[Stoves] Pellet stoves - risks

[Crispin Pemberton-Pigott]

Dear Andrew

Can we realistically run a pelleter at 280 C input and save energy? The output is already charring the material. Perhaps that is torrefaction on the fly, so to speak. If so, the MJ/kg should rise with processing. 

The pellets are have in Java are 8% moisture (Albasia). IF it gets really hot and was bagged, it should be zero.

Crispin


Frank on the large scale I doubt it is a problem because as you heat wood up through 100C and drying and then on to the evolution of some VOCs to this 280 C torrefaction range you are always in an endothermic reaction, let it slide above 330C and it becomes mildly exothermic, so with a bit of feed back it should be possible to stay around280C with no thermal runaway. By thistemperature presumably lignin is quite plastic so pelleting power should be lower.I'm not sure what chemical changes are taking place but I'm assuming some hydroxyl groups  are being lost, making the material less able to attract water i.e changing from hydrophilic to hydrophobic, so unlike sawdust pellets torrefied pellets should store better without attracting moisture and disintegrating. What are they like when dropped in a glass of water for an hour or two?

With large scale it will also be easy to incinerate the low cv offgas given off bythe process.

AJH