Desalting
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Electrostatic coalescer
An electrostatic coalescer is a pressure vessel with energised electrode grids, in which a high-voltage field coalesces water droplets in crude oil so they settle. Used without wash water it is a…
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Crude oil desalter
A crude oil desalter is an electrostatic coalescer operated with wash water mixed into the crude upstream. The water dilutes the salty droplets in the crude, and the coalescer then removes the…
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Wash water
Wash water is low-salinity water injected into crude oil upstream of a desalter to dilute the salty water droplets it carries. It is typically added at 3 to 10 per cent of…
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Mixing valve
A mixing valve is a throttling valve upstream of a desalter that shears wash water into fine droplets so they meet the salty water in the crude. Its pressure drop balances mixing…
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Pounds per thousand barrels (PTB)
Pounds per thousand barrels (PTB) is the customary unit for the salt content of crude oil: pounds of salt, expressed as sodium chloride, in one thousand barrels of crude. One PTB is…
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Demulsifier
A demulsifier is a surface-active chemical injected into crude oil at parts-per-million levels to displace the natural films that stabilise water droplets. With the films weakened, droplets can merge and settle. It…
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Interface level
Interface level is the height of the boundary between settled water and the oil above it in a separator, dehydrator or desalter. Controlled by the water outlet valve, it must sit below…
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A structured method for diagnosing high BS&W at a dehydrator or desalter outlet
High basic sediment and water (BS&W) at the outlet of an electrostatic dehydrator or desalter has a short list of possible causes. This paper sets out an order in which to check…
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Electrostatic coalescers
An electrostatic coalescer is a pressure vessel that uses a high-voltage electric field to merge small water droplets in crude oil into drops large enough to settle by gravity. The same equipment…
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Crude oil desalters
A crude oil desalter removes salt from crude by mixing in low-salinity wash water to dilute the brine, then removing the water in an electrostatic coalescer. Salt leaves dissolved in the water.…