[Gasification] On the subject of H2 and O (was N2 removal)

Sun Mar 18 12:14:59 CDT 2012

Making Ice with Vacuum
http://www.youtube.com/watch?v=pOYgdQp4euc

Check out the ideal gas law.

Thanks,
Kel

On Sun, 2012-03-18 at 08:10 -0700, Mark Ludlow wrote:
> “The steam produced in cavitation is like putting water in a bell jar
> and pulling a vacuum.  If there is enough vacuum the water will boil,
> converting it's temperature into energy for the phase change.
> Eventually you end up with a chunk of ice in the bell jar.”
> 
>  
> 
> Not so! Not enough latent heat is lost. Sensible heat must be removed
> also. In outer space, where there are huge radiative heat losses this
> applies. If folks could make ice with simple vacuum pumps, who would
> mess with refrigeration? It takes energy to evaporate water, not just
> vacuum.
> 
>  
> 
> Plus, when a gas is adsorbed onto a sieve, energy is released. It
> takes the same energy (and then some) to regenerate the sieves. No
> free lunch; no where.
> 
>  
> 
>  
> 
> From: gasification-bounces at lists.bioenergylists.org
> [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of
> sabbadess at aol.com
> Sent: Sunday, March 18, 2012 7:55 AM
> To: gasification at lists.bioenergylists.org
> Subject: Re: [Gasification] On the subject of H2 and O (was N2
> removal)
> 
>  
> 
> Hi Greg,
> 
> 
>  
> 
> 
> Sure.  Let's to a simple example so my feeble mind can follow it.
> When I drop cold chips in my gasifier there is some moisture content
> in the chips...this is liquid water in the wood cells.  As the chips
> burn down into the hearth they get hot and the water changes to steam.
> This phase change absorbs some amount of energy.  Then as the steam
> goes through the char, some of it does the water gas shift if there is
> enough heat.  This absorbs even more energy.  The remaining steam ends
> up as condensate in the cooler.  
> 
> 
>  
> 
> 
> The steam produced in cavitation is like putting water in a bell jar
> and pulling a vacuum.  If there is enough vacuum the water will boil,
> converting it's temperature into energy for the phase change.
> Eventually you end up with a chunk of ice in the bell jar.
> 
> 
>  
> 
> 
> The water gas shift will not happen in the phase change because there
> isn't sufficient activation energy availble to make the reaction go.
> If it did work that way, there would be hydrogen bubbles coming off
> boat propellers.  That would make a COOL rooster tail!
> 
> 
>  
> 
> 
> Gasifiers do not run a low enough pressure to vaporize the water, like
> the bell jar.  I can get the numbers if you want, but you need to be
> in -13psi range.  That's way more than we pull.
> 
> 
>  
> 
> 
> Any clearer or still muddy??
> 
> 
>  
> 
> 
> Stephen
> 
> 
> -----Original Message-----
> From: Greg Manning <a31ford at gmail.com>
> To: Discussion of biomass pyrolysis and gasification
> <gasification at lists.bioenergylists.org>
> Sent: Sun, Mar 18, 2012 10:09 am
> Subject: Re: [Gasification] On the subject of H2 and O (was N2
> removal)
> 
> Hi Stephen, thanks for the reply.
>  
> OK, I somewhat understand you, BUT, wouldn't water be doing a phase
> change in the core of a gasifier as well ?
>  
> What I was getting at, is if steam is produced in cavitation in cold
> water, then wouldn't the shift effect also happen within the core
> during phase transition (from water as a liquid, to water as a vapor,
> when heated by the core) within the same boundaries of effect as water
> to steam in the trailing edge of a propeller ? (all of these
> situations involve lower that normal pressure zones).
>  
> Aren't contrails produced in water vapor on the wing tips of an
> airplane because of this same pressure drop phase shift, causing a
> dew-point change?
>  
> The core of most gasifiers runs in a dynamic lower than atmospheric
> pressure ( a very low internal barometric pressure) (suction based
> units), so the same shifts should apply  during phase transition,
> shouldn't they ?
>  
> I understand that a pressure fed gasifier would behave differently
> (and I've personally observed this) than a suction based one, I'm
> speaking about suction based gasifiers.
>  
> Somewhat lost,
> Greg
>  
>  
> On Sun, Mar 18, 2012 at 8:26 AM,  <sabbadess at aol.com> wrote:
> > Greg,
> > 
> > The energy doesn't change.  The bond energy in the water is constant
> > regardless of pressure.
> > 
> > The cavitation issue is different.  It is a phase change phenomenon, not a
> > chemical change one.
> > 
> > Stephen
> > -----Original Message-----
> > From: Greg Manning <a31ford at gmail.com>
> > To: Discussion of biomass pyrolysis and gasification
> > <gasification at lists.bioenergylists.org>
> > Sent: Sun, Mar 18, 2012 9:02 am
> > Subject: [Gasification] On the subject of H2 and O (was N2 removal)
> > 
> > Greetings List.
> > Since we are speaking input air, I thought I might ask a somewhat
> > related question.
> > Water gas shift. I know there are many that have talked about this,
> > and I understand the basics.
> > However, here is the question.
> > At what negative pressure ( negative in/wc) does the shift move down
> > the temperature scale, to the point of being within the 1000 - 1200 c
> > area ?
> > We all know that propeller cavitation produces steam in water that is
> > 10 c (or there abouts), I have to assume (not being a chemist) that
> > the same negative pressure effect would also apply to other principals
> > when dealing with water.
> > --
> >  Regards,
> > Greg Manning,
> > Brandon, Manitoba, Canada
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> > 
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>  
>  
>  
> -- 
>  Regards,
>  
> Greg Manning,
> Brandon, Manitoba, Canada
>  
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