[Stoves] Calc. void space and pellet particle density

[Crispin Pembert-Pigott]

Dear Andrew

This was really useful:

>Of course we are starting with sawdust which is 1/3 the bulk density of dry
wood so in fact we have to squeeze a 30mm column of sawdust down to 3mm the
average force times 27mm is the energy necessary to do that, neglecting
friction, or are my numbers too far out? Tom Miles said the pressure
necessary is 2000psi so that seems to be an average weight on the 6mm column
of only 40kg (~400N) moved through 0.027m ??
I make that ~11Joules. The pellet has a mass of 0.378 gramme and a calorific
value of 7036 Joules so the which seems to give a very low figure of 0.16%
of the heat energy  is required in motive energy to compress the sawdust.
Unless my suppositions are wildly out the losses in the pellet making system
are high as we worked on 2.5%.

>Also the air space being greater than the solid space is more than I
expected.

The rest of the energy goes into heat, I suspect. In order to get that
density isn't it necessary to crush the cell structure of the wood,
releasing the lignin? 

Thanks
Crispin