[Stoves] Pyrolysis: No Air?

Ronal W. Larson rongretlarson at comcast.net
Sun May 17 22:33:34 MDT 2015


Dean and list:

	This follows other material from Kirk, Paul, Alex and Julien.   I would put the emphasis in defining the difference between the two terms on the word “char”.  Pyrolysis trying to achieve char and gasification trying to avoid it.

Ron

On May 16, 2015, at 6:10 PM, Dean Still <deankstill at gmail.com> wrote:

> 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:
> Hi All,
> When I look up the word pyrolysis I find the following:
> 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".
> 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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