## Re: FW: 2m Column

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• 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
Message 1 of 4 , Feb 2, 2002
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
condenser?

--- In new_distillers@y..., Tony & Elle Ackland <Tony.Ackland@c...>
wrote:
> Graeme,
>
For
> everyone else .. the question was essentially "how does a taller
column let
> you run it faster" ?
>
>
length, to
> get the purity you're presently getting. But to achieve that
purity, 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).
>
> 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
the
> existing reflux ratio, not a lot further will be going on in those
extra 6
> stages.
>
> But heres the trick - if you decrease your reflux ratio - eg keep
more,
> return less, you will degrade the effectivenesss of those stages,
but it
> doesnt matter - as you have so many of them "spare". But - you've
> increased your collection rate. So your 16 stages are now only
working
> like 10, but you're still happy with the purity, as its the same as
what
> you had prior. But you're collecting it heaps faster.
>
> And it doesnt require any more heat input. You're just using the
spare
> refining capacity of the taller column.
>
> Unfortunately, my calculations on this aren't too precise - so I
cant
> detail the exact trade-off between extra height and going faster.
Four
> times does sound heaps, but entirely permissable. All I can say is
give it
> a try. There will be benefit in going taller.
>
> Tony
• ... Just scale them up to keep the same number per meter ... 18 x (2/1.2) = 30 Tony
Message 2 of 4 , Feb 2, 2002
> On the subject of scrubbers I have 18 on the 1.2 column. How many
> should one have on the 2m?

Just scale them up to keep the same number per meter ...
18 x (2/1.2) = 30

Tony
• ... You will always need some reflux. Without that liquid flowing back down over the packing, there will be nothing to purify the rising vapour. You d just
Message 3 of 4 , Feb 2, 2002
> if i have a column tall enough eg 2 or 3 metres do i really
> need any reflux at all.

You will always need some reflux. Without that liquid flowing back down
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.

Tony
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