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soap titration questions
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My query is twofold.

I recently had to replace my fuel pump and injectors and was told that there was "thick gooop" in my tanks. I thought , "Surely he must be wrong! I have seen the fuel and tested it my self!" However, I got the truck back and immediately went to the bio-pump next o my garage (outdoor kept plastic 55 gal drum). On a hunch I pulled the nozzle out of my fuel filler tube andpumped a bit out into a clear jar so I could inspect it, and voila! Orange goop! It is the color of the biodiesel mixed with water, but it has chunks in it.

So I started thinking about the chunks and decided it must be soap. I also think the barrel must leak when it rains, because my wash/ dry tank is open top and I use clear hoses. I see that the fuel I put into storage is clear, and passes the frying pan test for water.

I got a soap titration kit and just tested my most and newest washed batch for the 3/27 (pass) and for soap. But the funny thing is; when I blanked the solutions for the soap test, I added the fuel and it went more acidic. I performed the test three times to check my process, and even double checked the indicator by adding HCL and KOH solutions to watch the indicator go from blue to green and back. This does not make sense to me. Does anyone have an idea why my fuel might be acidic? Also, I washed this last batch at least 10 times and still saw what looked like soapy bubbles on the surface.
 
Location: Knoxville, TN | Registered: December 04, 2010Reply With QuoteReport This Post
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Will you describe your biodiesel manufacturing process? Do you water wash, maybe with distilled water? You can check the pH of your biodiesel several ways. I used one milliliter of distilled water in one milliliter of biodiesel with stirring, then tested the liquid with pH test strips with a range of from 5 to 10. I think pure methyl biodiesel is about pH 7 (neutral).
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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I use a single stage process with KOH. I use tap water (treated surface water from nearby lake)to wash. I also brew beer so i have my tap water checked for mineral content every few years. It is very low in minerals and is about 7.5 pH. I could give a more thorough analysis here if it would help. I use distilled water for all testing.

I have always suspected too much soap production, as it takes me many washes to get clear water, so I have been slowly eeking my base numer down to see where the point of full conversion stops. I also use slightly less methanol. Right now I am at 17 gallons methanol, base 6 + titration for KOH, and 85 gal WVO. The oil is from two sources and usually titrates high (6-8)so I pre-treat with about 3.5 gallons glycerin from the last batch. This gets me down to a titration of about 3-5. I then drain glycerin, heat and process the oil. I mix for about 3 hours. Settle, cool, drain glycerin (save some for next batch). First two washes are sprinkled on then drained. From there on, I pump wash, then drain. Only a few seconds at first, then longer for each subsequent wash. I have only gotten an emulsion problem once with this method. However, I am not convinced it is effective since it takes me 10+ washes to stop getting soap bubbles on top. Even then I see some bubbles, despite the soap titration test showing ( if I can interpret thi correctly) 0 ppm, or more accurately, it shows a pH of my finished fuel at or below 4.6.

I don't use pH strips. I only have been using the indicator chemicals.

Any ideas why my soap test is so low? I usually take it at face value and put it in the truck, but this orange goop batch has me worried.
 
Location: Knoxville, TN | Registered: December 04, 2010Reply With QuoteReport This Post
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Initially I've got a couple of Ideas. Indicator solution can get old and go bad. I think phenolphthalein has a shelf life of about one year. I was testing with old test strips once and getting incorrect readings. Maybe something is wrong with the indicator solution. You could verify your 4.6 pH for your finished biodiesel product with pH test strips from Utah Biodiesel Supply, the strips have a range from 1-14, they cost somewhere between $8 and $14 telephone number (801)820-5753 . I've not made a lot of biodiesel. I think the lowest pH I got was 6.5. Under the right conditions methyl biodiesel can hydrolyse (water adds to the molecule) producing one molecule of methanol and one molecule of free fatty acid. If your biodiesel hydrolysed you might have free fatty acids pulling your pH down. You might titrate your finished biodiesel with fresh phenolphthalein solution, dry alcohol, and your 0.1 Normal caustic aqueous solution to see if there's free fatty acids in it and how much. Finished biodiesel is suppose to be about neutral (pH 7). pH is a measurement of acidity/basicity with water. If there's no water, it is something different than pH. Use distilled water 1 milliliter, and 1 milliliter of your finished biodiesel in a clean small glass container like a beaker, stir a lot, using proper test strips, measure the pH of the liquid, possibly using a clean eyedropper to put a drop on the test strip. It is puzzling to me that you have an acidic pH.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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Good advice on the pH strips. I've been meaning to get a digital one anyhow, for the beer hobby. I have used them before and liked them.

I just got my indicator solution very recently from Utah Supply, so I assume it is fresh, but it doesn't hurt to check. I will try the test for FFA's you recommend, but isn't that what the 27/3 test tells you? I'm not to clear of the actual chemistry going on here.
Thanks. Will update with results.
 
Location: Knoxville, TN | Registered: December 04, 2010Reply With QuoteReport This Post
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You water washes ten times and the biodiesel still appeared to have soap bubbles. Salt in water precipitates soap. Soap doesn't dissolve as well in hard water. Soap in water is a base, it doesn't dissolve as well in water that's already basic. Your wash water is pH 7.5 (basic) from a lake (has minerals dissolved in it). It would cost more money and trouble to water wash with distilled water, but it would work better. I found "pH Water wash test" Take pH of exiting wash water. If the pH is the same as before you started washing with it, your biodiesel is likely clean.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post



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I guess hat makes sense. I never thought about my water. Here is the breakdown of my water from 2009 (mine is listed as "Chapman".
water profiles TN

It seems low in most catagories compared to the region, and especially compared to other parts of the world whose water profiles I try to emulate when making certain styles of beer. I usually end up adding quite a bit of various salts and carbonates to my water to make beer.

I will definitely look into a pH meter or some strips.
 
Location: Knoxville, TN | Registered: December 04, 2010Reply With QuoteReport This Post
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I would recommend testing the acid number of your fuel instead of relying on pH. You basically titrate the fuel just like you titrate oil, the g/L number you get roughly equates to mgKOH/g fuel. ASTM spec is .5mg/g. You might not have the resolution to titrate in the .5 range so use 5mL of fuel and divide the result by 5.
As for the glop, the soap will continue to settle out, the bottom of a barrel will always have more soap than the top. If you fill the barrel rarely or the filling process is gentle (meaning doesn't cause a lot of mixing), over time you can accumulate a lot of soap. When there is a lot of soap and a small amount of water (like condensation on the inside of the barrel) it can cause problems.
 
Registered: September 16, 2006Reply With QuoteReport This Post
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I realize this thread is a tad old, but I didn't want to start a new one since this one was titled perfectly. I've just had the follow experience: I've started experimenting with dry washing using oak sawdust, using small bench tests; i.e., about a cup of sawdust and a liter of bio. The bio's original titration was 1g KOH, processed and passed 3/27 with flying colors. Performed soap titration and had ~ 1100ppm soap. I poured my cup of sawdust into a 1L glass bottle, poured bio in on top, shook up 2-3 times to ensure reasonable physical contact between sawdust and bio, then allow to sit for 20-30min. I then poured off the bio, straining through a paper towel and titrated for soap again. I use 1% bromophenol which turns my sample a dark inky blue with 2-3 drops. But with this sample, I added 2 drops, got a lime green; one more drop, back to original color;, one more drop, bright yellow!! Never even added the first drop of 0.01 HCl. So I did a "shake'em up" test and the water was crystal clear and the pH of the water was between 6 & 7.

Any thoughts, input, advice would be greatly appreciated. I'm not sure if I've made an error somewhere along the way or if the soap has been removed or just what is going on. Any suggestions and direction would be most welcome. Thanks in advance!!

- Jason
 
Location: The Volunteer State | Registered: July 07, 2011Reply With QuoteReport This Post
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