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Soap test quirk
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Just finished up a batch or fuel and have run it through the dry wash filter. I went to test it and when I mixed the alcohol with the bio it went bright yellow before adding any blue to it. The problem is that no matter how nuch blue I add it won't turn blue or even green.
Does anyone have any idea what might be wrong?
It has to be blue or at least green before I ad the acid, correct? The acid is suposed to turn it yellow.
Thanks in advance.
Jeff
 
Registered: December 18, 2009Reply With QuoteReport This Post
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Do the test with just the alcohol.
Your Isopropyl may be going acidic on you.




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Location: Utah | Registered: October 08, 2004Reply With QuoteReport This Post
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In addition to Graydon's advice, it may also mean that your fuel has very low soap content. Under about 50 ppm soap can produce this result in a soap titration.

Try adding a drop of dish soap to your "failed" titration and see if the color changes. Then, double the amount of biodiesel sample you are using in your titration which will increase the amount of soap in your test and may resolve this issue.

Hope this helps,

Bob


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Location: Moncure, North Carolina | Registered: April 21, 2001Reply With QuoteReport This Post
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Try adding the bromoblue to the alcohol before adding the biodiesel. Then before adding the fuel you can use the acid solution a drop at a time to get a color change to greenish or yellow. When you add the fuel if it does not change back to blue there should not be much soap.

If just for fun you want to see it go back to blue, add some of the lye titration solution that is used for oil titration.
 
Location: Virginia | Registered: March 17, 2007Reply With QuoteReport This Post
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Thanks for all the replies. The alcohol is fresh so I don't think that is the problem. I have tried adding the bromo blue before the bio and after. Either way it goes immediately to yellow before I ad the first drop of acid. For grins,, I put nearly a whole bottle of blue into the alcohol/bio mix and it never went blue or green . Stayed yellow the whole time.
 
Registered: December 18, 2009Reply With QuoteReport This Post
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Another thing to consider is that your BD maybe acidic. As I understand it, the ion exchange resins(amberlite et al) make your fuel more acidic as they remove things like soap. The more they need to remove, the more acidic the fuel. Try a titration for the Acid number - it's just like the titration for FFA in oil.
 
Location: Santa Cruz, Ca | Registered: July 29, 2006Reply With QuoteReport This Post



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Now THAT makes sense. Any idea what would make it that acidic? Would it be damaging to our engines? How would you neutralize it?
I think you may have nailed it.
THANKS!
 
Registered: December 18, 2009Reply With QuoteReport This Post
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fatty acids that are contained in the soap are released back into the biodiesel causing it to be acidic. the higher the soap content of the biodiesel going into the resin tower the more acidic the finnished biodiesel will be.


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Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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I've bought 99% iso from 3 different sources and in each case after adding 15-20 drops bromo to 100ml iso, i have never seen a color change to blue. It is always greenish in color.

I then add 3-4 drops lye solution to get a blue color.

Does this get the test to a good starting point and will this affect the outcome of the test?
 
Registered: July 15, 2010Reply With QuoteReport This Post
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Yes. You will think you have more soap than you do, as you will need more HCL to neutralize the NaOH you added.

My problem with the soap test is determining yellow vs. real light green when the soap content is at acceptable/near acceptable levels.
 
Location: Santa Cruz, Ca | Registered: July 29, 2006Reply With QuoteReport This Post
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Thanks for all the replies. I have a few more questions:
Does this mean that my titration calculations are off and I am adding too much KOH to the process?
I am not using an ion resin tower, I am using what is basically chaff. It is pulverized corn stalks, cobs, and chaff from other grains(cellulose). Looks like sawdust. Could this be acidic in itself?
In this state, would the biodiesel be safe to run or is it too acidic?
 
Registered: December 18, 2009Reply With QuoteReport This Post
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quote:
I've bought 99% iso from 3 different sources and in each case after adding 15-20 drops bromo to 100ml iso, i have never seen a color change to blue. It is always greenish in color.

I then add 3-4 drops lye solution to get a blue color.

Does this get the test to a good starting point and will this affect the outcome of the test?


This could possibly work... and it could be giving you a higher soap reading than you actually have it depends on how you do it.

For info whenever I do a soap test I force it to change colour by either adding the KOH titration solution or the HCl titration solution. That way I know I'm starting right at the point I'm looking for and anything else I have to add is due to the soaps (or catalyst, but that's a different subject and this is after your filtration so lets stick to soaps). There have been times where for various reasons the acetone/water I was using was either slightly acidic or slightly basic so this was really necessary. Others actually use a blank solution instead.

It should also be noted that the bromo blue is an indicator only. I've seen a few comments on here where people are thinking that if one drop didn't turn it blue adding more will. It doesn't work that way. It simply indicates the current pH of your sample.

quote:
Thanks for all the replies. I have a few more questions:
Does this mean that my titration calculations are off and I am adding too much KOH to the process?
I am not using an ion resin tower, I am using what is basically chaff. It is pulverized corn stalks, cobs, and chaff from other grains(cellulose). Looks like sawdust. Could this be acidic in itself?
In this state, would the biodiesel be safe to run or is it too acidic?


Titrations might possibly be off, it really depends on HOW acidic the iso you got is. I've never seen any acidic enough to make a major difference but it depends on how you do the titrations to begin with and what sort of working environment you have (chemicals in the air etc).

Chaff might be adding acid if it's not been prepared, I wouldn't think so though, but it's an easy enough test. Simply run some methanol through a little of it and then do a titration on the methanol before and after. If the after is significantly higher that's your answer. We've had some bad sawdust that wasn't dried properly that was doing this, that is how we figured out what it was.

acidic biodiesel
If you are not using an ion exhchange tower really the only way to get too acidic to use would be if the chaff or something else had contaminated it. Titrations are your friend here as well. Take a titration of the biodiesel as you would an oil sample. Then 'too acidic to use' depends completely on what you are using it for.

edit:
By the way from your descriptions it sounds like you might have just removed all the soaps, and the titration would tell you if any acidity had been added.

This message has been edited. Last edited by: BWilder,
 
Registered: February 25, 2010Reply With QuoteReport This Post



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