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A Layer of Accumulated Water at Ester Oil Tank

12/09/2015 9:42 PM

i have an open tank which keeps ester oil, a layer of water is accumulating at the flat bottom of the Atm tank, with the heating coils lying on surface of the bottom tank.

there is no slope to drain out of the water; the drain valve is slightly higher than bottom of the tank, therefore, a layer of water build up. it is hard to remove this water. the trouble is the Free Fatty Acid is building along the timeframe due to this water

the heating coil is giving the manual-labor removal of water even more difficult.

this ester oil will be pumped later on.

My question is, how to effectively remove this water? any hygroscopic chemical to use? How usually, Oil and gas industry practice to reduce the amount of trapped water in the tank within the physical tank, exclude the quality part explanation.

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#1

Re: a layer of accumulated water at ester oil tank

12/09/2015 9:58 PM

What temperature?

Other than the obvious fact this is a lousy design, when you say ester oil do you mean before, during or after transesterification?

Portland cement is a very good option that might also take care of the drainage issue.

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#3
In reply to #1

Re: a layer of accumulated water at ester oil tank

12/10/2015 12:13 AM

just about <80C.

is a process of esterification. after rxn, it dropped to this tank.

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#6
In reply to #3

Re: a layer of accumulated water at ester oil tank

12/10/2015 6:46 AM

Glycerine works quite well.

I think you mean to say - hygroscopic material that will not react with the product, perhaps??? This temperature rules out Glauber's salts, which was my first thought. I was serious about the Portland- it will work at that temperature, and any other product will have to be removed any ways, once it stops working.

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#8
In reply to #6

Re: a layer of accumulated water at ester oil tank

12/10/2015 9:25 AM

I'm not a chemist, and I don't know what ester oil derivative it is to start with, It sounds counter intuitive by adding Glycerin back into the ester oil, considering that at one point the glycerin was separated from the ester oil bonds by the induction of water by hydrolysis in the first place. ???

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#9
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Re: a layer of accumulated water at ester oil tank

12/10/2015 9:30 AM

Absolutely!!!!

That was the point of the emoticon- glycerine is VERY hygroscopic, but will also contribute to the issue as would glycols or other alcohols. Sulfuric acid would work, and likely add extra drain points at the bottom of the tank.....

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#10
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Re: a layer of accumulated water at ester oil tank

12/10/2015 9:43 AM

I breeze threw the comments, I didn't come across how they drain the tank.

Just putting this out there...... could it be a process issue up stream for the excess water accumulation at this point?.

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#14
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Re: a layer of accumulated water at ester oil tank

12/11/2015 8:46 AM

"upstream process issue..."- yes. And it sounds almost as if this is supposed to be a settling tank, which makes matters even worse.

His problem is that the material is quite warm, which accelerates the reaction rate. Also due to the design of the tank, with the flat bottom any water (or glycerine etc. that is still precipitating from the mixture) that builds up spreads out quickly, creating a large water/oil interface up to the diameter of the tank. So a little bit can go a long ways....

It's at this interface that hydrolization takes place. Ideally it would have been a centre or side cone tank with at least 30 degrees pitch, that would greatly reduce the interface area while allowing for complete drainage. As it is, any non crystalline material I can think of sufficiently polar to not enhance redisolution of the water is also likely to react with the ester (or something else, such as the tank walls...), and the crystalline materials will build up on the tank bottom and saturate, at which point they have to be removed somehow or be left to (hopefully) help drain further water.

If this is for biodiesel, the water and FFA both will cause further degradation and offspec material, or at least hassles for further esterification. It may also make the material harder to use as a chemical base stock, such as for sulphonation or amidization to make detergent products.

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#15
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Re: a layer of accumulated water at ester oil tank

12/11/2015 9:01 AM

Nice explanation, thanks!

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#17
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Re: a layer of accumulated water at ester oil tank

12/12/2015 2:18 AM

I Concur

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#21
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Re: a layer of accumulated water at ester oil tank

12/15/2015 2:32 AM

Trinitrotoluene works even better!

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#2

Re: a layer of accumulated water at ester oil tank

12/10/2015 12:02 AM

If the tank is open, insert a dip tube reaching as close as possible to the bottom, attached to the suction port of an eductor or other type of pump. When the chance arises, build a sloped false bottom in the tank, possibly cement as already suggested.

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#16
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Re: a layer of accumulated water at ester oil tank

12/11/2015 2:56 PM

If you go to the work of building a sloped false bottom, make sure you include a large enough sump with a drain valve for bleeding off the water.

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#4

Re: a layer of accumulated water at ester oil tank

12/10/2015 2:17 AM

It is very difficult to interpret what you are trying to say because of the apparent language difference, but I will make the attempt. I am going to show your post with corrections to reveal what I think you are attempting to say. I will then show a fully corrected post and ask if it is accurate. Hopefully this will help you to communicate better in future posts. Despite the difficulties here, I give you an A+ for spelling!

My attempt at correcting your post:

i I have an open tank which keeps that contains ester oil,. a A layer of water is accumulating at the flat bottom of the Atm non-pressurized tank, with the heating coils lying on the surface of the bottom of the tank.

t There is no slope to aid in draining out of the water the water out;. t The drain valve is slightly higher than the bottom of the tank,. t Therefore, a layer of water builds up. i It is hard to remove this water. t The trouble is the Free Fatty Acid is building along the timeframe (accumulating at the water/oil interface?) due to this water.

t The heating coil is giving making the manual-labor removal of water even more difficult.

this ester oil will be pumped later on.

My question is, how to do I effectively remove this water? Is there any hygroscopic chemical to use? How usually, Are there typical O oil and gas industry practices to reduce the amount of trapped water in the tank within the physical at the bottom of the tank. Please exclude the quality department explanation.

The fully corrected/translated post would be:

I have an open tank that contains ester oil. A layer of water is accumulating at the flat bottom of the non-pressurized tank, with the heating coils lying on the surface of the bottom of the tank.

There is no slope to aid in draining the water out. The drain valve is slightly higher than the bottom of the tank. Therefore, a layer of water builds up. It is hard to remove this water. The trouble is the Free Fatty Acid is (accumulating at the water/oil interface?) due to this water.

The heating coil is making the manual-labor removal of water even more difficult.

this ester oil will be pumped later on. <==(I have no idea why you are saying this)

My question is, how do I effectively remove this water? Is there any hygroscopic chemical to use? Are there typical oil and gas industry practices to reduce the amount of trapped water at the bottom of the tank? Please exclude the quality department explanation.

So, westdeap12, does this sound like what you are trying to say?

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#5

Re: a layer of accumulated water at ester oil tank

12/10/2015 3:00 AM

In the same way as the decant valves are used in the sludge tank at a sewage works! Wait until the water has risen above the level of the lowest valve in the tank, then open the valve.

When the opportunity arises, raise the floor of the tank using concrete, as already suggested.

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#7

Re: A Layer of Accumulated Water at Ester Oil Tank

12/10/2015 8:18 AM

In the refined fuels industry we slope the bottom of the tank and drain water off before pumping out fuel. In many point of sale operations the inlet pipe is not on the bottom of the tank so when your product is given to the customer you know there is no water in it.

Other solutions include alcohol which will bind the water with the oil but may not be as good for your product as it is in fuels.

If your tank is shallow or small enough you might get away with pumping continuously from a pipe with some sort of fitting on the end to draw the water from the bottom. The pumped mixture could be sent to a small tank where you can drain the bottom and allow the top to drain back to the main tank. The fitting could be a disk that sits flat and just off the bottom of the floor and draws the water in better.

Heating is another solution. Water will not condense from the air to a warm liquid and the water in the liquid will evaporate out. Only problem is in fuel, warm can also cause the water to entrain in the mixture and be virtually undetectable to observation.

Drew K

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#11

Re: A Layer of Accumulated Water at Ester Oil Tank

12/10/2015 10:27 AM

How deep is the tank?

I would install a pump and piping that terminates at the bottom of the tank to extract the water.

If the tank is less than 30 feet deep a simple high performance centrifugal pump with a mechanical foot-valve (check-valve) could be mounted on the top of the tank and the discharge piping routed into a waste collection tank or drain.

If the tank is too deep to use a centrifugal pump then a submersible unit could be used. There is a myriad of low cost, small, low-voltage, portable submersible pumps available that would probably work depending on the volatility of the application.

If you want/need the pump to be automated, a sensor could be mounted in the pump discharge piping that would shut the pump off when the ester content reaches the needed shutoff point.

This could be a viable temporary solution until the tank can be taken out of service to correct the bottom slope issues or it may turn out to be a viable permanent solution.

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#12

Re: A Layer of Accumulated Water at Ester Oil Tank

12/11/2015 12:21 AM

My first thought is to blow sodium-bentonite clay into the drain. That would absorb the water and the fatty acids.

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#13

Re: A Layer of Accumulated Water at Ester Oil Tank

12/11/2015 2:13 AM

I need to assume for this solution, that the tank drain valve is accessible from the inside. Remove the valve assembly to the workshop, and modify the tank side so that the suction point is effectively lowered. Probably, any farmer-Brown method will do, eg rubber suction hose, welded pipe section etc...

Remember, your floor is not sloped, so you can have the actual suction point some distance away from the side of the tank.

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#18

Re: A Layer of Accumulated Water at Ester Oil Tank

12/14/2015 3:20 PM

You need to ask yourself: Why is my product (ester) contaminated with water in the first place? If the water is a by-product, and not some steam leak, then maybe it is not avoidable. Last time I checked, esters formed from alcohols and acid anhydride do not have this problem, but do have a by-product of free acid.

Since you are not talking about chemical synthesis of esters, but you are speaking of transesterification of fats and oil to biodiesel, you need to understand that you cannot completely dry your feed stock with your present setup. That is where most of this water is coming from, I suspect. Get rid of the offending tank, or place another cone-bottomed tank upstream of it to collect water and allow the product to siphon off the top.

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#20
In reply to #18

Re: A Layer of Accumulated Water at Ester Oil Tank

12/14/2015 8:35 PM

Start with the first post and follow it down.

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#22
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Re: A Layer of Accumulated Water at Ester Oil Tank

12/15/2015 9:13 AM

I thought actually, that I did.

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#19

Re: A Layer of Accumulated Water at Ester Oil Tank

12/14/2015 7:14 PM

Find an appropriate pipe long enough to reach the bottom of the tank, attach a garden hose to the top of the pipe, making the other end of the hose lower than the bottom of the tank. A natural siphon will remove the water.

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#23

Re: A Layer of Accumulated Water at Ester Oil Tank

12/15/2015 9:22 AM

Why is a question I keep asking myself: Why are you not heat-treating your feed stock and driving off the moisture from it? In the oil and gas industry, they use something called a heater/treater to heat oil recovered from wells that emerges as an oil and produced water emulsion. The heat breaks the emulsion (by basically lowering the viscosity of the oil, and raising the interfacial tension between water and the oil).

Once your incoming feed stock is more dry, the transesterification should actually work better, with far less Free Fatty Acid being produced in the final product. Once you have a clean product, you can also continue with your present tank, but may I suggest the use of a centrifugal separator to completely remove any liquid phase not soluble in the ester oil product? Then your product will be a great deal more stable in storage, cleaner, better for the engines that you plan to run on it.

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#24
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Re: A Layer of Accumulated Water at Ester Oil Tank

12/15/2015 9:35 AM

In the oil and gas industry, they use something called a heater/treater to heat oil recovered from wells that emerges as an oil and produced water emulsion.

I believe they run it through a heated vacuum column, and the water will flash off before the oil, but not certain,

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#25
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Re: A Layer of Accumulated Water at Ester Oil Tank

12/15/2015 9:47 AM

That may well exist at the refinery, or a terminal where oil is being readied for pipeline injection, but the heat treating I referred to is a field unit process, usually found near tank batteries, where the output of a number of wells is pooled together, but in some instances of a higher producing well, the heater treater is located adjacent to a pump jack, and this may be because the salt water produced has caused corrosion problems in a transfer line in the past, I do not know about every instance. The heating process in the field typically has a fire tube that uses gas produced, or white gas (possibly), and the water in oil emulsion is flowed over the hot fire tube, then to a separating tank.

Field tanker trucks may come by and off load oil from the separating tank, after careful gauging of the tank, and sometimes the tank is removed from service until another tanker comes by and picks up the BS&W (bullshit and water, or basic sediment and water).

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