Petroleum-Water Seperation

Putting a heat source under a tank full of petroleum eh, can you warn me like a good two hours before you do it so I can run away...

if you want to speed the process up , I'd chill the tank to force the water into a frozen state, much much safer. Heating it will only cause the petroleum to evoporate quicker. And annoy the EPA...

Actually, heating the tank is a pretty common method in crude production and it is not dangerous if done properly.

Yes heating crude oil is in most cases essential inorder to pump it or use it directly as fuel i.e. in ships.

Your post said "Petroleum" which in Oz(U.K?) is considered as "Gas"(U.S.).

With the large number of subcontinent posters here (who obviously operate way out of their skillset) one gets a bit wary as to the intent of some of the posts.

The operative phrase "not dangerous if done properly" would be beyond the comprehension of some people....

My great grandfather used to use chilled distilling to separate water from his home brew mash. Evaporation wasn't an issue due to the cold winter temperatures (on the island of Hven), though I'm told the resultant "vodka" did a good job of warming you from the inside..

I understand that if it is done in a distillation column in the absence of air, it is very popular. And much safer, too.

I think that this .pdf book section has the information you need. It is specific to the separation of water from crude. Particularly read section 4.3.

http://balikpapan.spe.org/images/balikpapan/articles/51/Crude%20Oil%20Emulsions%20-%20PEH%20-Chapter%2012%20-%20compressed%20version.pdf

Are we doing homework now?

I think it's more of a rookie thing than homework.

Look at the history of the OP.

Third question: what is the relevance of the red bars and the numbers 1 to 5?

It depends on proportion. A heat source that gently agitates the mixture will help them separate. Too strong a heat source will make them roil and become even more mixed.

On the bottom.

Heating the mixture will help and I would likely install the heat x at position 2. I was not sure what you meant by petroleum but I am assuming some sort of oil with a wide range of C values; heavy and light.

The petroleum will be in three phases; dense non aqueous phase liquids (DNAPLs), light non aqueous phase liquids (LNAPLs), and dissolved or aqueous phase. There is also a gas phase that will be found above the liquid. Heating will reduce the solubility of the dissolved phase and likely create LNAPL, and the LNAPL will become increasingly lighter (they are volatile) and some will enter the gas phase. The DNAPL will become smaller in molecular size, say from a C₁₂ to a C₈, just enough to push it back to the aqueous phase or even to an LNAPL.

The reason I would put it at position 2 in the tank is to allow room for the water to collect without being forced back into a mixture through heating.

Heating crude oil insitu conditions is a good method of extraction and is found throughout the oil extraction industry. The objective is always to create lighter products that can be removed easier than the DNAPLs. DNAPLs are the bane of many oil spill cleanups in aquifers.

Well isn't it easier (and not expensive-for the long run) - to use filters/separators

there are a lot of them !!

I wouldn't have considered this an O.T. post...

Filter/separators are for fuel with a bit of water, coalescers are for fuel with a bit more water (but they don't remove as much water), underflow dams or oil/water separators are for water with some oil/petroleum on the surface (as long as you remove the collected waste before it pushes the water below the level of the outlet).

Ultimately it depends on the purpose of the design, if the OP is trying to clean wet fuel, settling time and draining off water is the first step then sending it through a separator. Working on the pipeline when a wet batch came in we would let it set a day or so then drain the water, if it was still cloudy we would transfer it to a different tank through the separators.

If it was worse than that we would send it back to the refinery and let them deal with it (never got that bad though).

One thing about heating wet fuel though. When observing a visual sample, the warm wet fuel can appear clear and bright, but when cooled it will revert to a cloudy/wet sample. The primary way I know to tell for certain is by running a small sample through a water detector pad (there are other analytical methods for determining water content).

Oh! Almost forgot to mention if this is ethanol blended gasoline/petrol then it is entirely different. Water will mix with the ethanol and be tough to detect until the ethanol is saturated with water.

Drew K

You tried centrifugal separators?

I never needed to use them, but understand they are for waste oil/fuel floating on the surface already. They are quite effective in the appropriate situation, but not as effective for water entrained in fuel.

Drew K

You are correct Drew. The dissolved components of petroleum are more difficult to remove or separate. If complete separation is required, an adsorbtion material like activated carbon (AC) would be required. A common dissolved component found in most petroleum products are phenols, and BTEX (benzene, toluene, ethylbenzene, and xylene). These products are always tested when investigating ground water contamination, as would an output of the C distribution. Hydrogen peroxide and insitu biological treatment followed by AC is a common method to resolve some of these problems. Heating a reservoir of the product is a good idea to force some separation.