Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: Bio-boy on January 19, 2016, 10:36:16 AM
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Does anyone do this or has at least tried it? I'm curious as to the importance of heating the bio prior to washing. Is it really a necessary process or is it an unnecessary use of energy.
Interested to hear your thoughts.
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I have done it a few times, even at this time of year, where the bio temperature was <5degs. It's not really a good idea, it will take more washes and increase the chance of an emulsion.
I usually water wash at around the 30deg level. Having said all that the whole washing process mainly depends on the starting level of the soap.
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I mist wash all year round outside, sometimes as soon as the glyc has dropped so still warm, sometimes the next weekend, it all ends up the same temp as the water pretty quickly anyway
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I always bubble wash down to ambient temp, which means I'll always have a couple of cold water washes. Doesn't cause any problems washing cold from my experience.
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Unnecessary use of energy IMHO, many years ago when I washed my bio I always used cold water from the tap, hosepipe spray gun on fine mist for the first 5-10L and then slowly open it up to full pressure rain mode.
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i always use hot water in my hot bio I say that because as soon as the glyc settle out around 30 mins its washed I just add 20lltrs water to around 160ltrs bio and paddle wash it for 5 mins works great and settles out in 5/10mins
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Water washing seems to improve cold weather performance of bio ref. a load of tests I did on HMPEs and put on the VOD. So for many years I've water washed using the processor pump.
Since fitting Frankinpump, I've had problems making emulsions (perhaps more accurately had no problem making emulsions), so I add sulfuric acid to the first water wash.
Where I can, I try and wash immediately after processing while the bio is still hot, but I always do so with cold water. On occasions when the bio's cooled I've noticed no detrimental effect (other than it's easier to make an emulsion).
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Well I decided to give it a whirl this morning. Having finished the 2nd stage reaction last Sunday I started washing this morning - Bio cold and water cold. What I did notice was that there was a lot more soap present than usual. I only had time for 2 wash cycles so not yet finished the process.
The presence of more soap could be one of two things......either it's the cold wash process or having deviated from my original processing protocol of completing a water wash cycle on completion of the 2nd stage reaction to kill any over reacting and hence excess soap production. I'm going with the latter.
I guess we won't know till I make my next batch.
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Well I decided to give it a whirl this morning. Having finished the 2nd stage reaction last Sunday I started washing this morning - Bio cold and water cold. What I did notice was that there was a lot more soap present than usual. I only had time for 2 wash cycles so not yet finished the process.
The presence of more soap could be one of two things......either it's the cold wash process or having deviated from my original processing protocol of completing a water wash cycle on completion of the 2nd stage reaction to kill any over reacting and hence excess soap production. I'm going with the latter.
I guess we won't know till I make my next batch.
Are you pump washing in the processor?
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Nope. Misting.
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Bio-boy,
The presence of what you think is more soap is possibly mono's, more noticeable because of the lower temperatures. Don't think I'm trying to push my or others methods on to you but when you get clear wash water with misting, it probably wouldn't be clear if you re-washed with your pump or a compressor. Really churning up the bio and water for 20 mins and then having clear wash water is (I have found) the way to guarantee soap levels of 10 to 20ppm and therefore less of other contaminants. (unless like me you end up with insoluble calcium soap in the bio, but thats another story)
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I've noticed since fitting Frankinpump and acid washing, the acid wash and one, possibly two subsequent washes are reasonably clear, the water having a slight bio coloured tint to it.
Further washes usually result in milky water and what looks like a thicker milky interface layer. I take this as being the start of an emulsion. If I leave the pump running for more than a couple of minutes an emulsion will result ... it's obvious it's an emulsion because it will break with acid.
If at the point of getting milky wash water, if I add a small quantity of acid to the next wash, the drained water returns to clear.
Does this sound similar to what you're seeing, Dave?
I also suspect that bio that's been emulsified and broken with acid is far more difficult to dry.
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Doesn't adding acid increase the soap? Always seems to, and massively, when I've had to break an emulsion using it.
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Bio-boy,
The presence of what you think is more soap is possibly mono's, more noticeable because of the lower temperatures. Don't think I'm trying to push my or others methods on to you but when you get clear wash water with misting, it probably wouldn't be clear if you re-washed with your pump or a compressor. Really churning up the bio and water for 20 mins and then having clear wash water is (I have found) the way to guarantee soap levels of 10 to 20ppm and therefore less of other contaminants. (unless like me you end up with insoluble calcium soap in the bio, but thats another story)
Dave, why would using the pump not create an emulsion with the presence of water?
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Doesn't adding acid increase the soap? Always seems to, and massively, when I've had to break an emulsion using it.
Not that I've noticed. Can you make soap with an acid?
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I don't think that adding acid can increase the soap, it converts the soaps to ffa's which is why it washes easier.
BB, why not try to pump wash your next batch after you have mist washed it, you may be suprised what it removes. Just make sure your pump system is purged of glycerol before you do it.
Just been reading the posts on this thread properly. It is impossible to create an emulsion mixing bio/water however aggressively if the soap level is low. Some pump wash from the start, using initial small bursts of only 30 seconds, building up to 20mins over several washes.
I have never fitted my wash tank with a pump which is why I use the compressor, my 1st burst of air is usually 1min and over 4 or 5 washes build the time up to 20 mins. I try to leave the mix to settle for 30 mins between washes. When the wash times build up to 10 mins, after settling I notice the emulsified layer between the water and bio. This is removed after the water and set aside to settle. It totally separates after a day or so into about 2/3 to 3/4 water and the rest monoglycerides (lets call these 2/3 converted bio) The mono's are poured into the glycerol for the next wash.
The mono/water layer is never the same amount batch for batch. If the batch is just on the 'cusp' of the 10/90 pass, they will me more. If too much chemical has been added to the last reaction then they will be less. The longer the batch is mixed for then the less chance of getting a lot of them.
Getting rid of the mono's depresses the temperature at which the finished bio will mist/gel and is very dependant on the water level of the finished bio.
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I don't think that adding acid can increase the soap, it converts the soaps to ffa's which is why it washes easier.
BB, why not try to pump wash your next batch after you have mist washed it, you may be suprised what it removes. Just make sure your pump system is purged of glycerol before you do it.
I thought pump washing would be too aggressive and create an emulsion. If that is not the case then I may well give that a try. How long does it take for the water to drop following pump agitation?
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I thought pump washing would be too aggressive and create an emulsion. If that is not the case then I may well give that a try. How long does it take for the water to drop following pump agitation?
Around 30 mins, but generally a longer time for longer washes.
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What prevents an emulsion from forming?
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What prevents an emulsion from forming?
basically by washing in an appropriate manner/time for the amount of soap the bio contains.
I have only compressor washed for the last few years and have found if the de-methed bio is settled so that the soap is less than around 400ppm an emulsion will not form even if the 1st wash is 5 mins. I once tried washing my bio with soap at 1350ppm and got an emulsion within 30 seconds.
It's a bit of a balancing act doing a really aggressive wash, but once you know what you are doing it beats bubbling/misting every time.
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I've always done an aggressive wash I use a 5 inch twin blade paddle running at 2850 rpm. I add 20ltrs hot water to 160ltrs of bio and wash 5mins first and 10mins second wash and the wash water
settles out in around 5mins