Sounds about right to me,knew someone would come up with an theory.
Glad to hear your experimental side is still alive and kickin.
Womble and Trigger,
Yes I find the same thing happens.
How I deal with my yellow grease is I put it in my hot tank with as much glycerol as I have. On average 400lts grease, 200lts glyc.The glyc has already pre-washed my best oil.
This is heated up to @ 65degs C (M67) and pumped into my 1000 litre conical. The glyc is run off and the oil run into cubies to settle.
Everytime I do this it reduces the volume of grease by 50 to 70% and the cubies have a layer of at least 50% good clear oil on top.
I do find however that the oil derived from this process needs something like 2 to 3 gms KOH/litre more to process than my best oil.
I haven't tried titrating the various proportions but I have a larger set up for this now that I am playing around with at the minute, I'll titrate it and let you know how it comes out.
I found that passing the yellow grease through a coffee filter seemed to release more clear oil. I'm guessing that this breaks up the crystal matrix releasing the oil and some free water that's held by entrainment. What I was trying to do was to see if I could process and dry yellow grease in a green house with out any extra heat input. This can regularly get the oil up to 40c but this isn't hot enough to get the yellow grease to go through a fine filter.
My new set up has a heating belt on it so I can introduce heat in colder times and get the temp higher. If this works out the way I want I have several different ideas to step on from there so I'll keep you posted on how I get on.
Hi Womble, I think that you are on the right track by looking at entrainment. As the crystals form they join up and trap liquid oil, food particles and water, preventing these from separating. An other way to break up entrainment is by physical agitation. If you mix the hell out of yellow grease with a paint mixer it becomes much more liquid and will filter much more easily. Perhaps the combination of mixing and the mild heat of the greenhouse will do the trick.
Ive just finished processing my first 1000 litres of oil that titrates at 15ml KOH. I have 2 more. The caustic stripping has now become a regular part of my routine.
Fill the processor with 150 litres of oil (titration 15ml)
heat to 60°
Add NaOH solution and mix vigorously for 10 minutes.
add 20% glycerol and pump mix for 20 minutes.
Reheat to 63°C
Oil titrates at 3 or 4 ml KOH
Process by 2stage process,
remove last of glycerol
reheat to 60°C
Dry the biodiesel
Conversion >98% ( zero dropout on the 30/270 test)
Soap <70ppm ( by soap titration)
water <200ppm. ( by carbide manometer)
Fuel ready for use.
The caustic stripping has proved to be totally reliable and very little work. Because of the method I use for glycerol separation it is difficult to be totally accurate about the yield of each batch but on average I am getting 137litres of finished biodiesel for every 150 litres of oil.
Thats very good IMB and as you say the method does not have the complexity of the A/E process.
Those are good numbers.
Certainly better than you would achieve if you were doing a straight base transesterification reaction.
Reducing the titration from 15KOH to 3KOH is about 6% FFA removed from the oil.
6% of 150 litres WVO is a loss of about 9 litres WVO
The remaining 3 KOH titration is about 1.5% FFA remaining.
The rule of thumb is that the loss of yield in a Base only transaction is between 2.5 and 3 times the FFA amount.
That means you would expect to lose about a further 5 Litres to 6 litres of yield into the glycerine layer.
If you were to do a straight base transesterification you would expect a loss of yield between 28 litres- 34 litres on your 150 litres WVO.
Unfortunately I am cursed with WVO that titrates around 1KOH so I will never know the satisfaction of routinely performing caustic stripping or AE.
One thing that would really be useful when making a post like yours is to include the amounts of chemicals used in each step.
For instance how much KOH and Water did you use in the initial caustic stripping stage?
You did a 2 stage base/base after the caustic stripping and it would be useful to know the amount of KOH and Methanol used in each stage
That would depend on what you describe as complexity when performing the AE stage.
They are different reactions, and are performed with different procedures.
I guess one complexity removed would be not having to dry the WVO before performing the caustic stripping.
On the other hand AE will give a greater yield
Thanks Dgs, the main advantage of this process is its reliability. If you caustic strip on Friday you know you will be able to process on Saturday and you know you will have fuel for the car on Monday morning.
I think it was Womble who said on one of the PM discussions a few days ago AE can be tricky especially for the beginner. I have a customer who bought his processor 2 weeks ago and has a regular supply of oil that titrates at 20ml KOH. Im recommending that he goes with caustic stripping at least until he has a dozen successful batches and has got confident with processing and testing. Then if he wants the extra yield he can try AE.
Nice job folks.
Thanks to English brewer called lojiuk for presenting us with the original idea and cheers to you imake and all the others over the last year and more recently for perfecting it into a usable method.
The recent hive of activity and collaboration on Ireland 'private' threads is starting to produce some fantastic results.
Yes it does and I will attempt to show why below. If my calculation is wrong then I will happily be corrected. A formula has been presented on the forum in the past but here is my first principles approach, based on faded memories of A-level chemistry(over a quarter of a century ago for me now)! For anyone not in the know, A-level is a UK/NI secondary school qualification for 16-18 year olds and is done before leaving school or progressing to university. So this calculation would indeed be a yawnfest for anyone with a PhD in chemisrty.
We titrate with 1g/litre (or 1mg/ml) base solution (either NaOH or KOH). I will factor in purity later.
Let M be the molar mass of our base (56g/mol for KOH and 40g/mol for NaOH). I know it is not exactly 56 or 40 but since we will always be limited (in our workshops) to not knowing the precise make-up of the FFA’s then we cannot know enough accuracy in the rest of the calculation to reliably discriminate between 56 and 56.1 in this part for instance. So 56 and 40 will do nicely.
That means we will have 1/(Mx10^3) moles of base in 1ml of titration solution.
Now one mole of base will neutralise one mole of FFA. I am assuming that each molecule of FFA contributes 1 H+ ion to the neutralisation along with one OH- ion from each molecule of base, to form one molecule of water. The rest going to make the soap/salt.
Now the molar mass of FFA varies widely but I will go with a mean of 280g/mol. Typically I think it could easily span 280+/- 5%, depending on the precise mix of FFA in the oil. I will use 280g/mol for the calculation.
So, in 1ml of the titrated oil there is 280/(Mx10^3) g of FFA per ml of titration. So if your titration was T ml then there is 280T/(Mx10^3) g of FFA in the test ml of oil. Now let Y be the mass of the 1 ml sample of oil (which you could actually weigh – though within our level of accuracy you can get away with assuming the pure oil mass values of 0.92g for canola and 0.925g for soy at 20C, again these are typical and do vary a little). Now let P represent the purity of your base. For instance P=90 for 90% pure base which is typically the case for most of us using KOH.
After all that, the mass % of FFA in your oil will be given by
%FFA = 280PT/(Mx10^3)/0.925 (I am assuming soy. If using canola replace 0.925 by 0.92)
If by way of a worked example, we use the numerical values which apply most frequently to us then we can reduce this to a simple relation between %FFA and T the titration value. To that end let us suppose we are using 90% pure KOH so P=90 and M=56. Plugging this into the formula gives
%FFA = 0.49T
(0.49 is correct to 2 significant figures (which is all the accuracy we can assume based on the fact that the 280 molar mass of the FFA is liable to vary by +/- 5% or maybe more)).
So essentially we have %FFA = T/2. Thus, if your oil titrates at 2ml then you have 1% FFA. If your oil titrates at 20ml then you have 10% FFA. At T=60ml it is 30% FFA (though at this titration level it may not be sensible to use 0.92 (Canola/Rapeseed) or 0.925(Soy) for your oil sample mass, rather actually measure it). This can help predict upper bounds on yields for caustic stripping of high titrating oil.
Fot T=60, at this loss of yield (30%) I guess, as has been pointed out earlier, if you were receiving regular supply of this kind of oil setting up in AE might be preferable.
If Wesley B sees any of this he may wish to run his eye over it because I make no claim to being a chemist.This message has been edited. Last edited by: Drum,
2001 Saab 93 TiD B50
2006 Mercedes C200 CDI (no DPF) B50 (for now)
In 2005 Neutral posted:
"The formula used in industry for calculation of free fatty acid percentage is:
FFA% = (v - b) x N x 28.2 / w
where v is the volume in ml of titration solution
b is the volume in ml of the blank
N is the normality of the titration solution
w is the weight of the sample of oil in grams
With NaOH the molecular weight is 40 so a 0.1N solution contains 4g per litre. That is the usual concentration used in industry.
Note that the formula contains 28.2 which is the molecular weight of oleic acid divided by ten. Oils are not made of only oleic acid hence this formula results in small errors, normally accepted. The range of molecular weights encountered in the used oil trade is from 270 for palm to 281 for canola.
For the homebrew titration the concentration of the solution is usually 1/4 of the above, 1g NaOH per litre. Sometimes it is 1g per litre of KOH.
To calculate the FFA from a homebrew titration use the following with a 1ml sample of oil:
FFA% = 0.766 x t for titration with 1g NaOH per litre where t is the volume of solution in ml for 1ml oil
FFA% = 0.546 x t for titration with 1g KOH per litre"
Because we usually use KOH with a purity of about 90% the FFA% of 0.564 needs to be multiplied by 0.9 which gives us 0.4914.
So the answer to your question is yes, the percentage of FFAs in an oil is very close to half the titration result in ml KOH?
If there is a moral to this story it is think 2 before you doubt IMB! ;-)This message has been edited. Last edited by: Drum,
2001 Saab 93 TiD B50
2006 Mercedes C200 CDI (no DPF) B50 (for now)
If you are unhappy with neutral's explanation and have further questions about how he came up with his information, I am sure he would not mind if you contact him.
Over the years I have emailed him many chemistry questions and he has always answered me promptly.
He is an Industrial Research Chemist (PhD) with 30+ years of alternate energy experience.
Indeed. Who in their right mind would ever doubt what IMB says.
I dont see it as being any less complex then AE, it seems to me it adds some steps. I guess this stripping technique would be less sensitive to water then AE, is that what you mean?
The problem I see with the stripping technique is the yield, your converting those FFA's to soap whereas with AE your converting those FFA's into esters.
At least that's how I understand it, or am I missing the big picture here as usual?
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
No your not missing anything, caustic stripping turns the ffa into soap which reduces the biodiesel yield for a given quantity if uvo. The advantage I see is that you don't have to work with sulfuric acid which requires much care!
" 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.
The stripping process is completely insensitive to initial water content of the oil, as water is used in the stripping process. However its important to dry the oil after stripping so that the base process works properly. Its also completely unaffected by any residual catalyst that may be lurking in your processor.
Im not trying to promote caustic stripping as better than AE but some brewers, especially beginners, find it simpler and more predictable. Like every method it has its pros and cons. The loss of yield is the major drawback and if thats a problem then AE is the way to go.
Just to give you an idea of the loss of yield I have done 8 batches of oil titrating at an average of 15ml KOH and the average yield has been 137 litres of biodiesel from 150 litres of wvo.
One interesting find was that the titration of the first batches was 20ml KOH and as the IBC emptied the titration dropped to only 10ml koh. I supose from that the worst most acidic oil was at the bottom and came out first.
At one time @ 3 years ago I did a e all the time.
I found it a pain in the backside. The worst thing was not working with the sulphuric, but the time the mix took for the titration to reduce. I actually set up a Stainless pressure tank so I could do this at @ 30psi, so I could get the temp right up without the methanol boiling off. Also I was going to do the base/base at pressure then go on to W B D.
My oil titrated at worst @ 5.0 and in the end I reverted back to 2 stage no titration with a good glycerol pre-wash.
As I started to amass more oil the slightly lower yield was not significant to me.
One of the significant things for me with a e is the dark coloured bio derived by this method. I hate dark bio.This message has been edited. Last edited by: Dgs,
The colour of AE biodiesel can be a problem especially here in Ireland where revenue and police regularly stop vehicles and check their fuel for colour. They are looking for the red and green dyes added to agricultural diesel and heating oil but a very dark coloured fuel will get their attention, attention most of us would prefer to avoid.
Caustic stripping lightens the colour of oil significantly. My 20ml KOH oil is almost black but the biodiesel from it is the normal golden colour.
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