[Stoves] [biochar] Charcoal as space filler in TLUD reactors

[Paul Anderson]

Kevin,

The objective of the filler is two-fold:

One reason is precisely to reduce the maximum flow of primary air.   
Without resistance, too much primary air can race through the loose pile 
of biomass, reach too much of the biomass at the same time, and have an 
excessive fire without much control. Control simply by a "gate" at the 
entrance of the primary air is usually insufficient.

Second reason is that burning embers at the top of loosely packed fuel 
can sometimes fall to lower areas of the fuel bed and ignite the raw 
fuel there.   This defeats the process of the pyrolysis front that 
starts at the top and should progress slowly and uniformly downward 
through the bed of fuel.   That migrating pyrolytic front is THE most 
important and distinguishing feature of the TLUD stoves.   Ignition at 
the top and having updraft are not the single-most defining 
characteristics of TLUD stoves (even though that is what the name 
says).   Maybe I should have called it Migrating Pyrolytic Front 
Gasification  (or MPFG), but TLUD is the accepted name now.    [And Tom 
Reed always thanks me for getting away from the Inverted DownDraft (IDD) 
name that was not well understood.]

Important note:  When the pyrolytic front correctly reaches the bottom 
of the batch of fuel, the combustion style changes to be Bottom-Burning 
UpDraft (call it BBUD if you must have an acronym, but note that at the 
start it was NOT IGNITED or lit at the bottom).   And there is no more 
migration/movement of a "gas-making" zone.

Also note:  When the batch has been pyrolyzed, the burning at the bottom 
is "char-gasification" and can be at forge temperatures that can damage 
the metal pieces.   There is still restricted flow of primary air.   The 
hot gases go upward.   IF additional raw biomass fuel is placed onto the 
top of that charcoal, it will be heated, dried, torrified, and 
eventually pyrolyzed, giving additional pyrolytic gases that can be 
combusted where the incoming secondary air enters.   But this is NOT 
operating as a TLUD stove (with MPFG).   This type of bottom-burning 
gasifier is well illustrated by the Oorja stove (former BP, now First 
Energy) in India.   It has a cast-iron cup in the bottom to protect the 
other metal parts, and that cup glows red-hot after continual use.   
[Technical note:   Stove testing should measure separately the emissions 
during each of the different combustion modes instead of just reporting 
averages that include emissions from two or more combustion modes.   I 
think we can do some of that at this summer's Stove Camps at CREEC - 
Uganda and at Aprovecho - Oregon-USA where emissions equipment is 
available.]

About terminology:   A bucket stove or mud stove or Rocket stove and 
many others can be ignited at the bottom of a container and they do have 
updraft, BUT they are NOT GASIFIER devices.   So the designation BLUD is 
not relevant.   UD and DD and TLUD are designations historically for 
gasifiers, which means that the gases are created in one place that is 
NOT the same place as the combustion or other use of the gases.

Paul                               (James, please get this onto the   
drtlud.com website in edited format.)

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.com

On 5/6/2013 1:17 AM, Kevin wrote:
>
> Dear Paul
>
>     ----- Original Message -----
>     *From:* Paul Anderson <mailto:psanders at ilstu.edu>
>     *To:* Discussion of biomass cooking stoves
>     <mailto:stoves at lists.bioenergylists.org>
>     *Cc:* Kevin <mailto:kchisholm at seaside.ns.ca> ;
>     biochar at yahoogroups.com <mailto:biochar at yahoogroups.com> ; James
>     S. Schoner <mailto:jss at bitmaxim.com> ; Hugh McLaughlin
>     <mailto:wastemin1 at verizon.net>
>     *Sent:* Sunday, May 05, 2013 6:33 PM
>     *Subject:* Re: [Stoves] [biochar] Charcoal as space filler in TLUD
>     reactors
>
>     Kevin,
>
>     The "charcoal as filler" is not about consuming the charcoal.
>     # Sorry, I missed that.
>      The charcoal is "almost" non-active in the pyrloysis of the new
>     biomass.   This is a discussion about limiting air flows with a
>     filler that mostly is inactive in environments that are at 650 C
>     without oxygen.
>     # Why do you feel it would be advantageous to limit air flow with
>     an inert filler? If the char was significantly larger or smaller
>     than the biomass fuel, it could significantly increase pressure
>     drop through the bed, and would likely reduce maximum flow.
>     # Thanks.
>          [ Note that I avoid using the word "inert" in this discussion.]
>     Best wishes,
>
>     Kevin
>
>
>     Paul
>
>     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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