[Stoves] Pyrolysis: No Air?

[Dean Still]

Kirk,

That's very interesting! Thanks!

You say:

"The small amount of added air supports the combustion of a small amount of
the gas to produce heat, but that air is soon used up and most of the fuel
pyrolyzes without added air."

I experience that a constant supply of air is needed to keep the TLUD
going. Without added air I see the gas making eventually stop so I've
wondered if the word gasification is a better descriptor. I agree that it
is a small amount of primary air which, if too much, makes too much gas and
then produces visible smoke since the mixing/time can't handle the overly
rich mixture.

Too little primary air and the reactions stop? You experience that no
primary air is needed to continue the reactions?

What about a Rocket or an open fire? No pyrolysis? Always has oxygen?

Best,

Dean

On Sat, May 16, 2015 at 8:34 PM, kgharris <kgharris at sonic.net> wrote:

>  Dean,
>
> Thank you for bringing this up.  I have never really thought about there
> being a difference between pyrolysis and gasification.  The definition of
> gasification in Wikipedia, "This is achieved by reacting the material at
> high temperatures (>700 °C), without combustion, with a controlled amount
> of oxygen and/or steam", is different from the definition of pyrolysis
> which is without additional oxygen.  Your statement seems correct according
> to this.
>
> As I read further in Wikipedia, there is a section on chemical reactions.
> Here there are 5 different processes which the fuel undergoes, pyrolysis
> being one of those.  This would lead me to believe that pyrolysis is part
> of the more general process of gasification.  Rather than it being one or
> the other, a TLUD would include both.  The small amount of added
> air supports the combustion of a small amount of the gas to produce heat,
> but that air is soon used up and most of the fuel pyrolyzes without added
> air.  The combination, including pyrolysis, would be gasification.
>
> I will look further to see if Christa Roth adresses this question in her
> Micro-gasification manual.
>
> Kirk
>
> ----- Original Message -----
> *From:* Dean Still <deankstill at gmail.com>
> *To:* Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> *Sent:* Saturday, May 16, 2015 3:50 PM
> *Subject:* [Stoves] Pyrolysis: No Air?
>
>
>    1. Hi All,
>
> When I look up the word pyrolysis I find the following:
>
>    1. *Pyrolysis* is a thermochemical decomposition of organic material
>    at elevated temperatures in the absence of oxygen (or any halogen). It
>    involves the simultaneous change of chemical composition and physical
>    phase, and is irreversible. The word is coined from the Greek-derived
>    elements pyro "fire" and lysis "separating".
>    2. However, I think that folks use it to describe what happens in a
>    TLUD, etc? Isn't that gasification not pyrolysis because of the presence of
>    some air?
>
> Best,
>
> Dean
>
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