[Gasification] Subject: Rice Husk as Gasifier Fuel

[Tom Miles]

Ferruccio,

I haven't heard of cristobalite being a problem with rice husk gasifiers. It
may be in the ash and not measured.

It was my understanding that peak temperatures are the primarily case of
cristobalite formation. You can see the temperature range for cristobalite
on a silica phase diagram.  Cristobalite appeared as a problem initially
when milled rice husks were burned in suspension in California. It was
collected as a fine particulate that was a health hazard when handled. The
burners had been supplied by a licensee that ignored the low temperature
design of the originators in Louisiana. Peak temperatures in the burners
were subsequently lowered to reduce the amount of cristobalite. Current
burners supplied for suspension burning husks, in Thailand for example,
limit cristobalite formation through temperature control.

Tom
      

> -----Original Message-----
> From: gasification-bounces at listserv.repp.org [mailto:gasification-
> bounces at listserv.repp.org] On Behalf Of Ferruccio Pittaluga
> Sent: Monday, March 03, 2008 12:49 PM
> To: gasification at listserv.repp.org
> Subject: [Gasification] Subject: Rice Husk as Gasifier Fuel
> 
> Dear all,
> it seems to me that a main issue is overlooked when discussing
> gasification of rice husk. The problem is the possible, maybe even
> likely, production of cristobalite (Silicon Dioxide,
> http://www.galleries.com/minerals/silicate/cristoba/cristoba.htm), a
> polymorph of quartz, but highly carcinogenic. I really do not know if
> significant amounts of this material are produced in gasification
> processes, but I know for sure that they are emitted at stack if you
> burn rice husk mixed with woodchips on moving grid hearth. Has anyone
> got additional information on this topic?
> Ferruccio Pittaluga
> --------------------------------------------------------
> DIMSET/SCL - Savona Combustion Lab
> pittalug at unige.it
> http://proxy.sv.inge.unige.it/SCL/
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