Re: 2-phase flow.



Peter Jason wrote:
Thanks for all replies.

I have the azeotropic details from Horsley
and the purpose of the exercise is to remove
a product from the other reactants to drive
the reaction to the right.

I am using two possible methods, the first
assembly is a modified heavy-entrainer Dean &
Stark head with the addition of a tap at the
bottom of its collection tube. I hoped by
this method to have infinite reflux with the
light (desired) component collecting in the
tube and any excess, together with the water,
passing back into the column to supply
reflux. Of course this is a semi-batch
distillation in that the liquid in the tube
will represent a collection at infinite
reflux. Alas, the levels in the D&S device
are never constant and the liquid (2-phase)
therein surges back & forth upsetting the
column equilibrium shown by a cycling
top-of-column temperature.

The other method I mentioned uses a standard
Quickfit reflux offtake set, with the same
type of problem.

Clearly I will have to get the glassblower to
set up a two-valve head, one for each phase.
Or perhaps a small metering pump to deliver
2-phase liquid.

If I understand correctly - you want to remove the top layer and let the
lower one flow back? If so it is possible, but the apparatus looks nothing
like a standard dean and starke!
I could probably sketch a drawing if you need one - or look up page 2 of US
Patent - US5210339 on http://gb.espacenet.com or
http://patft.uspto.gov/netahtml/PTO/srchnum.htm (NB - espacenet won't work
with IE7 on my machine - use Firefox, or if you use Uspto it needs a tiff
viewer installed). Patents are free on those sites. Anyway back to
drawing - just add a tap near the top of the sidearm about where HNO3 is
marked. A good glassblower can also add a condenser section below the tap -
that can help separation as the liquid flows through.


--
Ron Jones
Process Safety & Development Specialist
Don't repeat history, unreported chemical lab/plant near misses at
http://www.crhf.org.uk Only two things are certain: The universe and
human stupidity; and I'm not certain about the universe. ~ Albert
Einstein


.



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