quote:

So I wouldn't bother as you will end up with water and a toxic chemical you do not want.

Ant: there are no words to explain how much I appreciate you taking the time to give all that information. When you gave me your first warning, all that crossed my mind was the danger of some violent reaction (kinda like chlorine and sodium), so, if you hadn't brought up those facts, and providing I didn't find any data on line that would've been understandable for a complete layman, I would've probably gone head on into a very big problem. You probably saved my life. Thank you.
While I share your philosophy about people doing their own homework (as we say in my country, if you want fish, get ready to get wet.), the fact is that I don't have the knowledge to do chemical calculations, so I have to rely on experimentation. Thanks to you, this time I didn't have to.

Ant,

Here here! When you first mentioned the possible danger about mixing Sodium Hydroxide and Methanol, I too thought of a scary exothermic (very hot) reaction I caused (by accident) in 9th grade science class when I mixed HCL and some other strong base. That Tony and I thought the same thing must be an American educational thang' Well thank you for doing more research because I would have never even have imagined we could be creating such toxic and even worse, kind of silent chemicals. Thank you for keeping us on the straight and narrow.

Doug

quote:

that was a large amount of catalyst that had not been converted to soap during the course of the normal reaction.

That is why it is called the catalyst. It does not get consumed in the transestrification. The bit that turns to soap is not a catalyst but a reagent. It forms soap from the FFA. That is why we titrate, to get the right amount to do that.

The 5g per litre catalyses the transestrification whilst the titration amount makes soap from the FFA. The catalyst should be left over unchanged after the reaction but a little gets turned to soap because of water contamination.

quote:

I have a suspiscion that the acid that is being added is only neutralizing remaining catalyst in the biodiesel phase. I don't think it is neutralizing very much (if any) of the catalyst that would be stuck in the glycerin phase - otherwise, how could you explain 100ml of 34%(ish) concentration HCL being sufficient to cause an indicator change (which appears to be at the end point) in 100 L?

Well it is neutalising more than is in the bio phase. Firstly becuase half the catalyst would not be in the bio phase. It is not soluble in bio only in the methanol in the bio. Only a third of the surplus methanol is in the bio. At best you would have a third of the catalyst in the bio phase. As it is soluble in glycerine as well as the two thirds surplus methanol in the byproduct phase then most of it is going to be in the glycerine.

Secondly it is being pumped around all the time so neutralising the bio only would not really be possible.

Thirdly once you nuetralise some of the caustic the rest is going to redistribute in the pumped mix to maintain the distribution ratio it had to begin with.

The indicator is changing on the whole tank mix. Bio and byproduct together.

The fact it changes before you expect doesn't mean you can jump to assumptions on why it changed.

Only Graham or someone else who actually does this is in a postition to properly speculate on what they think is happening. I can't because I don't do the titrations and cannot see where the result might come from. I can only say that the amounts Graham reports represent about half the catalyst we would expect to be there.

As this seems to be enough it should be easy enough to just neutralise half the catalyst without fear of creating FFA from soap. Maybe even a little more.

If half is enough to stop the reverse reaction then it is an easy solution.


I find it easy to believe because if I only used half catalyst I would not expect to make much of a batch of bio.

quote:

I think the best solution is to simply cool it down, use KOH, and draw as deep of a vacuum as possible to distill the methanol off.

I think that is a great idea let us know how it goes.

quote:

the fact is that I don't have the knowledge to do chemical calculations, so I have to rely on experimentation. Thanks to you, this time I didn't have to.

Truthfully, I mostly just read and repeat what I can understand. Google is quite the reference book.

I make mistakes and you should check what I say. I had to edit the post with the table because I had carelessly reversed the effects of molecular weight on concentration. It is right now.

That is why everyone doing it should try and understand what is happening not just take anyones word as gospel. We are only human. I am far from perfect. The more eyes and minds on the task the better the chances we will get it right between us.

I was pleased to understand the acid estrification reaction more deeply than before.

quote:

That Tony and I thought the same thing must be an American educational thang'

That was my own first thought as well, hence the caution in what order you add what to what. Guess our schooldays were not so different.

Vaccum/rapeseed pump. I am almost done with my push pull reactor. It will do 100 gallon batches. I have a 5 gallon propane tank for the rapeseed chamber. If the highest vacuum is the goal. Do you all think that a big pump in the 100 gal a minute range is an overkill even though it will only pump 4-5 gallons of oil. I already have the pump "Goulds J04853" I am thinking that it would create a much better vacuum than a little pump as long as the venturi matches it. I already bought a 3/4 mazzie venturi so I guess I would need a larger venturi for this pump. Thanks in advance.
Dave

I've been seeing these air powered vacuum pumps at Harbor Freight. Has anyone considered using one of these with an oil pump to get a hard vacuum?

I have a motor mounted pump that is rated for 700psi at 11 gpm, but I'm not sure it'll handle the elevated temp. An automotive oil pump is my other option.

Hey there appreciated Jeddi minds,

Thanks for all this technical knowledge. Great thread!!

Anyone out there using a hot water heater tank for a push pull processor? There is not much on hot water tanks on Grahams website, just that barrels will not hold the vacuum.

Sweet Drewry,

I am just about to build a system as well. What are you using for a tank? Propane, perhaps? I was going to use a Grundfos 26-99 pump for the processor, will that do the job.... any comments? A bigger venturi is needed?

I have had a hard time finding what is needed for parts for a push pull. I was about to build a GL 1 day, but this seems to be quite an upgrade!

Thanks all...!

quote:

That is why everyone doing it should try and understand what is happening not just take anyones word as gospel. We are only human. I am far from perfect.

We all are. But some of us are farther than others...
In any case, I agree with you. It's not about taking anybody's word as the ultimate truth, but about using other people's comments as a guide to get as close to the truth as possible. But the fact remains that your post is the reason why I'm still alive.
But now, another question just occurred to me: If we use sulfuric to neutralize the lye, is there any danger of producing Me2SO4 in the process?

Remove by poster.

I am removing this post about Sulphuric Acid.

Just spoke to Brian at UtahBio and in the BioPro, they add about 100ml of Sulfuric Acid directly to Methanol and let it react for hours and then add the base (K/NaOH). So there is little real world evidence of creating Dimethyl Sulfate. Sorry to sound the alarm, I just panicked when after all my hard work, there was a slight chance I might end up face down in my garage. An explosion I can handle, but slow asphication I can not.

Whooaaa there.

You are both getting a bit carried away now. It's not that dangerous to use properly. All the two stage acid base people have been doing it for ages. I am sure it is perfectly safe to use sulphuric to neutralise a batch with. I have used it myself when seperating and purifying byproduct that had methanol in it.

Get a grip.

Just dont add conc H2SO4 to straight methanol without making sure there is the right molar quantity of water available to stop it from forming the toxic stuff.

Adding it into a batch is fine. Any small amounts formed will just want to methalyte something; FFA preferably.

We make Methyl ester. See the connection?

quote:

If we use sulfuric to neutralize the lye, is there any danger of producing Me2SO4 in the process?

No you have already removed the methanol and even if you missed some you would be making a little Me2SO4 in a lot of bio. It would find something to methalyte harmlessly or more likely never be formed because the catalyst is in the reaction too and would preferentially react with the acid and prevent the Me2SO4 reaction.

quote:

Will it definitely happen in our small quantities that we are using while neutralizing catalyst?

No it won't. Chill.

Thanks. I am chilling now.

Ok, now I'm chilling too. Thank you. (Phewwww... )

http://www.theregister.co.uk/2008/07/28/takeaway_biodiesel_fireball_horror/

Hey Guy's
A warning to us all, be safe.
larry

quote:

Originally posted by larryp:
http://www.theregister.co.uk/2008/07/28/takeaway_biodiesel_fireball_horror/

Hey Guy's
A warning to us all, be safe.
larry

I guess you did not realise that this is at least the third different thread where this subject has been posted.