How does heat help separate emulsion in heater treater?

[warmuz]

In the lower part of heater treater there is a U-type firetube which heat the inlet emulsion (oil+water).

I wonder how heat help extracting oil from water?

[gusgon]

Liquid-Liquid separation relays in the Stoke equations which determines velocity of separation. This is a function of liquid density difference and crude oil viscosity. Heat affects both. Makes density difference greater (direct proportionality) and crude viscosity lower (inverse proportionality), so the separation velocity increases. Heavier oils require larger heat input, higher temperatures as crude oil density are close.
Let me know wheather you need more information. I will be glad to provide it.

[warmuz]

Thank you very much for you answer.

yes, please provide more info.

Does the density of oil decrease because solution gas was released due to heat ?

Moreover, the separator temperature has to be between flash point and fire point of oil, hasn't it ?

[chunlin]

That is a complex discusion on temperature-wise. Yes, negtive effect of increasing temp is the reduction of difference between water and oil, which redcuing effectiveness of separation. HOwever compare it to the effect of reduction of visicosity, it is minor to the whole separatin process. You may see it in Stoke equation.
Temp should be controled not only because of lossing valuable light content in oil, but also the heat engery. Depend on API gravity, the heavier oil, the higher temp. For light oil, it may not need to be heated for separation.

[phutvuibuon]

Hi Chunlin, thank you for your information. Usually what is the range of the temperature of the flue gas inside the fire tube? Could it goes very high? Also, do you have any guides on sizing this emulsion treater? Thank you very much.