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Caustic stripping.
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Thanks IMB,I will do some blending tomorrow.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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I've got some stearic acid also named octadecanoic acid, it is a free fatty acid with 18 carbons in its carbon chain. Molecular weight is 284.50 grams per mole, Density is 0.9408 grams per millilitre at 20 degrees centigrade. So 1 litre of stearic acid weighs 940.8 grams and contains 3.30685413 moles. 3.30685413 moles of stearic acid would be neutralized by 185.5475852 grams of potassium hydroxide.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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Does that tally with my estimate of the percentage of FFAs in an oil being half the titration result in ml KOH?
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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Hi Jethro and welcome to the forum.
While I sympathize with your frustration I think engaging with trolls and sockpuppets ultimately serves no purpose. Nevertheless I hugely enjoyed your post.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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I conducted my experiment today to see if I could neutralise high titrating oil with glycerol "dosed" with an amount of KOH and methanol.

The reason I am doing this is the 3 stages of caustic stripping ie;
water/base addition, glycerol addition and drying could all be replaced with a single process saving time and energy.

I must say at this point I realise IMB has done a lot of work on caustic stripping and this method is not intended to replace the method he has had great success with, it is just an alternative if anyone wanted to try it.

This is what i did.
To 30 litres of oil that titrated at 5.5 KOH I added 8 litres of FFA's that titrated at 120 KOH.
The resultant mix titrated at 21 KOH.
From IMB's calculation, allowing for the lower purity of potassium I calculated 266gms of KOH should be used.
I decided to round this up to 300gms.

I dissolved the 300 gms in 600mls of methanol and mixed this into 30 litres of glycerol. This glycerol contained very little methanol and did not have any bio top layer.
The glycerol and oil were mixed in my processor at 50degsC for one hour.
The mix was allowed to rest for 1 hour then run off into clean cubies
My processor is polythene but is not very good for seeing through so the cubies were the best option,also the oil is very dark (a disadvantage of using FFA's) so I have had to wait until dark and use a light to see the oil/glycerol interface.

Results as follows;
Volume of oil 32 to 33 litres.
Titration 0.3 mls KOH.
Water content of oil 277ppm.

Can't quite believe the water,tested the sample 3 times and checked the KF with my 90ppm std, it gave 92ppm.

So it seems to have worked. It was really only like a glycerol pre-wash with a little methoxide added.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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First let me say that I am in no way put out by your experiment, in fact I am glad you have got involved, in most cases two heads are better than one.
The separation is always difficult, the glycerol is almost identical in colour to the oil in these cases and I find the easiest way is to calculate how much glycerol to expect and take a bit more.
0.3ml KOH is a great result and the low water content means that you can proceed directly to normal processing without delay.
I have some high titration oil here at the moment and will do a small batch by the same method in the next couple of days. Well done , congratulations.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post



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Thanks IMB,
Please let me know how you get on.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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Hi Dave (dgs),

I still have 100 litres of that awful oil from Rochdale. I was going to try AE, but I will gladly try caustic stripping if it is the easier way. It titrates at 18koh and consists of a mixture of kebab fat and cooking oil. It's the most disgusting stuff imaginable, but it's been melted once and is now a thick liquid. I really can't stand to touch it, because the smell even seems to pass through vinyl gloves and is impossible to wash off.

If you could kindly talk me through what to do (there seems to be various techniques, and I'm not sure which is the most effective), I will post my results.

Sorry to have been out of touch. I will be over to see you for a chat before long!

Kind regards,

David
 
Location: Leeds, UK | Registered: April 13, 2014Reply With QuoteReport This Post
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DGs, I want to try this today and just want to check my figures with you. My oil titrates at 15ml koh and I want to process 1 litre. I will dissolve 5.5gms of KOH in 16ml of methanol and add it to 1 litre of glycerol. I will then mix this with one litre of oil at 50°C for one hour, and settle for one hour.
Do you think the equal amounts of oil and glycerol is necessary, this may cause difficulties for someone who has a constant supply of high titration oil?
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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[QUOTE]Originally posted by imakebiodiesel:
DGs, I want to try this today and just want to check my figures with you. My oil titrates at 15ml koh and I want to process 1 litre. I will dissolve 5.5gms of KOH in 16ml of methanol and add it to 1 litre of glycerol. I will then mix this with one litre of oil at 50°C for one hour, and settle for one hour.
Do you think the equal amounts of oil and glycerol is necessary, this may cause difficulties for someone who has a constant supply of high titration oil?


Hi IMB, Yes your amounts seem correct. Just to clarify,I had to use equal amounts of oil/glycerol because of the height of my immersion. My processor is far from ideal when doing this sort of experiment. I do not think the amount of glycerol is critical at all,however if it were too small it would not be able to absorb all the water produced by the neutralisation reaction.
Where this ratio of oil/glycerol would be I do not know.Hope it works for you.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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Hi David,
Hope you are well.If the caustic stripping using glycerol works,it could well be the easiest option for you.
Have you titrated the Rochdale oil? It will really depend on the result of the titration how you proceed.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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David Shinn,
Sorry,just read your post again,I see it titrates at 18.
You may want to wait for the results of IMB's experiment today before proceering with the caustic stripping without water technique.
In any case the method with or without water represents a much easier option than acid estrification.
You will lose@ 10% of your volume,but in your case I'm sure you will not be too worried about that.
10% less smell perhaps!
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post



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Ill stick with the 1 ; 1 ratio for now , we can try reducing the amount of glycerol later.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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Yes, When the glycerol amount would be reduced to a certain level it eventually would not be sufficient to bring the water level in the oil to <500ppm,so then it would have to be dried which defeats the object.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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Just thinking ahead on this idea.
Is there any reason why a glycerol pre-wash can't be "dosed" with a pre-determined amount of methoxide for low titrating oil.
In this way if after the pre-wash we could get the oil to titrate
at zero,then we could add exact base amounts of chemicals and only do one reaction.
Come to think of it I used to do this years ago and have the oil so it wouldn't titrate,it was alkaline,but didn't realise what I was doing at the time!
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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I went ahead with the caustic stripping test but found that my large beaker only holds 1.5litres so I reduced the amount of glycerol to 500ml instead of the litre that Dgs used. I heated to 50°C and stirred for one hour, switched off heater and stirrer and settled for one hour.
After settling I titrated and got a result of 1.3ml KOH, so far so good.
I then tested the oil for water and got a result of just under 1000ppm. This is a little better than the levels when using NaOH and water, but not low enough to avoid having to dry the oil.

My test was the same as Dgs in every respect except the quantity of glycerol so I have to conclude that it is the glycerol that reduces the end water content and that a 1:1 ratio of oil to glycerol is necessary to achieve Dgs level of dryness.
My glycerol was taken from the bottom of my settling tank where it had been for about 3 weeks so it should have been fairly free of biodiesel.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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Thats good IMB. Shame about the water,but as you say it's the glycerol that makes that part if the process work.
I don't intend to do another experimental test at the moment.
On my next process however I will dose the glycerol with a calculated amount of methoxide as I glyc pre-wash. The way I am thinking is why leave any FFA's in the mix at all during the 1st reaction when they can all be removed before-hand. My best oil only titrates at @ 2.0, so during the pre-wash the small amount of water formed from neutralisation as well as dissolved water in the oil should mostly be absorbed into the glycerol.

It would be interesting,IMB if you were to test the water in your glycerol. I have found on the limited tests I have done that the glycerol ex pre wash usually has 1 to 2% water. when this gets to 3% and over, it's water reduction properties are greatly reduced.
 
Location: YORK UK | Registered: April 27, 2014Reply With QuoteReport This Post
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Hi All,

New to this conversation.
Ive been working on a new oil source that titrates much higher ( 8 NAOH ) than I am used to.

Ive tried several 200L batches using the 80/20 base/base process, but have ended up with
only about 60% of the oil being converted to BD.

Im trying to come up with a way to improve my process. As I dont have a stainless processor,
I want to try Caustic stripping to see if that helps.


I am using an old style appleseed processor - so dont have a way to mix the oil vigorously without unloading the processor into a cone bottom tank, which Id like to avoid.

Has anyone tried an eductor on their processor to increase the mixing to work with the stripping process?


Thanks,
John
 
Location: Georgetown, KY | Registered: July 31, 2007Reply With QuoteReport This Post



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As you have found out 8ml NaOH (11mlKOH) is just too high for 2 stage processing.
An eductor might provide enough extra mixing to do the job providing you have a powerful pump, the Harbour Freight/Clark TAM105 pump might not be up to it.
Another option might be to heat your oil in your appleseed and then pump it into a 55gallon drum, add the water/Naoh, mix with a drill mixer for 10 minutes, add the glycerol and pump it back into the appleseed.
You should be able to reduce the titration to around 3 ml KOH without a significant loss of yield.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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DGs, testing glycerol with a water content as high as 2% is difficult with the carbide manometer as this represents 20,000ppm. But I take your point that the amount of water already in the glycerol will affect how much water it can absorb. My glycerol is a mixture of first and second stage product but has not been used for prewashing so should be about average water content.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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