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To drain after acid or not to drain?
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Still new here... 2nd AE batch...

1st batch i drained 2-4 liters after the acid stage and settling and it worked beautifully.. titration dropped big time.

This time, I drained an entire 35LB cubie and it was still titrating at 20ml (starting number)... so I turned on the pump and remixed and then tried again before it settled and it titrated at 5ml...

So i'm not sure what's going on here... Oil was dried, followed the same process as before for the acid stage... but the results were very different... any thoughts?

So where do you determine the cutoff point for draining, and how much do you drain? how do you know how much to drain off?
 
Registered: February 06, 2008Reply With QuoteReport This Post
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ski
-cautic in the reactor from the previous base stage neutralized some or all of the acid. it takes very little caustic to screw things up! Tom


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Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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quote:
Originally posted by ski2liv:
Still new here... 2nd AE batch...

1st batch i drained 2-4 liters after the acid stage and settling and it worked beautifully.. titration dropped big time.

This time, I drained an entire 35LB cubie and it was still titrating at 20ml (starting number)... so I turned on the pump and remixed and then tried again before it settled and it titrated at 5ml...

So i'm not sure what's going on here... Oil was dried, followed the same process as before for the acid stage... but the results were very different... any thoughts?

So where do you determine the cutoff point for draining, and how much do you drain? how do you know how much to drain off?


Above a starting titration of ~20ml KOH, draining is a must to ensure a successful base stage. Below a starting T of ~14ml KOH draining is not a requirement, it may be beneficial but not completely necessary. Somewhere between the two, it's optional. The reason for draining is to remove the water that is created from the esterification. In the process of draining, some methanol will be lost since the water and methanol are in the same layer. You will also be draining some sulfuric which is in the same layer. It's the removal of some of the sulfuric that reduces the titration after draining.
The amount to drain is a factor of how much water you want to remove before proceeding with the base stage. At a starting titration of 20ml KOH that dropped to 4ml. I personally would drain somewhere around 6ml per liter that's in the processor.

I think you posted your recipe in the long acid thread, I'll see if I can find the details in there tomorrow if time permits. If you want to post your recipe details in this thread to save some time though I won't complain. Smile

You should always titrate the mixture as it is completely mixed not after it has settled.
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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OK here's the process i used... closed propane reactor.

FYI I titrate with NAOH and use KOH for conversion because i bought a titration kit and it came with NAOH so I convert.

So oil T @ 20Ml NAOH after drying
Heat to 131 and add 2ml/L of Sulfuric and 12 L methanol
mix and let cool 12 hours
reheat and remix and let settle again
drain bottom (first time it was 1 liter.. 2nd time it was whole cubie) (QUESTION ABOUT THIS LATER)
remix and titrated at 5mL NAOH
heat to 131 and Added KOH and 12 more L methanol (QUESTION ABOUT THIS LATER)
settled glycerine and moved on with process

Question 1- with oil T @ 20 NAOH - how much should I drain off the bottom before remixing and moving on with base stage?

Question 2- Can someone check my math... T of 5 NAOH

(5 x 1.5583) + 7.79 g = 15.5815 g/L

I have 90% KOH, so I use 1.5583 to convert from NAOH to my KOH and use 7.79g as my base number for KOH.

First batch took FOREVER to wash... second batch seemed to be more in line with a 3 stage wash and bubble method..

thanks!
 
Registered: February 06, 2008Reply With QuoteReport This Post
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#1
if the draining works like its supposed...I recently had one that off the wall...you should be able to drain about 1/2 of the methanol volume..if you can watch for a can in what draining out, then stop.

#2
where did you get the 1.5583? the factor to convert koh to naoh is 1.4..
so 5(titration)*1.4 + 7.79(KOH base) = 7 + 7.79..

I think you should have run a 2nd acid stage the ending titration is still high.
you might want to make up some KOH solution for titration..its easy 1g per liter of water.

-dkenny


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Location: RTP, North Carolina | Registered: December 15, 2004Reply With QuoteReport This Post
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Originally posted by dkenny:

#2
where did you get the 1.5583? the factor to convert koh to naoh is 1.4..


based on what i read... 1.4 is the number for 100% KOH but I have 90% KOH purity, which, I THINK is supposed to be 1.5583 instead of 1.4???

And I will make some KOH solution once I run out of the NAOH... just used the NAOH because it came with the titration kit I bought. I'm not afraid of math- so I'll convert until i need to make a new batch.
 
Registered: February 06, 2008Reply With QuoteReport This Post



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Ski,
Thanks for reposting your process,

The question of how much to drain depends largely on how much water is present in the oil at the start of the acid stage and how much water was created from esterification.
We all know that water is bad for making bio. My general rule is below 1% H2O going into the base stage to have a successful transesterification. .5% is much better, even lower, even better. This is all geared toward reducing soap formation in the base stage, improving the yield of bio.
Assuming you have 0% H2O going into AE and you see a reduction of FFA from a T of 20ml NaOH to 5ml NaOH, you will have created somewhere around 5ml H2O per liter of oil.

The H2O is also going to be combined with the excess methanol and Sulfuric. Some of this "layer" is going to be below the oil and some will be interspersed with the oil. If your going to go directly into base processing after AE, then it would be advantageous to drain an amount of water that gets you below 1% H2O (preferably less) before adding your methanol caustic mixture.
Draining at least 5ml of the lower phase (water/methanol/acid/others) per liter of oil in the processor should get your water% below 1%.
The amount to drain is not as easy to figure out as it appears since there are other variables that impact whether or not there is even a lower phase that can be drained, methanol input qty has a large effect on that.

Just keep asking, when you get stumped on something. There are lots of people here willing to help if we can.

Q2- The math looks good, It looks like your adjusting for the purity in your math which is correct. Making your own titration solution of 1g/L distilled water is a good move though as dkenny pointed out.

HTH
 
Location: central virginia | Registered: March 13, 2008Reply With QuoteReport This Post
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Cool... thanks for the help... i wanted to make sure i was going down the right path.

Did my first soap test today (with the bromo blue) and it passed with flying colors.. it's dry and sparkly and into the tank it went! First batch in and the truck runs great. Second batch passed too and is drying and the 3rd is de-mething... 4th already in the drying/reacting chamber.. the process is rolling now... And i'm officially expecting my first "screw up batch" any day now!!

Still need to fiddle with some things to get the process streamlined. And then will need to build my still to recover the meth... but all in all I think I'm officially up and running!!

Thanks for all the help!!
 
Registered: February 06, 2008Reply With QuoteReport This Post
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