But, Stephen, temperatures can rise above 900 C when burning rice hulls. If we operate at low temperatures (450 C) in burning rice hulls, are we not inevitably making a lot of smoke? Even at relatively low average combustion temperatures, will there not be a tendency for hot zones to form within the combustor?
Paul Olivier On Sat, Jun 15, 2013 at 2:44 PM, Stephen Joseph <[email protected]>wrote: > 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/ >> >> >> > > _______________________________________________ > 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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