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Oil versus Water

02/16/2014 12:12 AM

New member here. Here is my problem. I own a boat yard and we have a very large shop that is heated by two waste oil furnaces. Now we burn appr 4000 to 5000 gallons of waste oil a year (in about 6 months). We produce our own waste and we collect waste oil from various other sources. Generally supply is not an issue. The really large issue is removal of water. Our main supply tank (the tank outside that feeds the day/run tank inside) is a 1200 gallon tank with a drain valve and piping at the bottom and the supply fitting (the one supplying the gear transfer pump) is about 16 inches above the bottom drain. I know that gravity does most of the work as far as separating the water and oil, but we always have two forms of unusable oil. One of these is emulsified oil/water and the other is sludge. I believe I have a handle on converting the waste sludge into usable fuel by mixing it with diesel fuel or older gasoline we have on hand from defueling vessels.

We are experimenting with a thin ratio of appr 10 percent additive into the sludge. This is carried out in a 250 gallon vessel with another gear pump circulating constantly to ensure a complete mix. I will post results after this is complete. Now the real problem is the emulsified water and oil. I know you can heat the oil/water mixture and evaporate the water from the oil but this is very time consuming and it uses a lot of energy in the process.

The other issue with heating is that we can easily burn 80 gallons of oil in a 24 hr period. I know of centrifuges but they are also a very slow method. So, what are any suggestions? We have cleanable 80 and 40 mesh screen filters basically all in the piping for our heater/oil plumbing. You would not believe the amount of crap that is in waste engine oils. We do not burn vegetable oils, only waste engine oils. I am looking for the most effective method of solving my problem. Thanks in advance!

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#1

Re: Oil versus Water

02/16/2014 8:31 PM

If not already so arranged, I would baffle the storage tank so that incoming waste oil goes into the larger part, with a slot or some holes say 6" up from the tank bottom to allow gravity flow into the smaller section. Take the combustion oil from this small section, passing it through a Racor® type of filter. IIRC, this type can trap modest amounts of water, which can be seen and drained. Have bottom drain valves on both sections.

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#2

Re: Oil versus Water

02/16/2014 10:55 PM

I gather that what you are burning would be similar to #6 Bunker Oil but with some additional water in it. If so there are commercial filters made specifically for getting the crap out of the #6 oil. It might also be useful to use a reverse flow heat exchanger to preheat the feed oil to the burner and circulate the excess oil back to the tank. With this heat exchanger the return oil to the tank heats the oil going to the boiler. This is a very efficient method both from a heat and $ perspective. The system would be piped and equipped very similar to burning #6 but burning your used oil. Any boiler repair outfit that services big boiler, such as Cleaver-Brooks, could assist you with the technical answers.

Depending where you are located and the states regulations, there may also be financial incentives or regulatory benefits to doing it this way.

Good Luck, Old Salt

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#3

Re: Oil versus Water

02/16/2014 11:06 PM

The best way we discovered was allowing the water to freeze by leaving the drums outside on a cold day and then pumping the oil out .This was on a small scale using 55 gallon drums ,but I wonder if it could be done on a larger scale by having a primary tank outside and piping it inside.You would have to periodically have a heating element to melt and drain the water , we just rolled the drums back in.

I assume your tank is inside to maintain viscosity and access but just a thought.

I wonder if it would be possible to apply a refrigerant and actually freeze the tank

itself to achieve the same result .Finally have you ever tried Aquasorb brand filters

they remove a lot of water but on your scale I guess would be expensive.

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#4

Re: Oil versus Water

02/16/2014 11:10 PM

Hi. I am just a novice but it seems to me that if "supply is not an issue", then the emulsion can be accumulated and, given enough storage capacity, the emulsion will slowly separate and the fractions can be drawn from the bottom as fuel and from the top to be processed as waste water.

Another thought is that you can expose the emulsion to a lipophilic substrate to help extract the oil. A Google search on ~~~ oil mop international ~~~ brings up several sources for oil adsorbent pads as well as the address of Oil Mop International, Belle Chase, Louisiana. This company's business is separating oil from water. Maybe they have a more pertinent answer??

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#5
In reply to #2

Re: Oil versus Water

02/16/2014 11:18 PM

The outside storage tank is equipped with a shelf below the oil intake to try and keep the water down, so to speak. It also has an internal heat tube that travels from one end of the tank to the other and then back again. When I built this tank I tried to think ahead and fabbed up what I thought might be needed in the future. I also made a clean out door on the top with a ladder inside for sludge removal if needed. The furnaces are metered at the burner and are supplied with appr 35 lbs of oil pressure via 1/2 inch piping. At each burner their are oil regulators to then reduce the pressure before mixing with compressed air. I am not sure I can return any oil back to the tank with changing out both furnace supply pumps due to the lack of flow. Additionally, the closest furnace has about 70 ft of pressurized oil line running to it and the other has about 140 ft. I would guess the oil would be substantially colder when it finally reached the day tank, even with insulation. I had a thought today... What if I fabbed up a crude water separator in between the outside gear transfer pump and the inside tank. At this point I am thinking of using the flow o oil from outside to inside (which has to be done anyway), but run it through a series of sch 40 pipe that turns the oil up a straight pipe for a distance (say 8 or 10 ft) then turns through a u bend and travels back down to the bottom. At the bottom tap a 1/2 npt hole and drop further down to collect the water. Then repeat. Basically, use the flow of the oil when filling the day tank to separate. I would assume the fast the flow the more effective. That outside gear pump is fast. I could even restrict the flow just above the bottom to increase the oil's velocity before hitting the turn to try and "sling" more water out??? It is a crude design in my head right now. What are your thoughts? I suppose it would work in the same theory as a centrifuge. Also, I am very familiar with Racors. Got a bunch of them in stock. Tried them, they reach full capacity very quickly and are expensive to replace elements. Even when I stock the filters. They do work quite well in engine applications that are requiring around 20 to 30 gph, but this pump runs around 20 to 30 gpm.

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#6
In reply to #4

Re: Oil versus Water

02/16/2014 11:25 PM

How would the oil absorbent pads or other oil absorbent materials aid the filtration of the oil to remove water? The flow rates through these are terrible and get less efficient as they get loaded with oil and then water.

Good Luck, Old Salt

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#7

Re: Oil versus Water

02/16/2014 11:27 PM

I have not tried those filters. I will look into them. Thanks. I am familiar with oil absorbent pads, booms, and loose bags. We use it often in our salvage operations and to generally clean up around the yard. Heck, even the old yard loader runs around with a couple of pads in it below the four wheel steering valves due to leakage! I wi definitely give them a call though. Thanks! As far as our scale, around here we are larger than anyone else recycling oil into heat. The barrel trick works great, but even with our engine driven transfer pump it can take an hour to pump off 50 gallons when it is 10 or so degrees outside. I guess I want my cake and I want to eat it too... I want to separate most of the water out, but I do not want to take forever and spend a bunch of money. Haha. I know where this generally leads...

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#8

Re: Oil versus Water

02/17/2014 4:33 AM

I am surprised that the emulsified oil cannot be made to burn, remembering the demonstration of water on a HOT oil fire in my RN days.....

I would hope that a filtered emulsion, using its own form of injection method, added to the boiler, would when the furnace is already running on water free oil and really hot, could be added to the fire in place........I would expect it to burn and add a great deal of heat to the boiler....cleaning the firebox at the same time!!

I have personally have never ever tried it myself!!

Here are some links that may prove helpful particularly the first one:-

http://fire.nist.gov/bfrlpubs/fire00/PDF/f00036.pdf

http://link.springer.com/article/10.1007%2FBF00790142#page-1

This one promotes emulsion burning to keep boilers clean!:-

http://www.sciencedirect.com/science/article/pii/S0082078477803330

With some thought and design, it should be relatively easy to achieve, ESPECIALLY if some extra type of mixing is used, ultrasonics may be a way, to make the emulsion even better for burning.....

Let us know what you actually do in the end.....

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#9

Re: Oil versus Water

02/17/2014 8:04 AM

When I was investigating the biofuel diesel systems there was a company that supplies absorbent pellets that can be cleaned by heating and had extremely long life so if you search the reclaimed vegetable on google you should find it and other items. One of my past associates had a cooking oil reclaiming business and he sold it by the tanker truck load and used two small centrifuges. They ran day and night but removed all water and down to 2-5 micron of solids. I also have a friend that produces food grade animal oils and he uses centrifuges and there is nothing slow about his process as he ships 40,000 liters every month.

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#10

Re: Oil versus Water

02/17/2014 9:21 AM

Oil+Water - easiest Water Separation is with ElectroCoagulation.

Burn-all easy to high flame temperature is with Oxygen Enriched Air - even to the extent of 100% O2.

You will find a lot of vendors doing these -Google the Bold heads

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#11
In reply to #8

Re: Oil versus Water

02/17/2014 11:36 AM

Subsequent experimentation, around the time of the BP gulf oil spill, indicated that the hardest part of maintaining combustion in a unit such as the OP has is the maintenance of a consistent emulsion. If not done the flame cannot be maintained by automatic devices or manual adjustment.

This problem is also one that the processors of oil emulsions by burning have encountered for years. Several ways to reduce this effect, but certainly not eliminate the problem, are available but on a one-of-a-kind in-house development basis. Oil/water emulsions are very subject to ambient conditions. An emulsion of the "chocolate mousse" concentration can be difficult to treat in one area but easier in another area.

Some in the business say there is a lot of witchcraft or spirituality involved with getting good results. I can't verify that because our spills didn't leave the river or bays and get to the ocean.

Good Luck. Old Salt

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#12

Re: Oil versus Water

02/17/2014 1:17 PM

Have you considered mixing Methanol/Ethanol with the emulsified oil?

also look at this for an answer.

http://www.ncbi.nlm.nih.gov/pubmed/22698673

or this:

http://www.alken-murray.com/860-1.htm

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#13
In reply to #8

Re: Oil versus Water

02/17/2014 11:57 PM

"I would expect it to burn and add a great deal of heat to the boiler....cleaning the firebox at the same time!!"

Wouldn't that depend on the oil / water ratio - or more specifically the combustion energy to water phase energy ratio?

If the emulsion was sprayed into the boiler wouldn't the water absorb thermal energy because of the heat of vaporization of the water? What would that do to the pressure in the combustion chamber?

Do these things atomize the fuel before injection into the boiler?

Maybe get your hands on some old diesel unit injectors and find a way to adapt them to your process; maybe mixing in some good stuff with the wet stuff before injection to ensure a much higher fuel combustion energy to water phase energy ratio?

What causes a steam explosion?

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#14
In reply to #13

Re: Oil versus Water

02/18/2014 4:17 AM

Have you ever seen the demo of water (any temperature) being added to a hot oil fire (any oil that will burn by the way)?

Here are some videos of this happening for your edification, the first one is interesting at about the 4 minute mark, so be patient!:-

http://www.youtube.com/watch?v=NC45vREoEOg

This one takes less time if you are in a rush:-

http://www.youtube.com/watch?v=ljeiZpZ32vw

And this one, due to a "time warp" is even quicker:-

http://www.youtube.com/watch?v=-V9gwRkMysk

Did you actually look at any of the links I included in that previous post? One of which even mentioned the cleaning effects of added water to an oil burner....you may not have posted if you had done some reading first!!

We used to clean running Gas Turbines in the RN with both fresh water and crushed walnut shells (not at the same time!) to clean the turbine blades without dismantling!! That was in the 60's and 70's....

I am personally convinced that it should be easily possible to burn an oil emulsion within an already burning hot oil fire, using the emulsion injection as a sort of "wet" afterburner, not as the main fuel....

Not forgetting someone's else idea of possibly adding alcohol to the emulsion, if it proves difficult.....alcohol absorbs water and is itself easily burnt.....but I do not think that it needs that....

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#15

Re: Oil versus Water

02/22/2014 7:53 PM

If the emulsified oil/water is allowed to float on the removed water, it may be possible to skim it off with a rotary skimmer. Good idea or bad?

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