[Stoves] Chimneys, rice husks [Ovens]

Sat Jun 15 01:10:25 CDT 2013

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 <tmiles at trmiles.com> 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:stoves-bounces at lists.bioenergylists.org] *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 <pugoclaire at yahoo.com> 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:* "ajheggie at gmail.com" <ajheggie at gmail.com>
> *To:* Discussion of biomass cooking stoves <
> stoves at lists.bioenergylists.org>
> *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" <crispinpigott at gmail.com> 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
>
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>
>
>
> --
> 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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-- 
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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