[Stoves] propensity for density not always 'compensity'

[Legacy Mail]

The problem with the heating of the mass is also compounded by the fact that the augur if one is being used, wears out quickly. The hardened steel augurs I have seen had to be rebuilt or replaced every few weeks. the other option (between high pressure temperature extrusion and at the opposite end, reverting to added binders is the softening and randomising of alignment of the fibers inherent in many biomass materials. That process requires working pressures of only 12 to 18 kgs per cm^2 , often ( if paper is involved) far less than that. Increasing density is more a matter of infilling the "hairy matrix" with denser materials. Normal range is .3 to .5g/cc but adding dense fines of eg., char or hard wood sawdust , to a really well pulped fibrous slurry  example can increase it to .8. 
really high density briquettes are often harder to ignite. more duration and better for commercial heating or other process operations--true, but the issue for the household cook is often more one of ease of startup and rapid rise to working temperature with a minimum of smoke. A medium to lighter density briquette 
is often a better choice in that setting.

Sent from my iPhone

On Jun 12, 2013, at 1:00, ajheggie at gmail.com wrote:

> [Default] On Wed, 12 Jun 2013 12:53:02 +0700,Paul Olivier
> <paul.olivier at esrla.com> wrote:
> 
>> How does lignin soften to become a binding agent using a meat grinder?
>> This would be truly wonderful, if it were true.
> 
> It won't with a meat grinder, you will need some sort of binder, like
> boiled starch or clay.
> 
> Lignin plastisises under high pressure and heat, the heat is normally
> derived from the friction of the material passing through the die. At
> these pressures the cell walls collapse and then the lignin re sets to
> form a pellet that is denser than the wood it was made from. All these
> systems use a lot of power and the expensive dies wear.
> 
> The Shimada press is the one that produces a hexagonal log with a hole
> down the middle, often blackened on the outside from the heat from the
> press walls. 
> 
> Similarly rotary die extruders  use pinch rollers to punch small
> amounts of feed through the holes.
> 
> 
> Have a look at:
> 
> http://www.fao.org/docrep/x5738e/x5738e0j.htm
> 
> 
> AJH
> 
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