Technology Unit

The process starts by mixing the raw crude oil with an appropriate amount of washing water also known as dilution water. The washing water as a volume percent of the crude oil processed could oscillate between 3 and 10%, depending on the API gravity of the crude oil – the heavier the crude oil, the more the water required. Demulsifiers are added to the crude oil in this process step.

In order to promote the effective mixing between the organic and aqueous phases, and ensure the proper dilution of the salts and minerals in the aqueous phase, a mixing valve is used. This is a common globe valvewhich causes a pressure drop and, as a result, a shear stress over the droplets that promotes an intimate water and oil mixture. The main aspect that needs to be considered is the pressure drop, whose value it is about 10-50 psi and varies according to the flux through the valve (automatic differential pressure controllers could be used). In addition to the mixing valve, upstream premixing device could be used, such as spray nozzles at the point of water injection or static mixers, between the water injection point and the mixing valve. High delta pressure in the mixing valve promotes smaller droplets, which is positive because it improves the contact among the phases; however, very small droplets could yield a more stable emulsion, which could cause problems in the separating vessel. Therefore, it is very important to balance both effects in the selection of the operation pressure drop.