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

[Ron]

Tom et al

   Any cite for the 5-7% value?

   Your last sentence is confusing to me with the word "gasifying pyrolysis gases" in it.  Paul is striving for only pyrolysis, and don't think he is proposing a packed charcoal bed.

Ron



On Apr 28, 2013, at 2:19 PM, "Tom Miles" <tmiles at trmiles.com> wrote:

> Paul,
> 
>  
> 
> It’s a great idea to use char as a filler but there is a cost.  I am sure that you will find that a small percentage of the charcoal “filler” will be consumed as charcoal will burn in direct contact with air or through reduction of the char. You will always have a little excess air or moisture in the bed.  When charcoal is used as a packed bed for gasifying pyrolysis gases charcoal consumption is estimated at 5-7%.  
> 
>  
> 
> Tom
> 
> 
>  
> 
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Ron
> Sent: Sunday, April 28, 2013 1:08 PM
> To: biochar at yahoogroups.com; Paul Anderson
> Cc: biochar at yahoogroups.com; Eckhardt, Bradley D; Discussion of biomass cooking stoves
> Subject: Re: [Stoves] [biochar] TLUD advances -- Two more uses of char
> 
>  
> 
> Paul et al
> 
>  
> 
>   This is to recognize and applaud the "char filler" suggestion you received from NASA's Dr. Jack Bacon.  I like it and hope we can hear soon from some who may have tried it.  My guess is that there is some maximum char volume above which Andrew's observation today of char combustion will prevail.  
> 
>  
> 
>    You correctly talked of the pyrolysis front.  Equally, users should be thinking about char combustion if any char particle gets hot enough while the upward flowing primary air still contains O2.     Upflowing primary air can get to char easier than fuel since there will be no/little exiting gases from the char.
> 
>  
> 
>   Good note.
> 
>  
> 
> Ron
> 
>  
> 
> 
> On Apr 28, 2013, at 10:01 AM, Paul Anderson <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 Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com
> 
> 
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