[Stoves] rice husk pellets

Fri Jun 14 14:44:24 CDT 2013

A rice mill in Mali used a Chinese downdraft gasifier for generating power
for many years. I didn't know about it until after I visited Bamako. It is
likely that it was pretty crude and robust because we kept  hearing about it
up to the mid-1990s. I don't know if it is still in operation. Crispin sent
us pictures of a rice husk gasifier in Cambodia. 

We got into extensive discussions about amorphous and crystalline silica in
rice husks  when evaluating its impact on a boiler in Thailand. The80-90%
amorphous silica number is one that is repeated on the internet but not
necessarily substantiated in literature.  According to one source, "at
burning temperatures of 550 C - 800C, amorphous silica is formed, but at
higher temperatures crystalline silica is produced."

Tom

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Richard Stanley
Sent: Friday, June 14, 2013 12:03 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] rice husk pellets

 Paul,

Good insights which far more and far better educated and more focused  on
the subject need to know about. Might I  suggest you contact wikipedia and
submit that correction directly.

Thanks,

 Richard 

On Jun 13, 2013, at 9:41 PM, Paul Olivier wrote:

Richard,

I would question the statement that RHA contains about 85 to 90% amorphous
silica.

A significant proportion of it should be in crystalline form.

Paul

On Fri, Jun 14, 2013 at 11:05 AM, Richard Stanley <rstanley at legacyfound.org>
wrote:

Paul. 

Answer is that I don't know, to all of your  questions Paul: It was not our
focus at the time. The rice hulls that were being anerobically decomposed
were an eyesore and a real danger to the kids in the area who would play on
them, sometimes falling into deep caverns created by the collapse of the
structure on decomposition  often with tragic results. As a result the use
of that resource became somewhat taboo for the briquette maker   The silica
content in the ash of combusted rice husks is however relatively well known
published figure.   Here is this citation from wikipedia..

The densification  of rice hulls for the low pressure wet process we follow,
making effective briquettes out of such requires that it is either made soft
and "mashy" or so  fine as to serve as an infilling for a fibrous lattice
work. 

Richard

On Jun 13, 2013, at 6:57 PM, Paul Olivier wrote:

Richard,

I assume that we are still taking about rice hulls. I supposed that this
pile of rice hulls is being decomposed anaerobically. If this is the case,
do you know how much methane is being released? You talk about a high silica
content ending up in the ash. Have you checked the composition of this ash?

On Fri, Jun 14, 2013 at 8:47 AM, Legacy Mail <rstanley at legacyfound.org>
wrote:

hi Trevor &Frank,

I am no expert on the stuff as it seems to vary considerably from what we
have seen in practice.   Where it is left to  decompose in huge multi acre
50 ft tall mounds, (eg Mbale Uganda), you observe  a glutenous mass which
can work very well even with other granular solids (sawdust, charcoal fines)
right off the mound.  Take it off the fields dry (in such as Bamaco Mali )
and it has to indeed be blended with softened fibrous material. In either
condition (whether gluten or fiber bound) the high silica generates lots of
ash. 

Richard

Sent from my iPhone

On Jun 12, 2013, at 22:11, mtrevor at ntamar.net wrote:

I suspect the high silicacontnt and loose nature will not compact well.
However if macerated and retted, then mixed with other stuff--- then maybe.
I suspect Richard Stanley could provide more info 

Michael N Trevor

Marshall Islands

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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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