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

Thu Mar 6 17:08:45 CST 2014

Dear Paul and Stovers,

Most pellets here in the States must pass the required tests so all burn the
same. But I have tested pellets made of paper, chicken manure, cow manure
and many other components. What we are talking of doing we will likely make
pellets from one extreme of the spectrum to the other.  I would think the
quality of the pellets (what they are made of) would be of main concern and
then shape (void space when packed) and air control to match. I, as you
know, do not test stoves but testing the different pellets for char and ash
left varies and this a variable you would want to control. 

Regards

Frank

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Paul Anderson
Sent: Thursday, March 06, 2014 11:35 AM
To: Discussion of biomass cooking stoves; Willem J. Kuipers - Netherlands &
TZ; Bob Fairchild
Subject: Re: [Stoves] Cuber and size of densifying machines. (no longer Re:
The wood and char and fuel "debate" )

Stovers,

Crispin wrote, in agreement with Dean, and I have added the emphasis on
Crispin's words:

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.

Simply, stove devices should NOT be constructed for a specific fuel UNLESS
that fuel is specified and can be supplied.   The issue is just like using
an incorrect grade of gasoline in your automobile.   LEADED gas will not
burn like unleaded.   Super premium is different from regular.    And pellet
sizes are different from each other (assuming that the pellet materials were
also the same, which might or might not have been the case in what Dean has
mentioned.)

Most of the TLUD stoves that have been tested have not been the ones with
serious control of the primary air supply.   Hence the problem that Dean
mentions.   

I do not know of any tests of emissions from different pellet sizes that
have been conducted in TLUD stoves that have serious control of primary air.
One more research topic to add to the list of things to do.

Personal comment:   I have had my hand involved with the development of the
"Champion Family" of TLUD stoves:
1.  Champion TLUD that won the first Cat Pee Award at Aprovecho Stove Camp
2005.   We just had a blocker on the primary air inlet.

2.  Champion by Servals (India):   Still with a rather rudimentary control
of primary air (a disk into a cone).

3.  Mwoto (for BEIA project by CREEC in Uganda):    It has a slider control
of primary air directly on the fuel cylinder, but we had not perfected it
then and did not make much of an issue about closing off the primary air
through tiny gaps such as at the ends the strips that hold the slider in
place..  

4.  Quad (by Awamu in Uganda):  We made a better slider door and placed it
onto  a "snout" for primary air.   But we did not seal with great care.
Also, the tab-and-slot construction left tiny  air leaks that proved to be
too much uncontrolled air.   This was discovered at the July 2013 Stove Camp
at Aprovecho where we progressively sealed better and better the stoves
being tested.   The best sealed stove won one of the Cat Pee Awards.   That
was seven months ago, and we have stopped production of the Quad stove with
tab-and-slot construction (and have sealed better the existing units.)

5.  Troika Bingwa (by Awamu in Uganda):   This stove is just getting out to
the users.   It has a tightly sealed fuel chamber with a slider over the
primary air entry.

Note:   Do not underestimate the impact of even a very very very small leak
of primary air if you expect to have turn-down of a TLUD stove.

Of all the other TLUD stoves, most have no attempt to control the primary
air.   The unit by Prof. Nurhuda does seem to have excellent primary air
control (but I do not have one of those stoves, and there are additional
issues to be considered.)

I hope that these comments are useful for everyone dealing with natural
draft TLUD stoves.   Comments pro or con are most welcome.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD  
Email:  psanders at ilstu.edu   
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 3/6/2014 11:38 AM, Crispin Pembert-Pigott 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

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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