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

Tom Miles tmiles at trmiles.com
Thu Mar 6 13:34:20 CST 2014


Dean,

 

US heating pellets are usually about 35 lb/ft3 or 0.56 g/cm3.

 

We make a fuel brick with the German (RUFF) brick machine  that has a
similar density and is hard to light. So we start the fire with lower
density cordwood or kindling and then use the bricks for heating overnight.
These machines are all very expensive. The Chinese firelog machines that I
worked with in Russia made good briquettes and logs for heating but the
machines didn't last very long. That has probably improved.  

 

Tom

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Dean Still
Sent: Thursday, March 06, 2014 11:21 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" )

 

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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