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Caustic stripping.
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I thought I would start a new discussion because I think it may become an important part of our processing technique. First my thanks to Trigger for bringing this to our notice. He got the idea from an English home brewer who has sucess with the idea but when he posted it on a forum, not our forum, the idea was rejected out of hand. My thanks also to Breathnach for supplying me with some truly horrible oil.

I followed the recipe exactly.
I titrated the oil and got a result of 18 or 19 ml KOH.
I heated 1 litre of the oil to 60C.
I dissolved 3.5gm NaOH with 40ml water and added it to the oil.
Mixed for 10 minutes.
Added 200ml of glycerol.
mixed for 20 minutes.
Allowed to settle for 1 hour.

Below is a picture of the mixture before settling, I would have to admit it did not look promising at this stage.


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www.imakebiodiesel.webs.com
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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After one hour of settling the dark layer at the bottom was still indistinct so I left it to settle overnight and it looked like the picture below. Now the moment of truth, I titrated the oil again and got a result of 4.5! I repeated the test to make sure I had not made a mistake.



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The reduction in acidity is dramatic. However the oil looks cloudy and I suspect that there is a fair amount of water suspended in it. I will test both the original oil and the stripped sample for water content and post the results today. Even if the water content is high a few hours with the dryer would sort that out.

www.imakebiodiesel.webs.com
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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Thats very interesting alright, certainly better than working with sulphuric needing contant heat & pumping to reduce titration.


"In times of universal deceit, telling the truth will become a revolutionary act" - George Orwell
 
Location: Ireland | Registered: May 14, 2012Reply With QuoteReport This Post
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wonder how much the titration result was influenced by the fact that there would be byproduct in the mix, or would there be?


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Even after 24 hours there will be some glycerol suspended in the oil but not much.
I was right about the water. 660ppm in the original oil and >1600ppm in the stripped sample so 6 hours in the dryer would be needed before processing.
As I see it there are pros and cons to this method compared to AE.

Pros
Caustic stripping is simple, the calculations are easy and do not change from batch to batch.
Its predictable so you know when it will be ready to start processing.
You dont have to clean out your processor each time or dry the oil beforehand.
You dont have to handle concentrated sulphuric acid.

Cons
The FFAs are converted into soaps and washed out with the glycerol so the total yield will be lower than with AE.
The residual water must be dried off before processing.

I cant take this method any further as I never have oil titrating above 6ml KOH. Anybody want to try a batch? I would be happy to advise. Alternatively does anyone have some terrible oil they want to donate so I can do a batch by this method?
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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I'll give it go.
I've been really busy lately so haven't been able to 'experiment' as much as I like but I've been meaning to try this as its seems quite quick and straight forward.(which means in most cases turns into an all day thing)

P.s I've also invited the original inventor of the idea(lojiuk) to the discussion.
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post



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Great stuff Trigger, let us know how it gos.
In response to Biotoms concern that the remaining suspended glycerol might simply mask the acidity of the oil, I have repeated the titration every day, there has been no change in the result so far.
I hope Lojiuk will contribute here as he is the person with most experience of this method.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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I carried out the experiment tonight using the above intructions.
I done it twice,one with NaoH and the other with KoH at 5g per litre,which is the NaoH equivalent(NaoH 3.5x1.4=5) and I also have a mixture of both.
Ill post the before and after titrations for all three tomorrow.
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post
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Sorry for the delay in joining.......good weather, lots of golf, and the wife!! Decided to change from lojiuk to rosedale.

Good to see someone has seen previous threads from another forum and taken notice and keen to pass on and experiment. I found the OTHER forum can be hard work and too many have a trumpet stuck where the sun don't shine !!

This is my third summer using this method. Only during the summer will I use “caustic stripping” as I tend to stock the semi/solid oils and high titrating oils and leave the good liquid stuff for the winter, and go back to KOH (I make glyc logs so the only reason for KOH is it stays liquid)

Most of this summer oil titrates around 5-8 (NaOH solution).

I use a separate 205 drum (top removed) with heater fitted and heat approx 150-160 litres of oil to 50-60deg. The remainder of the drum is filled with 30-35ltrs of glyc added for washing.

Titrate oil: And use these values below with amount of NaOH added to water

X = The amount the titration value has lowered after 10 minutes of washing oil with just water/NaOH mix
Y = The amount the titration value after 20 minutes of glyc washing after X has been done (approx. 30-35l of glyc added)

WATER NaOH X Y
300ml 300g 2 3
400ml 400g 3 4
500ml 500g 4 5
600ml 600g 5 6

I drop 20 litres of waste glyc after 2 hours as this is used for glyc logs and is still warm.
After 24 hours I drop the remaining waste glyc. It’s usually about two weeks before I process this oil (top up drum with another 30 litres of good dry oil to do 180 batch two stage method 20/5 litres of Meth and never get a problem to get a clear 27/3 test.

The figures above are only a guide and do vary, and more so with the amount of glyc added and the strength of the glyc . I use base figures of 3.5 for NaOH and 5 for KOH, if you use more then you can expect a bigger drop in titration value.

Hope this is of some help to those wishing to experiment and hopefully add to my findings, these were done some three years ago. I have tried varying the times for mixing but found no value for longer than I have put.

Typically now I just add 400grams (cupful) of NaOH to about 300ml of water, have just about given up on measuring, so nowadays go by a cupful and a scratched water line on the outside of a bottle. If you add to much NaOH to water you will find the NaOH solidifies at the bottom.

You can use both Catalysts and mix them. Not sure why but I found KOH glyc far superior than NaOH glyc………and gives a lower end titration value. Might just be me???? But worth experimenting with.

Have also tried using Methanol instead of water, but found NaOH and KOH are more soluble in water.
 
Location: Salisbury | Registered: July 22, 2013Reply With QuoteReport This Post
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where does the glycerin come from? do you mean you drop X ltrs of soap?


" I don't know what I don't know until I know"
1994 GMC 6.5 Tubo 2005 Dodge ram 3500, 3 VW's 2000, 2002, 2005.
 
Location: Manitoba Canada | Registered: March 24, 2009Reply With QuoteReport This Post
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Hi Rossdale and welcome to the forum,you'll find plenty of open minds and little judgment here.
I'm just about to titrate the oil I done last night using your method above.

Another forum member'imakebiodiesel' has done it already (using some truly nasty oil) with a fantastic drop in titration(think it droped from 18 to 4.5)-a titration drop of about 14!!

The only way of using this type of high titrating oil before would have involved a acid pretreatment which although works well,can be complicated process to learn and involves handling some corrosive acids which isn't kind to our steel tanks or hands.

If we can all have the same success as 'imake' did this would mean all the nasty high titrating oil that we would never think of using before would now be within our reach.

Im not sure I understand what you mean by this -
quote:
WATER NaOH X Y
300ml 300g 2 3
400ml 400g 3 4
500ml 500g 4 5
600ml 600g 5 6


Regards and welcome-Trigger
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post
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OK so I got some oil from my local k fried chicken
I titrated the oil and got a result of 6 ml KOH.
I heated 2 litres of the oil to 60C,
I dissolved 3.5gm NaOH with 40ml water and added it to the first oil.
I then dissolved 5g KoH with 40ml water and added it to the second oil.
Mixed for 10 minutes.
Added 200ml of glycerol to each
mixed for 15 minutes.
Then transferred into 2 glass jars.
Allowed to settle for 1 hour and noticed a glycerol drop just after 1 hour.
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post



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I was meant to titrate the samples next morning but ran out of time so I titrated 24 hrs later.
Titration had halved from 6 to 3.
This isn't the great titration drop that imake got as the glycerol alone could have contributed to a 2 ml titration drop.

I must say however I did change my titration fluid recently and I've a niggling feeling it isn't right,also the lcd on my trusty thermometer decided to mess about while heating the oil(good excuse to buy a new infrared one)

So I would have to say my experiment was inconclusive.
I'd like to get some oil that's titrating above 10 from a friend I know and do this again more accurately with different/new titration fluid.

These are the samples next morning--
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post
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quote:
X = The amount the titration value has lowered after 10 minutes of washing oil with just water/NaOH mix
Y = The amount the titration value after 20 minutes of glyc washing after X has been done (approx. 30-35l of glyc added)

WATER NaOH X Y
300ml 300g 2 3
400ml 400g 3 4
500ml 500g 4 5
600ml 600g 5 6


Think I know what you mean by this now.
Have you measured separately how much the acid wash has lowered titration and then how much the glycerol wash lowered titration?
WATER NaOH X Y
300ml 300g 2 3 water/NaOH mix lowered titration by 2(x)and glycerol wash(y)lowered it a further 3(total reduction in titration was 5
400ml 400g 3 4 (total reduction=7)
500ml 500g 4 5 (total reduction=9
600ml 600g 5 6 (total reduction=11)

Maybe I'm over thinking-time for bed Roll Eyes
 
Location: County down, Northern Ireland | Registered: August 10, 2008Reply With QuoteReport This Post
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Welcome to the forum Rosedale, as you can see your method is causing a bit of a buzz here. I have a hunch that this technique is going to work better with very acidic oil. Using 3.5gms NaOH in 40ml of water per litre I achieved a reduction from 19ml to 4.5ml KOH. A similar dose in Triggers medium acidic oil only went from 6 to 3.
What seems to be happening is simple saponification. The NaOH/water is reacting with the FFAs and producing soaps. Glycerol has a strong attraction to water and helps remove it from the oil. The soaps, especially Na soaps are heavy and will settle into the glycerol layer. Just the same as the biodiesel reaction, saponification is a reversible reaction and like biodiesel it needs a bit of help to push it towards complete conversion. I believe this is why the process goes to about 3-5 ml KOH and no further.
Waiting a few weeks would let the excess water settle out but here in Ireland most of us have powerful dryers attached to our processors so we can remove the water in a matter of hours.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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A friend gave me 15 litres of oil that titrated at 18ml KOH. I decided to try caustic stripping on it . I heated it up on a gas ring in a steel bucket to 50C. I mixed up 52 gms of NaOH and 600ml of water and added it to the oil. I stirred with a stick for 30 minutes and then added 3 litres of glycerol and stirred for 30 minutes.
I would have to admit here that stirring for 1 hour is very boring and I would wander off and do other things from time to time.
I left to settle overnight and the titration had only dropped to 11.
I reheated but added no more caustic and this time mixed with a drill mixer for 15 minutes. After settling for 24 hours it had reduced to 6.
Mixing is very important, both how long and how vigorous.
I have added a section to my processor manual on the subject as follows...

CAUSTIC STRIPPING.

Caustic stripping is a simple and reliable way to reduce the FFA levels of high titration oils, a significant improvement in colour is also achieved.
Essentially stripping involves heating up the oil to 50 degrees C and adding a strong solution of Sodium hydroxide ( NaOH, drain cleaner) and water to the oil and mixing it thoroughly. The NaOH, water and FFAs combine to produce soap (saponification)and water. Glycerol is then added and mixed with the oil and as the glycerol settles to the bottom of the vessel it takes most of the soap and water with it. The improvement to the oil is quite spectacular, on my first try I achieved a reduction in titration of 19ml (KOH) to 4.5ml (KOH)!

I would suggest two methods, the first can be used if you only occassionally collect high titration oil in small quantities. This method will strip 15 litres at a time and can easily be done as part of your glycerol pretreatment.

In a 20 litre steel bucket heat up your high titration oil to 50C. Add the solution of NaOH( see details below) and stir vigorously for for 30 minutes. Add 4 litres of glycerol and stir for 30 minutes. Transfer to a 20 litre cubie, screw on the cap and leave to settle for at least a week. You can save yourself a lot of labour by using a drill mounted paint stirrer. Give it a 20 second buzz once a minute instead of continuous stirring.
After settling you can simply pour the improved oil into your processor and top up with ordinary oil and process as usual.

The second method is for those unfortunates who have large quantities of high titration oil and need to process whole batches of it.
Fill your processor with 150 litres of high titration oil and heat it up to 50C, add the correct amount of NaOH solution ( see details below) and mix using the pump at full speed for 60 minutes. Pour in 30 litres of glycerol (20%) and mix for 60 minutes. Leave to settle overnight.
Drain off the glycerol and set aside.
Titrate to make sure it has worked, Top up the processor to 150 litres with low titration oil and reheat to 64C. Put on the dryer and run it for 6 hours. Titrate a sample of the oil, Reheat to 64C and process as usual by the 2 stage method.
CAUTION, the dryer will demeth the oil so make sure your vent hose is directed out of your workspace. Use 20% methanol when processing regardless of how low the titration is.

Here are the directions for mixing up the NaOH solution.
CAUTION, always add NaOH to the water gradually, stirring all the time. Never add water to NaOH. The solution will become very hot. Always wear gloves and eye protection.


TITRATION/ gms NaOH per litre of oil/ ml water per litre of oil.

6 - 10 ml(KOH)/ 2.0/ 20.
10-15 ml(KOH)/ 2.5/ 30.
15-20 ml(KOH)/ 3.5/ 40.
20-25 ml(KOH)/ 4.5/ 50.

These instructions are still provisional and I would welcome any input from anyone doing full batches.

This message has been edited. Last edited by: imakebiodiesel,
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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We have always taught that stirring with a stick (Round) is a waste of time and effort,as you found, it should at least be flat. Jim.
 
Location: Cape Town | Registered: May 17, 2006Reply With QuoteReport This Post
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I think the problem is that the reaction is hindered by the presence of all that oil and glycerol,so its hard for the molecules of water FFA and NaOH to contact, Vigourous stirring is needed to keep them moving.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post



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Free fatty acids reacting with sodium hydroxide or potassium hydroxide produces soap and water. That acid-base reaction is called neutralisation. Saponification is Mono, di or triglyceride fatty acid esters reacting with NaOH or KOH and water to produce soap and glycerine. Saponification and neutralisation are not the same thing. Even though the reaction may be called neutralisation, that doesn't necessarily mean the products are pH 7. A weak acid and a strong base make a pH basic product like sodium or potassium soap.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
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Thank goodness somebody knows their organic chemistry. Looking at the process outlined so far, what would enhance this reaction, higher temp? longer mixing times? more NaOH? more water, less water?
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
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