[Stoves] SIZE OF PELLETS

[Andrew Heggie]

On 5 February 2016 at 20:04, Julien Winter <winter.julien at gmail.com> wrote:

> Beyond that, are considerations of easy fuel handling, and pellet strength.
> We can get denser, stronger pellets if they are smaller.
>


Julien has a good point there, and the others about size of particle
relating to power output.

If you consider that much of the heat and force necessary to
plasticise the lignin is  derived from the friction of the wood
passing through the die then it is easy to see that there will be more
binding effect at the skin than the inside, and after all this is all
that is needed to hold the pellet together. The crushing forces should
also be better in a small die, these are necessary to collapse the
cell walls which is what makes the energy density of the wood pellet
greater.

The other thing is weren't animal feed pellets the precursor to fuel pellets?

In this regard I remember the smaller 6mm pellets being chicken feed
and weaner pellets, 8mm was a similar mix of cereals  for dairy cows
and we had 11mm pellets of sugar beet pulp. I believe the density went
down with size. I'm seeing the same sizes for pellets here in UK.


Yibo Huangfu has sent a photo, too large for the listserv, of a
machine I guess he makes which I attach below. It shows different
shapes can be made. AJH
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