Drying Bio

[Julian]

Been thinking.  Bit of a strain for me these days and probably a deeply flawed thought but … glycerine has an affinity for water and it seems to dry oil reasonably well.  If that's the case could it be used to dry bio too?

Would be simple for someone with a water test kit to check out … Dave.

If it works, the whole bio making process could then be carried out with minimal energy input … Dave's ambient processing and periodic mixing.


Waiting to be shot down in flames!

[dgs]

Good idea Julian but it won't work. It will dry it but also contaminate it with soap and glycerine and probably unreacted oil.

i've used pure glycerine before water washing and it gets rid of soap really well. It can be used many times before the soap content gets too high to be any further use. Big downside is the price of the stuff.

[Julian]

Do we know that the bio will have a greater propensity for soap than the glycerine? 

I'd have thought given the proven efecacy of a glycerine/water wash to remove soap before full water washing, it's got to be worth a try.  In any case the soap will settle out in time as will any glycerine.

[dgs]

The soap would rather stay with the glyc, but as the glyc contains roughly 35% soap inevitably some will be left in the bio. As you use sodium any soap would settle quicker than K however your spec for Na soap is something like 44ppm. I think you will have to wait a long time for it to settle to that level.

Give it a try, do you have a soap test kit.

[Julian]

Yes somewhere … I'll see if I can find it.

[nigelb]

I've not got any kits left but I'm sure I've got a full bottle of bromophenol blue knocking about somewhere.

[Julian]

Thanks, Nige but I know I still have some left … somewhere.

[dgs]

Just some thoughts here;

When I do my version of the 5% prewash I estimate the amount of suspended glycerol still in the mix after S1. This is usually about 3.5 litres after overnight settling.

After the methoxide addition on S2 which is usually around 500mls I mix for 1 hour then add 4 litres of water which creates about a 50/50 mix of water/glycerol.

Instead of letting the wet glyc just settle I bubble very gently. This bubbling action seems to separate the wet glyc from the bio much more efficiently than just settling. So much so that after bubbling for about 18 hours the soap level is in spec ie <66ppm.

I still then water wash once or twice to get clear wash water, leaving the bio (after excess water has fallen) at about 1200 ppm water.

I'm wondering if an extended drying period without heat would dry the bio enough. Using the turbo dryer with dried air may work if it were left on for several days. I'll try it on the next batch, changing the silica gel probably about twice per 24 hours.

[dgs]

I'm on with a drying cycle at the moment (without heat) I'll put the method and results on a new thread when I know something.

[Julian]

I tried drying a couple of bio samples with glycerine.  The glycerine used was as drained after first and second stages and it hadn't been used for washing oil.

Sample one was from a batch sample which had lost all the orange juice appearance and the other from the processor which had sat for a couple of weeks whilst I drained water that dropped out, but still had the orange juice appearance.

I shook up both samples and after a couple of days they both had reasonably clear bio sitting over a bottom layer of glycerine.  I soap tested the washed and undried batch sample and got an instant yellow colour … so very little soap.

The same test on the "non orange juice" glycerine dried sample, as far as I could acertain (I've always found judging the colours in this test difficult as they are so subtle) gave a value of 4560ppm.

So you were quite right, Dave.  Although it certianly seemed to dry the bio it did add back a considerable amount of soap.

Yet another heroic failure!

[dgs]

At least your expt gives us an answer.

There is a way to do this but it takes a little work to 'de soap' the glycerol.

Crack the glycerol with conc sulphuric. Separate the middle layer of 'spent glycerol' it will be acidic so needs neutralising with K or Na in water or methanol.

It will then be wet so needs drying, then you could use it to dry your bio.

I used to buy this spent glyc from Prime Power in Pickering when they were in business. i used it to de-soap my bio.

There is a company called Brocklesbys in North Cave (nr bridlington) they had a plant that
used to produce bio from glycerol. It may be worth a phonecall for some spent glyc.

[Julian]

Interesting, but it sounds more economical and much less hassle to spend a couple of quid heating the bio!

[dgs]

No getting away from it, the electric method is the most convenient.