Separating Mixed Grease and Oil

This is a good description of how oil skimmers work.

grease and oil are both hydrocarbon based. Grease is an oil that has has been treated/mixed to make it semi solid so it will not run out of bearings.

http://www.barks.com/2002/02-04feat.html

Do you want to separate the grease from the oil, or the grease and oil from something else? I've spent 6 years working on the issue, need more details.

Thanks askjoet for your query.

Oil is mixed with Grease and and they have to be separated as if solid particles are filtered out from the oil. Grease is not to be separated into Oil and soap.

I hope this is clear.

With best regards.

It seems like a rather simple question:

"Can any one suggest how to separate mixed grease and oil?"

It says nothing about separating them from water, so the info on skimmers is useless. It does say they are mixed, presumably together, so the question is how to separate grease from oil or vice versa (same thing?).

My thought is that if the mixture is first heat high enough to melt all the grease, the two materials should stratify. Then, without disturbing the layers, cool the volume until the grease becomes a solid again. Then you may drain off the oil. Be careful not to cool so much that constituents of the oil begin to solidify as well.

If the two are mutually soluble you can distill the oil off.

Expensive though.

Grease is a mixture of oil and a fine solid material. Traditionally, a clay similar to polishing compound, only finer, is used as the solid. Modern greases use other solid materials such as MoS2 which give the grease better lubricating properties. If there is excess oil in the grease I believe the easiest/cheapest way to remove the oil would be filtration. A high-pressure filter cake system would work well. Much cheaper but slower would be a tall column (pipe) with a filter "sock" around the bottom that allows gravity to do the work of pushing the oil through the filter as fresh feed is added at the top.

Bill Morrow

You know, he did not really say what kind of "grease" and "oil" he was talking about! If he was talking about industrial lubricants, then I would say you are 100% correct. If he was talking about cooking oils and resultant "grease" from animal fats, then my answer above would be correct.

Even his clarification is hard to understand. Since he talks about "not" separating the grease into "oil" and "soap", that reinforces my interpretation, for you can take animal fat, heat it and mix in some lye or other chemical, and render it as "soap".

In what other way could you interpret "soap"? I am not saying you are wrong, most of the questions here relate to industrial processes, but his inquiry is very unclear.

Agreed. I hope he will consider the responses given and ask follow-up questions, providing more detail in the process.

Bill Morrow

Thank you all for your responses.

I am talking about separating the Industrial Grease and Industrial Oil ( Hydraulic / Lub ) mixed. My question was how to separate it if they are mixed in bulk.

Two questions:

What is the approximate ratio, by volume, of semi-solid grease to liquid oil in the mixture?

Also, is your goal to to salvage primarily the oil or the grease, or both, and for what purpose, re-use as a lubricant, burning as a fuel, or other internal use, or to sell to another company for a similar purpose? This could make a difference in the technique(s) used, degree of purification required, and the applicable costs.

Thanks for your reply.

Ration of Oil to grease is around 80:20 and i wanted to slavage both and reuse it if possible.

I guess the next question, which I think that I asked already, is what purpose you plan to re-use the oil and grease. The filtration method would separate the solids from most of the liquid, but the liquid may not represent the same composition as the original oil, having obtained some oil from the grease as well. Vice versa, the grease may be "contaminated" by some of the other oil(s). If this is not a concern, then basically check the vicscosity of the oil to see if it meets your needs. Then check the grease by what ever measure you think is necessary. Depending on the fineness of the filtration and the time and weight (resulting in pressure) of the mixture, the grease may have a varying liquidity. You may then want to mix in some oil or remove some oil, depending on which way you need to vary the liquidity.

Thanks STL Engineer.

But what type of filter i should use ? I hope it is to be surface type. But what micron rating ? With this filtration accumulated Greas on the surface wil also have contamination filtered out from the oil. So what is the solution and procedure ?

It is not in a serious application so littles bit of contaminated oil will also serve the purpose.