[Stoves] China study of TLUD with pellets. Was Re: [Stoves] Going back to 3-Stone Fire [Was Re: China and cookstoves]

Sorry for my silence, but I have had 4+ days on other pressing issues.  I am STILL trying to catch up with messages since 16 Dec.. 

I thank Andrew for his mostly supportive comments about “TLUD” as a  name with specific meaning. 

I have some serious questions about the Chinese research of a TLUD stove with pellets, referecned in Crispin’s message:

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Dear Friends

 

The paper:  https://ijabe.org/index.php/ijabe/article/viewFile/2963/pdf Effects of biomass pellet composition on the thermal and emissions performances of a TLUD cooking stove is a TLUD pellet-fueled cooking stove.

 

Ron commented: “This achieves a record low for TLUDs of 10% efficiency – whereas Julien, Kirk, Paul and others are at 40% and more.”  

 

The paper reports the fuel efficiency (the energy available in the fuel fed into the stove v.s. cooking energy the stove delivers to the pot). The numbers reported by the sources, if using the WBT, are the heat transfer efficiency values (actually, an approximation of it – it is not exact). These two efficiency metrics are incompatible unless the system produces no residual char, which would be unusual for a solid fuel stove.

 

Regards

Crispin

1.  About the TLUD name:  Interesting that Crispin and the Chinese authors all say “TLUD” as if they think that such a name actually does denote a quite specific type of cookstove technology.   Well, that is good.   We do not need to be thinking of other UD-TL stoves when we read the name “TLUD”. 

2.  Three times the publication says:    “a typical Chinese household biomass stove without a chimney”    was selected [was tested} and fueled with different kinds of biomass pellet fuels.  I was not aware that a TLUD stove was “a typical Chinese household biomass stove” or that it is “a popular TLUD Chinese biomass stove” (Section 4. Conclusions).   Maybe someone could better inform us of numbers and models, etc.  Todd Albi sells Chinese-made TLUDs in America, so I assume some of those stoves are sold in China also.  But the one in the photo is not one of the models sold by  Silverfire.us.    I would love to have a TLUD success story from China.   But I am a bit skeptical about it being “typical” there. And  are there any test results (from Jim Jetter at EPA or Aprovecho or other not-in-China testing centers) of the stove in the cited study?   Can anyone send more photos?

3.  I struggle with equations and calculations (Section 2.5.1), so I cannot make comparative comments about the Chinese methods vs. elsewhere.   I might be wrong, but I do not see any inclusion of the charcoal that came from the TLUD at the end.  That leads to some questions:
A.  Was there no charcoal to measure?   If they run a TLUD as a charcoal burner stove after the pyrolysis stage is finished (and until all the charcoal was consumed???), that would be very inefficient and pull down the % efficiency calculation.

B.  Or was the char just discarded as “no longer being pellet fuel” and therefore judged to have been “fuel used”???

4.  Section 3.2.1 says  

As shown in Figure 4, at the beginning of the test, the water temperature in the pot increased slowly. This stems from the fact that fuel with a high moisture content often requires additional energy to vaporize the fuel  moisture resulting in a low net energy release rate. During this fuel-drying phase the emissions can be high.

Interesting, this reported “fuel-drying phase”…”at the beginning of the test” is not like TLUD stoves that I know, where fuel drying occurs little by little as the MPF (decending pyrolysis zone (AJH is correct)) progresses.   A drying phase at the beginning of a fire would occur when the fire is at the bottom and the initial rising heat is partially used to dry the fuel pile above the hot zone.      Perhaps someone can explain what happens in the authors’ usage of their TLUD stove.

5.  The photo of the stove in operation shows what appears to me to be a very high-power flame.  And the Conclusions recommend

Further study should be done with different stoves testing a diverse range of fuels [to] try discover which fuel attributes and which stove architectures combine to deliver superior performance.  

So the researchers acknowledge that “stove architectures” can be adjusted, implying that there was not an attempt to have the existing, typical, popular stove adjusted to give its best performance with three types of pellet fuels that were not WOOD pellets (not included in the research) but which might be the type of pellets for which the stove was optimized (if ever optimized?).

6.  Finally, in the last paragraph before the conclusions, we read:

The WBT protocol, Version 4, specifies a different stove operating sequence [than the Chinese testing]. The EF (PMi) s dramatically different because of the combined effects of the very different test sequence and calculation method. The test sequence changes the combustion efficiency and combustion conditions. With its different fire management sequence, the combustion temperature, oxygen supply, mixing states and the differences in fuel evolution result in an EF (PM) that is strongly at variance  with the test sequence employed in this work.

Well, that says much.  Comparing apples and oranges.  Perhaps others who are more into the details of testing might want to try to sort out what are the different stove operating sequences.  Perhaps BOTH are good.   Or only one.   or neither?   But until someone sorts that out, the fuel efficiency numbers cannot be compared with numbers from other testing systems.

Paul

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