[Stoves] Chimneys, rice husks [Ovens]

Sat Jun 15 04:10:10 CDT 2013

I paul

Not if you use the design with an inner fire box and an outer pyrolysis
chamber as is Mr Khois design.  In fact it is the main reason why I
recommended this design configuration and sizing to PED.

We did a large research project with the Australia Government research arm
ACIAR to optimise the design.

I have measurde the rice husk temperature in this outer chamber and it
stays pretty uniform at around 450C after the initial drying and
torrefaction phases.

Regards
Stephen
On Sat, Jun 15, 2013 at 5:55 PM, Paul Olivier <paul.olivier at esrla.com>wrote:

> 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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>>>>>
>>>>>
>>>>> ****
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Stoves mailing list
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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/
>
> _______________________________________________
> Stoves mailing list
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