[Stoves] Pyrolysis: No Air?

[Stephen Joseph]

HI Guys

Read the terminology page Cordner Peacocke and I put together on the IBI
web site.  Pyrolysis can take place in an atmosphere where there is a small
amount of air.  Usually at levels below .2% of the theoretical amount of
air required to completely burn a biomass to CO2 and water.

Albrecht Kaupp wrote a very good manuscript ion on gasification in the 80's
and explained this very well.

Regards
Stephen

On Mon, May 18, 2015 at 2:33 PM, Ronal W. Larson <rongretlarson at comcast.net>
wrote:

> 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:
>>
>>
>>    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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