Hello Michael, Thank you for your suggestions and question. My comments are as follows: 1. I have considered experimenting with high silicate ash from the foot of Mt. Canlaon, in northern part of Negros Oriental. The ash is free and my partners with the 11th IB of the Philippine Army in Negros Or. and the Memorial Elementary School in Canlaon would bring the ash to Dumaguete City. If this does not work, I’ll follow up on the TLUD route.
2. Jon & Flip Anderson (Aprovecho volunteers) have shown me their work with insulating bricks to form the combustion chamber in Timor Leste. The insulating bricks are weak, fragile bricks which require a strong, heavy duty shell exterior (e.g. cement)to protect the combustion chamber and to support big cooking pots. I still think that tiny insulating “clay marbles” between the heavy duty, all clay, fired kalan and combustion chamber is the most practical way to pursue. I am hopeful Rolf and ECOWORXX can find a way to produce these insulating clay marbles or pebbles cheaply. 3. For those who have not seen a coconut husk – it is a by-product of COPRA (mature coconut meat) production. Every 3 months, the coconuts are harvested, cut into 2 halves, and meat is extracted and dried to make copra. The husk and inside shell is dried in roof-covered sheds or storage buildings to make “bucong” – the fuel we use to fire the eco-kalans to 900 degrees Celsius. To use the “bucong” or coconut husk with shell for fuel in a rocket stove, it is requires chopping the husk with a machete into narrow wedges (like a cantaloupe) and a combustion chamber opening as wide and as high (5.5”x5.5”) as that of the eco-kalan. Rebecca Vermeer Eco-Kalan Project in the Philippines British Columbia, Canada From: mtrevor Sent: Friday, June 14, 2013 1:44 AM To: Discussion of biomass cooking stoves Subject: Re: [Stoves] : Re: Insulation and stove life Rebecca Why not gassify rice hulls in a TLUD and then use the low cristobalite "tough" high silicate ash to mix your insulation. Perhaps take a lead fom Aprovecho's play book and fire your liner in multiple wedge shaped pieces negating the need to break things up. How do to "prepare" your coconut husks for use in a rocket stove? Michael N Trevor Marshall Islands From: Rebecca A. Vermeer To: Paul Olivier Cc: Jon Anderson ; [email protected] Sent: Friday, June 14, 2013 8:25 PM Subject: Re: [Stoves] : Re: Insulation and stove life Paul, I currently use wood ash as insulating material between the kalan and combustion chamber of the eco-kalan (a rocket stove using wood, charcoal, coconut husk, shell, fronds and other parts of the coconut tree). The eco-kalan uses 75-85% less firewood and therefore a lot less ash is produced compared to traditional kalans and other traditional cookstoves in Negros Oriental, Philippines. A shortage in supply of ash is one fact or which affects sales of eco-kalan. I have considered making an insulating material using a 50-50 mix by volume of rice hull & clay in the form of pellets or bricks which would be broken to pieces after firing. I would fire the pellets or the bricks along with the eco-kalans up to 900 degrees Celsius. Will there be significant formation of cristobalite under these conditions? Would handling the fired pellets or the breaking of the bricks be a health hazard? Thanks, Rebecca Vermeer From: Paul Olivier Sent: Friday, June 14, 2013 12:07 AM To: Rebecca A. Vermeer Cc: Jon Anderson ; [email protected] ; larry winiarski Subject: Re: Fw: [Stoves] : Re: Insulation and stove life Rebecca, If we directly burn river hulls, there should be a lot of cristobalite formed. If we gasify, this problem should be minimized, provided channeling does not occur. Also there might be cristobalite in the particulate matter in the combustion gases. With rice hull pellets in a TLUD we have a lot less channeling, and a lot less particulate matter. Therefore the rice hull pellet becomes an attractive fuel for these and many other reasons. Thanks. Paul Olivier On Jun 14, 2013 1:44 PM, "Rebecca A. Vermeer" <[email protected]> wrote: Hello Paul, Larry just told me that the silica content of rice hull ash is over 90%. At the ETHOS 2013 Conference, I saw a TURBO stove developed in the Philippines which used rice hull for fuel. Given your comment below regarding cristobalite “which is a nasty carcinogen” and severely hazardous to human health (see link below), would you recommend the use of rice hull as a household fuel for cookstoves? Rebecca Vermeer CRISTOBALITE LINK: http://nj.gov/health/eoh/rtkweb/documents/fs/1657.pdf From: Paul Olivier Sent: Wednesday, June 12, 2013 12:01 AM To: Discussion of biomass cooking stoves Subject: Re: [Stoves] : Re: Insulation and stove life Paal, One thing I look for on my burner is that all burner holes support a flame throughout the process. If channeling occurs during the process or if char is being burned as the process comes to a close, then one can see burner holes that do not support a flame. This means that CO2 is being discharged from the burner holes, and of course CO2 does not burn. When CO2 is formed, this represents a big inefficiency, since combustion takes place far below the pot. When this happens the sides of the reactor can easily turn red hot and melt. I do not know how it is possible to spot the presence of CO2 if the top of the reactor stays open and does not have a lid with burner holes. If one turns up the fan a bit too high resulting in channeling, it can happen that only a few holes (among a total of 80 in my case) do not support a flame. If I turn the fan down a bit and shake the reactor, this problem is immediately corrected. Also the effect of the presence of CO2 can be spotted by the cook in another way. The distribution of heat to the pan is not even. Also many of the positive characteristics of biochar are lost when biochar is combusted and is reduced to ash. The combustion of biomass and biochar takes place when channeling occurs, and the combustion of biochar takes place if the fan is not turned off at the end of the process. Rice hull ash and rice hill biochar are not at all the same thing when it comes to growing plants. Also rice hull ash can easily contain cristobalite, which is a nasty carcinogen. Under ordinary conditions, no farmer should be handling this stuff. Thanks. Paul On Wed, Jun 12, 2013 at 1:06 PM, Paal Wendelbo <[email protected]> wrote: Ron By end of flame the color of the char is red to yellow, that indicate a temperature of 700 to 800 ˚C and when there is no smoke, complete combustion has taken place. Is that not good for biochar? Regards Paal W _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://stoves.bioenergylists.org/ -- Paul A. 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