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

Sun Jan 7 05:27:49 CST 2018

Dear Andrew

I have been looking into the combustion of hydrogen and I think the idea that hydrogen does not make water vapour in a small gasifier at all is not going to hold up. Let's keep looking.

According to the hydrogen promoting guys the ignition energy is SO LOW just about anything will make it react. In other words the gas doesn't have to reach 570 C to auto-ignite‎. It will accept any input above 0.05 MJ.

The TLUD experiments from Julien report temperatures above 600 and I suspect the thermocouples are all under-reporting.

I see now that the two different approaches described by Hirendra will probably give different results: the ‎TLUD with a glowing bed through which the distilled gases immediately under it have to pass in one type, and the continuous updraft where the oxidation layer is always under the distillation zone is the other.  In the latter case the hydrogen will not pass through a 'fire' in any sense and if it remains under 570 it will not auto-ignite.

Some gasifiers are run up to 1100 C so I am not including them. Just the ones we have been calling 'pyrolysers' for some reason that is not nearly as clear now that we have discussed it more.

Back in the land of real and small gasifiers, the reactions in the little TLUD's take place in the presence of air so the availability of oxygen is not the limitation, right? At the moment, from what I have read, that if I fed hydrogen into the primary air supply of a TLUD it would all emerge in the gas stream above. If you try it, stand well back.

Regards
Crispin

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

_______________________________________________
Stoves mailing list

to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
https://nam03.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.bioenergylists.org%2Fmailman%2Flistinfo%2Fstoves_lists.bioenergylists.org&data=02%7C01%7C%7Ca8ada2a12cd94efbfede08d555b8e546%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636509174956870795&sdata=QFJYHT%2BMNfUPCd5WfRI3VfukSOZA%2BmpvCK6r01vV604%3D&reserved=0

for more Biomass Cooking Stoves,  News and Information see our web site:
https://nam03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fstoves.bioenergylists.org%2F&data=02%7C01%7C%7Ca8ada2a12cd94efbfede08d555b8e546%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636509174956870795&sdata=7YyFbLkG24MpljhmCtBRPHg76ifKINPaNSLsji9UHLU%3D&reserved=0