[Gasification] [Stoves] Natural draft TLUD turn-down

Tue May 20 14:14:08 CDT 2014

Crispin (and all),  [CC; gasification list]

   This is a very interesting conversation regarding ND TLUD power 
(heat) variability and its implications, and (as you know) I do have a 
keen interest in this topic since being introduced to the TLUD 'stove' 
concept back several years ago (by Dr. Anderson, when he came to Ontario 
to demonstrate his small "Champion" stove and similar devices at the 
Laepple farm in June 2009), especially since the TLUD is one of the few 
simple technologies that can produce biochar cleanly at a small (or 
possibly at a medium) scale for local use ~ while producing (hopefully) 
useful amounts of energy (heat).

   What I am working on right now here in Toronto might interest you or 
others on this list.
  I have been approached by a business in Toronto that would like to be 
able to implement a small-scale char-making technology at their 
manufacturing site in the Toronto area (GTA) that would utilize the 
(dry) 'residuals' from their food production process in order to make 
heat energy that could lower their (fossil) energy use [natural gas 
costs] while also turning their (dry) 'food waste' into a biochar 
(and/or high-char ash) that could be re-integrated back into a (wet) 
food composting system (vermicompost) that is already being implemented 
onsite at their operations here in the city.

  The primary use of the heat would be to heat up water, but it would 
also be welcome if it could be used in the preparation of the 'raw' food 
(drying, roasting certain products to a certain temperature -- i.e. an 
'oven') that goes into their recipes, which includes 'fair-trade' 
sourced (temperate and tropical) foodstuffs that have been either grown 
or imported into Canada in bulk, and which are prepared on-site 
(including de-hulling etc. of several of the key ingredients).
   Essentially, this company would like to know if it might be possible 
to come up with either a "customized" or an "off-the-shelf" system that 
has a fairly small footprint (about the size of a shipping pallet 
<http://en.wikipedia.org/wiki/Pallet#Dimensions>, or ~16 sq. ft = 40" × 
48", as commonly used in the food industry) that would be able to meet 
the following requirements:

  * Provides space heating and/or hot water heating (for their kitchen),
    with the possibility also for using the heat for "roasting" their
    ingredients (@ ~140 Celsius max. -- possibly using a heat exchanger,
    if necessary).
  * something flexible and rugged
  * can accept multiple fuel inputs (different sized feedstocks,
    different moisture/energy content -- not just woodchips)
  * no smoky emissions (after-burner, if necessary) so that it can meet
    local emissions regs

   Of course they are interested also in custom of "commercial" 
gasifiers [as well], but small systems (stoves) that could do the job 
they are seeking might suffice, although they probably want the system 
to be as automated (hands off) as possible to that the minimum amount of 
human intervention is required... although it would need to be as 
low-cost as possible (almost a "DIY" system -- they could actually make 
it themselves since they do have some expertise, including a machinist & 
a "master builder" who has built and operated a series of gassifier 
stoves for several years and "who is more than capable of manufacturing" 
something -- if they had the 'plans' for an open-source system/design 
that could do the job).

  Ideally this company would be interested in seeing 2 or 3 designs that 
might work for them (a few devices that they could initially assess)... 
so that they could work with the designers to get more details.  They 
would then choose a final design that they would then incorporate into 
their head office (operations), but then possibly also into a "franchise 
system" that they are designing (and that would operate like a "food 
truck" would in /any/ city ~ except instead of the truck being 
electricity or natural gas or propane-powered, the 'portable' food 
production/processing system would operate partially off of its own 
'waste'... and/or wood chips [or pellets] that could be produced or 
supplied locally ~ possibly even from chipped shipping pallets that have 
/only/ transported food products -- i.e. clean, 'food-grade' "green 
waste" like the type that can be found at the back of nearly every 
supermarket in the country... including all the broken ones.)

Regards,

   Lloyd Helferty, Engineering Technologist
   Principal, Biochar Consulting (Canada)
   www.biochar-consulting.ca
   48 Suncrest Blvd, Thornhill, ON, Canada
   905-707-8754
   CELL: 647-886-8754
      Skype: lloyd.helferty
   Steering Committee coordinator
   Canadian Biochar Initiative (CBI)
   CURRENTS, A working group of Science for Peace
   http://www.scienceforpeace.ca/currents/
   President, Co-founder & CBI Liaison, Biochar-Ontario
   National Office, Canadian Carbon Farming Initiative (CCFI)
   Organizing team member, 2013 N/A Biochar Symposium:
     www.carbon-negative.us/symposium
   Member of the Don Watershed Regeneration Council (DWRC)
   Manager, Biochar Offsets Group:
            http://www.linkedin.com/groups?home=&gid=2446475
    Advisory Committee Member, IBI
   http://www.linkedin.com/groups?gid=1404717
   http://www.facebook.com/group.php?gid=42237506675
   http://groups.google.com/group/biochar-ontario
   http://www.meetup.com/biocharontario/
   http://www.biocharontario.ca
    www.biochar.ca

"Producing twice as much food with diminishing resources, without further loss of natural habitats and biodiversity and in a changing climate may be the greatest challenge facing humanity."
    - Lloyd Helferty

On 2014-05-19 7:38 PM, Crispin Pemberton-Pigott wrote:
> Dear Roberto
>
> I agree with your analysis. There is a lot of merit in keeping the 
> secondary flame in close proximity to the top of the fuel bed. The 
> most important is that the secondary flame is harder to put out with a 
> slight breeze (because it relights). The second is that when the 
> primary air is turned down to control the power, the secondary flame 
> is able to remain hot enough to stay alight. Combined with external, 
> down-drafting secondary air preheating (not like the Peko Pe) one can 
> maintain the secondary air feed ration under different primary air 
> conditions.
>
> Read and heed! TLUD's are not succeeding in meeting the turndown 
> ratios required by ordinary cooking. To burn clean at different burn 
> rates, whatever the fuel, you have to control both the primary and 
> secondary air flows.
>
> While a 'double controller' can work, turning the secondary air down 
> at exactly the same time as the primary leads to a 2-3 minute period 
> of very high PM and or CO and VOC's because of the retained heat in 
> the fuel bed and stove body. This is worse if the combustion chamber 
> is ceramic or cast iron.
>
> If the secondary air feed it an automatic, buoyancy-driven ?supply, it 
> will draw in additional air as required during the cooling-off period. 
> This explains the strange layout of the air supply in a Vesto Stove 
> which tried to address the problems inherent in David Hancock's (very 
> advanced at the time) 1984 Tsotso Stove (which is still in production).
>
> Regards
> Crispin in Seoul enjoying spring
<snip>
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