Comparing different WVO dewatering methods

Collecting, filtering and dewatering of WVO SVO vegetable oil. For Biodiesel producers too.

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Comparing different WVO dewatering methods

Postby SunWizard » Fri Sep 10, 2010 4:41 pm

Here is a good article comparing dewatering methods for machinery, the same methods we are using apply:
Removing Water Contamination from Oil
With this chart being a quick summary:
Image

A fluid driven CF if you keep the outlet open to air will remove some dissolved water similar to vacuum distillation, and like this device:
OilPure Vacuum Jet Dehydration
Last edited by SunWizard on Wed Sep 22, 2010 8:15 am, edited 1 time in total.
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Postby HoldOnTight » Sun Sep 12, 2010 9:13 pm

That is what I'm talkin about!

This list is not complete. We know some people use salt... I don't know if it removes dissolved.
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Postby HoldOnTight » Mon Sep 13, 2010 6:01 pm

HoldOnTight wrote:That is what I'm talkin about!

This list is not complete. We know some people use salt... I don't know if it removes dissolved.


After more thought, there are two somewhat popular methods of dewatering that really come under one category. I thought it relied on polar attraction at a molecular level, but I was wrong.

Salt and baking soda each are electrostatic contaminants that are easily removed from oil because of the combined molecular weight is much heavier than water. Settling or introducing new oil at the bottom of a tank with either electrostatic contaminant as a method of water separation should be quite effective, especially for those who are using cold upflow technique, but not having great success with removing the most complained about contaminant, water. Based on this knowledge, I think it is clear that electrostatic forces easily separates water using stronger forces than that which attracts water to FFAs in oil - polar forces.

Salt and Baking Soda (another salt) dissociate in the form of ions and formed by the electrostatic forces of attraction of ions. Ionic attractive forces are much stronger than the dipole forces exist between polar molecules. Therefore the term "polar" is not used for ionic substances.

Furthermore, it is well documented that either of these break an emulsion. I can testify from personal experience.

Sun, I think adding ionic force or electrostatic forces are an appropriate category of dewatering that could be added to the list.


What is exciting about this? If salt or baking soda can remove water using electrostatic forces, which are much stronger than polar forces, then why wouldn't it also reduce FFAs??????????!

Thoughts?
Late 99 Ford F-250, Designed and installed at home, 30 kMi on VO. WVO temp at solenoid valve is 185-195+F, winter-summer.
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Postby SunWizard » Mon Sep 13, 2010 8:34 pm

HoldOnTight wrote:Sun, I think adding ionic force or electrostatic forces are an appropriate category of dewatering that could be added to the list.

That goes under the category shown in the chart as coalescing.
What is exciting about this? If salt or baking soda can remove water using electrostatic forces, which are much stronger than polar forces, then why wouldn't it also reduce FFAs??????????!

Thoughts?

Baking soda added + suspended water + FFA makes soap, which is an emulsifier and hygroscopic, which adds to the water holding effects of FFA. But it does lower the FFA, similar to caustic stripping.
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Postby HoldOnTight » Mon Sep 13, 2010 10:25 pm

HoldOnTight wrote:
HoldOnTight wrote:That is what I'm talkin about!

This list is not complete. We know some people use salt... I don't know if it removes dissolved.

REVISED:
Salt is an electrostatic contaminant that are easily removed from oil because of the combined molecular weight is much heavier than water. Settling or introducing new oil at the bottom of a tank with either electrostatic contaminant as a method of water separation should be quite effective, especially for those who are using cold upflow technique, but not having great success with removing the most complained about contaminant, water.
Salt dissociate in the form of ions and formed by the electrostatic forces of attraction of ions. Ionic attractive forces are much stronger than the dipole forces exist between polar molecules. Based on this knowledge, I think it is clear that electrostatic forces easily separates water using stronger forces than that which attracts water to FFAs in oil - polar forces.


Sun, What is the basis for calling this technique, "coalescing." I think it is the focusing on the effect and not the cause. I think electrostatic separation is a more useful because it focuses on the mechanism of the technique. Nontheless, the use of salt is exciting because it should also filter FFAs in addition to water through settling.


I think I've got some higher FFA oil that sat around in the bottom of a barrel with exposure to air. I was going to burn it, but I think I'll save some for testing the above. (crackle test, initial FFA test, salt dewater:& FFA stripping, then final FFA & crackle tests).
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Postby coachgeo » Mon Sep 13, 2010 11:03 pm

how about a combination of some of the methods.

For example adding On gal. of salt water per 50gal, stir it in good. Run thru fav. CF system (dieselcraft, Bud's copy etc.) like one normally would and see if this gets more water out/ lowers FFA?
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Postby John Galt » Mon Sep 13, 2010 11:53 pm

coachgeo wrote:how about a combination of some of the methods.


I use gravity plus absorbent polymer. The VO tests dry to HPT and Vapor test.

If any residual dissolved water is present I'm not concerned about it.
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Postby zoochy » Tue Sep 14, 2010 12:36 pm

John Galt wrote:I use gravity plus absorbent polymer.


How often do you dry your polymer and what volume (or mass) of water is evaporated?
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Postby John Galt » Tue Sep 14, 2010 10:50 pm

zoochy wrote:
John Galt wrote:I use gravity plus absorbent polymer.


How often do you dry your polymer and what volume (or mass) of water is evaporated?
I air dry the polymer when the flow through the column is noticeably reduced. I don't know how much water is evaporated.
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Postby zoochy » Wed Sep 15, 2010 12:38 am

John Galt wrote: air dry the polymer when the flow through the column is noticeably reduced. I don't know how much water is evaporated.


So the polymer swells when it absorbs water? (hence the reduced flow)

It would be interesting to weigh the polymer before and after drying it... I think you're onto something.
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Postby John Galt » Wed Sep 15, 2010 12:12 pm

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Postby David » Fri Sep 17, 2010 10:11 pm

The chart is interesting.
I have always been of the opinion that gravity cannot remove dissolved water because in being dissolved it is the same weight as all the other oil so there is no reason it would sink in a reasonable time frame at least.
This is borne out by my experience of settling for over a year where I found the sample still held small amounts of water.

I use a combination of methods being settling, evaporation and heat.

I settle the oil in IBC's for however long I can, usually 6-9 months.
When the oil comes out it is very clear and clean but still always has some dissolved water.
I put it in my " Processor" which is a 200 L drum with a pump, nozzle to squirt the oil back into itself and a water type filter.

In winter, I heat the oil with my Veg oil burner which helps drive off the moisture and speed up the process. In summer it doesn't seem to be needed although i may shortly rig up a good length of black irrigation pipe for a solar heater.

The oil is pumped back into itself through the 1/4" irrigation nozzle which causes it to splash and aerate and i have a small fan on the top of the drum sucking the moist air out. A while back I " Improved" the processor and saw somewhat erratic performance over the old one, particularly in humid conditions. I recently found if I turned the fan around so it was drawing air from the drum instead of blowing it in, the drying times fell dramatically.

I cannot think or explain what the reason for the substantial difference is, I have just proved that there is one!

I can now dry 200L of pre-settled oil in about 20min although I run it 30 to make sure the oil has had time to do a few passes of the 1 or 5um filter which it is pumped out through anyway. Even after a couple of thousand L of oil, the main thing I see in the filter is bugs, dog hair and a few chunky crumbs.

My oil will pass a HPT no matter how hot I make it with no bubbles at all.
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Postby HoldOnTight » Sat Sep 18, 2010 4:51 am

David wrote:The chart is interesting.
I have always been of the opinion that gravity cannot remove dissolved water because in being dissolved it is the same weight as all the other oil so there is no reason it would sink in a reasonable time frame at least.
This is borne out by my experience of settling for over a year where I found the sample still held small amounts of water.

I use a combination of methods being settling, evaporation and heat.

I settle the oil in IBC's for however long I can, usually 6-9 months.
When the oil comes out it is very clear and clean but still always has some dissolved water.
I put it in my " Processor" which is a 200 L drum with a pump, nozzle to squirt the oil back into itself and a water type filter.

In winter, I heat the oil with my Veg oil burner which helps drive off the moisture and speed up the process. In summer it doesn't seem to be needed although i may shortly rig up a good length of black irrigation pipe for a solar heater.

The oil is pumped back into itself through the 1/4" irrigation nozzle which causes it to splash and aerate and i have a small fan on the top of the drum sucking the moist air out. A while back I " Improved" the processor and saw somewhat erratic performance over the old one, particularly in humid conditions. I recently found if I turned the fan around so it was drawing air from the drum instead of blowing it in, the drying times fell dramatically.

I cannot think or explain what the reason for the substantial difference is, I have just proved that there is one!

I can now dry 200L of pre-settled oil in about 20min although I run it 30 to make sure the oil has had time to do a few passes of the 1 or 5um filter which it is pumped out through anyway. Even after a couple of thousand L of oil, the main thing I see in the filter is bugs, dog hair and a few chunky crumbs.

My oil will pass a HPT no matter how hot I make it with no bubbles at all.


David, 20 min. is fast. Can you post a picture? What is the relative humidity when you dry 200L of oil in 20 min.?
Late 99 Ford F-250, Designed and installed at home, 30 kMi on VO. WVO temp at solenoid valve is 185-195+F, winter-summer.
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Postby HoldOnTight » Sat Sep 18, 2010 5:12 am

[quote="HoldOnTight"
REVISED:
Salt is an electrostatic contaminant that are easily removed from oil because of the combined molecular weight is much heavier than oil. Settling or introducing new oil at the bottom of a tank with either electrostatic contaminant as a method of water separation should be quite effective, especially for those who are using cold upflow technique, but not having great success with removing the most complained about contaminant, water.

Salt dissociate in the form of ions and formed by the electrostatic forces of attraction of ions. Ionic attractive forces are much stronger than the dipole forces exist between polar molecules. Based on this knowledge, I think it is clear that electrostatic forces easily separates water using stronger forces than that which attracts water to FFAs in oil - polar forces.
[/quote]


This technique is definitely not "coalescing." If you understand the mechanism, electrostatic forces, it is quite different from coalescing. You can't even consider it coalescing because based on the above mechanism, it will remove ALL 3 forms of water! Coalescing does not.

Nontheless, the use of salt is exciting because it should also filter FFAs in addition to water through settling, because of the electrostatic mechanism!

The chart you provided isn't exactly correct either. The techniques used to generate the chart is based on less than perfect application of the techniques involved, but this is one of the most comprehensive drying technique effectiveness charts in the public domain and it is representative of the common techniques and approaches used and their results.

What I like about Sun's meter is it gives a more accurate measure "on the fly" so I'm going to have to make one when I get a little more time (winter).

Sun, can you post some pictures of your sensor & meter so we can see how you implemented this? e.g. is the sensor internal to a tube or dangling by the wires or...?
Thanks
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Postby David » Mon Oct 04, 2010 9:41 am

HoldOnTight wrote:
David, 20 min. is fast. Can you post a picture? What is the relative humidity when you dry 200L of oil in 20 min.?


I can do a pic but it will be pretty boring and ugly. the processor is tucked away in a very unsightly corner of a lean to shed. It might be better to do a vid and then I can give a description as well.
Just picked up a new SLR with full HD video and a shooter/veg nut mate who lives close by just picked up a killer sharp lens so I'll go steal that off him for a bit and see what I can knock up.

I was having problems with humidity when I had the fan blowing into the oil and when I wasn't warming it up in winter. It was pretty cool here yesterday and raining and I still managed to dry 200L of oil in under 3 hours without heating it and it was raining the whole time.
It would have been faster than 3 hours, i don't know how long for sure, i set the thing going and that's how long it was before I got back to it and somewhat to my surprise found the oil was well and truly dry already.

It seems I have overcome the humidity problem and I think the main factor was sucking the moisture off the oil rather than pushing it in as I was with the fan blowing into the oil. Thinking about it, What I am doing now is more along the lines of evacuating the moisture from the top of the oil rather than pushing air into it.

It's working well in any case.
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Until then, it's just more endless gloom and doom Veg folk law.
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