[Stoves] Chimneys, rice husks

[Lanny Henson]

<1.  An alternative to a chimney is a vent hood.  Could that work in a Maasai home?>


If your family size stove is efficient there may not be enough hot exhaust for a hood system because you have to heat the whole hood and duct to make it draft.

Hoods with stacks and heavy brick chimneys will usually draft themselves naturally but you can’t count it.

A thin metal chimney will create the best draft.

Too tall a chimney can pull too much heat from the stove;  about 2 meters of draft should be enough to make any stove cook but, 

2 meters of stove and chimney will not get you out the roof so a draft diverter maybe a solution. A draft diverter is like a very small hood and the stove pipe extends up in the draft diverter.

 A draft diverter is small enough to heat with a small stove and create enough draft, but does not add draft to the stack below the draft diverter. If the upper chimney section it too hot and has more draft than the lower chimney the upper pipe draws in some room air through the draft diverter. 

Draft diverters also help with wing blowing back down your stack.

Lanny

  ----- Original Message ----- 
  From: rongretlarson at comcast.net 
  To: rbtvl at aol.com ; Discussion of biomass cooking stoves 
  Sent: Friday, June 14, 2013 11:37 AM
  Subject: Re: [Stoves] Chimneys, rice husks


  Bob:

     Nice note.  Thanks.   

  1.  An alternative to a chimney is a vent hood.  Could that work in a Maasai home?

  2.     Marc Pare (cc'd) spent quite a bit of time in Viet Nam cleaning up a terrible problem with smoke for brick kilns that were mostly using rice husk combustion by switching to pyrolysis of husks (and saving money to boot).  Any complaints in Maasai territory on their technology?

  3.   Re making bricks, could that be done with "waste" heat from a charcoal-making stove? I am wondering if anyone on the list has ever put one raw brick (or pottery, etc) in the combustion region of a TLUD to make home-made bricks or crafts.  At 16 bricks to the $, it probably doesn't make sense, but that is not the brick price in Colorado.  You also might find some benefits in retained heat cooking using a just-fired hot brick.

  Ron.


------------------------------------------------------------------------------
  From: rbtvl at aol.com
  To: stoves at lists.bioenergylists.org
  Sent: Friday, June 14, 2013 8:59:30 AM
  Subject: [Stoves] Chimneys, rice husks

  The public health folks, from harvard, Berkeley and the CDC, I have talked to, being only a physicist myself, have all agreed to the need for chimneys in indoor, poorly ventilated wood burning settings like we find with the Maasai.   To prevent burns when touched and thatch fires the chimney must be not be  too hot until it is clear above the roof.   So our Maasai women installation teams make a brick chimney.   Our present best brick maker uses rice husks to fire the bricks.  He is in Mto wa Mbu where rice is grown and marketed in the rift valley and gets the husks cheaply. We can get 16 pretty good bricks for a dollar.  The husks work well.  Chimneys have to be designed well so that they get the smoke out without throwing away too much energy of course.  Ben Franklin is our guide.  But also I think a reasonably good chimney helps when stoves don't work quite right or start to deteriorate or aren't used optimally.  I know lots of stoves don't easily accommodate chimneys and that should give pause to introducing them in poorly ventilated homes no matter how cheap or efficient at boiling water.    Bob Lange. Maasai Stoves and Solar. 
  Sent from my Verizon Wireless BlackBerry
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