De-meth times

[Adamski]

How long does de-meth take you guys?
I do 180L batches use 20% methanol and not WBD and it takes me 3hrs to reclaim 8L consistently.
I use a homemade condenser which is 4 PD's together
I find this the worst bit of the whole process, its boring and costs on electricity.
Has anyone got any ideas on reducing demeth times, without going into over complicated stuff like flashing squirrel evaporaters. I was thinking of building a new condenser, but this could be costly (more than a tenner)  and time consuming.

[K.H]

Have a word with Julian about how he does it,he should be along soon

[Tony]

Takes me about the same time.

Didn't Julian experiment with air bubbling the hot bio in the processor to get more vapour out?  Makes sense as the rising air bubble will surely pick up a lot of Meth on the way. I seem to remember that you could overload the condenser if you bubbled too much which sounds great to me.

[K.H]

Yes he runs a compressor,i nicked his idea for drying my oil

[Julian]

Slow demeth can be caused by several things.

You can check how the condenser is performing by fitting one of these ... http://www.biopowered.co.uk/wiki/Tips_and_wrinkles_1#Condenser_tell-tail  if it's inadequate you will see carry over collecting in the jar.

If the condenser is not carrying over then it has to be the flow round the vapour circuit.  I've tried several designs of venturi and I'm now using a four port unit which is slightly better than the standard design.

However the other item which could effect things is the pump.  I use a Leo pump and I'm starting to suspect that the performance of these pumps is poor compared to a TAM.  I now use the Leo and a small Mono in parallel to get better performance from a venturi with the standard 8mm throat.  The difference in vacuum between running one and two pumps against a closed valve is quite marked.  But I don't know the flow rate.  Even with two pumps and the four port venturi, I still don't get carry over from a twin condenser.

I have tried introducing low volume and low pressure air and it does improve things but I believe it creates a dangerous situation by changing the atmosphere within the processor from over rich to flammable.  Best keep the introduction of air for drying oil, a task which it performs very well.

[Adamski]

Yeah, I definitely get carry over from the condenser. I can see it in my vapour return line. I've tried throttling the venturi back using the valve but I can't see any improvement.
Looks like I'm going to have to improve my condenser.
Would a condenser made from 4 lots 8mm copper pipe twisted in a spiral and then housed in a larger pipe for the water be better than my quad PD? I think I could get quite a large length of 8mm pipe coiled up in a 4" pipe. I've seen people are using similar designs to this, so hope it works, a project for the winter nights I think!

[Tony]

You'd be better off with a single 25ft coil of 12mm microbore in a big water tank.  Can't contest that for dwell time and surface area, and no need for pumping.  It's what I'm building for my 500l processor

[Julian]

There could be other issues at play.  Does the condensed Methanol and air flow have a good chance to separate?  On my condenser I have a plenum to allow separation.

What sort of Methanol flow do you get from the condenser, if you can see it?  Drips, continuous trickle or a good flow?  I'd describe mine as a continuous trickle.

[Head Womble]

What volume is your water supply, does it get warm towards the end ?

[Carrington]

When I'm de-mething I only use a compressed air bubbler but I do put the air through a heat exchange so its nice and hot when it goes through the bio. My condenser is 2M 3" pipe with 2 1/2 pipe cooling pipe inside x 3 length's running horizontal , the meth flows out lovely

[Tony]

Sounds like a scaled up GL... do you WBD?

[Carrington]

No but my whole process is rather different to the main stream.

[Tony]

Would you be willing to share the process with us or is that a trade secret?  You've piqued my curiosity

[Carrington]

Hi tony
Ive sent you a message

[Adamski]

Tony - sounds interesting and simple. How big is a large tank? 500L? I take it that you plan on just submerging the micro bore in the tank and have the venturi drive the vapour flow they it and the water just stays in the tank?

Julian - my processor was built by jrl so just what he does as standard. There's probably a few inches from the T-piece for the vapour return and the bottom of the methanol pipe which is in the collection drum. I would descibe it as a continuous trickle. What is a plenum?

Mark - Yes my water tank warms up (200L water butt) when it was in the garage next to the processor it would rise about 10c by end of demeth. I have now moved it outside the garage, with about a 3metre run from condenser. I haven't seen a improvement on demeth times tho.