[Stoves] A heat-resistant insulation mix

[larry winiarski]

Xavier

Jon anderson and wife Flip been making making many self firing clay /organic mixes --adding some form of potassium salts  to a bout 50-50   volume mix of clay organic. they have got potash water from leaching wood ashes.   Horse dung with urine also seems to work well. If you increase the draft temporarily with a chimney extension and fire hard for several hours. the stove becomes a miniture kiln and vitrifys the inner linning to brick. The potassium appears to act as a flux to lower the temperature at which the clay will vitrify.  I think others on the stove list (Crispin?) have made similar suggestions It looks very promising Check what Jon and flip have posted

God Bless

Larry
  ----- Original Message ----- 
  From: Xavier Brandao 
  To: stoves at lists.bioenergylists.org 
  Sent: Monday, August 08, 2011 3:07 PM
  Subject: [Stoves] A heat-resistant insulation mix


  Stovers,

   

  I wanted to submit another question related to the institutional rocket stoves (IRS).

  We encountered a problem with the insulation mix we used. In Benin, there are only a few oven to produce ceramics. They are already used for bricks and NANSU (kind of Jiko) ceramics. Demand for NANSU ceramics is huge from metal craftmen. So big that one of them grew tired to wait, and made his own ceramics, with a simple wood fire. It is of poor quality, and it breaks easily. Since this option and building our own oven was not possible (too expensive and we are not ceramists), we needed to find an insulation which didn't need to be cooked. That is also why we want a metal domestic charcoal stove.

  So we followed a recipee described in the IRS manual. Between the inox combustion chamber and the sheet metal outer body of the stove, we used a mix of 6 parts wood saw dust and 1 part of clay. On the stoves we made in the military camp (where they prepare from dawn till dusk), the mix almost completely burnt after a few weeks of use, leaving only a thin powder at the bottom of the space between the inox and sheet metal layer.

   

  We don't have anything to analyse it, but we are pretty sure the powder pile at the bottom is clay powder, the same clay powder we put in the mix. The sawdust burnt because of the heat. Small smoke was coming out of the small holes in the outer layer of the stove when in operation, certainly because the sawdust was burning. We thought that was the plan : the sawdust would burn and leave holes in the mix, making a kind of insulative ceramic. The strange thing is that it didn't burn like that in the two first stoves we made. At least not that we know.

  Maybe is it because we then used water to mix the sawdust to the clay? The mix clay-sawdust for the camp stoves was dry.

  Or perhaps with such a thin layer of inox (1mm), the sawdust is meant to burn completely, and 6 parts is too much for 1 part of clay. At one point or another, the only thing left would be a pile of clay.

   

  We are thinking about different things. We need to do without ceramics.

  For the next stoves we'd like to replace inox layer + insulative mix by bricks. It will be less expensive. We want to try to cut standard size clay bricks to the size of our combustion chamber (it seems bold) and put them in the sheet metal box. Then to bind them with something strong. And perhaps had an extra layer of cement + clay, I think this is what you recommended Crispin, to prevent users from breaking the bricks when pushing the wood. We need something heat and shock resistant, long-lasting, efficient and cheap, and that seems like the best solution.

   

  As for the stoves left empty, it seems that the cooks don't complain. Somehow, they are still efficient and clean. Air is also in insulator. But we need to refill them. We think to avoid using sawdust, and put a mix of clay + cement + water.

  Do you think that would resist heat and last? What are your experiences of making insulative layer, without the help of ceramics? And with cheap and wide-spread material? Rock-wool for example is too expensive and too rare. People here advise us to use laterite. It is cheap and to be found everywhere, heat and shock resistant. Metal workers use laterite bricks for furnaces. But I doubt about the energy efficiency, compared to clay.

   

  Thanks in advance,

   

  Xavier



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