[Stoves] Drying fuels in the homes (was about Torrefication Re: Along the apparent "ambient humidity dry" -bone dry- torrefation- pyrolsis-char continuum

Frank Shields frank at compostlab.com
Wed Feb 29 11:24:44 CST 2012


Richard,

 

Thinking to start drying the briquette to let moisture go off then place a
previously moisture free briquette above and increase heat to bottom
briquette to produce vapors the then re-condense on the cooler inner surface
of the hole in the upper briquette.  Then when using the upper briquette a
good flame from the coating quickly heats up the stove. Something like
that
..

 

Frank

 

 

Frank Shields

42 Hangar Way

Watsonville,  CA  95076

(831) 724-5244 tel

(831) 724-3188 fax

frank at bioCharlab.com

 

 

 

 

 

 

From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Richard
Stanley
Sent: Tuesday, February 28, 2012 7:13 PM
To: Paul Anderson S.
Cc: Chua He; Nolbert Muhumuza; Discussion of biomass cooking stoves
Subject: Re: [Stoves] Drying fuels in the homes (was about Torrefication Re:
Along the apparent "ambient humidity dry" -bone dry- torrefation-
pyrolsis-char continuum

 

Dear PAul and Friends of the super drying regime, 

 

I kindly refer you to my colleague, Rok Oblak's holey briquette rocket
stove. It is developed now in at least five other nations and in use daily
that we know of (Uganda, Tanzania, Malawi, Chad, Philippines) but Rok will
be able to convey much more thru his own site: 

      http://mdulastove.wordpress.com/

Sadly this does little for char briquetters or for the higher pressure
briquette processes where the aromas are long driven off beforehand
just one
more bit to the growing knowledge pool. 

 

The idea is to stay below torrification temperatures for two reasons that I
can think of off the top of my head;

1) The briquettes do not want to be heated to their flash point 175 - 250ºC
for reasons of safety (ver definitely smoke- and very likely, spontaneous
combustion)

2) A hot briquette is too hard and (again unsafe) to handle 

 

The third logical reason for not drivign pre combustion heat to higher
levels..has recently been noted by the grop as the need to not waste energy
venting off otherwise combustible gasses; 

 

The distillation the materials in the process as Rajah recently pointed out
is the technically interesting part for most of you but to just see the fuel
giving off such aromas then see it tossed into the fire or stove with near
smokeless immediate ignition is pleasing indeed.

 

Cute, but the king-has-no-clothes question is: how does one get the stove
hot in the first place: The idea emerged around a safari camp fire in rural
Kenya a few years back and has found a few homes in like hotel and ongoing
fire hearth situations. But for cooking the big thing is to achieve the
immediate and smokeless start up. Thats the main design issue we all have to
get over is we are to ever approach the convenience of gas or other non
solid fuels. 

 

We are all adding a charge of  fuel wood, charcoal, briquettes, whatever and
trying to find a way to make it near smokeless: we light a match – near
smoke free in itself–then burn kindlng to "build up the fire" 

What if we "built down" the fuel load in the first place. Look at a pellet
stove very little fuel very  continuous feed. Alternatively ( as no
continuous feed mechanism has popped up which is both safe and reliable for
village stove use at least) we could redesign the fuel shape --for graduated
exposure to combustion  itself.   

I have been toying with the idea of conical briquettes that would ignite
only a very small ring of fuel at the start and build form that to the full
mass as the heat front enlarges to the full surface. Kobus Venter, John 

DAvies and I tossed the idea around in 2005-6  but we never went ahead with
it. 

 

viz., this garden variety 10cm OD 35mm ID X 60mm cylinder height hollow core
ag residue briquette, with an added 40 mm ( ?? ) cone height. 

 

Call it the starter briquette if you will. (done in the freebie google
sketchup 3d program)

 

 

 

Anybody every try this ? Its easy enough to alter the piston to form the
cone. 

hmmmm

 

Pressing on,

 

Richard Stanley

www.legacyfound.org

 

 

On Feb 26, 2012, at 2:52 PM, Paul S. Anderson wrote:

 

Stovers,

I have changed the Subject line so that this thread is about fuel DRYING,
specifically inside the homes.

The prior discussion has removed from me any interest in actual
torrefication of fuels destined for TLUD usage.

Also, "oven-dried" is NOT the same as "torrefied" (which is higher
temperatures such as 250 C and above.)

And "oven-dried" is NOT the same as "baked" (like what happens to a cake or
bread which, if not removed, can be blackened especially on the outside
while the inside can still be moist.)

"Oven-dried" means "dry", as in minimal moisture, MC =  0 to maybe 3
percent.  But does not require baking the heck out of it.

I especially like Richard Stanley's comment about naturally dried
briquettes,



 

Then if desired, drying them alongside the heated stove wall at temps up to
about 80--100 ºC  for 10 to 20 minutes will then drive off the aromas
without smoke still retaining the more carbon dense material in tack but now
bone dry.


In my opinion, this should NOT be called "pre-torrefication" because that
implies that torrefication is an objective, which is not the case.




<SNIP and edits>   Eucalyptus for fending off mossies, neem leaves for
congestion in the chest etc etc--as you desire).





<What PSA snipped> It then ignites with a bare minimum of smoke in the
stove.


The sentence order here is important.  I was always thinking the burning of
the briquettes (such as with eucalyptus or neem) was giving the desired
impact into the room.  Now I think that it is the drying process that needs
to be developed.  Does Richard agree?  or can modify?

So, let's have a fuel dryer (some sort of rack that holds briquette pieces)
built around the housing where a TLUD stove is radiating some heat outward
from its outside cylinder.  As the briquettes are drying, they are giving
off the aroma and the medicinal benefits.

Paul

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