If you’ve been making Biodiesel for any given amount of time, chances are you’ve seen an emulsion and maybe even had to deal with one yourself. They’re a royal pain in the butt, aren’t fun to see, and generally just cause more pain & heartache than they’re worth. Because it’s such a common part of making Biodiesel, we’ve decided it was high time to talk about emulsions, what they are, how to prevent them, and then how to fix them if you do get one. So, here comes Emulsions 101.
What Is An Emulsion?
In short, an emulsion is a combination of water, Biodiesel, soap, sometimes glycerin and unreacted oil. They can be very liquid, bordering on what skim milk looks like to flat out cottage cheese looking. No matter what they look like, they just aren’t fun to have around.
For a much more in-depth explanation of what an emulsion is, check out this great article: Jack Jones Article On Emulsions Essentially, the soap binds the water and the oil together and “emulsifies” them into a big, white, goopy mess.
Here’s what an emulsion looks like:
It reminds me of a white milk-shake. All nice, white, & frothy….
Emulsions can look like light skim milk, a dark vanilla ice cream shake, or even thick & chunky like cottage cheese or cheese curds. But, no matter how you slice it, it’s something you really don’t want to see.
How To Prevent Emulsions
The greatest way to deal with emulsions is to not get one in the first place. Here’s 5 tips for keeping them far far away from your Biodiesel.
1) CHECK FOR WATER IN OIL AND ELIMINATE IT!
ALWAYS check your oil for water content and if it’s wet (say higher than 5000 ppm or 0.5%) then remove the water.
Water + Oil + Catalyst = Soap (and lots of it!)
Soap + Oil + Water (a.k.a. water washing) = Emulsions
So, how do you remove that pesky water? Well, heat and time and, if possible, some mixing. The more of these used, the better.
Check Out This Article on how to dry Biodiesel as it gives some great tips.
The same concept in the article also works for drying waste oil before it’s processed. In our Feb. 2009 Newsletter, we talked about tips & tricks for detecting water and tips on how to eliminated it as well. If you didn’t have a chance to read through it, we highly recommend it.
Quick Water Removal Method
Here’s a really basic method that I use in my personal BioPro 190 processorthat works really well. You can modify this to your own equipment as well.
A- Turn on the manual heat for 18-24 hours with the lid off
B- Return to unit & drain off any water plus 1-2 extra gallons
of “interface” oil
C- Then turn on the heat & stirrer for 6 hours with the lid off
D- After 6 hours, test for water content. If below 0.15%, process.
Now, for those without a BioPro, here’s basically what we’re doing and if you follow these principles, you can acheive similar results.
A- Apply heat via a heating element to bring oil up to about 130-140 F
(NOTE: If you have poly tanks, learn your upper heat limits and don’t exceed them. It’s usually about 120 deg. F)
B- Have a fan running over the top of the opening (this creates a “low pressure air system” above the tank and the moisture naturally will move from the oil to the low pressure and get blown away by the fan)
C- Circulate the oil. You can use a pump, an impeller, air bubbles, whatever you want. The goal is to just circulate the oil.
2) ENSURE THE BIODIESEL IS FULLY REACTED
If you have a lot of unreacted oil mixed in with the Biodiesel, when you attempt to wash it the oil will get in the way & also cause an emulsion. To test for full reactions, just use the simple 3/27 Methanol Conversion Test
Basically, you add 3 mL Biodiesel to 27 mL of Methanol at 68 to 72 Deg F. Shake it, let it sit for about 5-10 minutes and check for any oil drop out. We carry a Biodiesel Conversion Test Kit that makes doing the test extremely easy (and it’s cheap too!) We even have a video available that shows how to do the test.
If your Biodiesel doesn’t pass this test, just re-react it. Doing a re-reaction is pretty simple too and can yield you much higher quality Biodiesel anyway.
Here’s the method I use:
A- Times your methanol & catalyst originally used by 30% (0.30)
B- Add this new amount of catalyst & methanol together & dissolve
C- Heat your Biodiesel back up & add this mixture to it & reprocess
D- Run the pump, impeller, processor, etc. for 2 hours, then allow the glycerin to separate again
E- Remove glycerin & retest for full reaction
F- Repeat again if necessary
3) DRAIN ALL OF THE GLYCERIN BEFORE WASHING
When Biodiesel is made, a lot of that soap ends up down in the glycerin layer. When you drain the glycerin from your processor, be sure that you’re getting all of it. If you don’t, water can mix with the glycerin and also kick off an emulsion as well.
To be safe, I ALWAYS drain my glycerin 3 times. Here’s how I do it.
A- Drain glycerin until you see Biodiesel then close the valve
B- Let the processor sit for AT LEAST 5-10 minutes
C- Come back & drain again (you’ll be AMAZED at how much glycerin will sometimes come out)
D- Let it sit again for another 5 minutes
E- Drain again, but this time drain AT LEAST a 1/2 gallon of Biodiesel out as well
By doing this, you ensure that you get all the glycerin out (unless you’re draining from an Appleseed/water heater style processor…but that’s a whole other issue that we’ll cover in another newsletter later).
4) ADD VINEGAR TO THE REACTED BIODIESEL
Another trick to keep emulsions at bay is to add about a gallon of vinegar to your reacted Biodiesel before washing it. This mild acid works to keep soap from forming between the oil and water. In some cases it can even help break emulsions too.
5) HEAT THE BIODIESEL AND USE HOT WATER TO WASH WITH
Before washing your batch of Biodiesel, be sure to heat it back up to at least 80 to 90 deg. F. Cold Biodiesel and water don’t really do too well together and the chances of getting an emulsion go up quite a bit the cooler the Biodiesel is.
Also, if it’s at all possible, wash your Biodiesel with hot water. The hotter the better. It’s the same concept as washing a greasy pan after you’ve cooked a couple hamburgers. The grease will wash out of the pan much faster if you use hot water.
How To Fix An Emulsion
Breaking emulsions is pretty simple. You just have to understand what got you there in the first place and then back out of it.
If you remember from above, an emulsion is just a mixture of oil and water. They aren’t chemically bound together, they’re just really well mixed. To break this mixture, you can use the following methods
1) ADD SALT WATER
This method is BY FAR my favorite method because it works so well and so fast.
Here’s how to do it.
A- In a 5 gallon bucket, add about 1-2″ of rock salt (ie. water softner salt)
–NOTE: ANY salt will do, but Sodium Chloride seems to work the best
B- Fill the bucket the rest of the way up with hot water
C- Dissolve the rock salt into the water
D- If possible, heat the emulsified Biodiesel back up to about 90-100 deg. F
E- Slowly add the salt-water mix to the emulsified Biodiesel
F- Using a stick or a stirrer (DO NOT USE A CIRCULATION PUMP) gently mix the salt water into the Biodiesel for about 30-45 seconds. (If using a BioPro, hit the manual stir for about 15-20 seconds)
G- Allow the mixture to sit for at least 3 hours but overnight is best
H- Return and drain off water
I- If there’s still an emulsion, repeat this process.
Here’s a link to some pictures of how well it works:
And, here’s a link that explains why it works so well:
2) ADD VINEGAR
This method has been tried by others and found to be effective at times.
A- Heat the Biodiesel back up to about 90-100 deg. F
B- For every 50 gallons of emulsified Biodiesel, add 1 Gallon of Vinegar
C- Gently mix in the Vinegar
D- Let the mixture set for several hours
I’ve seen limited success with this method, but others have indicated that it works.
3) ADD GLYCERIN FROM A PREVIOUS BATCH
This method was discovered by Jack Jones, the person that taught me to make Biodiesel years ago. It involves adding glycerin from a previous batch of Biodiesel to the emulsified mess.
A- Heat up the emulsified Biodiesel to about 90-100 deg. F
B- Add half of the glycerin from your previous batch to the mix & stir
C- Let sit for at least 2-3 hours
D- If it hasn’t broken yet, add the rest of the glycerin and stir again
E- Let sit for another 2-3 hours
If this method doesn’t break the emulsion, consider using the Salt Method as it seems to be the most effective.
And there you have it!
1- What Emulsions Are
2- Why They Happen
3- How To Break Them
Here’s wishing you an emulsion free brewing session!