[Stoves] Cuber and size of densifying machines. (no longer Re: The wood and char and fuel "debate" )

[Dean Still]

Hi Tom,

In Uganda the pellets were too dense and were hard to light. Do you know
the density of USA heating stove pellets?

Best,

Dean


On Thu, Mar 6, 2014 at 11:02 AM, Tom Miles <tmiles at trmiles.com> wrote:

> Richard,
>
>
>
> You probably mean 0.6 g/cm3 (37 lb/ft3) which is very good that's better
> than most commercial wood pellets. For reference the dry density of sawdust
> is often about .160 g/cm3 (or 10 lb/ft3). The loose density of straw is
> about 0.08 g/cm3 or (5 lb/ft3). The press roll on a pellet mill exerts
> about 142 bars (2000 psig). If you can get those densities by selecting
> materials, wetting, pressing at 12 bar and drying you are doing very well.
>
>
> Tom
>
>
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Legacy Found
> *Sent:* Thursday, March 06, 2014 10:46 AM
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] Cuber and size of densifying machines. (no longer
> Re: The wood and char and fuel "debate" )
>
>
>
> Crispin, what densities are you seeking. We have seen densities of up to
>  0.6kg/cm^3 by use of really fine granular material charcoal sawdust and
> certain other ag residues as infiller in hand presses generating only about
> 12 bars pressure.
>
> I have not attempted pellet production but have no doubt that high
> pressure is not needed: Rather its more about attention  to blend particle
> density and size and variations between these (sorting coefficients) that
> makes the difference density wise.
>
> May look into it if anybody is interested in the fuel pellet world.
>
> Richard
>
> Sent from my iPhone
>
>
> On Mar 6, 2014, at 11:38, Crispin Pembert-Pigott <
> crispinpigott at outlook.com> wrote:
>
> Dear Friends
>
>
>
> I agree with Dean on this score. The air flow through the pellets strongly
> affects the way they burn if the device is constructed such that the fuel
> contributes a significant element of air control.
>
>
>
> These devices
>
> <image002.jpg>
>
>
>
> Are 'cubers' in that they are producing densified lumps that can be put
> into a stove. But they will work best in a large stove such as is used in
> China for space heating and cooking.  The input material is straw and other
> stover.
>
>
>
> The mechanism is an eccentric roller running inside a perforated cage at
> maybe 60-100 RPM. As Tom notes, power consumption is about 110 kW.
>
>
>
> So far I don't think the product is economically viable as there is a
> subsidy involved. What we need is a breakthrough technology that will make
> densified fuel without the need for heat.
>
>
>
> Regards
>
> Crispin
>
>
>
>
>
>
>
> Hi Paul,
>
>
>
> I have seen the very small pellets sold for heating stoves in the US burn
> very cleanly. Larger sized pellets did not burn as cleanly.
>
>
>
> Best,
>
>
>
> Dean
>
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