Hi Keith and DHAJOGLO ;
DHAJOGLO Wrote :
> >This is true also though it should be cautioned
> that a closed
> >reactor with enough head space and enough temp
> (say, 75 deg C) and
> >you will get methanol vapor from your solution at
> the top and the
> >reaction will not proceed as far.
Keith wrote :
> Anyway, what seems to happen in the situation you
> describe is that
> the vapour condenses on the underside of the lid and
> drips back in, not a problem.
In a pressure vessel with headspace that is at
atmospheric pressure, the only thing that will raise
the pressure upon heating is methanol vapors. This
accumulation of methanol vapors would reduce the
amount available for reaction. I had assumed I would
pressurize the vessel with dry compressed air before
introducing the methanol (say to 30 psi or whatever
was appropriate). This would keep the vessel pressure
higher than the vapor pressure of methanol, so
preventing the methanol from boiling. Some vapors in
the headspace is normal (that's why everyone
recommends the fumeless reactor design). What we want
to prevent is the boiling of methanol. Pressurizing
the vessel beforehand would do this.
Then when the reaction is complete, slowly releasing
the pressure would allow any excess methanol to boil
off due to the high temp of the solution. My plan
includes two pressure vessels with a heat exchanger to
pre-heat the next batch with the heat from the
finished batch. I just picked up a brand new
statinless steel tube in shell heat exchanger for
about $80 at a junkyard. The benefit of this heat
recovery increases as the process temperature
increases.
Comments from the list member more experienced than me
(this includes almost everyone) are welcomed.
Best Regards,
Peter G.
Thailand
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