4 replies to this topic

[sp3d2]

Hi guys.

EDD has two different location of water injection into crude oil which are before mixing valve and via water header above the electrod plates.

My question is,

1) what is the usual percentage of wash water (WW per total crude flow) should be supplied to this type of Desalter? is it 3 or 6%?

2) which route should I be giving more wash water? is it the one before mix valve or via top water header?

FYI, this desalter is treating heavy crude with density hovering around 0.878 kg/m3.

Thanks

Edited by sp3d2, 02 May 2012 - 10:08 AM.

[Technical Bard]

The total wash water to a desalter depends on the crude properties (gravity, viscosity, emulsion stability characteristics), the salt content and quantity of the connate brine and the quality of the wash water.

For heavier crudes (<24°API) with relatively high salt content I would recommend 8-12%, with 4-6% fresh and 6-8% recycle water. For intermediate crudes (<32°API)you probably need 5-8% and light crudes could be 3-6%. For these, half fresh and half recycle is probably reasonable. 3-6% seems a little low for a 30°API crude like yours - but if your connate brine is not high in salt, it might be ok. What is Cameron (who sells EDD) telling you?

[sp3d2]

thanks for the reply. I will check with Cameron also.

By the way, we are not using recycle water, we are using complety fresh wash water supply to EDD. Only the Effluent water of EDD being recycled to first stage Desalter before EDD.

My concern is how to distribute that 5 - 8 % to EDD. which section should be more. For example is if im giving 5% wash water, whats the correct practice? 3% via mix valve to mix with crude and another 2% for the dilution water inside the vessel?

[sp3d2]

and sir, what does it mean by connate brine? thanks

[Technical Bard]

Connate brine is the water that is mixed with the oil coming into the refinery, usually it is a small portion of the produced water from the oil field.

When I say recycle water, I mean the first second stage brine being recycled to the first stage. The fresh water is fed to the second stage. Some refiners use a mixture of "fresh" water with water recoverer from the crude/vacuum overhead drums, partly to recover any phenolic material.

Most of the water should be fed with the feed. My understanding of the EDD and other desalters is that only a small amount of the fresh water is fed to the header above the grids (like 0.5-1%). But again, get Cameron's opinion - it's their technology.