What does the amount of demulsifier injected depend on?
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I’ve seen that the amount of demulsifier injected is adjusted based on the salt content in the crude oil; this salt content is monitored online, and the signal is sent to the device responsible for injecting the agent, thereby controlling the amount of demulsifier injected. Why is it related to the salt content? What else is it related to?
The function of a demulsifier is to break down the oil-water interface film, reduce the resistance to droplet coalescence, and accelerate the separation of oil and water. A high content of raw salt requires increased water injection, and the large amount of water makes oil-water separation by electrodeposition difficult. It is mainly related to the properties of crude oil. The effectiveness of demulsifiers varies depending on the type of crude oil
If the addition amount is insufficient, demulsification does not occur, and desalination is not possible
The online monitoring of salt content mentioned by the poster, along with the ability to control the dosage of demulsifiers used, is really too advanced for our small-scale equipment. We keep the injection level at 40PPM; if the salt content after dehydration is high, we inject a bit more.
It is also related to the matching degree of mixing intensity, electrodesalination temperature, and electric field strength, as well as the residence time under the field strength and the specific gravity difference between oil and water.
A poor desalination effect is not necessarily due to the demulsifier; it could be a problem with your electrodialysis unit. Of course, there is also a certain amount of crude oil; if the demulsifier is not effective and the water content in the crude oil is high, then the salt content will also be high. Therefore, it cannot be simply concluded that it is a problem with the demulsifier or electrodesalination.
This logical, feedback-based injection method is quite novel and gimmicky, but it seems like you’ve been tricked by the demulsifier manufacturers. The amount of salt remaining after separation is related to many factors, and it is not simply linearly correlated with the amount of demulsifier used. Processing volume, changes in crude oil properties, blending of contaminated oil, desalination temperature, water injection volume, water quality for injection, water injection method, mixing intensity, interface level, electric field...
The demulsification efficiency of demulsifiers is highly dependent on the properties of the crude oil; it is generally necessary to select the most suitable one by testing which demulsifier performs best. Currently, refineries try out various demulsifier manufacturers to determine which one works best before choosing to use their products
It is necessary to test whether a demulsifier is suitable for crude oil; if it is not effective, adding more of it will be of no use.
The salt content in crude oil is removed through water injection for washing. However, during the washing process, thorough mixing leads to the emulsification of oil and water; it is necessary to use demulsifiers to break this emulsion state and separate the oil from water, so that the salts contained within can be removed through dehydration. Therefore, the amount of demulsifier injected is only related to the demulsification effect. On the other hand, the demulsification effect is not solely dependent on the demulsifier; it is also related to many parameters such as mixing intensity, water injection volume, and electrodesalination temperature. Therefore, the selection of demulsifiers is quite important; they should be suitable for the crude oil being processed and possess good broad-spectrum efficacy to adapt to variations in the crude oil. The appropriate dosage can then be determined through testing, and no major adjustments to the injection amount are needed, unless there are significant changes in the properties of the crude oil.