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

Greg Manning a31ford at gmail.com
Sun Mar 18 11:19:24 CDT 2012


That, I will agree with :)

If anyone out there has more information on the impact of lower than
atmospheric pressure on the temperature difference adjustment that it
causes on the principal of water to gas shift, I would greatly
appreciate it.

Greg.



On Sun, Mar 18, 2012 at 10:30 AM,  <sabbadess at aol.com> wrote:
> Greg,
>
> I can't answer why you are seeing higher temps than calculated.  It
> certainly does prove the impact of moisture on gasification, though.
>
> 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 11:12 am
> Subject: Re: [Gasification] On the subject of H2 and O (was N2 removal)
>
> lol, Stephen
> I understand you, it's just that in the core, in the restriction, I
> was reading Tom Reeds Superficial Velocity paper, and IMO the flow
> rate at  4 in/wc suction would cause quite a drop with a velocity of
> +300 ft/sec. (NOT VOLUME)
> What I'm saying is that when there is too much moisture I understand
> the energy transfer to the water is quite great, and the W/G Shift is
> low (or none), however, with inlet air that has been run through an
> "air dryer" (like the ones used in automotive paint booths) AND, very
> dry feedstock, the core temperature (just under the hearth) is WAY
> higher than if I run just normal air, and reasonably dry feedstock,
>  The difference is greater than the energy balance that I calculate,
> so one of two is the answer,
> A) my balance is skewed, OR,
> B) there is "extra" heat energy in the later portion of the process,
> that I cannot account for. (assuming a greater W/G shift, would bring
> it back in line)
> Greg
> On Sun, Mar 18, 2012 at 9:54 AM,  <sabbadess at aol.com> wrote:
>> 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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>> --
>>  Regards,
>> Greg Manning,
>> Brandon, Manitoba, Canada
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> --
>  Regards,
> Greg Manning,
> Brandon, Manitoba, Canada
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-- 
 Regards,

Greg Manning,
Brandon, Manitoba, Canada




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