All There has been a lot of work done on formation of crystobalite. The rate of formation is both a function of time and temerature
If you have low temperatures (450c) and short times (<60 minutes)you wont produce it. Mehta in India did a lot of work on this in the 80's and published a book on rice husk ash cement if I remember correctly Regards Stephen On Sat, Jun 15, 2013 at 5:20 PM, Paul Olivier <[email protected]>wrote: > Tom, > > I found this news report: > > http://www.ipsnews.net/2009/10/thailand-renewable-energy-not-so-clean-and-green-after-all/ > Not such a nice story. > I do not think it's a good idea to burn rice hulls or rice straw in either > power plants, brick kilns or household stoves. > > Paul > > > On Sat, Jun 15, 2013 at 1:10 PM, Paul Olivier <[email protected]>wrote: > >> 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/ >> > > > > -- > 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/ > > >
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