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

[Paul Anderson]

Crispin,

The pyrolytic gases that are created at 550 C will include thase at 450 
and 500 C, so the 550 C temperature does not produce only or even mainl 
clean gases.   Even at 700 C is will still be mainly tarry gases.

Let's see what the book say.

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 12/26/2017 11:25 AM, Crispin Pemberton-Pigott wrote:
> Dear Paul
>
> I am preparing a long message dealing with the earlier question about 
> what happens when biomass is heated in the absence of oxygen. The 550 
> C comes from that investigation.
>
> "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."
>
> Riaz Ahmad  a rare contributor to this list, is looking into this. He 
> is ‎a PhD candidate in the Biomass Key Laboratory at CAU. He has built 
> a gasifier that can operate as a TLUD with an ascending or descending 
> oxidation zone, at any oxygen level of choice. He is going to apply 
> the decombustion theory to reverse engineer the gases produced to 
> determine what fraction of the available solid fuel just got consumed. 
> This entails analysing the gases before they are burned instead of after.
>
> I have a book recommended by 'my gasification expert' which I will 
> pass along in that message.
>
> The mix of gases produced under different conditions is well know, 
> actually, and forms the basis of the distillation of biomass and coal 
> industry.
>
> A precondition for getting a smokeless end to a TLUD burn is that the 
> temperature must be above 550 so no tarry gases are formed. We must 
> carefully define 'smoke'. There will be CO, possibly a lot, but no 
> *visible* condensed smoke. It is obviously a subjective assessment, 
> but I was pleasantly surprised to see at least some of the fires burn 
> out very nicely.
>
> Regards
> Crispin
>
>
> 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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