[Stoves] Pyrolysis: No Air?

Crispin Pemberton-Pigott crispinpigott at outlook.com
Sat May 16 17:58:01 MDT 2015


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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