Further Fractionating fabrication Frustrations
- A question for anyone who can help.
If I retrofit my reflex still with a condensing unit that allows
recirculation of my distillate to promote fractionization (if that is a real
word), how do make sure that the distillate actually recirculates and
doesn't just pool? An additional concern is pressure build up in a looping
I have seen two designs. One has basically a cooled extension of the column
with a valve to the regular condenser. My guess is that this valve serves
as a pressure relief primarily, but I imagine there is a degree of vapor
that passes through and is not recirculated. The second design is basically
a condenser with an open top which the vapor enters at a mid-point, rises,
hopefully condenses before it exits and then trickles back down into the
Reflux column via a port in the side just above the packing. I assume this
design is open ended so as to allow for pressure relief.
In the first example I see how the distillate simply flows back, and I
imagine the amount sent on to the condenser is of little significance, but
there is loss none the same. The second system raises concerns for me as
well. Is the loss of vapor through the open top a concern? I would guess
it would not be if this unit is tall enough, but how is this gauged?
Additionally, since this unit is an external loop, isn't there going to be a
problem with column vapor rising up through its outlet as well as its inlet?
Maybe I am over thinking all of this, but I want to get it right. Which is
better, are these real issues, and are there other designs I should
Finally, wouldn't increasing the flow rate through the coil in the head of
my still accomplish the same thing as either of the above?
Thanks for your help with all this. I hope it doesn't keep you up at night.
I need to let it go and get back to Sundays sermon as I haven't figured out
how fractionating columns relates to Palm Sunday.
AFAIK the way to stop the pooling is to make sure that gravity is
working for you. Introduced back into the column, the condensed
liquid will fall back down the column before turning back into vapour
and rising back up again.
Pressure release - yes, that's the reason for the open ended design
on a 100% reflux system.
How do you kow you're not losing loads of good stuff to the air? You
over-engineer your condensor to make sure that all the liquid is
taken out of the expanded gas well before releasing it into the open.
> Additionally, since this unit is an external loop, isn't theregoing to be a
> problem with column vapor rising up through its outlet as well asits inlet?
That's exactly the problem that I had with my modified still. The
Nixon / Stone design has the inlet and back-flow pipes sharing the
same tube - vapour rises to the top of the tube, liquid flows back on
the bottom. This seems like the best design, other than playing with
a non-return valve on the flow-back pipe, which is my next project.
Watch this space!
> Finally, wouldn't increasing the flow rate through the coil in thehead of
> my still accomplish the same thing as either of the above?Yes, if your head returns the distillate back down the column. You'd
not get as fine a level of control doing this, but it'd more or less