Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: neisel on April 30, 2014, 08:57:46 AM
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Fed up with water washing taking as long as the conversion process, I'm going to give the 7% pre-wash process a go.
The process I use currently is 80 /20 2 stage no tit, KOH, water wash, spray dry. It works well but most times I'm doing too many water washes for my liking, sometimes 7 or 8 or 9, which is a PITA.
Unless I've read it wrong, peeps seem to be doing this 7% pre-wash by removing the glyc after 2nd stage full conversion, adding it back & then adding 7% water.
The 1 question is this.
After the 2nd stage is done, the oil left to settle, tested & I have 100% conversion can I just leave the glyc from the 2nd stage in (& or add from the first stage glyc to bring it up to 6-7 litres as needed), turn the processor back on & venturi in my 7% of hot water?
Has anyone tried mixing the glyc with the water outside the processor & dosing it back by venturi?
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You can add the 1st stage glyc back and add 7% water, or some folks just leave 2nd stage glyc and add a bit less water.
Not tried mixing the glyc with water first but it mixes readily so it shouldn't be a problem, try it and report back.
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I've not heard of anyone doing that either, so as chug says, give it a go.
You could if you have a condenser, recover usable methanol, by adding back the first stage glycerin and then recover methanol in the normal way. When that's finished move onto the 7% water wash ... no possibility of contaminated methanol that way.
In my process, I then do an acid pump wash followed by one or two pump washes all of about 5%, checking that the pH of the wash water, finishing with drying with the venturi and condenser.
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I don't introduce any acid, acetone or anything else.
Would that change anything for me using the 7% wash?
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I have also been doing the acid wash and followed by 5% water washes on my last two batches and it works well for me.
I dont remove 2nd stage glyc, i add back in 1st stage (de meth opitnal) then a 5% (of wvo volume) water wash, then settle and drain.
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I don't introduce any acid, acetone or anything else.
Would that change anything for me using the 7% wash?
The idea of the acid wash is to neutralise the soap in one wash, so in theory it should cut down the number of washes you need to do. There's info on the wiki, here ...
http://www.biopowered.co.uk/wiki/Water_washing_titrated_acid_method
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I don't have any way to calculate how much acid to add.
I do have some 36% hydrochloric acid. It'll be about 135 litres of BD, add 100ml to the 7% water, venturi in, keep fingers crossed or ???
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There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).
For KOH and other acid strengths you can mathematically adjust the result.
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what would the calculation be if using vinegar?
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Julian,
Do you think no acid would result in an emulsion?
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You're asking the wrong person ... one of my very few talents is emulsion creation!
I know many people have pumped washed without acid and it's worked out fine for them. Give it a go ... what's the worst that can happen?
There are lots of ways of breaking an emulsion ... ask me how I know!
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I'll give it a go & report back.
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There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).
For KOH and other acid strengths you can mathematically adjust the result.
So am i right in saying that, if my vinegar is 4.25 acidity the multiplier would be 2.4 as to 0.12 for concerated acid?
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Well, so far so good.
I had a cloudy 100% conversion after stage 1 - 148 litres of very nice WVO, 20 litres virgin meth & 978 grms of KOH processed for about 90 mins & left to settle for 65. Forgot to mention in the opening post that I glyc washed this before adding any chemicals.
Dropped out 11 or 12 litres of glyc leaving 5 or 6 or 7, added 10 litres of very hot water with a splash of hydrochloric acid by venturi & no emulsion! For the first 20 seconds or so it looked like I was poaching eggs but that went away almost instantly & now I've got a sort of milky coffee coloured concoction circulating with no emulsion lumps.
I'll give it an hour & another hour to settle & then start pump washing. It'll be interesting to see if it does require fewer water washes.
Ideally I'd like to be able make a batch in 1 day.
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There is a rule of thumb which Carington came up with, which is multiply the amount of NaOH use in the reaction in grams, by 0.12 to give you the ml of concentrated acid circa (95%+).
For KOH and other acid strengths you can mathematically adjust the result.
So am i right in saying that, if my vinegar is 4.25 acidity the multiplier would be 2.4 as to 0.12 for concerated acid?
Sums have never been my strong point, but I make it 2.82. I don't think it's reall that critical.
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Well, so far so good.
I had a cloudy 100% conversion after stage 1 - 148 litres of very nice WVO, 20 litres virgin meth & 978 grms of KOH processed for about 90 mins & left to settle for 65. Forgot to mention in the opening post that I glyc washed this before adding any chemicals.
Dropped out 11 or 12 litres of glyc leaving 5 or 6 or 7, added 10 litres of very hot water with a splash of hydrochloric acid by venturi & no emulsion! For the first 20 seconds or so it looked like I was poaching eggs but that went away almost instantly & now I've got a sort of milky coffee coloured concoction circulating with no emulsion lumps.
I'll give it an hour & another hour to settle & then start pump washing. It'll be interesting to see if it does require fewer water washes.
Ideally I'd like to be able make a batch in 1 day.
Did/does that mean you were/are going to run the 7% wash for and hour? If so I think that is a little excessive. I usually only run the pump for a minute or so once the water is in.
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Yes, I ran it for an hour.
I'm no expert but I find it hard to believe that running it for a minute would be effective, or as effective as running it for a longer period even if it wasn't for an hour.
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When you do a 50/50 shake up water test do you shake it for an hour?
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Yes, I ran it for an hour.
I'm no expert but I find it hard to believe that running it for a minute would be effective, or as effective as running it for a longer period even if it wasn't for an hour.
It just needs mixing, nay, mingling together, not thrashing to death which is what happens each time it passes through the pump.
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The acid should be added to the first wash (after the 7% wash), otherwise you're trying to neutralize the gly as well as the soap.
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Julian,
To make sure we're on the same page I'm talking about the 5 or 6 or 7 litres of glyc with the 7% water. Are you saying that only needs to be run for a minute?
I'm sure I read on here somewhere in threads about 7% pre wash that the processor needed to run for an hour, which did seem rather long to me. The wiki page says 15-20 minutes.
The acid should be added to the first wash (after the 7% wash), otherwise you're trying to neutralize the gly as well as the soap.
That makes sense, thx.
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Julian,
To make sure we're on the same page I'm talking about the 5 or 6 or 7 litres of glyc with the 7% water. Are you saying that only needs to be run for a minute?
I'm sure I read on here somewhere in threads about 7% pre wash that the processor needed to run for an hour, which did seem rather long to me. The wiki page says 15-20 minutes.
The acid should be added to the first wash (after the 7% wash), otherwise you're trying to neutralize the gly as well as the soap.
That makes sense, thx.
I think about 10 mins was the generally the accepted time, but personally even that seem a long time to me. Then my set up seems prone to making emulsions since I fitted Frankenpump, so I err on the cautious side.
Like just about everything biodiesel, it's what suits you, your oil and your processor ... nothing's written in stone. I'd have guessed that with reduced glycerin (missed that bit before), 7% water and an hours pumping, there would have been an increased risk of an emulsion, but more power to you, it worked.
If you're happy with an hour stick with it. What seems to work for me is running just long enough to suck the water in plus a minute or so. It's what ever rocks your boat, but if you're looking to process in a day, it's an area where you perhaps could save some time.
I know Head Womble did some excellent tests with 7% prewashing and concluded that it was extremely effective. I think he tried various volumes and run times, so that might have been where you saw the hour.
Mark ... were your tests and results ever put up on the wiki?
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I guess it depends on the capacity of the pump, it needs to be at least long enough to turn over the contents of the tank, with a 30LPM pump and 150 litres thats 5 mins, back in the days when I washed I used to run 160L batch for 10-15 mins
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I know Head Womble did some excellent tests with 7% prewashing and concluded that it was extremely effective. I think he tried various volumes and run times, so that might have been where you saw the hour.
Mark ... were your tests and results ever put up on the wiki?
Julian, my testing on prewashing was rather limited, however what did come from the tests was that the prewash greatly reduced soap PPM (my tests were also checked by NigelB).
I can't remember the numbers right now but they were posted on here, I think on the acetone wash thread.
A wiki page was started but due to having to move my setup and now having limited time I never finished it as I wasn't happy that it was comprehensive.
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If a wiki page was started, I can't find it. It must have just been a forum thread.
Provided you'd run enough tests to prove its efficacy, which I seem to remember you did quite conclusively, I don't see that anything more is required.
Have you got the thread bookmarked?
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No bookmark.
The thread was about acetone washing.
If my memory is working I think I removed the wiki page (due to not being complete) but had it saved on my PC, alas it would have been lost when the hard drive gave up.
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I'd be interested to know peoples thoughts on whether a pre wash is worthwhile if you are demething and settling out the soap. I've done it both ways but I'm leaning towards not bothering with the pre wash because 1 I suspect the methanol you recover after a pre wash is watery, and 2 I put the glyc into my wvo settling tank so my guess is it would do more by way of dewatering the wvo if it wasn't already full of water from the pre wash.
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No bookmark.
The thread was about acetone washing.
If my memory is working I think I removed the wiki page (due to not being complete) but had it saved on my PC, alas it would have been lost when the hard drive gave up.
Found the thread ... http://www.biopowered.co.uk/forum/index.php/topic,860.0.html all 15 pages of it.
And found a pertinent wiki page ... http://www.biopowered.co.uk/wiki/Using_acetone_to_aid_soap_removal
Was it the acetone page you were referring to or one on 7% water wash tests?
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I'd be interested to know peoples thoughts on whether a pre wash is worthwhile if you are demething and settling out the soap. I've done it both ways but I'm leaning towards not bothering with the pre wash because 1 I suspect the methanol you recover after a pre wash is watery, and 2 I put the glyc into my wvo settling tank so my guess is it would do more by way of dewatering the wvo if it wasn't already full of water from the pre wash.
If you try to recover methanol after a 7% prewash, it will be unusable. However, there's nothing to stop you recovering it before the wash, I do that it the time. As far as I can tell it has no detrimental effect.
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This is the thread I was referring to.
http://www.biopowered.co.uk/forum/index.php/topic,995.msg11072.html#msg11072
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This is the thread I was referring to.
http://www.biopowered.co.uk/forum/index.php/topic,995.msg11072.html#msg11072
Some really good data there it would be a shame not to have it available on the wiki.
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An update after trying 3 batches using 7% pre-wash.
Pretty much got this nailed down now & am pleased with the results.
Yesterday's batch was 140 litres of disgusting, stinky crap that I have been saving over the winter, waiting for hot weather. Some liquid, some solid, some very solid, LOTS of bits of batter & other crap, and wet.
Heated & circulated, dropped out 5 litres of water which apparently wasn't all of it judging by the 1st stage conversion ratio, glyc washed with 18 litres.
16% methanol, 5.8gpl KOH, poor conversion with 45% drop out. Using same ratio of meth & KOH got a cloudy 100% conversion on stage 2.
Left the new glyc in & venturi'd in 10 litres of hot water for a 7%-ish pre wash, circulated for 15 mins & when dropping it out after waiting an hour I took a little more out than was strictly required to make sure I got all the soap. Doesn't really matter as I run all the water wash drop out through a settling Burco to recover any fuel for the next batch.
This seems to have worked well as 3 x 15 litre hot water washes @ 70-80 degrees later I had a crystal clear 50/50. The high temp also saves time & speeds up the drying stage when I get to it.
In the past I've been frustrated by having to do too many water washes, sometimes w. washing would take as long as every other part of the entire process combined. Now with this method I can make a complete batch in one day, albeit a long day if I use sh1te oil.
BTW, never had an emulsion (3 batches) & now do not introduce any acid or anything else to prevent one. It seems to work fine without acid.
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Just fine tuning this a little bit.
Made a batch today & after stage 2 was completed I went straight to the pre-wash without waiting for the glyc to drop & without doing another 10/90. Turned the machine off at the end of stage 2 & immediately venturi'ed in about 10 litres. Figured I'd got the calcs right so the conversion was complete & there was no point waiting for glyc to drop when I was only going to mix everything up again.
Worked fine, no emulsion.
Just as a control I'll do a 10/90 tomorrow after I've finished the 4th & final water wash & dried it. My car would run on VO so it's not really a big deal either way.
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Well done!
It's gratifying when a plan comes trogether.
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Anyone ever done 2 x 7% pre-washes on the same batch?
I did last night after making emulsion. It finally cleared this morning & I thought I've probably made a shit load of soap from all the acid so I'll just start again.
Seemed to work pretty well. 4 x 15 litre water washes later I had a 50/50 pass.
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Struggling to understand two 7% washes.
A 7% wash is done by adding water to the bio before the glycerin is settled and mixing for a period. Glycerin and water are then settled and drained off.
Anything after that is simply a wash.
Chemistry isn't my strong point, but can you make soap with acid ... I thought it required a base.
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Soz, didn't make that clear.
I drained everything that wasn't BD after the emulsion had disappeared, added some first stage glyc back in & 7% water & started the water wash cycle from the beginning, again.
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Ah, I see.
Unsurprisingly ... no I've never done that!
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Never had an emulsion?
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Errrrr ... one or two!!
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The last time I had an emulsion I didn't do 2 x 7% pre-washes & ended up doing about 14 water washes.
This, apart form the hiccup with the emulsion, was the normal amount of water washing. I may be wrong but I can only think it was the second pre-wash taking out the majority of the soap that made the difference.
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Mark has proved the efficacy of a single prewash quite conclusively.
Perhaps similar tests should be done for a double wash, ie with soap tests before and after the washes.
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That would be interesting.