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

Tue Feb 28 21:13:13 CST 2012

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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