[Stoves] Chimneys, rice husks [Ovens]

Sat Jun 15 02:55:43 CDT 2013

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 <joey.stephen at gmail.com>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 <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/
>>
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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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