[Stoves] TLUD advances -- Two more uses of char

Wed May 1 12:16:39 CDT 2013

Thank you Dr. Anderson for including me in these emails concerning charcoal use in pyrolytic gasification stoves.

It is very interesting to follow these detailed discussion as well as educational. It helps us here in our  Engineers Without Boarders work here at Johnson Space Center, since we are somewhat new to this technology, but also have a specific application for these stoves.

It greatly helps on the learning curve, and please keep us in the loop on these discussions,

Brad

From: Stephen Joseph [mailto:joey.stephen at gmail.com]
Sent: Sunday, April 28, 2013 8:18 PM
To: Discussion of biomass cooking stoves
Cc: biochar at yahoogroups.com; Eckhardt, Bradley D
Subject: Re: [Stoves] TLUD advances -- Two more uses of char

Hi Paul

Yes you can quench with water.

Yes it can be put in an airtight container but it is not foolproof that it wont combust when the container is open.  Oxygen can be chemisorbed in the biochar and then react with the carbon lattice and produce heat such that the carbon turns to CO2.  This is also know as filtration combustion.  Biochar that has been produced at low temperatures is usually more reactive than higher temperature biochar but not always. It is both a time temperature and ash composition determine reaction.  The science is fascinating.

Regards
Stephen

On Mon, Apr 29, 2013 at 10:23 AM, Paul Olivier <paul.olivier at esrla.com<mailto:paul.olivier at esrla.com>> wrote:
Stephen,
Is it OK to quench biochar with water?
Can biochar be put in an airtight container where it then cools off?

Paul

On Mon, Apr 29, 2013 at 7:04 AM, Stephen Joseph <joey.stephen at gmail.com<mailto:joey.stephen at gmail.com>> wrote:
All

Japanese quench biochar with ash.  This also helps to functionalise the surface of the biochar and make it more active

I actually use a mixture of soil and ash as the heat can help release locked up phosphorous.

Regards
Stephen Joseph

On Mon, Apr 29, 2013 at 2:01 AM, Paul Anderson <psanders at ilstu.edu<mailto:psanders at ilstu.edu>> wrote:
Dear all,

These two and many other "tips" need to be collected and told to TLUD stove users.   One avenue is in Christa's Manual,   Another is in stove manuals and at training sessions.   And at websites, etc.

1.  Charcoal to extinguish hot charcoal:   When dealing with small amounts of hot charcoal as in the residential TLUD stoves, one easy way to extinguish hot charcoal is to dump it into a somewhat larger amount of already extinguished (cold) char.   The cold char takes up much of the heat, extinguishing the hot char.   Be sure that it is well mixed and sufficiently cooled to avoid re-ignition.  This is best done in containers that can be sealed.   Containers of metal or ceramic are best, but even wood could be used if the quantity of cold char is sufficient to prevent the hot char from reaching the sides.   As always, be careful because oxygen to a small hot ember can lead to much greater combustion.

2.  "Space fillers" in loose fuels in TLUD devices:

General note about fuel in TLUDs:
In general, dry biomass fuels in TLUDs need to appropriately fill most of the air-space in the fuel chamber.   This is accomplished with smallish pieces such as wood chips, pellets, short-cut twigs, and shells of seeds.   Also, careful packing with vertical wood-segments or straight-ish reeds can occupy the space.   But twisted sticks and long-ish pieces that bridge inside the fuel chamber leave too much space unoccupied.   In those cases, the space can be appropriately occupied by adding small pieces, as named above.   Shake the TLUD to assure that the pieces have settled in well, and add more as needed.   These fillers will also pyrolyze and become charcoal.

Inert materials as "space fillers":   Technically, the space fillers could be inert materials such as ball bearings or pebbles (of rock that will not shatter with this heat) or fired clay balls.  Although they could function effectively, they would require separation after the batch is unloaded and cooled.   But there is one material that solves these inconveniences and costs.  It is charcoal.

Charcoal as a space filler:   TLUD stoves make charcoal. Therefore, charcoal is not a fuel for TLUD stoves.   However, small pieces of charcoal (but not charcoal fines) can also be used as "space fillers" to solve the need to restrict air flow in the fuel chamber.   The char will not pyrolyze and will not burn (char-gasify or oxidize) as the pyrolysis front moves downward through that biomass fuel.

a.  Char is abundant for TLUD users, and at no additional cost, and is not consumed.

b.  Unlike small pieces of biomass as fillers, char pieces cannot catch on fire and then fall down to the lower areas of the fuel chamber and igniting fire there.

Charcoal as a reducer of thermal output:   Clearly in the above statements when charcoal is used as a space filler, the fuel chamber contains less biomass and therefore less heat will  be generated (which is desirable for simmering and some other cooking needs).

Another variation is to have well packed (mainly straight) wood or reeds or stems as a vertical bundle in the middle of a TLUD fuel chamber.  Then load in small charcoal all around the bundle to fill in the remaining space.   When used (pyrolyzed), the fuel will yield heat in proportion to its cross-sectional area of the fuel bundle, not of the entire cross-sectional area of the fuel cylinder.  This is because the annulus of char is essentially non-combustible at the pyrolytic temperatures in the TLUD reactor.

Variations of all of the above need to be tested and even measured.   (This will be utilized at the Stove Camp at Aprovecho 22 - 26 July 2013).

Note:  Credit for much of the above goes to Dr. Jack Bacon, a senior scientist at the NASA Johnson Space Center in Houston, TX.   Jack, a leader in the local chapter of Engineers Without Borders (EWB-JSC), suggested charcoal as fillers during discussions in April 2013 with Paul Anderson about an EWB project to use TLUDs for heat in a fruit dryer in Rwanda.

Dr TLUD

--
Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>   Skype: paultlud  Phone: +1-309-452-7072<tel:%2B1-309-452-7072>
Website:  www.drtlud.com<http://www.drtlud.com>

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Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
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