Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: dgs on June 18, 2015, 12:53:06 PM
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Just scanning some old posts and came across this one from Manfred from his thread 'pump wash gone wrong'
Pump wash gone wrong.
« on: March 01, 2014, 10:50:11 am »
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After a perfect 10/90 on a 90 ltr mix I did a pre wash then 3x 10 ltr pump washes. Result the water was sparkling clear. So being the sort who prods wet paint to see if it's dry I did one more wash. Bum soapy water with a white interface. No worries I put 2 ltr of Glycol and mixed, looked ok so added 10 ltr of warm water. Instant mayonnaise so I added acid until split. Peed me off as I didn't want to do this because of interfering with the acid soap test. So now I'm back to square one. Has anyone else experienced this ?
I am almost sure what you have experienced is an emulsification due to a high amount of monoglycerides being present. They don't show up in a 10/90.
I have had this happen many times. After several aggressive washes with my compressor (wash water clear) I decide to do one more, then forget about the time and leave the thing (lets say) 45 mins. Leave it to settle, approx 30 mins. When running off the water there is the emulsified layer between the water and bio. Very thick, like white sauce.
I have to be carefull with this nowadays as I react at ambient. I only heat after a clear 10/90 and leave the last reaction glycerol in the mix. I heat to 55degs and mix for 30 mins just prior to de-mething. This seems to convert the mono's so
I don't have the problem anymore.
For some reason I've found if they are going to show it will be at the back end of the wash cycle.
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I did post about this prob over on VOD. Apart form the leccy what is the advantage of ambient conversion how much longer does it take
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I did post about this prob over on VOD. Apart form the leccy what is the advantage of ambient conversion how much longer does it take
Probably up to 30% longer, thats all. It's really convenient not to have to keep re-heating between reactions. I've been trying to glyc wash at ambient recently, although the glyc separates ok I don't think it works as well. I usually glyc wash using the M67 set-up / tam120/ 1000litre conical and do 2 batches at once.
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I usually react straight from glyc wash so I'm usually still at 50 ish
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Back end of the wash cycle. More like bite you in your backside when you think it's all done.
Having a similar problem with some palmy crap I'm using up. Real good pass, reclaim some meth then wash. Cold water then all of a sudden Bang. White tendrils hanging in the water. I carry on some more then dry. When settled for a week I get fallout in my drum so decant into smaller cubbies to force some more out. At least I know it's the oil so I'm watching for it.
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Hi Manfred, Yes, they come along, those naughty mono's, Captain Mannering Sir and bite you in the bum!
On the serious side if you want to be bothered you can get rid of them by doing a further reaction even with a clear pass. Use about 0.5 gms/litre KOH and react for @ 30 mins.
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So do a third small conversion after a pass should get rid of them.
Ok I will be doing a batch on Monday so will give it a go. Will see if I can get a good wash again.
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Try it and let us know.
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Try it and let us know.
Didn't try it this time. Dried the oil, pre wash with added mets. 360g NaOH usually gives me a 80/90% pass then 80/120g to full conversion. This time though only got a 10% first pass. It took 3 stages with Dubble the amount of NaOH to convert it. Instant 10/90. Didn't want to add more because of the quantity already used. Bubble washed to about 120 ppm soap so did a pump wash to finish, big mistake. There back.
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Try it and let us know.
Didn't try it this time. Dried the oil, pre wash with added mets. 360g NaOH usually gives me a 80/90% pass then 80/120g to full conversion. This time though only got a 10% first pass. It took 3 stages with Dubble the amount of NaOH to convert it. Instant 10/90. Didn't want to add more because of the quantity already used. Bubble washed to about 120 ppm soap so did a pump wash to finish, big mistake. There back.
Hmm, you know I've had this minimum KOH thing in my head for the last year or so. After a post I put on VOD Maurice_Mynah came up with the way he processes. Basically he glyc washes then uses 7gms/litre KOH and leaves it for a minimum of 4 hours at 60degs. I never quite managed the 7.0gms with my old processor, think I once did 7.2
Point is after processing all that time (4 to 7 hours) I never once got a hint of mono's when water washing. It seems to me that there are 3 ways to avoid them;
1 Process for a longer time at temperature.
2 After a clear 10/90 do a small re-process at temp with a very small amount of catalyst.
3 if you process at ambient (like I do ) leave the last reaction glycerol present, heat to de-meth and use this heat to re-mix at temperature before de-mething.
Trouble is with mono's they are invisible as far as a 10/90 is concerned. Also for those who bubble/settle there could be lots in their bio and they will never know.
As far as specs are concerned they will come under the category of free and bound glycerine which from memory is 2400ppm so they are best removed. Good job we both water wash Manfred.
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dgs - you process at ambient temperature???
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dgs - you process at ambient temperature???
I certainly do.
http://www.biopowered.co.uk/forum/index.php/topic,2442.msg30857.html#msg30857
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The conversion of mono-glycerides to bio is the final step of the conversion process. Triglyc.=>Diglyc=>monoglyc=>methyl ester. Each stage is a reversible reaction. So there will always be some mono's present.
They can be reduced by driving the reaction to the right i.e.
Feedstock (oil) + reactant (methanol)+catalyst <=> product (bio) + By-product (glycerol+ water)+ catalyst (which also forms soaps)
The reaction is driven to the right by removing something from the right hand side or adding something to the left hand side. By adding more methoxide you are adding to the left hand side. This is a bit of a simplification of a complex reaction. I'm sure a chemist can explain better.
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The conversion of mono-glycerides to bio is the final step of the conversion process. Triglyc.=>Diglyc=>monoglyc=>methyl ester. Each stage is a reversible reaction. So there will always be some mono's present.
They can be reduced by driving the reaction to the right i.e.
Feedstock (oil) + reactant (methanol)+catalyst <=> product (bio) + By-product (glycerol+ water)+ catalyst (which also forms soaps)
The reaction is driven to the right by removing something from the right hand side or adding something to the left hand side. By adding more methoxide you are adding to the left hand side. This is a bit of a simplification of a complex reaction. I'm sure a chemist can explain better.
Just Google Le Chatelier's principle - that will tell you all about equilibrium reactions.
Here's a start... https://en.wikipedia.org/wiki/Le_Chatelier's_principle
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The conversion of mono-glycerides to bio is the final step of the conversion process. Triglyc.=>Diglyc=>monoglyc=>methyl ester. Each stage is a reversible reaction. So there will always be some mono's present.
They can be reduced by driving the reaction to the right i.e.
Feedstock (oil) + reactant (methanol)+catalyst <=> product (bio) + By-product (glycerol+ water)+ catalyst (which also forms soaps)
The reaction is driven to the right by removing something from the right hand side or adding something to the left hand side. By adding more methoxide you are adding to the left hand side. This is a bit of a simplification of a complex reaction. I'm sure a chemist can explain better.
I'm so not a chemist , it's all a complete mystery to me, but the explanation of "pushing" the reaction in one direction or the other by adding or subtracting from either side, is brilliant ... suddenly why a normal two stage reaction works makes sense!
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Yes, you can think of an equilibrium reaction as a see-saw with the reagents on the left and the products on the right. Remove some product and the see-saw tips down to the left. Then Le Chatelier's principle comes into play and tries to balance the see-saw by making more product. It can only do it if there are sufficient reagents on the left hand side of course and you're right, that is why we remove the glyc after stage 1.
Nick
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So are these Monos a product of using the 10/90 to reduce the Chems to get a clear pass instead of titrating and doing a 80/20 split. If so what % overdose on stage two do you think would clear them up. Also if you did overdose stage two would it create excess soap or would the excess Chems come out with the glycerol.
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Bill and Twenty4Seven,
I realise the principles of the reaction but what I'm trying to say is that because the mono's are effectivley invisible to the 10/90 test then if you de-meth and settle who knows what % you still have in your bio.
I know I'm guilty of always looking into these things with too much detail and after all have never had any troubles with any vehicles using bio over the years, but I always try to get to the bottom of things (even if there is nowt I can do about it)
Intentionally creating an emulsion with the mono's at the back end of water washing makes them 'visible' and they can be removed.
Manfred, I wish I could answer your question with any degree of accuracy. I don't think they show themselves because of using the 10/90 and not titrating. Even titrating is not accurate on oils titrating above @ 3.0 (a factor of something like 1.15 has to be included into the base + titration formula.)
Why don't you stay on the safe side and add 'say' 30 gms KOH to a 150 litre batch after a clear 10/90 and see what happens when you wash OR leave the last reaction mixing for an extra 30 or 60 mins. After all I didn't get any mono's using the MM process, but up to 7 hours was a hell of a long time to mix!
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Yes that's what I was suggesting, you will always have mono's and who knows how much. At least until you water wash to 'flush them out' of hiding.