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Breaking Emulsions With Salt Water
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posted
I had a discovery a couple months back that I kept forgetting to post.

It's about breaking emulsions with salty water.
It works absolutely amazing!

You can break a 100 gallons of emulsified Biodiesel very quickly by adding (2) 5 Gallon buckets of salt water to it.

Here's how:
1) Add 1-2" of rock salt to the bottom of a 5 gallon bucket
2) Add hot water to the bucket (as hot as you can get it)
3) Let it all dissolve.
4) Add it to the emulsion
5) Stir a little
6) Sit back & watch the magic occur

If it doesn't break, just add more salt water.

This message has been edited. Last edited by: Graydon Blair,




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post
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And now some explanations on why salt works.

This was sent to me by a Matt Rogers.
It's his explanation on how they break emulsions in large industrial plants....

He's given me permission to post it.
=================
First of all, I'll admit, I don't make biodiesel. I'm a Chemical
Engineer in an esterification plant. We make materials VERY similar to
Biodiesel and we wash them on a regular basis. We often deal with
emulsions and the problems/headaches they cause. Here are some things
that may be helpful for some of your readers. Please feel free to
repost this entire article.

Temperature is EXTREMELY important. 90 C (195 F) is the ideal temp for
washing any oil/water batch. It greatly reduces the chances of making
an emulsion. I could go into depth on why, but it deals with solution
thermodynamics and you probably don't wanna know. Just know that it
helps a LOT! Often, just heating a batch up to 90C will break the
emulsion.

For everything below, remember, every batch is different. What works
for one, may not work as well for the next. WE ALWAYS test out
different solutions to an emulsion problem in lab prior to doing it in
the plant. It helps to formulate a plan if you know what works best
before you start adding random stuff to the batch. It's very easy to
do if you have some decent scales. You can get great gram scales pretty
cheap nowadays. Use simple ratios to calculate how much to use on the
large scale vs the bench scale and do a few quick trials with samples
before doing it on the big scale.

Sometimes, you can actually break an emulsion by just adding a little
more water. It's weird, but too little water in a wash can be very bad
at times. We often use more water than we expect we will need while
doing washes to help avoid problems.

In a pinch, salt (sodium chloride) is great for washing emulsions. Now,
I can't PROMISE that absolutely no salt would remain in the product, but
we use it ALL THE TIME here. It's actually our first choice when we
have a "problem" with a wash. Remember, salt is insoluble in oil but
highly soluble in water. Salt actually has an EXTREME affinity to
water and hates oil, so if you follow your initial wash with what we
call a "tap water wash", you will get all the salt out with no problem
and since the soap left with the first wash, you shouldn't have near the
problem with forming an emulsion in the second wash. Also, salt is very
cheap. :-)

If salt doesn't work, there are a few other very nice options. We
usually try a little isopropanol (isopropyl alcohol, IPA). This is VERY
easy to get from your local drugstore/Wal-mart/grocery store in a 70% or
sometimes 80% solutions. It's cheap! Also, it's not a big deal to have
a little water in there since you are doing a wash anyhow. I know in
industry, we use IPA cause it seems to work better than any other
alcohol. I'll be honest, I haven't tried methanol yet. I'll give it a
shot. But, feel free to try the IPA, I think you'll find it works
better. Also, IPA helps to break up any foam that may form on the
surface while you are washing the batch.

We have found that if you get too aggressive in trying to neutralize
your leftover acid (you use too much base) then that's when you get into
the most trouble with forming emulsions. If you suspect you have a lot
of acid left in the batch, then it's best to split the neutralization
into two parts and do two neutralization washes where you use half as
much base and then a third tap water wash. (I don't mean that you are
splitting the batch in half, just that you wash out half the acid in the
first wash and the rest in the second wash). However, if you already
have a mess, then you can always back-add a little acid (mineral acid)
to the mix to "reverse" your adding too much base. We have used
phosphoric acid simply because it is easily available in our plant,
however I would bet muriatic acid (concentrated hydrochloric acid) would
work just as well and can be purchased at any hardware store very cheap
as a masonry cleaner. BE VERY CAREFUL WITH IT, IT IS VERY CORROSIVE TO
BOTH FLESH AND EQUIPMENT. Oh and a little goes a long way.

Glycerin to break emulsions?
I admit, I have never used glycerin to break an emulsion. It, like
salt, has a high affinity for water and doesn't like the oil layer much
at all. The one major problem I see with glycerin is that it increases
the viscosity of the water if you use very much. That's bad because the
higher the viscosity, the longer it takes an emulsion to split. I guess
a small amount wouldn't change the viscosity much, and if it works, then
that's proof enough.

Finally, after a batch is washed and the water is been split off, we
always heat it up to 120-130 C (248-266 F) and bubble nitrogen through
it to aid in drying it. Of course, most people don't have nitrogen
available to use, so try compressed air. Just know that the dryer you
get the air, the faster it will dry the batch.

You can put together a very simple compressed air dryer by feeding your
air in just above the bottom of a vertical PVC pipe through a "T" (say 8
feet high), have the pipe 90 over and then back down to feed into
another one through a "T". Leave a few inches on each vertical pipe
below the feed so that you will have a place for your water to collect.
Put a small drain cock on the bottom of each vertical pipe and leave
them barely open so the water can drain out. Make sure you use pipe
that is rated to handle the pressure your compressor can supply. You
can add more stages if you wish, it all depends on how much space and
time you have. Putting the dryer in a cool, place is ideal. This is
very crude, but it works pretty well. Basically, if you allow the air
to cool while compressed, much of the water will naturally condense out
of it on the inside walls and run down the vertical pipes. This would
leave you with relatively dry compressed air for very little cost.
Should cut drying time quit a bit.

-Matt Rogers




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post
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And here's Part II from him.
==========================
I can give a little on the "why" here below. To get into the chemistry gets REALLY nasty. But the physical side of it is pretty simple.
There are a LOT of things that affect emulsions, here are a few of the basics.

1. The difference of the densities. If the two phases have the same density, they will NEVER split! There simply isn't a reason to split. There is no driving force. Lucky for us, most oils are less dense than water. The greater the difference between the two densities, the "easier" two fluids will separate into two distinct layers. (The difference in densities can be seen as a "driving force" to splitting the materials). So, how do we apply that? Well, we know that oils expand quite a bit upon heating thereby lowering their density. But water stays relatively the same in volume and so we can regard it's change in density upon heating as negligible. Result: Heating the emulsion to just below boiling point of water will increase the driving force and greatly help in splitting it out because the oil's density decreases while water's stays the same. If you hit the boiling point of water, then you'll be agitating the batch-not good for splitting it out. Adding salt increases water's density (along with monkeying with the soap's ability to dissolve the two phases into each other).

2. Viscosity...
As you heat oils, they become less dense, we established that above. However, it ALSO decreases the oil's viscosity. The thicker an oil is, the longer it takes to split out. So, once again, heat is GOOD! Heat doesn't affect water's viscosity very much at all, so once again, negligible.


Now, those are both PHYSICAL discussions on emulsions. Next you get into the chemistry. It gets complicated really quick. We can simply say that salt, IPA, (along with a whole host of other things) will "monkey" with the soap's ability to work and hopefully allow the batch to split.

Oh, one other thought, the air sparge could cause the color to go a little dark which would indicate some partial oxidation of the batch. I suggest trying that on a small scale before trying it on a big batch. 120 should be low temp enough so that it minimizes the effect of the air, but still try it on a small scale first. Always better to be safe than sorry.
=============================================

We've tried salt a few times and it works AMAZINGLY well!

Cheap, simple, & works great!
-Graydon




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post
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Graydon,

Thanks for your post.

Clearly salt will break emulsions.

Question are: What effect does this have on fuel quality, if any?

Does it change the results of any of the ASTM tests? If it did, which would it effect? How many washes does it take to get enough of it out?


Andrew

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Location: Northern California | Registered: February 27, 2006Reply With QuoteReport This Post
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If you thoroughly rewash the Biodiesel, all of the salty water should wash out (for many of the reasons discussed above).

If you get all of the salt back out, it shouldn't affect the ASTM results at all.

A while ago I spoke to a producer that used salt-towers to dry their Biodiesel on a regular basis and still passed the full ASTM on a regular basis.

This is because salt doesn't like Biodiesel. It'll fall right out of it & not dissolve into it (this is why it's important to dissolve the salt into water before putting it into an emulsion)

Not sure how many washes it takes to get it out, but my guess is that if the commercial guys who are passing the full ASTM are using it to dry already washed Bio & still passing, it probably won't dissolve into the Bio; thereby not causing any detrimental effects.

That said, I've not tested it myself against ASTM though to see if it works or not.

I'd imagine though that it'd wash out just like the glycerin will after you've used it to break emulsions.

-Graydon




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post
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Excellent !
I used salt once and that was after having saturated the wash water and letting it cool down.I figured I'd give it "just one more pass" as I wash several times with one lot of wash water until saturation occurs.
Well, unlike my regular washes which are done hot this one was done cold and to top it off I forgot it so that neat little industrial spray head was just a pumping away until all that was coming out was a steady stream,no spray, it was that thick.
Enter salt.I took table salt straight up, not mixed, and spread a few good handfuls over the lot and then watched as it all started to break in moments, not minutes.Works exceptionally well.
Should I do something that stupid again (never know) I will venture into the salt water solution(!) to rectify it.
The residual salt will wash right out using clean warm water afterwards.
Actually this has just given me an idea; I have been getting probs using city water vs well water that I had before, it taking more washes to get all the soaps out.Wonder if tossing in a salt water mix on the second wash would help ?
Won't be until Spring now though.



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Location: :-) Great White North eh ? | Registered: December 10, 2004Reply With QuoteReport This Post



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Hello Graydon

Yes, Neutral and others have been recommending the use of salt to break emuslions for years.
 
Location: ลึก ประเทศอินเดีย | Registered: March 03, 2001Reply With QuoteReport This Post
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Excellent write up Graydon!
 
Registered: May 16, 2006Reply With QuoteReport This Post
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Spray your "orange juice" BioD with salt water and watch it clear before your eyes.

Also a great WVO dewater method too.
 
Registered: May 16, 2006Reply With QuoteReport This Post
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your right it does work, just like I said back in 2006. but it is good to bring up for all the newbie's like you said.old news is always new to someone.
 
Registered: July 04, 2006Reply With QuoteReport This Post
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Grayden: one thing?? Please tell us that this emullsion was not made in the Bio-Pro
 
Registered: July 04, 2006Reply With QuoteReport This Post
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heh heh heh....
Oh, I've broken many emulsions. In BioPro's and in other equipment.

While BioPro's are great, they aren't miracle workers. You still can't defy physics or chemistry in one.

If you add oil that's too wet or is too high in FFA you're GONNA make a lot of soap, and if you hit it with water and a mixer, it's going to make one heck of a lovely emulsion.

I've not made many emulsions in BioPro's, but, it's still possible...

Several of my customers have though. Most of the times it's because they failed to dewater their oil even when they knew it was wet. Wink

-Graydon




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post



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Great write up Graydon!(Shane from SC here!! LOL!!) Anyway, we discussed lots of soap. Here is a pic of the dried product after 80 ish gallons of wash water and 3 mists,4 bubbles, and setling in between.


Here is the result of the shakem test with the same oil from the bottle.


I went out and added some salt water to the jar and it broke instantly. Now my question. The bio is clear and dry, but according to the shakem test, there is soap in it. Do I salt treat the dried batch in the wash tank? How do I do it? Thanks in advance.
 
Location: SC | Registered: August 16, 2008Reply With QuoteReport This Post
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That looks like an emulsion to me. That being said, how was your conversion? If you are having trouble with the wash, it may not be completely converted!
 
Registered: January 22, 2006Reply With QuoteReport This Post
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Graydon, I never had much success using salt on emulsions. I found that I only got a partial clearing which left a thick layer of emulsion between the water and the biodiesel.

I swear by adding the glycerol from another batch - it clears instantly. I must have done something wrong with the salt.
 
Location: Scotland | Registered: March 19, 2006Reply With QuoteReport This Post
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quote:
Originally posted by dondy:
That looks like an emulsion to me. That being said, how was your conversion? If you are having trouble with the wash, it may not be completely converted!


Hey Dondy. My 27/3 test passed with ease. No settling even after 5 days. Did another one just for kicks out of the washed bio, and it is twin to the first one. Single clear phase- zero settling.
 
Location: SC | Registered: August 16, 2008Reply With QuoteReport This Post
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I've just experimented with a number of different solutions in an attempt to break a heavy oil/water/soap emulsion. A mixture of biodiesel and glycerol seemed to work better than expected. Has anyone else tried.
 
Registered: July 30, 2006Reply With QuoteReport This Post
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woke up this morning to, 75L of emulsions in the processor.. found this link and tried the bucket of salty water.. it cleared in moments, I still have 20L or so to sort out, but will leave a few hours and look again.. fed my other 50L through my home made 5kg bio-mass filter with bio2pure.. xtal clear fuel... Thanks...
 
Location: Stroud | Registered: October 12, 2008Reply With QuoteReport This Post



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Bio_Ken,

Pre-mix the salt with extremely hot water and mix until as much that dissolves can dissolve (about 5 mins), then add to your mixture.

And, yep, Graydon's salt water trick saved my butt once, too!

- JC
 
Location: Western PA | Registered: August 15, 2008Reply With QuoteReport This Post
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Can I use regular table salt or does it have to specifically be rock salt? Is there even a difference?

Thanks, clint


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Location: Vancouver Cananandanada | Registered: June 14, 2008Reply With QuoteReport This Post
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