Centrifuging Biodiesel

[dgs]

The replacement pump should be coming mon or tues, so at the moment I can't do any centrifuging.

So just to summarise re the last batch (190 litres)

De-methed with the compressor, then bubbled for 12 hours. all glyc was removed, then settled for 48 hours.
At this point the soap was 83ppm. I then centrifuged it once (with fuge at only 70psi) it did remove quite a bit of glycerol, but as liquid, not as a paste) after fuging the soap reduced to 70ppm.

I then fuged it again with the smaller jets fitted at 100psi and about the same amount of liquid glycerol was removed. the soap level was then 35ppm.

It was then left to settle another 48 hours (couldn't re-fuge because pump returned) and ran off the glycerol in the bottom pipe, there was 12mls.

I've then left it another 48 hours and this morning there was 3mls of glycerol in the bottom pipe and the soap level is down to 15ppm.

Now I don't know how accurate these next figures are but obviously there is a correlation between residual soap and glycerol left in the bio. I suppose at this point we should really call the glycerol (glycerine) as there is no methanol left.

when I have 'cracked' glycerol using concentrated sulphuric I have found that roughly @ 30% of glycerol is soap ( from the amount of ffa layer and titrating the layer) if this is indeed correct then my last soap titration of 15ppm (which I think equates to 3mls in a 200litre batch) means that there is another 9mls of glycerine in there.

I may be 'way off' with my thinking about this relationship, but what is interesting is the en14214 specs re soap and free glycerine. soap (koh derived) 66ppm free glycerine 200ppm.

I will centrifuge the batch again when I get the pump and as long as it gets up to the correct pressure I hope that will result in leaving the glycerine as a paste on the sides of the bowl.

[Chug]

No accurate measurements Dave, but from my observation of glyc that had been sitting for a long time was roughly a third brown soapy phase and two thirds black phase, and IIRC previous experimenters with glyc contents also arrived at similar third soap.

I think Paul Carrington has some experience of gly cracking but I may be confusing him with someone else.

[dgs]

Good to know Chug, thanks for that.

I have cracked glycerol a few times, not to recover ffa's but to obtain the 'spent glycerine' as it is void of soap.
I used it to de-soap the bio before water washing, as indeed I did with pure glycerine. However with a bit more experiance and patience I now just de-meth which usually reduces the soap to <100ppm if it is left to settle a while. Then I decide if there is enough time to just let the batch settle or if I should water wash.

I just used to add the sulphuric at 4% to the glycerol in cubies and leave them in the sun. I found separating the layers was a pain. I think a tall, narrow plastic conical is best with a series of taps on it. It needs some heat to be efficient.

When my friend 'Russ' was in business producing bio commercially from glycerol, he had 4x 10000 litre tanks for cracking. he kept the glycerol at 90degs for 12 hours (after de-mething) he used to use 2000 litres of conc sulphuric per week and get his glycerol in 28000 litre tankers. A big set up but economics caused him to close.

he built a still for the bio, it was nearly like water to look at, it used 80k/w of heat!

[Julian]

Didn't Jules indulge in that for a while?

[dgs]

I'm sure he did, the ffa layer makes good burner fuel.

[dgs]

I would certainly agree that centrifuging WVO through a pressure driven device would not be a good idea. With bio I'm not so sure.

I have recieved the new pump and set it up yesterday. I'm pleased to say it easily pressures up to 100psi+ and still with about 2 litres /min going through the by-pass.
When switched off the fuge now takes 70 seconds to come to a standstill. The glycerine left in the bowl is left as a liquid and not a paste, so not as easy to quantify the result.

Because of this, as the fuge is running down I lift it onto a small container so no contaminated bio runs into the tank.

I've just been calculating the specs again re soap and free glycerine, 66 and 200ppm. On the face of it these seem reasonable amounts, but together they equate to 61mls of glycerol left in a 200 litre batch which seems a massive amount.

The next time I centrifuge a settled batch I will do soap tests before and after to try and calculate the amount of glycerine left in the batch.

[dgs]

I centrifuged the last batch after washing and drying and sure enough there was a very small amount of glycerol left in the bowl. Strangely enough it is quite liquid whereas on the last smaller fuge it had to be wiped off the bowl.

This being the case, I am aware that as the fuge decelerates some glycerol could run down and weep through the exit (jet) holes. (now it is up to pressure of 100psi it takes about 75 seconds to stop) so I am ready with a small tub and as the fuge runs out of liquid and starts to wind down I lift the fuge onto the tub. I let it drain then wash all the parts down into the tub with a wash bottle containing bio.

My intention was to let the contents settle, pour off the excess bio then transfer the last @ 50 mls into a separating funnel and measure the glycerol. I duly did this and kept checking the tube for the dropped glycerol but there was none there. Then I noticed a small pool on the bench and the bottom tap had been leaking, damn.

I will repeat on the next batch and hopefully quantify exactly how much glycerol the fuge has caught.

[Bio-boy]

Dave, whether or not you are looking to purchase a centrifuge from them their site is very informative and may help diagnose some of your problems and assist with setup:

https://www.oilybits.com/downloads/OILYBITS_CENTRIFUGAL_FILTRATION_HELP_SHEET.pdf

https://www.oilybits.com/downloads/OILYBITS_OB_SERIES_CENTRIFUGE_SERVICE_INSTRUCTIONS.pdf

I've actually been in talks with them this week with the intention of purchasing an OB-050 wall mountable kit.

It's great to see all your investigative work into perfecting each and every batch of Bio that you produce.

I will be posting another sample to you tomorrow for testing.

[knighty]

careful, the wall mount ones make a hell of a noise - the vibration from them resonates through the wall

(or it did in the one I saw/heard anyway)

[dgs]

I'm sure you are correct knightly, the resonance created by my fuge can be ear shattering, If it's in that mood I put a couple of silicone pads between the mounting plate and the base. The buzz at 100psi can be too much.

I will expect your sample Bio Boy.

Since switching over to the big fuge I have realised that what I thought was slight glycerol contamination in the small fuge was probably corrosion out of the bowl, sorry if i confused anyone.
I cleaned out the bowl a couple of days ago after centrifuging about 760 litres of finished bio. It was totally clean, absolutely nothing in it. It seems as if aggressive water washing creates a product that is virtually contaminate free.

[Jamesrl]

careful, the wall mount ones make a hell of a noise - the vibration from them resonates through the wall

(or it did in the one I saw/heard anyway)

And even noisier if you mount it on a drum, the only way I got one quiet enough to use was to suspend mine with bungie band from a roof joist in me shed.

That is the sole reason for making a bowl fuge.

[Bio-boy]

I'm going to fix it to he wall with rubber dampers.....

http://www.ebay.co.uk/itm/LAND-ROVER-DEFENDER-90-110-130-AIR-FILTER-MOUNTING-RUBBER-COTTON-REEL-ERR2337-/131613309740?hash=item1ea4c3bb2c:g:WGMAAOSwxCxT42~d

It's going to be placed inside my garage and when in operation I don't necessarily need to be in there. On the odd occasion I need to be I'm sure some ear muffs could be on hand to help me overcome any excessive noise.

[knighty]

you'll be ok if the garage is detached... not much good if it's on the side of your house :-o

don't want to slag them all off.... but the one I saw made the garage walls hum from the outside... no biggie because it was detached but a bit of a pain if it's on the side of your house :-o

[Bio-boy]

It's a good job it's a detached garage then. 

[dgs]

I did get a lot of information from the oilybits site when I was setting the thing up. What I would say Bio-Boy is that unless you intend to go the bubble/settle route (which in the long term is what I am looking at) then from what I have found centrifuging well washed and dried bio seems to be a bit of a waste of time. Nothing gets left in the fuge because there in nothing in the bio to get left in the fuge.

A 200 litre batch takes about 20mins to go through, so the buzzing doesn't last for long.

Be careful with your pump selection, most do not give the output that they say. If you use a 50 size it will be the same as mine(I think these things are mostly manufactured by the same people) and to get the thing spinning at 8000rpm+ to do the job with bio you will need to create 100psi in the hydraulic line feeding the fuge.
The oilybits site recommends the puisi viscomat 200/2 pump and from experience this will not supply enough pressure to do the job (even though its' spec suggests it will) So i ended up using the 230/3 and even then it only has a little to spare when running at 100psi. You can really hear the gears churning hard as the by-pass is wound in to get it up to 100psi.

Just to clarify some of my earlier posts. I reported that after fuging my bio with the old smaller oc20 dieselcraft fuge that I found a small amount of brown/black residue in the bowl (which I did) however the anodising on the bowl has started to deteriorate and i think what i was looking as was tiny pieces rust that I had wiped off. Sorry if I confused anyone.