[Stoves] Correcting a misconception that approaches myth status

[Paul Anderson]

Stovers,

This is about Crispin's story and showing slow progress, but it is 
progress.

On 12/16/2014 12:51 AM, Crispin Pemberton-Pigott wrote:
>
> There are dozens of ways to make a stove work improperly. Paul and I 
> have tried all of them, I think. Paul told me that a TLUD fuelled with 
> wood could not be refuelled. We were on the back patio of my home in 
> Ezulwini Valley in Swaziland and he went off to do something, leaving 
> a small TLUD can-stove running,. I fed in some wood vertically and it 
> worked just fine. I continued to do so and it continued to run long 
> after it should have gone out. Thus I proved to myself (and Paul) that 
> TLUD's can be refuelled but not too much at a time. OK, that was 
> valuable and contradicted received wisdom.
>
His story is correct.   I remember it well (now that I have been 
reminded).   But it also tells us something about the progression of our 
science.

Back then, the importance of the MPF (Migratory Pyrolytic Front) had not 
been realized.   What Crispin did then in 2002 was what BP-Oorja, 
Biolite and Philips and others did years later.   They were all trickle 
feeding additional fuel into the TLUD well above the pyrolytic zone.   
Heat from below was (and still is, if you do it) sufficient to pyrolyze 
the new fuel by heat WITHOUT the small flames of the pyrolytic front at 
that fuel.   The char can be fine, but probably a little different (not 
made at the higher temperatures of the MPF).

And when the MPF reached the bottom, and with new fuel placed on top of 
the char (not into the hot zone), the unit switched over to operating 
with Bottom Burning (BB) as a rather normal UpDraft gasifier.   And that 
leads to higher temperatures in the bottom (air coming onto charcoal) 
and the need for the different materials (cast iron, ceramics, special 
metals) to protect that hot zone.

As I have written in "Micro-gasification Terminology: An Instructional 
Summary of MG", available at my website.   See: 
http://www.drtlud.com/wp-content/uploads/2013/11/micro-gasification-terminology-14nov2013.pdf 

> Therefore, there are actually two types of TLUD (device name) 
> gasifiers, one being TLUD-MPF and the other being TLUD-BB. The two 
> types are quite distinctive in operation, and deserve separate 
> recognition and study. The common usage of the "TLUD" name today means 
> more than the TL of "Top-Lit" can signify. ...... snip ...  In 
> essence, TLUD is a name for the small updraft gasifier 
> processes/stoves and is not a description of what process (MPF or BB) 
> is actually happening. However, we expect that in common usage, the 
> TLUD name will designate TLUD-MPF, unless the UD-BB mode is specified.
However, many people continue to ignore the transition from MPF to BB.   
Back in 2002 I had no clue about this.   Now I consider it essential 
knowledge for understanding the variations within micro-gasification 
technology.   (Note that I wrote "micro-gasification technology" and not 
"TLUD technology.")

I repeat:
> However, we expect that in common usage, the TLUD name will designate 
> TLUD-MPF, unless the UD-BB mode is specified.
Of course I can only suggest and request.   People will do what they 
want to do, sometimes unfortunately.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

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