Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: simonallen on March 26, 2015, 07:32:20 AM
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Hi Guys,
New here but i've been doing a lot of reading :-) And I have a quick question.
When processing Bio it is my understanding that only a course filter is required of the oil before processing? If this is right, and the rest of the "stuff" drops out with the glyc, do I have to filter the glyc afterwards to get rid of the dropout before I use it to prewash my next batch of bio?
Starting on my GL processor build today or tomorrow, so will be getting to process some fuel in the coming weeks.
Thanks in advance ;D
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After glyc washing dispose of it then use the glyc from the batch you have just glyc washed to do the next one
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A few bits in the oil won't do any harm, although with a closed impeller pump they can cause a blockage; open impeller (like the TAM105) is fine. Julian suspects they may carry water with them which is detrimental to the chemical process. But yes they will drop out with the generated glyc, and settle to the bottom of that glyc over time.
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cheers guys
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... Julian suspects they may carry water with them which is detrimental to the chemical process. ...
Stole my thunder!
Make that "strongly" suspects.
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The bits of debris could well hold water, however the ability of glycerol to absorb water is massive. Ex-process glycerol contains roughly 1% water, yet will still reduce the water in oil from 800ppm to 350ppm. Even glycerol at 4% water will still reduce dissolved water in oil.
If glycerol is still present after glyc washing (in other words if it is not all drained) it has a positive effect on the process if the oil still has a titration. As water is produced from the FFA neutralisation it is consumed by the glycerol present and reduces saponification. I am pretty sure this is why the AAF method works so well. When oil is added to methoxide, glycerol is produced earlier in the reaction.
A while ago imakebiodiesel on infopop did some experiments where he added 2 litres of glycerol in the processor with the oil and methoxide, resulting in lower soap levels and lower KOH requirements. He got really good results even with non glyc washed higher titrating oils.
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I get a reduction of 10 to 15% of Kohl used when I do a glycerol pre wash with high titrartig oils
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Hi willbuild,
Yes, the glycerol pre wash is a really efficient thing to do. Have you ever titrated your oil after the pre wash. What I would recommend you try if you are using higher titrating oil is enhancing the glycerol. If your oil titrated at (lets say 5.0 KOH )
If you add 50% of the titration as gms/litre KOH, so 2.5 gms/litre into 2 to 3 litres of methanol. Mix this with your glycerol before adding to the oil.
After the pre-wash you should find the oil has no positive titration, all the FFA's have been neutralised 'in the presence of glycerol' which means any water produced from neutralisation has been absorbed bt the glycerol. You should find that your process is even more efficient.
The oil I usually have titrates very low, @ 1.0 KOH, so I don't have to add KOH to the glycerol but I still add methanol and I use a lot of glycerol for the pre-wash. 60 litres of glycerol, with 5 litres of methanol into 190 litres of oil.
After the pre-wash I usually have around the 25% conversion level. 7.5 mls dropout with 10/90.
The 5 litres of added methanol is then deducted from the methanol amount for the 1st 'normal' reaction. I now use a mamimum of 14% methanol using this method, and have had the added methanol amount down to just over 12%
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dgs.
If you are using 60 litres of glycerol for 190 litres of oil to you have a source of glycerol ? 190 litres oil oil wont produce 60 litres of glycerol, or does your process ?
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Hi Steve,
Yes, my process creates nothing like the glycerol that I add. I have a few local friends that are only too happy to give me their glycerol. They don't pre-wash even though I have told them about the benefits.
I look at it that they are giving me their residual chemicals for free.
I'm sure it is a physcological thing when you've not done it before, adding horrible looking black glycerol to nice clear oil.
From testing I have done, the pre-wash process uses @ 3.8 gms of KOH/litre of glycerol. Of course there are many variables. As to the methanol used out of the glycerol, I don't know.
Unless the oil you are using is very wet, the glycerol can be used several times and in that case would benefit with some methoxide enhancement.
The important thing is that after the pre-treatment process the oil will not titrate ie it is alkaline. This means that when the methoxide is added there will be little or no wastage of chemicals used up making soap.
A while ago as an experiment I glyc washed 30 litres of oil that titrated at 21 KOH. I used 30 litres of enhanced glycerol and ended up with 27 litres of oil that titrated at 0.3 and was <500ppm water. The power of glycerol.
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Am processing a 100 Ltr batch of high tit oil. 15gr of Kohl per ltr using Dr pepper test gave me 82% conversion.
I have another 100 ltrs of the same oil that I will try the wash with the meth and kohl method.
l will post my results in a few days time.
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Wow! lots of KOH. What does your oil titrate at.
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This bacth, 15grs 1st stage 85% conversion added 300grs to get a clear pass.
Total 1800 grs for 100 ltrs.
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if you glyc washed this batch then the chemical requirement means it still titrated at something like 10. With a FFA level so high the liberated water level will be high, something like 0.3%, so its like pouring 300 mls of water into your processor when you add the methoxide.
Your oil must titrate at something like 15 before you glyc wash. You will still be able to reduce the titration to nil using the enhanced glycerol technique, but one of the problems will be that the glycerol from your process will be very wet to start with. You will have to add more than 30 litres to have any chance of getting the water down to less than 500ppm.
Have you ever considered caustic stripping.
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Have plenty of glycerol, so that isn't a problem
If my oil titrates at 10 is it 5gr per litre in the glycerol wash?
I have not heard about caustic stripping, where can I read up on it?
Thanks for your help.
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Yes, thats correct.
With the oil titrating so high I am not sure if 5 gms/litre of oil would do it, but try. If you have to add more, then do. The important thing is to have the oil non-acidic before you add the methoxide, so any water created from the FFA neutralisation is done during the glyc wash stage and therefore is removed by the glycerol. If it is easier for you the koh/methanol (methoxide) can be added after the glycerol. you just have to remember that you will lose the FFA portion of the oil (which is about 50% of titration) so about 5 litres when doing any of these methods.
I will try to send a link to the caustic stripping.http://biodiesel.infopop.cc/eve/forums/a/tpc/f/5367078823/m/3897002473/p/4
To save time the charts you need are on page 4 and the experiment I did with the oil that titrated at 21 is on page 6
The biggest drawback with this method is that after the stripping process you have to dry the oil, whereas using the glycerol method the glycerol does the job for you.
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Have done another 100 ltr batch.pre washed with 25 litres of glycerol with 5 litres of method and 5gr per litre of Kohl.
Leftover night to settle. Next morning I did a 10/90 test and had no conversion.
So did my 1st stage, 7 litres of meths and 7gr per litre kohl.
10/90 test gave me a fall out of 4.5 ml. Added 3 litres of meths and 5gr per litre of Kohl to get a clear pass.
1st 100 litres batch needed 18gr per litre.
2nd 100 litre batch 17gr per litre.
1st batch produced 68 litres of bio.
2nd batch produced 88 litres of bio.
Both batches where done with the same oil.
:)
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Thats a good result willbuild.
Although the KOH amount used is similar the yield of bio, some 20 litres more is a massive increase.
Because most of the FFA's have been removed with the glycerol present, when your methoxide was added far less water would have been produced and less product lost to saponification.
I still think you could improve by adding even more KOH/methanol to the mix when the glycerol is in there, add enough so the oil is alkaline if you try to re-titrate it.
Nevertheless a good result, Well Done.
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I will set up to titrate, I did titrate when I first started two years ago but have not done since.
I will repeat the process in a few weeks time.
Am I right in thinking that the 1st stage glycerol will not be as high in water content as only 7 gr per litre of kohl was used in the first stage. Normally my 1stage has 15gr per litre.
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It is the other way round, the 1st stage glycerol is higher in water as this is when the FFA's are neutralised producing soap and water. That is why when calculating chemical requirements for the second stage from the result of the 10/90, the residual amount of oil should be treated as new oil,ie only adding the base amount of KOH for full conversion.
The glycerol enhancement method is actually like an extra 1st stage, so if you get the oil to slightly alkaline before the 1st 'normal' stage, then in thoery the rest of the oil will convert on @ 8gms/litre.
Dave.
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Processed an oil last week with a titration of 25 so I tried caustic striping at 4grs per litre of naoh and 4 lts of water for 100 lts of wvo.
After drying the oil the titration turned red with just 3 drops of fluid.
I then processed in 2 stages using 8grs of Kohl per litre with a conversion of 87%.
Had 80 litres of wvo with a value of 45, so stripped last night using 4grs of naoh and 4lts of water and left overnight.
This morning after drying it had a value of 12.
Did a enhanced glycerol wash with 8grs per litre of Kohl and 3 litres of methanol, did a 10/90 test with no conversion.
After 3 stages I have a clear pass having used 9grs per litre.
Glycerol is back in and has had water wash and am waiting for it to settle and will then see what the conversion rate is.
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Hi willbuild,
Those seem very good results for oil titrating so high. Are you titrating with KOH or NaOH. Here is a link to IMB's chart where he gives the amount of NaOH for various titrations, If the link shows all the thread the chart is on page 4.
http://biodiesel.infopop.cc/eve/forums/a/tpc/f/5367078823/m/3897002473/p/4
The conversion rate on your 25 titration batch is excellent, you have only lost the FFA portion of the oil. If the batch titrating at 45 is similar you will get @ 77% yield.
Where on earth do you collect oil from that titrates as 45?
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Fed in 75 lts of wvo and have 60 lts of.bio i think thats 80%.
I get the oil from a fried chicken take away, it's colour is a dark brown almost black. There oil normally titratates at around 25.
I normally pick up 60lts every week off them but they left the oil change 10 days on this occasion.
My titration fluid is naoh, when measuring the 1gr I use a scale that measures to two decimal places.
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There is something that doesn't add up with your figures willbuild.
Don't get me wrong, not criticising, just a comment.
When we titrate with KOH roughly 50% of the titration is FFA%. When using NaOH roughly 70% of the titration is FFA%
So your titration of 45 means there is @ 32% FFA's present which would be lost to soap and water either during the stripping stage or the base stage. This means that if the rest of the process was 100% efficient the maximum yield you could have would be 68%, yet you have ended up with 80%
Are you sure your titrant is correct and did you blank your IPA before adding your sample. IPA can be quite acidic.
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Yes I do blank it, it takes only 3 drops for ipa to turn red after adding the turmeric.
A few weeks ago I titrated a sample of new oil to see what the result would be and found that with just 3 drops of fluid it went from yellow to red.
My solution is about 3 months old and my ipa about 10 or 12 months old.
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Hmm, I'm puzzled. But then I'm always puzzled about something.
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Sent you a pm Simon...
Oh, and hello you lot, I'm back!
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'ello! Ow bist?
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I'm fine Tony ta :)
I've never really really been away just forgot my log on details but have been lurking a lot.
It went real quiet on here but has pepped up a lot recently- good stuff