Settle tank / separator ponderings

[Tony]

I've been pondering this one somewhat.

I've got two large steel tanks thanks to Mark, plan is to convert one into a big processor (work partly under way for that already) and use the other as a settle tank for the finished product.

My problem is that currently I use 120l drums for settling and periodically I have to clean them out of solid soaps at the bottom.  Not so easy on a large steel tank.

What if, instead of settling in a separate tank, I settle in the processor?

With NaOH this would lead to blocked pipes, but what if I leave the bottom valve open but into a hard plumbed steel tank below the reactor to capture soaps?  They'll settle into that rather than block pipework then.  Of course then we're into the territory of how to empty that out of soaps - but perhaps if it has a water coil in it I can melt them out?  It may also be able to double as a Glycerol separator.

Of course that does tie the processor up for the duration of settling, but then I've only got enough storage for one batch to settle at once anyway.

[Julian]

Go back to the seperate sellting tank idea and investergate CIP (Clean In Place) or COW (Crude Oil Washing) type systems.  Both a bit like an eratic, high pressure/volume lawn sprinkler.

[julianf]

When you empty your current tanks, how solid is the soap?

My soaps (etc) are never that hard.  I leave the 205 ltr drum on a tilt upside-down, and it 'slimes' its way out (and then it goes back into the reactor with the pre-process glyc wash, and comes out again with the glyc)

Anyhow, if yours is never *that* hard, then, so long as you have a wide enough bore pipe on the bottom, with the weight of the bio above it, id think it will come out.   However, i dont think it will be perfect, as there will be some on the slope of the (i assume) cone etc, in the same way as it settles on the ridges around the insides of a standard clip top.

[Dickjotec]

I settle in a clip top and have no difficulty using a spade to cut up what settles and dig it out. I only have to do it about 3 times a year. I do use NaOH it might not be so easy with potassium.
Dick

[Head Womble]

I've got an easier solution, titrated acid pump washing, followed by an acetone wash.

Come on, even Jim's trying it.

Julian, funny we were only talking about high pressure washing the other day.

[Rotary-Motion]

put a tray type vessel in the bottom and when you need to get the saop out pull it up on wires, something size wise it just drops in the diameter

[Tony]

I quite like the tray idea.  Good lateral thinking that is.

Would work great on my current settle drums but this steel tank is domed top and bottom with only a smallish aperture for access.  Sure I could make it bigger with a grinder but I do quite like the idea of being able to seal it to stop the stored bio from oxidising.

[julianf]

How much pressure would you be happy with?

Even a slight pressure will move any gloopy stuff from the tank.  You just need to be *real* quick on the valve when it moves!

[Tony]

I'm imagining a 1" valve with the weight of bio over it won't shift anything, you're thinking compressed air?

I think the tank is rated to 10 bar (before my welding weakens it anyway) but my pants certainly aren't

[Jamesrl]

I'm imagining a 1" valve with the weight of bio over it won't shift anything, you're thinking compressed air?

I think the tank is rated to 10 bar (before my welding weakens it anyway) but my pants certainly aren't

Check out the skid mark barcode in the back of your pants to find out what farting pressure they'll take.

From that info you should be able to calculate the total SWP of'm.

[julianf]

I still think the main issue isnt blocking the pipes, but the residue that settles out on the sides of the cone etc. and will then get mixed in with your product when you pump out the bio.

[Tony]

I still think the main issue isnt blocking the pipes, but the residue that settles out on the sides of the cone etc. and will then get mixed in with your product when you pump out the bio.

I was thinking (in addition to a possible drain valve at the very bottom) of having two valves up the side, one just above the other).  Bottom valve you'd drain off any HMPEs/monos/whatever until it runs clear, then the one above it goes to wherever you want the fuel.  It would be fine to always keep a pool of bio at the bottom (even if it's 100l or so) and the the batch size of new fuel to settle just sits on top of it.

The bottom drain would only be for occasional hardened soap draining (if such a thing is possible through a valve - this is the bit I'm not convinced on - some of my NaOH settled soaps are fairly hard and have to be cut out with a spade/trowel).  This is why I'm thinking of a separate sedimenter for it all to drop into.  I have a rather nice 55l tank for this with integrated coils.

Here's the top of it - it could lay on it's side:



I originally got it for making a pumped Methoxide mixer but for bigger batches I'm just as happy mixing up a few 25l drums worth of Methoxide on one go.

[julianf]

Its curious - i have 2-off those 400ltr why-waste stainless pressure vessels.  I bought 2-off as they seemed like a good thing to get. 

One has been my reactor ever since, and the other....

...im still trying to work out what to do with!


400ltrs is too small for bio storage (ive accquired a 1200ltr oil tank for that) and, personally, i have no real issue with a couple of 205ltr clip tops for settling (although i have considered the 400ltr tank a number of times!)

I think, eventually, it may end up as a buffer tank / thermal store for our home central heating system, and not be used for bio at all!