[Gasification] Some fresh fuel !

[AJH]

On Tue, 20 Mar 2007 10:31:40 +1200, doug.williams wrote:

>While coppice willow is an excellent fuel wood, the harvesting chip size 
>still limits it's application as a gasifier fuel. You will notice that there 
>is a noticeable amount of green bark in the relatively small size chip, and 
>in the packed bed of gasifiers, forms large ash particles. The amount of 
>fines in the chip also reduces the interstitial space of the packed bed, and 
>assist to hold the ash in the bed preventing it from ejecting with the gas 
>stream. The high levels of sodium and potassium in the tip wood and bark, 
>act as a eutectic flux, and the ash particles fuse into a sintered clinker.
>
>The other problem was to get this crop into a drying mode as quickly as 
>possible, because it begins to decompose in hours of cutting.  This aspect 
>alone in my opinion, reduced the ability of willow to be a reliable source 
>of gasifier fuel, and as time passes, it would seem that it has found a 
>market as a boiler fuel, rather than for gasifiers.

Just a late comment to say that I have found exactly the problems Doug
states for willow Arable Short Rotation Coppice chips in gasifiers
when used as a boiler fuel in a stepped grate staged combustion
boiler, to the extent the de ashing augers could not cope and the
maintenance interval for removing fines from firetubes decreased from
14 days to 3.


Andrew Heggie