[Stoves] Chimneys, rice husks [Ovens]

Sat Jun 15 10:25:48 CDT 2013

Paul,

You are jumping to conclusions about health risk based on your own
assumptions and no data. You have raised a well-known issue. Now put your
candidate stoves under a hood at a recognized lab and let health
professionals analyze the risk. 

This recalls a point that we hear from health professionals that the is too
little solid field research on health impacts of household energy. Is a
stove burning rice husk any better or worse than one burning wet dung or
wood? Where's the data?

Tom  

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Paul Olivier
Sent: Saturday, June 15, 2013 3:52 AM
To: Discussion of biomass cooking stoves; Josh Kearns
Subject: Re: [Stoves] Chimneys, rice husks [Ovens]

Stephen,

What I am trying to do now is to highlight the danger of directly combusting
rice hulls.

If the rate of gasification remains low (at 100 kg/M2), I do not suspect
that cristobalite will be formed in a TLUD.

I sent some rice hull biochar from my gasifiers to Josh Kearns.

I hope that he tests it for the presence of cristobalite.

Thanks.

Paul

On Sat, Jun 15, 2013 at 5:29 PM, Stephen Joseph <joey.stephen at gmail.com>
wrote:

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:

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-gr
een-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%20Strate
gies%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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-- 
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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-- 
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/ 

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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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