[Stoves] Pyrolysis: No Air?

Dean Still deankstill at gmail.com
Sat May 16 19:10:58 MDT 2015


Hi All,

Seems to me that the word gasification might fit the TLUD process better?
The primary air controls the amount of oxygen, the rate of reaction?
There is no pyrolysis in a Rocket or an open fire?

*Gasification* is a process that converts organic or fossil fuel based
carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide.
This is achieved by reacting the material at high temperatures (>700 °C),
without combustion, with a controlled amount of oxygen and/or steam.

*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".

Best,

Dean

On Sat, May 16, 2015 at 4:58 PM, Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

>  Dear Alex, Dean
>
>  That Reed reference is a good one. As biomass is about 40% oxygen by
> mass, there is a real chance one can have some combustion without any air
> at all. There is almost enough oxygen to burn all the hydrogen ‎in most
> biomass. That is a heat source that could leave all the carbon behind, in
> theory. In practise there will always be CO and H2 in the output from a
> retort.
>
>  Regards
>  Crispin
>
>
>  Dean,
> There being oxygen in the chemical structure of biomass and oxygen in the
> spaces and cracks, a strict abstinence is difficult. In one of the Reed/Das
> handbooks there is a graph of the pyrolysis-gasification-combustion
> continuum, where the x axis goes from say zero to %200 of stoichiometric
> oxygen/air. I think ( always roughly) gasification fit in the %20-%80 range
> with pyrolysis below and combustion above. The char and gas yield % was in
> there too. I'm sure folks could argue endlessly about where exactly to
> place the demarcations.
> Alex
>
> On Sat, May 16, 2015 at 6:50 PM, Dean Still <deankstill at gmail.com> wrote:
>
>
>    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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