[Stoves] Chimneys, rice husks [Ovens]
Otto Formo
terra-matricula at hotmail.com
Sun Jun 16 02:16:19 CDT 2013
I very much agree with you, Paul O.
Stoves and fuel are linked together, like Paal allways says, and a certain preparation of fuel is needed, one way or another.
Chared pellets are still quite "dense" and can "easily" be moved or even carefully transported longer distances.
Gasjifier units and pellets, are very much linked together and will solve a lot of issues, conserning emmissions, tranportation of fuel/biochar and health problems, related to "risky" biomass, too.
Otto
Date: Sun, 16 Jun 2013 07:07:00 +0700
From: paul.olivier at esrla.com
To: stoves at lists.bioenergylists.org
Subject: Re: [Stoves] Chimneys, rice husks [Ovens]
Tom,
In the design of household stoves, I do not think that we should advocate the direct combustion of rice hulls or any other biomass with an appreciable amount of silica. Even in supposedly sophisticated commercial applications in Asia, things can go seriously wrong. I believe that TLUD technology is far better in this regard than direct combustion, but even here, I can point to two ways in which cristobalite can end up in biochar and fly ash in the processing of loose rice hulls. Loose rice hulls are generally messy and dusty, and when processed in a TLUD, they emit particulate matter that more than likely contains cristobalite. Until someone can prove to me that this fly ash dies not contain cristobalite, I back away from promoting the processing of loose rice hulls in a TLUD.
I am hopeful that if the rice hull is formed into a pellet, the possibility of cristobalite formation within a TLUD can be minimized. It is hard for air to form a channel through dense pellets, and pellets do not (should not) contain a lot of fine dust. One big advantage of using pellets is that the price of the TLUD drops substantially. One big disadvantage lies in the cost of the pellets.
Therefore I call on funding organizations to step in and help create a competitive infrastructure and supply chain that assures that pellets are reasonably priced. They could also help out in showing farmers the benefits of biochar. The sale of biochar might be terribly important in offsetting the cost of pellets. If farmers in Dalat (where I live) already understand in part the benefit of incorporating rice hull biochar into the soil, why can't other farmers be taught the same?
Thanks.
Paul Olivier
Thanks.
Paul
On Sat, Jun 15, 2013 at 11:49 PM, Tom Miles <tmiles at trmiles.com> wrote:
>From my experience with industrial rice husk burning in Thailand I suspect that it is likely that a health hazard is not from the combustion process itself, where emissions are controlled by control devices, but from the management of the fuel and the ash which can create what are called fugitive emissions. Devices used at plants like AT Power are designed to remove fine particulates. If their smoke stack is in compliance then that is not the problem. (If it is out of compliance then the problem may be corruption, not technology.) We don’t have similar complaints from communities in the US where rice husks are burned at the same scale but where fugitive emissions are tightly regulated. In one case fugitive cristobalite silica was an issue for the ash handling system but that was resolved.
Testing combustion and fugitive emissions could determine if a household that burns a few kg per day of husks for cooking is going to create a health hazard similar to an uncontrolled plant that burns 20-30 tons per hour. As far as I know that has not been done.
If ash or char from burning rice husks in domestic or industrial devices is determined to be hazardous then it should be appropriately identified, labeled, and handled. Since rice husk is perhaps the largest potential domestic fuel source in a desperate world it is likely that survival will be chosen over potential health risks. We can’t abandon rice husk as a fuel. We have to find ways to make it work. TLUDs may be part of the answer.
Tom
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Richard Stanley
Sent: Saturday, June 15, 2013 9:13 AM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Chimneys, rice husks [Ovens]
Paul,From the side lines,… that appears to be solid research. Aside from a few bribe-oriented complaintants, most report what you are concerned about and the partners and sources of funding for the groups doing the reportage are good as well. I guess then it is a question of whether or not binding and blending of the rice hulls with other biomass effectively retards cristobalite formation -- or has no effect on it--or enhances it, for that matter.
Richard Stanleywww.legacyfound.org
On Jun 15, 2013, at 12:20 AM, Paul Olivier 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 havea 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 neighboringfarmers 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 hullsare 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/
--
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
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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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