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

[Richard Stanley]

Crispin,
Thanks for the correction. Id like to blame it on the heat here in Nicaragua mid day but its just sloppy typing.

We regularly see bqs produced locally by the wet 12 bar process, specking out  -at ambient humidity,  at 0.25 to 0.3 grams per cc 
Viz; ~500cc briquette volume (dimensions; 10cm dia X 7/5cm tall with a  35mm ID center hole), weighing in at 130 to 150 grams.  
 
Surely some of the 'pelletiers' in our list have toyed with meat mincers right ? Who has experience in this did they fall apart or ?? What fiber integrity was still resident in the extruded  mass to hold them together ?

Am all ears.. Anybody: insights   Looks a fun project.

Richard 



On Mar 6, 2014, at 1:02 PM, Tom Miles 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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