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Mixing and static batches
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I don't want to muddy up the really long acid thread or hijack anyone elses thread so I figured I would start this one.

I know a couple of guys are having good success with only initial mixing of the Acid/methanol/oil.
I'm wondering why this is since it is counter to most chemical reactions.

I have a couple of theories behind why I think this may not be hindering their reaction results.
The main one being if the SG of the methanol/acid/water layer is low enough it doesn't stratify, effectively keeping the ingredients in contact with one another. Though the reaction may still take longer due to the reduced amount of energy going into the reaction.

I'm interested in hearing about the individual process(es?) from those that are experiencing these results.
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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DoubleD
-as you know I am from the mix and sit camp Big Grin. I've done it both ways, but always get lower T if the mix just sits. I think the continuious mix causes more fa's to break from the tryglicerid,to become ffa's, so you end up with higher ending T. I could not figure any other reason for this. As long as the heat is on, I have never seen any phase seperation after the chemicals are mixed in. Also, it could have something to do with the black junk that settles out while sitting, possably by keeping this crud in suspension slows things down?
-high heat ae requires constant mixing to keep the condesed methanol mixed in, other wise it will sit on top, and not be there for the reaction. Tom


" I don't know what I don't know until I know"
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Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Could your good results have more to do with your mix containing less H2SO4 than we have been accustomed to using. As you've stated it's not stratified.
I think the black stuff may just be the "burnt" VO. H2SO4 has a way of ripping the hydrogen and Oxygen off of organic compounds leaving behind the black carbon. Just like when you spill a little H2SO4 on a piece of wood, or wipe up a little spill with a towel and it turns that spot on the towel black. I've seen the same black at the bottom AE batches. It appears to have a thicker consistency than the VO or maybe it's just more visible.

The FFA creation requires H20 to be present to form through hydrolysis. Assuming there is no water in the batch to start with FFA can't be created. A Fatty acid contains an OH functional group that is not present while it's bonded to a glyceride. The addition of H2O is necessary to donate the OH to the Fatty Acid creating a Free Fatty Acid.
For every molecule of FFA that is esterified one molecule of water is created so that same one molecule of water could create one molecule of FFA.
Theoretically you could only create the same amount of FFA as you had to sart with which would leave you with no water in the mix.
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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My best guess would be the water created during the reaction if allowed to sit settles with the methonal layer.

When continued mixing is employed during AE we have seen consistent results that it very negatively impacts ending T. This maybe due to the water now more easily interfering with the reaction since it is in 'solution'.

We know that adding bentonite (water absorbing agent) allows us to do constant mixing with little to no effect on ending T, so this seems to be at least part of it. Any thoughts?
 
Location: Buckeye | Registered: July 07, 2009Reply With QuoteReport This Post
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DoubleD
-Yes I do think the fact I use less acid than most others where using resulted in the lower T values
-Your great explenation on how the ffa is formed, kind of rules out my theory of more ffa's being created, so maybe it is the crud, which would include water from the process, being held in suspension that causes this anomally or could it be that the acid mixure needs to be resident with the wvo, and not mixed around for the reaction to complete. Tom


" I don't know what I don't know until I know"
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Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Buckeye,
The miscibility testing that I did indicates that the methanol, water, and sulfuric are completely miscible and don't seperate into layers from one another.
We can have this layer migrate to the bottom, top, or evenly dispersed throughout based on the SG of the mixture.

This brings me to the question of titration practice. If you draw out a sample to titrate after the mix has settled and stratified, the titration won't be an accurate representation of the combined batch. Sampling from the center of the mini batch will give a false low titration since the layer that contains the Sulfuric will likely not be in the center but concentrated closer to the top or bottom. Suppose you take your sample this way and get a titration of 4ml. You then mix and take another sample and the titration is 8ml, this doesn't necessarily mean that mixing raised the titration, it means you titrated a more representative sample.

Tom,
I agree that the lower amount of acid that you use equates to a lower ending titration than we have been accustomed too.
The "no mixing" success though must be a factor of the mixture staying suspended. Since your starting FFA% is relatively low to start with and doesn't require draining before base processing this suspended mix would be optimal for you. What if someone is using higher titrating oil though and is required to drain before base processing. Would it be better to ensure the aqueous phase is located at the bottom of the processor? In this case, wouldn't mixing be required to keep prevent stratification?
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post



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doubleD
-I don't have any experiance with high T wvo, but it would seem to me, that if phase seperation occurs, on high T wvo, then mixing is a must, as in HTAE, followed by a period of settling and then drain. I also agree that the batch must be mixed well prior to final T Tom


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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of course this begs the question..
how much mixing is too much? nay or just enough to change the top to bottom. maybe once in 30 minutes..thoughts?

if you can keep the temp without mixing..this might be the best.
but what about those of use who cannot maintain temps with mixing?

the little blue pump at 10gpm..what about a valve on the output to reduce mixing?

maybe I'll try this on my next batch..all i have to change is the valve position,
other thoughts?

i'm thinking that the water/acid/methanol don't separate so a complex setup to mix only the upper layers will not help. I think double but it best, forgive me if I quote it wrong, but depending on the density of this mix( water/acid/methanol) compared to oil..it float/sink/or mix..the bixing being key..this would allow AE to work without active stirring..

-dkenny


ps I think threads of this nature at great off shoots of the 'main' thread. ok i'm not the greatest word smith, but these types of thread are needed. ok typing skills,,marginal also.. Smile


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Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post
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quote:
Originally posted by dkenny:
of course this begs the question..
how much mixing is too much? nay or just enough to change the top to bottom. maybe once in 30 minutes..thoughts?

I think it would work sufficiently, It's similar to what a Dr. Pepper mini batch would be. I don't know if it would be as fast as intense mixing but is certainly worth testing.

Little blue pump? It's slow enough already. I use one on my drying barrel and it struggles to keep things mixed as it is.

quote:

i'm thinking that the water/acid/methanol don't separate so a complex setup to mix only the upper layers will not help. I think double but it best, forgive me if I quote it wrong, but depending on the density of this mix( water/acid/methanol) compared to oil..it float/sink/or mix..the bixing being key..this would allow AE to work without active stirring..

I feel a homogenous mixture may have good merit for lower titrations that don't require draining, but where draining is required...
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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