[Terrapreta] Terrapreta Digest, Vol 11, Issue 70

[Larry Williams]

   Nikolaus-------Is it possible for you to post some pictures of  
both the atmospheric kiln, pressure kiln and product? Thanks for the  
explanation of the process-------Larry


-------------------------------------------------
On Dec 27, 2007, at 1:10 PM, Nikolaus Foidl wrote:

> Dear Gerhard!
>
> I only heat the Wood up to 280 degrees Celsius .In my atmospheric  
> kiln this
> takes some 3 hours. ( Gas outlet temperature from the gas tube). I  
> still
> don't know how many time it will take on my new high pressure kiln.  
> The
> torrefied wood is very brittle as most of the hemi cellulose is  
> already gone
> and the cellulose is partially charred. Try with a range of  
> temperature lets
> say from 240 to 320 degrees. The arrow hardening effect is because  
> you get
> in a very short time a complete elimination of cellulose and hemi  
> cellulose
> in the outer layer and then the lignin left at about 300 to 350  
> degrees gets
> over the melting point closing all pores and insulating the wood  
> toward the
> inside. After cooling down the lignin will harden out and render very
> abrasive resistant.( same effect you get in the piston -pellet  
> presses when
> you pelletize sawdust).If you are below this melting point then the  
> lignin
> just gets stripped of the cellulose and hemi cellulose and the  
> reminding
> lignin structure is brittle.
>
> Best regards Nikolaus
>
>
>
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