[Stoves] Distillation and oxidation Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )

[Andrew Heggie]

On 7 January 2018 at 02:31, alex english <aenglish444 at gmail.com> wrote:
> Destructive distillation of wood was the term back in the 1930s when my
> grandfather wrote a high school text book.
> Attached;
>  is a slide on pyrolysis stages from our national labs senior scientist
> responsible for bioenergy and the tar sands pyrolysis.
> and two images of google word use search between 1800-2000 for pyrolysis and
> destructive distillation.


Good graphs of the change in terminology from destructive distillation
toward pyrolysis. I knew the term but considered it more to do with
the making of simple organic compounds from wood before organic
chemistry really took off with the petrochemical industry.

The wood gas distillation produced acetic acid and methanol amongst
many other chemicals. I have posted in the past about an acetic acid
plant in Germany which pyrolysed beech logs, distilled vinegar and
used the other gasous products in a spark ignition engine to power the
plant. charcoal was a less valuable by product.

There have been a flurry of offlist e-mails which I have replied to
without realising they will not be seen on stoves.

Anyway your slide clearly shows agreement with what Tom Reed said all
those years ago, there is an exothermic stage and here the range is
given a bit wider as 280-500C but the salient point is that the oxygen
bearing compounds given off do not include water beyond the drying
phase. So in the final stages the  gases CO and H2 are favoured as I
have said earlier.

Whilst acknowledging there may be a means for disociating all the
elements in wood and recombining the oxygen with the hydrogen it does
not happen in simple stoves or gasification.

Andrew