Dear Paul T.,
Thank you for that clarification. Very useful. I agree with all, especially about flame-cap mode not being very applicable to the stove-size TLUDs, because of smaller diameter and, if being used with the concentrator lid, the lid itself can prevent the flame-cap from being close enough to the newly added fuel.
About the barrel size units, your experiences with Norm are enlightening. As you say, in normal TLUD function, the barrel becomes approximately 40% full of char. The empty top 60% means that the newly added fuel will be a considerable distance below the upper rim over which the air for flame-cap operation must pass. It is flame CAP, not requiring the air (or much of it) to actually reach down all the way to the new fuel.
I would imagine that a 200 Liter barrel that is only 50% filled with fuel for TLUD operation would end up with only 20% of the bottom of the barrel with char. That increased distance (80% of the barrel height) might just be too great for the flame cap to function. That would be an interesting experiment, but only as an experiment because nobody is advocation TLUDs only half filled at the start.
Paul A.
Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email: psanders@ilstu.edu<mailto:psanders@ilstu.edu> Skype: paultlud
Phone: Office: 309-452-7072 Mobile: 309-531-4434
Website: www.drtlud.com<www.drtlud.com>
From: Paul Taylor <potaylor@bigpond.com>
Sent: Tuesday, December 4, 2018 1:29 PM
To: Anderson, Paul <psanders@ilstu.edu>; Norman Baker <ntbakerphd@gmail.com>; Kirk H. <gkharris316@comcast.net>
Cc: Julien Winter <winter.julien@gmail.com>; biocharFIRST <wmknauss@gmail.com>; Art Donnelly <art.donnelly@gmail.com>; Vi Rapp <VHRapp@lbl.gov>; Dean Still <deankstill@gmail.com>; Ron Larson <rongretlarson@comcast.net>; jg45@icloud.com; Ryan Thompson <ryan@mtnaireng.com>; Jarod Johnson <jjohnson0423@hotmail.com>; Dave Lello <dave@lello.me>; Erin Peiffer <epeiffer1@udayton.edu>
Subject: Re: Flame cap on top of finished TLUD pyrolysis
HI Paul A.: I was not intending to include stove operation in my point about flame cap operation after completion of a TLUD cycle.
A dual operation of a stove may also be of value, but requires those additional explorations you raise, partly because of the different geometry in small stoves. The question of how small the device can be relates most to convection/combustion dynamics, providing that fuel is sized and fed appropriately for vessel – it is not all added at once, so it is pyrolyzed piece by piece. Small SS funnels have been run in flame cap mode.
A Kon-Tiki mode operation (which is a flame cap device that is optimized for vortex convection dynamics, efficiency, ease of use, and nutrient quenching of the produced char) has been explored in terms of parameters of vessel size and geometry, feed rate etc, although I have not published my own work. The vortex has a size determine by the properties of the air, and for effective vortex the vessel diameter is better above 50cm, and better with steeper walls, and improved with convection-designed heat shield. That relates well to a 55g drum sized TLUD.
While a smaller diameter TLUD could be converted to flame cap operation it will operate less well in the vortex mixing mode, which will likely be also interfered with by the TLUD after burner geometry. That may be compensated for because stove TLUDs are being developed with sophisticated ND air control, which can be further refined to serve in flame cap mode as well.
The beauty of the Kon-Tiki is that the convection driven vortex provides both primary and secondary air for the pyrolysis and combustion, and the mixing of pyrogas and air, in an elegant, simple, self-regulating way. The operation is open to view and the job is to manage and regulate the fuel increments. A drum TLUD lends itself to continuation in that mode after closing off the primary air.
Another advantage of the dual operation (in the drum TLUDs I work with) is that it removes the dilemma of when to close off primary air and extinguish the TLUD. TLUDs often don’t operate ideally, so additional time is needed to carbonize stranded incompletely-carbonized biomass. Norm and I solved this problem in the drum by doing a wet-carpet snuff and closing the vessel, thus providing an anoxic environment and time for completion of carbonization in the dry red-hot char. We experimented with flaring at a small hole any further pyrogas produced (like in a pressure cooker hole – and we could also observe this at our thermocouple holes).
In duel operation, after the primary air is closed off, when the MPF reaches the bottom, further carbonization can continue in the TLUD char, safely preserved in the bottom half of the vessel, while flame cap operation takes over in the top half fed by incremental fuel additions. Further pyrogas evolved from the TLUD char in the bottom half is burned in the flame cap, so no smoky end at that point.
Generally a flame cap, at least in a Kon-Tiki, can be managed to avoid any smoky end, although there may be increased CO emissions. Emission measurements do show very clean operation of a flame cap in a Kon-Tiki, marred intermittently by the disturbance of the flame cap which tends to occur when a piece of fuel is added. Areas of quenched flame will lead to bursts of methane and particulate emission, which increase the time average emission readings, so, yes, the fuel introjections must be managed with awareness and understanding – as most things must in our interconnected world.
Again, the transfer of this experience to TLUD stoves is not automatically of value because stoves have a primary purpose as cooking appliance, and economic, convenience, emission and cultural parameters enter on top of convection geometries and volume of char production. In a drum TLUD it is clearly a potential benefit for all the reasons mentioned above and below. The goal in this case is clean convenient, economic bulk char production. Some work and money goes into creating an effective, low-emission, convenient drum-sized TLUD, as Norm and I pursued.
A 200L drum TLUD produces about 80L of char, and when run in dual mode it can produce 180L, making more effective use of the machine and time capital. That being said, routine “commercial” operations of TLUDs may rather forgo those benefits for simplification of routines and controls – just run more TLUDs at 40% vessel-volume efficiency.
Paul T.
On 12/4/18, 6:26 AM, “Anderson, Paul” <psanders@ilstu.edu> wrote:
To Paul T. and Norm and all,
What you wrote is very well stated about having a flame cap operation in a TLUD that has finished the pyrolysis of the migratory pyrolytic front (MPF). It should be explained that well to everyone who works with or uses TLUD stoves.
A key part of that explanation is the statement:
>Running a TLUD to completion, then closing off the primary air and converting to flame cap mode
Without entry of more primary air (which comes in at the bottom), there is no loss of created charcoal.
When the primary air is left open, it is less clear that flame cap functions occur, or to what degree. But closing the primary air makes the issue clear.
Research questions relate to how small of diameter (and for a specific fuel type) of the fuel container can the TLUD have and still have sufficient heat from the flame cap to cause the pyrolysis of the new fuel on the top of the non-burning charcoal. Ambient temperature, wind, insulation, the entry of the “flame-cap-air” coming through the secondary air passages (vs. over an open top), and other factors could be significant. One factor would be if the TLUD is ND or FA.
The questions also relate to whether the flame cap operation is for char making only or is also for having a cooking fire (which sets additional expectations). For char making, this makes sense. For cooking, there could be some issues.
Also, it is important to remember that a TLUD device has the ability to let additional air enter via the primary air inlet (and/or it could have leaks). That would allow for some controlled amount of char-burning that might be crucial for maintaining sufficient heat above for the new fuel to pyrolyze. Questions include: what is the NET gain (or loss) of char?
Needed to be said also is that the new fuel on top needs to be added at an appropriate rate (interval and amount), and there is no known research about that rate, as far as I know. We are at the interface of TLUD and Flame Cap technologies.
Paul A.
(Sometimes Norm (who has worked considerably with Paul Taylor) attributes things to Paul and even I am not sure if he means Paul A. or Paul T. Paul T. has done major work with TLUD technology and should be appropriately recognized.)
Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email: psanders@ilstu.edu <mailto:psanders@ilstu.edu> Skype: paultlud
Phone: Office: 309-452-7072 Mobile: 309-531-4434
Website: www.drtlud.com<www.drtlud.com> <www.drtlud.com>
From: Paul Taylor <potaylor@bigpond.com>
Sent: Tuesday, December 4, 2018 1:23 AM
To: Anderson, Paul <psanders@ilstu.edu>; Norman Baker <ntbakerphd@gmail.com>; Kirk H. <gkharris316@comcast.net>
Cc: Julien Winter <winter.julien@gmail.com>; biocharFIRST <wmknauss@gmail.com>; Art Donnelly <art.donnelly@gmail.com>; Vi Rapp <VHRapp@lbl.gov>; Dean Still <deankstill@gmail.com>; Ron Larson <rongretlarson@comcast.net>; jg45@icloud.com; Ryan Thompson <ryan@mtnaireng.com>; Jarod Johnson <jjohnson0423@hotmail.com>; Dave Lello <dave@lello.me>; Erin Peiffer <epeiffer1@udayton.edu>
Subject: Re: Dates for TLUD Summit
Running a TLUD to completion, then closing off the primary air and converting to flame cap mode can preserve the TLUD char and continue to make biochar until the reaction vessel is filled. This maximizes use of the volume of the vessel, and its heat shield if any, makes the device easy to start in the TLUD mode (primary air supply) and easy to continue in the flame cap mode (a nice base of coals and heat). The vessel-shield-combustor-chimney arrangement of the hybrid can be optimized for the duel use, to exploit the natural convection flows that are exemplified in the Kon-Tiki, and to allow access to load fuel. We discussed this while developing the ring of fire. Those convection dynamics in fact provide insight to optimize some aspects of secondary air supply and mixing in a straight TLUD.
Paul
On 12/3/18, 9:40 AM, “Anderson, Paul” <psanders@ilstu.edu> wrote:
Norm and all,
Please remember to include Dave Lello to receive these messages. I have also added Erin Peiffer to be informed of the Summit. This would be a very good event for her. (Starting her PhD at Oregon State Univ. in January, with experience with TLUDs already.)
The agenda at the TLUD Summit will probably develop as we know more of who has what to do (in the stove testing lab) and to present about. We can collect a list of topics to discuss, even if the proposer of the topic does not have anything to present about it.
I do not want to be responsible for making that list nor for leading / organizing the Summit. A volunteer or two will get lots of help from the rest of us. I am happy to help “organize the group” once we have more clarity
For the list of “Not TLUD topics” that could be of interest, I could inform about:
A. Efforts for large-quantity charcoal production and PBR (Pyrolytic Biomass Reduction)
B. Use of charcoal for char-gas to run internal combustion engines.
I am active with both of these topics.
Norm, at another meeting last week (at Univ of Dayton), the presence of a flame cap in a TLUD stove was mentioned. I see the two as being distinctly separate. The presence of a flame above some biomass (sometimes a goodly distance above a layer of charcoal that covers the lower biomass) does not function in the same was as a flame cap in the sense that it is used (by Kelpie Wilson and others). You may present your reasoning, but expect at least me to challenge that usage of the flame cap explanatory name.
Paul
Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email: psanders@ilstu.edu <mailto:psanders@ilstu.edu> Skype: paultlud
Phone: Office: 309-452-7072 Mobile: 309-531-4434
Website: www.drtlud.com<www.drtlud.com> <www.drtlud.com> <www.drtlud.com>