[Stoves] Technical about TLUDs (was Re: GLASS for stoves .)

[Paul Anderson]

Chrispin's message below is very useful and confirms that there are 
TLUDs that can end without smoke (and some are smokey).

1.  It would be useful if we could get more info from the Indonesian 
testing.  Which of the tested TLUDs were ending with smoke?  Not so 
important to know the brand names, but to study the stove 
characteristics so that the causes of the smoke can be determined and 
then corrected.

At this point I will disagree with Crispin's explanation.  This 
difference of thought can be settled by science, and I am happy if he is 
correct.  But I offer a different PART of the explanation.

It is easy for all of us to agree that smoke from TLUDs at the end (or 
at other times) is mainly because of loss of the secondary flame.   
Issues are 1)  insufficient gases, 2) loss of the "pilot" or sustaining 
flame/spark, and factors (gust of wind, some difference in the fuel for 
a moment) that cause those situations.

My scientific disagreement relates to this comment (empahsis added):
> they [TLUD stoves] have produced all the tarry gases they will, and 
> *_it has been cracked in the hot char_*. 
That cracking situation occurs in downdraft gasifiers that have a hot 
bed of char through which the pyrlolytic gases must past. Check those 
resultant (post -charcoal) gases and see that they are quite clean and 
(with some filter, cooking and maybe scrubbing) they can go to internal 
combustion (IC) engines.   These are clear gases, even when cooled for 
use in IC engines.

But the hot TLUD gases are never that clean.   They are transparent 
while still hot in the TLUD chamber above the created char, but if 
allowed to cool, they will become visible and will be called "smoke".   
Without the fire of the secondary combustion, smoke will be emitted.

The cracking of the pyrolytic gases ("smoke") requires passing throught 
a much hotter bed of charcoal than is found in TLUD stoves.  (Tom Miles 
and probably some others can comment on the temperatures in the char-bed 
of downdraft gasifiers where some air for O2 is entering to burn 
(oxidize or char-gasifiy) the char.)

I do not know of any studies specifically analyzing the TLUD gases while 
passing through the char layer or in the area between the char and the 
secondary combustion zone.  Probably has been looked at somewhere.

Quick proof of the smokey gases in a WELL-FUNCTIONING TLUD (which will 
end without any released smoke) is to extinquish the secondary flame and 
see the billowing smoke.   Be ready to relight it quickly !!!!

So, I am delighted with Crispin's observation about some TLUD stove 
models being consistently functional without smoky incidents at the 
end.  Those are the vast majority of the TLUD stoves in use. (Poorly 
functioning stoves do not get used or accepted.)  We are expecting TLUD 
stoves to have a great year in 2018 as more and more Stovers join these 
efforts.

Season's Greetings to all !!!

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

On 12/25/2017 6:21 PM, Crispin Pemberton-Pigott wrote:
>
> Dear IH
>
> Some TLUD’s have a smokeless conclusion to their combustion cycle. I 
> found it interesting to see the difference. We were testing a lot of 
> stoves (30?) for the Central Java Pilot and there are definitely two 
> groups of TLUD’s: those that end in a cloud of smoke that require one 
> to jump and run, and the others which have no smoke surge at the end 
> at all.
>
> It is the latter category that are processing the biomass at a 
> temperature above 500C. That is the secret. When that is done, they 
> have produced all the tarry gases they will, and it has been cracked 
> in the hot char. The distillation gases are produced immediately below 
> the red hot char so the processing can be above 550 at all times once 
> it is lit well.
>
> This clean ending permits the TLUD to be used indoors with ease. Many 
> thousands are being used following the success of the pilot project.
>
> Regards
>
> Crispin
>
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