Ok, I've done 15 or so of these, so statistically I've got this down.....

First off, I'm not looking for the absolute cheapest, but the fastest and highest quality. This means I'm using electrical energy to heat at every step, and running the air compressor.

My oil titrates anywhere between 0.5 to 0.75, just so you know. I use 5 grams + titration.

Here's my process...

1) Heat the waste oil to 175-180 F 15 minutes. It takes 15 minutes to get to this temp.

2) Most all the crud and water fall to the bottom during step 1; drain it off.

3) Start the NaOH/MeOH mix to let the NaOH dissolve while the oil cools down to 140-145 F

4) When oil is aournd 140-145 F, start mixing in the NaOH/MeOH. The lower temp of the mix will drop the oil temp to around 135 F.

5) I agitate on and off for an hour... When the glycerine starts to settle, I agitate and wait for it to start to settle again. The reaction is happening and as long as it's in solution, there's no need for continous agitation.

6) VERY IMPORTANT. At the end of this hour, I add 5% hot water (120 F). People call this the pre-wash. What you are doing is killing the reaction..This is a good thing, because you are also killing the side reaction of MAKING SOAP! The closer in time you can stop the reaction, the less total soap formation.

This is important in the wash and dry end of it.

7) I let everything settle for 45-60 minutes, then drain off the glycerine/water solution. It settles quickly.

8) There are only two washes needed. The first is 30% hot water (120 F). I start by prop washing for a few minutes to get it mixed thoroughly, then throw my air compressor in for my "bubble wash on steroids". This lasts for 30 minutes. I let it settle for 15 minutes. I change the water and again add 30% volume 120 F water and repeat. You will see the "methyl ester fuel lube" starting to become very translucent. After settling 15 minutes, it already looks almost dry. Drain the water.

9) I get the heat up to 120 F if it isn't already there and crank on the air compressor. Within 10-15 minutes, it's clear. I turn the heat off and let it continue to bubble 10-15 more minutes to remove the last of the water. when it's below 100 F, in the tank it goes.

SOTD

Hello SOTD, Very interesting, thank you for sharing that with us

Are you sure adding the 5% water stops the soap-making side reaction?
This is not a trick question, I am not a chemist. It would seem to me the water would help the soap making reaction but I could be wrong.

SOTD;
I am with Tilly on this. Interesting. What to you do with the water/glyc mix? Is it still viable for making soap later?
Another question; what is the oil feedstock?

This process is exactly what i need to do, I've been collecting wvo for a couple months know and have almost 200 gallons and still have yet to make a successfull batch!

quote:

1) Heat the waste oil to 175-180 F 15 minutes. It takes 15 minutes to get to this temp.

What model heater are you using for this step, and will a plastic drum hold up to these temps?

quote:

5) I agitate on and off for an hour... When the glycerine starts to settle, I agitate and wait for it to start to settle again. The reaction is happening and as long as it's in solution, there's no need for continous agitation.

Is this step done in the processor or the wash tank. If in the processor(agitate is done by cycling the pump on and off?) If in the wash tank(agitate is done with a drill/propellor or a broom handle?!)

quote:

The first is 30% hot water (120 F). I start by prop washing for a few minutes to get it mixed thoroughly

To mix the water into the BD?

quote:

8) There are only two washes needed. The first is 30% hot water (120 F). I start by prop washing for a few minutes to get it mixed thoroughly, then throw my air compressor in for my "bubble wash on steroids". This lasts for 30 minutes.

Do use a regular air chuck or something customly fabricated?

quote:

9) I get the heat up to 120 F if it isn't already there and crank on the air compressor. Within 10-15 minutes, it's clear. I turn the heat off and let it continue to bubble 10-15 more minutes to remove the last of the water. when it's below 100 F, in the tank it goes.

Do you blow air above the BD or into it.

Any pictures of the process would help too!!

How large are your batches? Heating the oil up to 175F in 15 minutes seems pretty fast.

Also... after you add the water for the "pre-wash" , do you circulate / stir aferwards? For how long?

I did three test batches that I let go for 6 hours before I added the 5% water. Every one of those batches took 3-4 washes to remove the soap (not just 2)...The water was a LOT whiter with these washes, and my yeild, while close, was slightly down.

Stopping the reaction sooner definitely reduces soap production.

I give the glycerine mixture to the detail car wash behind me; they use it for degreaser. I don't know if the soap making process would stay the same or not. My advice would be to try a glycerine pre-wash and use that glycerine with your particular recipe to see if your results are the same.

I wouldn't try the initial heating in plastic. HDPE has a max of about 200 F, but it doesn't have any real structural stability at that temp.

The air line is just PET hose (the milky white plastic) from Lowe's. I weigh down the end of it and it rests at the bottom of the reactor. The PET is resistant to methyl esters, unlike PVC.... Sized it accordingly for air volume.

My heaters are water tank heating elements. I have 110V 1500 Watt for the 5 gallon, and (2) 240V 3500 Watt for the 55 gallon pre-heat drum.

I've done this with 5 gallon batches and 21 gallon (80 Liters of oil) batches. You just have to size the heater and air volume for each. Scale-up, if you will.

I'm redesigning my bigger reactor to take advantage of some other things I'm toying with...we'll see how that goes when I get the time....

SOTD

SOTD, so you're using two 240 v elements to achieve 175 degrees F in 15 minutes right?

I have one element in my reactor which is a 4500 watt at 240 but it is wired to 120 volts. It takes me about 2 hours to get the oil up to 125 degrees.

If you are running your elements on 240 volts, have you had any elements fail? Burn out?

Wayne

SOTD,

this is similar to the rate at which commercial biodiesel producers make fuel- heat helps the whole process happen faster, including washing.

I think that water in the pre-wash helps your wash happen faster not because it stops the soapmaking reaction but because it makes the byproduct layer 'more' attractive to soap, so less of it stays in the biodiesel layer and causes you problems in the wash.

Mark

Wayne,
No elements burn out. Just make SURE you always have them immersed....

Girl Mark,
Interesting point on the soap, but if this were the case, wouldn't the soap migrate out regardless of the time that the reaction was stopped?

(The proper term is hydrophilic-attracted to water....hydrophobic-repels water)

I allowed the same amount of time AFTER adding the water before I started washing.

SOTD

Forgive me if I seem kinda dumb about this but wouldn't adding water make more soap and less BioD? And am I getting this right you're doing all of this in your reactor?

SRD ,
Yes it is all done within the reactor . The prewash meathod has been shown to actually increase the yeild in most studies by other memebers . I have used the meathod with really great results in the past , but never did measure the yeild vs normal meathods . For more information try searching for prewash .
Shannon

Read through this thread with interest, it seems to me adding 5% water for the glycwash/prewash after the reaction has run for an hour or so would be too late to stop or affect soap production as this would surely have happened during the early part of the reaction when the NaOH/KOH reacts with any FFA's present to form soap, I agree that if water is present in the oil from the start then this will create more FFA's and thus more soap, I lean towards Mark's theory of the glyc having an affinity with water and water having an affinity with soap meaning less soap ends up in the biodiesel and more in the glyc.

Chug

quote:

Originally posted by Chug:
I lean towards Mark's theory of the glyc having an affinity with water and water having an affinity with soap meaning less soap ends up in the biodiesel and more in the glyc.

Chug

I will again state the question of if this is indeed the case, and the soap was all made at the beginning, and based on water in the oil (which is always dewatered the same way, at the same temperature...and the oil titration is extremely repeatable) how does this explain the differing amounts of soap based on when the reaction was stopped?

With the proposed theory, it would not matter when the reaction would be stopped with the pre-wash, yet it does....

Statistically, I now have over 23 batches to base my results on...

SOTD

SOTD ,
What they are saying , and I think is correct , is that you have the same amount of soap . The water has a better ability to carry soap so more of the soap goes to the glycerine layer than normal with the water . I did tests with doing the same thing , but performing it twice and had almost completely clean fuel after allowing separation . This was not because I made no soap , but be cause the water helped to carry it away . If you want proof of this do a soap test on the fuel and on the by product both ways and add the two values together . They should add up to about the same amount of soap in the total batch , but more will be in the glycerine on the one with the prewash used . Nuetral did alot of testing on this meathod a while back and posted some of the results here somewhere , try searching for them and it will explain exactly what is happening .
Shannon

STOD,
any thought about how well this would work on oil that titrates between 3 and 5 KOH ?

-dkenny

I will never do another batch that does include a Glyc pre wash. I’m sold on its ability to shorten the time it takes to wash your biodiesel.

I have no idea if “the closer in time you can stop the reaction, the less total soap formation”, is correct or not.

Sign of the dollar certainly believes it because of repeatedly making batches that end up with different results.

Let’s say he is right. What is worse under reacted fuel or fuel that has more soap? I can wash my bio to deal with the soap. There’s not much I can do with about under reacted fuel, except test it and do another reaction. Something I have no interest in doing.

My system uses one of the 1” Harbor Freight pumps. I always react for about two hours because I worry the little pump isn’t adequate for a 65-gallon water heater.

Hello Reggie

It depends on whether the biodiesel is under-reacted due to not enough NaOH or not enough methanol.

If the reaction runs out of methanol first the NaOH seems to continue making soap until it is used up.
If it runs out of NaOH first it is likely to have less soap.

If you wish to have high conversion biodiesel always make sure you have plenty of NaOH/KOH and methanol in the reaction.
This should give you high conversion, slightly lower yield and slightly higher soap.
Wash as much soap out as you feel comfortable with.

Reggie, do you recover your excess methanol?

That's my only concern with doing the glycerine prewash thing. I'm afraid I'll end up with water in my methanol. If there is any real risk of this happening, I'd rather wash more and still be able to reclaim my methanol. Methanol is the most expensive ingredient involved in BD making so the more methanol or the purer the methanol the better.

Wayne

shouldn't distillation take the methanol out of the water??

quote:

Originally posted by dodgeram:
If you want proof of this do a soap test on the fuel and on the by product both ways and add the two values together . They should add up to about the same amount of soap in the total batch , but more will be in the glycerine on the one with the prewash used.

How I am reading this is that you think I only did the pre-wash on certain batches (if I am wrong, please correct me).

The pre-wash was done on ALL batches, including the 6 hour delayed ones. The fact that the soap is hydrophilic and goes with the water would not change based on a 6 hour delay. The amount of soap was different with the batches that were allowed to go longer.

This is fact, NOT speculation.

Working for several years at Dow as a research chemical engineer has taught me a little bit about experimental control...I am not saying this to act superior, I'm saying this so you understand this is not a hack job.

The reaction is complete; As Tilly points out, you need to have enough of both chemicals in there for that. The times of reaction based on temperature were verified by the chemist, Neutral.

I stated in the beginning that my goal was to show that high-quality fuel could be made relatively quickly. I do not care about expense or other factors; that was not the goal.

Statistically, I have proven this out; my goal has been met.

As long as the chemistry is correct, this should speed up the batch process no matter what type of oil is used.

SOTD