In some industries, as in biodiesel production, upon reaction, there will be several products with different properties (density) generated inside one chamber, and it's crucial to separate each of them.

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In the lab, we can accomplish this using a separation funnel

Or decantation can also be an alternative when lab-instrument is absent.

But now I wonder how it's done on an industrial scale?

  • 1
    $\begingroup$ I'd rather search for some kind of centrifugal separator. You basically speed up the decantation process increasing apparent g acceleration. Depending on what exactly is your process there should be many industrial grade devices ready to buy. $\endgroup$
    – carloc
    Commented Dec 25, 2021 at 13:28
  • $\begingroup$ Industrially , hydrocarbons are separated by distillation. In one application , (paraxylene from metaxylene) by freezing. $\endgroup$ Commented Dec 25, 2021 at 16:58

1 Answer 1


I would use

  • A tall narrow storage tank to separate layers into long cylinders one on top of the other with several valves at appropriate heights.

  • Wait for them to settle

  • Insert a densitometer or install manometers to make sure they are stratified.

  • Open one valve at a time at the middle height of desired liquid with a controlled flow as to have no turbulence or remixing of different liquids.

  • Divert the discharge to a second tank for further refinement if needed.


In response to OP's comment as to control of the valves:

There are electrical signal-controlled valves routinely used in industry that can be controlled by a digital densitometer such as the photo.


elect valve

  • $\begingroup$ "open one valve" - that would still require human involvement (as in lab scale separatory funnel), which i am sure will be inefficient at large scale continous plant. Can't imagine giant container, operator still required to open the valve, waiting for all required sediment to exit out, and then close manually everytime $\endgroup$
    – gardin
    Commented Dec 25, 2021 at 7:35
  • $\begingroup$ there are motorized valves that can be controlled by a manometer. like the roof solar water heater valves that open by a thermostat or from a control panel. $\endgroup$
    – kamran
    Commented Dec 25, 2021 at 7:55

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