[Stoves] Chimneys, rice husks [Ovens]

rongretlarson at comcast.net rongretlarson at comcast.net
Sun Jun 16 09:42:36 CDT 2013 

Stephen: stove list, adding two biochar lists 

Three question areas - because I sense several major - maybe new - recommendations from you below. 

1. I met Mr/Dr Khoi at the GACC meeting and thought his was a TLUD design. Can you point me at a site where the design is drawn and explained? ( have looked a bit, unsuccessfully) 

2. I have been long impressed by your use of solid state theory with biochar - but I had previously thought you were talking only about changes after char placement in the soil. 
- Have you written up this idea of coating the biomass input to a pyrolyzer with a clay to improve CEC? 
- Any experimental data yet in the field for char with and without a clay coating during firing? 
- If one was making pellets out of almost anything, would you recommend always a clay binder? (This has to be cheap.) 

3. There are more than a few biochar proponents arguing for higher temperature char production (more adsorption/absorption - 700-800 C?). You have long preferred lower temperatures I believe.(with or without clay). Care to suggest an optimum T? 

Ron 
----- Original Message -----
From: "Stephen Joseph" <joey.stephen at gmail.com> 
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org> 
Sent: Saturday, June 15, 2013 4:29:34 AM 
Subject: Re: [Stoves] Chimneys, rice husks [Ovens] 


Hi Paul 

No we are pyrolysing them in the outer chamber so they are not subjected to direct combustion. 


Mr Khoi's stove is not a TLUD. I would not recommend people use TLUD stoves for rice husks unless they cover the husks with wet clay and then dry the clay. This coating has the advantage of keeping the temperature down and also activating the surface 


In any of my TLUD work I try to get people to coat their biomass in an iron rick clay to improve both CEC and yields. 


Regards 
Stephen 


On Sat, Jun 15, 2013 at 7:40 PM, Paul Olivier < paul.olivier at esrla.com > wrote: 





Stephen, 

Are you burning rice hulls at a temperature less than 450 C? 

Paul 






On Sat, Jun 15, 2013 at 4:10 PM, Stephen Joseph < joey.stephen at gmail.com > wrote: 

<blockquote>
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: 

<blockquote>



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: 

<blockquote>
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: 

<blockquote>




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: 

<blockquote>



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: 

<blockquote>




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/ 
</blockquote>



-- 
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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</blockquote>


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</blockquote>



-- 
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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</blockquote>


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</blockquote>



-- 
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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</blockquote>


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