ppmw (plus particulate matter to <0.3 um in size) from natural gas to ensure natural gas quality and protect downstream equipment such as compressors, gas turbines, amine or glycol absorbers, molecular sieves, PSA's, metering stations, mercury guard beds, gas fired heaters or furnaces, heat exchangers or gas-gas purification membranes.

In the Natural Gas industry, gas/liquid coalescers are used for recovery of lube oil downstream of a compressor. All liquids will be removed but lube oil recovery is the primary reason for installing a coalescer on the outlet of a compressor. Liquids from upstream of the compressor, which may include aerosol particles, entrained liquids or large volumes of liquids called "slugs" and which may be water and/or a combination of hydrocarbon liquids should be removed by a filter/coalescing vessel located upstream of the compressor. Efficiencies of gas/liquid coalescers are typically 0.3 Micron liquid particles, with efficiencies to 99.98%.

Liquid-liquid coalescers can also be used to separate hydrocarbons from water phases such as oil removal from produced water. They have been also used in pyrolysis gasoline (benzene) removal from quench water in ethylene plants, although in this application, the constant changing of cartridges can lead to operator exposure to BTX (benzene, toluene and xylene), as well as disposal issues and high operating costs from frequent replacement.

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