How does centrifuge machine separate water particles from oil?
In: Engineering
The same way that just letting it settle in earth’s gravity does, but faster.
If you let an oil water mix sit long enough undisturbed, it will separate, because they are of different densities. The more dense substance will settle to the bottom and the less dense substance will settle at the top, because the earth’s gravity pulls harder on the dense material per unit volume. Much like if I have packing peanuts and steel balls in a box and lightly shake it.
The centrifuge spins. When we spin a container whatever is inside it “wants” to go in a straight line, but that’s not possible when it is in a container. From inside the container it seems like a force is pulling it to the outside. The faster the container spins, the more this apparent force is. This apparent force in centrifuges gets very high, kind of like if the force of gravity was multiplied by 10 or more. Thus speeding up the process that would normally take a long time in earth’s gravity.
It multiplies the force of gravity to 2 different substances. The heavier object seperates from the lighter object faster and more completely (less emulsions) than they would under normal gravitational forces.
This not exactly an ELI5 answer, but the area you area asking about involves *cyclones*. My experience has been with [*hydrocyclones*](https://en.wikipedia.org/wiki/Hydrocyclone) in the separation of sand and silt from well water. There are many applications of this general principle. There are non-liquid versions of this for woodworking shops trying to [manage dust](https://www.google.com/search?sca_esv=7e0a5ff40af74da5&q=woodworking+dust+cyclone%27&tbm=vid&source=lnms&sa=X&ved=2ahUKEwiG1ZjhveGEAxVuK0QIHaPWCZMQ0pQJegQIChAB). Here is an explanation of the principle for [oil rigs](https://www.oilsandsmagazine.com/technical/mining/froth-treatment/naphthenic/hydrocarbon-cyclones).
Water is denser than most oils (maybe all oils?? not sure), so if you put any acceleration on a water/oil mixture, the two liquids will respond different amounts and end up separating.
Gravity alone does this; if you just let a water/oil mixture sit, the oil will float to the top/the water will sink to the bottom. In weaker gravity this separation would still happen, but slower, and in stronger gravity the separation still happens, but faster.
A centrifuge creates “artificial gravity”, aka centrifugal acceleration, toward the outside of the spinning cylinder and it can be way, way stronger than Earth’s gravity so it can separate liquids a lot faster. The water ends up on the outside of the cylinder, with the oil on the inside, and if you place valves or little holes in the cylinder you can let one liquid out while the other stays trapped inside.
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