[Stoves] Fw: : Re: Insulation and stove life

Fri Jun 14 01:44:12 CDT 2013

Hello Paul,
Larry just told me that the silica content of rice hull ash is over 90%.  At the ETHOS 2013 Conference, I saw a TURBO stove developed in the Philippines which used rice hull for fuel.  Given your comment below regarding cristobalite “which is a nasty carcinogen” and severely hazardous to human health (see link below), would you recommend the use of  rice hull as a household fuel for cookstoves? 

Rebecca Vermeer

CRISTOBALITE LINK:
http://nj.gov/health/eoh/rtkweb/documents/fs/1657.pdf
From: Paul Olivier 
Sent: Wednesday, June 12, 2013 12:01 AM
To: Discussion of biomass cooking stoves 
Subject: Re: [Stoves] : Re: Insulation and stove life

Paal,

One thing I look for on my burner is that all burner holes support a flame throughout the process. If channeling occurs during the process or if char is being burned as the process comes to a close, then one can see burner holes that do not support a flame. This means that CO2 is being discharged from the burner holes, and of course CO2 does not burn. When CO2 is formed, this represents a big inefficiency, since combustion takes place far below the pot. When this happens the sides of the reactor can easily turn red hot and melt. I do not know how it is possible to spot the presence of CO2 if the top of the reactor stays open and does not have a lid with burner holes.

If one turns up the fan a bit too high resulting in channeling, it can happen that only a few holes (among a total of 80 in my case) do not support a flame. If I turn the fan down a bit and shake the reactor, this problem is immediately corrected. Also the effect of the presence of CO2 can be spotted by the cook in another way. The distribution of heat to the pan is not even.

Also many of the positive characteristics of biochar are lost when biochar is combusted and is reduced to ash. The combustion of biomass and biochar takes place when channeling occurs, and the combustion of biochar takes place if the fan is not turned off at the end of the process. Rice hull ash and rice hill biochar are not at all the same thing when it comes to growing plants. Also rice hull ash can easily contain cristobalite, which is a nasty carcinogen. Under ordinary conditions, no farmer should be handling this stuff.

Thanks.

Paul

On Wed, Jun 12, 2013 at 1:06 PM, Paal Wendelbo <paaw at online.no> wrote:

  Ron

  By end of flame the color of the char is red to yellow, that indicate a temperature of 700 to 800 ˚C and when there is no smoke, complete combustion has taken place. Is that not good for biochar?

  Regards Paal W

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-- 
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
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