[Stoves] [biochar-stoves] Adding fuel to TLUD ..... was Re: A review ofchronological development in cookstove assessment methods: Challenges and wayforward
Ronal W. Larson
rongretlarson at comcast.net
Fri Nov 27 18:35:05 CST 2015
Paul etal
Thanks for your comments BELOW - with which I agree.
Since I started this “added early thin layer” thread, let me emphasize that I was talking only of trying to increase the TDR in the early stages of the TLUD operation - so that water might be brought to a boil more quickly. I was not attempting to have a larger TDR available at any time.
The important variable here is O2. I was trying to think through whether this early added material might be beneficially consumed. Placement of the secondary air holes relative to the top of the added biomass (or vice versa) will need to be optimized.
I am not claiming this to be worth doing. This could easily foul up emissions - as you have pointed out. But I would like to see some data on this.
Ron
> On Nov 27, 2015, at 4:30 PM, Paul S Anderson <biocharstoves-7xpll at wiggiomail.com> wrote:
>
> Dear Crispin,
>
> Please check my publication in Boiling Point, 2007 (eight years ago), available at my website in Quick Picks or directly at
>
> http://www.drtlud.com/wp-content/uploads/2012/08/BP53-Anderson-14.pdf <http://www.drtlud.com/wp-content/uploads/2012/08/BP53-Anderson-14.pdf>
>
> It discusses both TLUD and AVUD methods. The AVUD method is the basis of the Chip Energy Biomass Furnace (in the range of 200,000 BTU or 50 kW thermal). And I have made AVUD functional in as small as a gallon container (4 liters). And several hundred of the Chip Energy Biomass Grill were made and sold (with a plancha top).
>
> Contrary to what you wrote about the system that you mention:
> 1. The new fuel on top cannot be piled on in large quantities. Reason: The heat that rises up to the new fuel will first dry the fuel, and then torrify and eventually pyrolyze. too much fuel to be dried at one time results in high moisture in the gases, capable of making them non-combustible until getting to torrification temperatures.
>
> 2. Therefore, some degree of frequent fuel feeding is needed. Works great while the user is happy sitting there feeding occasionally. OR if the user has the money to pay for automatic feeding.
>
> [Now that pellets are obtained so easily in so many places, I should probably return my attention to this type of unit plus some small automatic fuel feeder. Related to the Chip Energy Biomass Grill. Anyone interested in this should write to me directly off-line at psanders at ilstu.edu <mailto:psanders at ilstu.edu> ]
>
> 3. In the AVUD processes, there is not any upward MPF (migratory pyrolytic front) because the pyrolyzed fuel keeps collapsing onto the lower char bed and air-inlet/grate. Also, any primary air entering is into a bed of hot char where the O2 will be consumed, leaving nothing of O2 to go up to the pyrolytic front, therefore no flaming (glowing) pyrolysis as is found in TLUD stoves. Instead, AVUD has retort style pyrolysis unless the char is being removed and the fuel is getting low enough to receive some of the O2, which is the case in the Chip Energy Biomass Furnace, which is a wonderful char maker and can run 24/7 for days and days.
>
> 4. This is BB gasification, which is Bottom Burning. It is not related to being LIT at the top or at the bottom. It is Bottom BURNING. [Anything that is Bottom LIT is by definition also Bottom Burning, so that is why I dislike the insinuation that BLUD (which is BBUD with static location of burning) is anything like a TLUD technology.]
>
> Bottom BURNING is the case of virtually all gasifiers until Tom Reed and Paal Wendelbo built TLUDs that are LIT a the top. But the pyrolysis does NOT STAY at the top. It eventually gets to the bottom and becomes BB (and without any further MPF activity). And the combustion processes transition over from MPF to BB Bottom Burning.
>
> 5. You put Chakrabarti's paper at your website.
> http://www.newdawnengineering.com/website/library/Papers+Articles/Chakrabarti,%20H/BIOMASS%20GASIFICATION%20Hirendra%202013.pdf <http://www.newdawnengineering.com/website/library/Papers+Articles/Chakrabarti,%20H/BIOMASS%20GASIFICATION%20Hirendra%202013.pdf>
> You are welcome to put mine from Boiling Point 2007 there also. People correctly listen to and read what you provide, and we all want what you write and say to be as accurate as possible.
>
> Paul
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu <mailto:psanders at ilstu.edu>
> Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com <http://www.drtlud.com/>
> On 11/27/2015 3:41 PM, Crispin Pemberton-Pigott wrote:
>> Dear Paul
>>
>> There is another way to operate the TLUD which is what the aforementioned Hirendra Chakbarti's company makes.
>>
>> Start the stove in the regular manner.
>> When the pyrolytic front is well established start loading fuel on top but not a thin layer - lots.
>>
>> The MPF burns to the bottom and the ignited bottom of the net fuel burns upwards. For a short time it has two fronts.
>>
>> The bottom burns out and the char and turns all to ash. The upper MPF moves upwards without flaming. New fuel is added on top to keep the front buried in the pile.
>>
>> After some time the bottom is opened on the side and ash withdrawn, dropping the pile with the MPF somewhere above the ash and under the raw fuel. More fuel is dumped in top.
>>
>> This produces gas which is very wet. The gas is drawn off by a pipe and cooled to remove the water.
>>
>> The process is continuous. It can be controlled by means of the primary air flow. There is no secondary air as the combustion is elsewhere. In a stable operating condition it is a BLUD gasifier that can be operated continuously.
>>
>> It is the inversion of the Cambodian rice hull gasifiers I described a couple of years ago. Those feed the fuel in from the bottom and take the rice hull char off the top with the gas going up, and the MPF going down. It also runs continuously. Both can be fueled episodically.
>>
>> Regards
>> Crispin thinking this BLUD approach has not been tried within this group of experimenters.
>>
>>
>> On 11/27/2015 12:10 PM, Ronal W. Larson wrote:
>>> 4. Here is an idea that I wonder if you (anyone) has tried. (I haven’t)
>>> a. Start a TLUD in the normal way - maximum primary air may be best (since mostly we want high power only at the beginning).
>>> b. As soon as the pyrolysis front is clearly well established - then add a “thin” layer of the same (?) combustibles on the top.
>>> c. There should be no ignition at the bottom of the new layer, as there is no oxygen there. But new pyrolysis should occur - so increased power. The top of the new added layer could ignite, if there is plenty of secondary air there.
>>> The down side of this is that you probably need to control the secondary air so that you don’t have too much latterm Most os us never do this. But there could be some inherent control of the secondary (that secondary follows primary naturally)..
>>>
>> This has been done many many times. It is a way to extend the duration of the TLUD operation. You are correct that causes an increase in the pyrolytic gas creation but does not increase secondary air (except through increase of draft from more burning gases). It is a good way to put soot on the bottom of the pot. Note that this is anoxic pyrolysis via the heat, with no small flames (glowing pyrolysis) present as is found in the MPF (migratory pyrolytic front).
>>
>> Actually two conditions are possible.
>> 1. As you describe, while the MPF is also functional and descending.
>> 2. After the MPF reaches the bottom (and stops because it transitions into char-burning at the bottom). This is how people make their unit become "continuous" (at least until it chokes up with too much char or ash). But it requires the very frequent attention to the feeding of the fuel, thereby losing one of the desired aspects of TLUD batch operation (consistent flame without needing to add more fuel during the batch time of the MPF).
>>
>> Therefore, what you describe certainly has been and is frequently done. Actually, I did that in the testing in 2005 that won the Cat Pee award at Aprovecho. Then I did not understand it fully. Trickle feeding of fuel into TLUD stoves does work, has pros and cons, and is likely to be done by some individuals with or without their understanding of why or how it works and its limitations.
>>
>> Paul
>>
>>
>>
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