Tom, I have read in many articles that cristobalite can form at temperatures of about 900 C. http://www.jicosh.gr.jp/old/niih/en/indu_hel/2004/pdf/42-2-24.pdf In burning rice hulls, temperatures can easily exceed 900 C. If cristobalite forms and is breathed in, human health is severely impacted: silicosis, tuberculosis, cancer and so forth.
*Silica (SiO2) is a constituent of the ash produced by the combustion process. Different types of biomass fuels contain different quantities of silica. The International Agency for Research on Cancer has classified silica as a human carcinogen. Long term inhalation of airborne silica particulates can cause lung cancer or other related health problems. As rice hull ash contains high levels of silica (~15%), its use as a biomass fuel presumably increases the risk of developing silicosis-related illnesses, and care should be used in handling the ash.* http://www.reap-canada.com/online_library/IntDev/id_eco_sugarcane/7%20Strategies%20for.pdf *Silica (SiO2) is the main mineral component of rice husk ash (RHA) (85-90 per cent). It carries serious health risks, particularly to the respiratory system.* http://www.dhf.uu.se/pdffiler/cc7/cc7_web_art4.pdf Cristobalite can be present in both the ash and fly ash. If someone designs a stove to burn rice hulls or rice straw, he has to be sure that temperatures remain below the point of cristobalite formation. Paul On Sat, Jun 15, 2013 at 11:18 AM, Tom Miles <[email protected]> wrote: > Paul,**** > > ** ** > > After discussing rice hull combustion and gasification at some length you > are now saying this is dangerous. Why, specifically? You have discussed the > potential to emit cristobalite but there is no evidence of the hazard it > presents. What evidence do you have that burning rice husks or rice straw > is a health hazard?**** > > ** ** > > Tom **** > > ** ** > > *From:* Stoves [mailto:[email protected]] *On > Behalf Of *Paul Olivier > *Sent:* Friday, June 14, 2013 8:56 PM > *To:* JJ Claire; Discussion of biomass cooking stoves > *Subject:* Re: [Stoves] Chimneys, rice husks [Ovens]**** > > ** ** > > JJ,**** > > I would not recommend that you burn rice hulls ir rice straw.**** > > In many cases this is quite dangerous.**** > > Paul**** > > ** ** > > On Sat, Jun 15, 2013 at 9:40 AM, JJ Claire <[email protected]> wrote:** > ** > > Greetings one and all,**** > > I visit the Philippines often and usually stay about six months a year. * > *** > > I often use a rice hull stove. I would like to get a plan to build a **** > > concrete stove. I am also wondering if there is such a thing as building > **** > > an 'oven' using cement and/or concrete? I would like to build one, **** > > a white model if possible, [vice a black model], if such a plan is **** > > available and if the technology would be practical. We have a **** > > lot of rice hulls and not all that much firewood. **** > > I would be open to heating the oven with firewood and then **** > > maintaining the heat level with or by burning rice hulls. I have**** > > a lot of rice hulls and want to make the best use of the hulls.**** > > I currently use the wood ashes to make lye so I can make soap, **** > > but I have not used any ashes from rice hulls to make lye. I**** > > wonder if making lye with rice hulls is possible.**** > > The rice hull stoves we use are sort of a metal pail with a wire rack. ** > ** > > I am looking for a stove, hopefully one that is hot, medium and cool, **** > > for cooking with rice hulls over a long number or years. **** > > On our island, rice hulls are still burned to 'get rid of them', and **** > > believe it or not, rice straw is still burned. I often ask neighboring**** > > farmers to bring me their straw and provide them a small bit of **** > > cash for doing so. We use the rice straw for making compost.**** > > We add some rice hulls to the compost. Most of the rice hulls**** > > are burned for fuel to cook with. We add the char from the cooking**** > > process to the garden. I am wondering if we are making the best**** > > use of the rice hulls and if the plans I am speaking of by post **** > > are available. **** > > Please inform, I am open to suggestions and direction.**** > > Blessings,**** > > JJ**** > > **** > > *From:* "[email protected]" <[email protected]> > *To:* Discussion of biomass cooking stoves < > [email protected]> > *Sent:* Friday, June 14, 2013 5:02 PM > *Subject:* Re: [Stoves] Chimneys, rice husks**** > > > [Default] On Fri, 14 Jun 2013 17:37:30 -0400,"Crispin > Pemberton-Pigott" <[email protected]> wrote: > > >We are experimenting in Indonesia with draft-operated buoyancy balancers > to limit the pull to the ideal even when combustion conditions change in > the large wood stoves. They are easy and cheap to make. They are mounted on > the side of the stack of all oil furnaces. > > We have used them on pellet stoves (which have their own id fans) to > limit draught on an insulated ss chimney that rose through 4 floors. I > wasn't entirely happy with the idea as it raised the possibility of > the boiler room getting combustion products if the seal wasn't good, I > would have been happier if the air was sucked from outside. In fact > there was subsequently a problem but this was down to poor > maintenance. > > AJH > > _______________________________________________ > 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/ > > > **** > > > _______________________________________________ > 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. Olivier PhD > 26/5 Phu Dong Thien Vuong > Dalat > Vietnam > > Louisiana telephone: 1-337-447-4124 (rings Vietnam) > Mobile: 090-694-1573 (in Vietnam) > Skype address: Xpolivier > http://www.esrla.com/ **** > > _______________________________________________ > 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. Olivier PhD 26/5 Phu Dong Thien Vuong Dalat Vietnam Louisiana telephone: 1-337-447-4124 (rings Vietnam) Mobile: 090-694-1573 (in Vietnam) Skype address: Xpolivier http://www.esrla.com/
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