Separation principles with basic calculations part 1

Typical Vertical Separator

Imagine, you have mixture of two fluids, How will you separate them as efficiently as possible ?

First thing come into mind for separation of two fluids is, let them to be settle by themselves first. Put mixture into some box or vessel, it may happen both will separate by themselves.

Can it be happen ?

Yes, ot can be happen, if both of our fluids are immiscible, than it can be settle if we allow them to be set in any disturbance free environment.

In no agitation mode, they can settle with help of gravity. Heavier fluid will go down due to its higher mass (here we consider same volume of both fluids).

So, we can say, high dense fluid will be settle down to lower part of vessel.

That is basically Gravity separation. Same principle applies to separate oil and gas also. In certain pressure temperature conditions, when oil and gas mixture (which comes from wells) allowed to settle for fix timings, then gas (less dense or lesser mass) fluid occupies upper portion and liberate out from oil and oil will reside in lower portion of vessel.

This vessel separates oil and gas (and many times water also), so it's called separator.

Here, inside separator, force acting on drop of separated drop of gas (which is inside oil now) is,

F = mg.

Where force (F) is applied on gas bubble.

m is mass of liquid bubble of size of that gas bubble minus mass of gas bubble. (Rules of buoyancy).

And g is gravitational constant (9.8 m/s2)

And force which resist this gas bubble's upward movement is, resistance force which applies on this bubble (because our bubble is in oil, so it have to oppose this resistance force to come out of oil)

Is called, drag force. Which is,

F = P(pressure)*A(area)*C(drag coefficient)

Here, P = (1/2)*(Density)*square of (velocity)

Here, its density of gas.

(Don't mug up, just remember basics, and conversions

F = P*A

F = m*g

And, density = mass / volume.)