Stirring the settling bio

[Tony]

Might seem a bit counter-intuitive but I've been trying this with good results.

I noticed that bubbling helps with settling, long after meth has been driven off. Sometimes putting drums in the boot of the car where they jiggle around during transport settles a little soap extra out.  The last two batches I've let to settle for a few days, then violently stirred up with a drill and paint mixer (lots of nasty froth on top), left a few more days then done the same thing (much less froth on top).

The resulting bio has settled really well, lovely and clear and very little soap, much quicker than if just left - I think.

I wonder if mixing it all up encourages suspended soap molecules to stick to the larger bits which then settle faster?

[Dickjotec]

Interesting how long did you mix for? I might try it with the next batch.

[dgs]

Hi Tony, I noticed in a previous post you mentioned something about estimating the amount of soap from the amount of bubbles you get when pumping the bio.

I have noticed when doing my version of the 5% prewash the wet glycerol splits after bubbling for a few hours. What then falls looks more like soapy water than wet glycerol. In this respect I'm sure you are correct in that after bubbling and removing the glycerol there could be some soap left in the mix.

Soap tests before and after your mixing proceedure would be good.

[Julian]

I wonder if this is another possible use for an ultrasonic transducer?

[Tony]

Literally just a 10-20 second blast with the mixer until I've seen it all turn over a few times.  It's quite a big paddle so the whole batch really swills about.

For final stage filtering I did have a mono pumping out to 25l drums which was too gentle to see the state of the finished bio, I've switched back to a noisy and violent vane pump and can see from how quickly the bubbles disappear from the filtered bio how soapy it is.  There is a definite relationship between bubble longevity and soap level.  If I set aside filtered bio that hasn't had the bubbles all disappear on their own, more soap will drop out in the coming week.  But if the bubbles all pop immediately and it goes back to a smooth liquid surface, that's good to go and I don't get further soap dropout.

I have thought about trying to put some kind of loudspeaker in a plastic bag into the settle drums to see if that helps too.  Maybe singing to it would help?

[Julian]

Garage might be appropriate.

[Tony]

Garage might be appropriate.

Or drum and bass.

[photoman290]

what about a bit of grunge.?

how about just pumping it though the vane pump straight back into the barrel.

[Tony]

I used to leave a small pump on turning it over many many years ago but that failed sadly.  And I worried that a connection coming off would lose the batch.  I guess a CH circulation pump would achieve the same thing.

[Tony]

The last two batches I made I didn't bubbled for 24h while still hot (fresh out of the processor), but did stir a couple of times with the paint mixer.

One has settled OK, bit slower than normal, one is still extremely soapy.  They were made days apart.

I suspect this is because the bubbling while hot is important to drive off trace methanol, so I should probably carry on doing that.  (I only demeth up to 90c to avoid water in the distillate).