Re: FW: 2m Column
- Tony, if i have a column tall enough eg 2 or 3 metres do i really
need any reflux at all. could i run it without a condenser at the top
of the column and just have it coming out into a normal liebeg
--- In new_distillers@y..., Tony & Elle Ackland <Tony.Ackland@c...>
> Your email address doesnt like me, so I'll reply publically .....
> everyone else .. the question was essentially "how does a tallercolumn let
> you run it faster" ?length, to
> Your 1.2m column presently does about ten redistillations up its
> get the purity you're presently getting. But to achieve thatpurity, you
> need to run it at a particular reflux ratio (I'm assuming about 4 -eg you
> keep 1 and return 4 parts back to the column).the
> By increasing the column length to 2m, you'd now have about 16
> redistillations (HETP) happening.
> But you know you only need say 10 for the purity - so if you keep
> existing reflux ratio, not a lot further will be going on in thoseextra 6
> But heres the trick - if you decrease your reflux ratio - eg keep
> return less, you will degrade the effectivenesss of those stages,but it
> doesnt matter - as you have so many of them "spare". But - you'veworking
> increased your collection rate. So your 16 stages are now only
> like 10, but you're still happy with the purity, as its the same aswhat
> you had prior. But you're collecting it heaps faster.spare
> And it doesnt require any more heat input. You're just using the
> refining capacity of the taller column.cant
> Unfortunately, my calculations on this aren't too precise - so I
> detail the exact trade-off between extra height and going faster.Four
> times does sound heaps, but entirely permissable. All I can say isgive it
> a try. There will be benefit in going taller.
> if i have a column tall enough eg 2 or 3 metres do i reallyYou will always need some reflux. Without that liquid flowing back down
> need any reflux at all.
over the packing, there will be nothing to purify the rising vapour.
You'd just have a tall pot still.
If you didn't insulate the column, then there might be some condensing
happening on the sides of the column, and refluxing, but thats not what you
want. Its too uncontrolled, and wont do the job properly. You want the
reflux to be a deliberate action, generated above the top of the packing
(so that it gets to flow down over all the packing). If it were just off
side cooling, then its not using the full height of the column, and it wont
be distributed well through the packing.
A taller column will allow you to run less reflux (eg say 3:1 instead of
4:1), but it will always require reflux, and still a good proportion of it.
A taller column is only of use if the reflux is using all that height.