[Stoves] Chimneys, rice husks [Ovens]

Sat Jun 15 02:44:56 CDT 2013

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 <paul.olivier at esrla.com>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 <paul.olivier at esrla.com>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 <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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>>>
>>>
>>> _______________________________________________
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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/
>>
>
>
>
> --
> 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
>
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>
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> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://stoves.bioenergylists.org/
>
>
>
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