[Stoves] TLUD before 1985 needs documentation

Wed Jan 19 13:35:33 CST 2011

Dear Paul

Thanks for picking up on the obvious implications, including the statements
in Christa's recent publication.

Your question and my statement are not on the same page, however: I said
they have been making top-lit updraft stoves since 1958.  You are referring
to TLUD "gasifiers" which are sometimes discussed as a completely different
device, sometimes not. You also referred to TLUD with a link - I didn't
check the link, I am providing the info I have. I think the design
originates from an even earlier Russian stove.

The company is called "Silver". Photos of one of their products are
attached.

All coal fires are gas fires. In some cases (fluidised beds) they operate in
a manner that is clearly different from a batch-loaded stove, even if
periodically refuelled. The stove I referred to is not a fluidised bed
combustor. It is batch loaded and lighted on top.

The Silver Stoves pyrolyse the fuel in a downward moving pyrolysis front
de-volatilising the fuel until it is charred. It then continues to burn the
char which in the case of coal has a name of its own: coke.

I don't think there is anything all that unusual about this. It is a batch
loaded stove that works as you describe.  So I am not propagating a rumour,
I am reporting on an old product. They have something like a dozen models.
The company is 53 years old.

The stove consists primarily of a vertical round container with a controlled
air supply at the bottom (a rotating 'flower' at the back), a grate at the
bottom that can be dumped by rotation around a horizontal bar, and the
ability to shake the grate axially to create air space for primary air to
travel upward if it gets blocked (something missing from John Davies' TLUD
packed bed gasifier). 

The operating method includes filling it, placing ignition fuel on top,
igniting it, opening a top access hole (see photo) for air to get the fire
going, then closing that hole to limit top air and to draw pyrolysing air
through the fuel (using heat in the chimney instead of a fan), the charring
of the fuel creates a combustible gas of volatiles at the top which burns
into a heat exchanger then vents gases up the chimney. The switch from a
'coking mode' to a 'char burning mode' is by opening the bottom air supply
following which the char is consumed. I didn't check to see if it is from
the bottom up or the top down or the whole thing slowly at once.  It is
purely a batch stove with a burn max of about 12 hours.

The descending pyrolysis front dehydrates then devolatilises the fuel
progressively, something clearly seen in a plot of the dilution of the
combustion gases by water vapour. Bottom-lit stoves tend to dehydrate all
the fuel at once (and make a great deal of smoke in the process).
Batch-filled cross-draft stoves are just TLUD's on their side.

So it sounds a great deal like a TLUD gasifier to me so I am modifying my
statement to include 'gasifier' as the combustion type, as it is one.
Perhaps you can point to a significant difference that would put this stove
in a category of its own. It is basically larger version of the Davies
packed bed gasifier made from cast iron with a pretty shell. It is pretty
clean burning (see attached chart) though the CO can be reduced with a small
change to the over-air supply.

Incidentally the thermal efficiency is about 90% on a non-condensing mode.
Quite an achievement.

Regards
Crispin

++++++++

I respectfully request proper and adequate documentation to support your
statement.
>> There is a company in Turkey called SILVER that makes TLUD stoves and 
>> has been doing so since 1958.

I found something that might relate, but certainly does not substantiate
being TLUD combustion technology:

http://www.alibaba.com/countrysearch/TR/solid-stove.html

As the "unofficial self-appointed historian of all things TLUD", I state
that data is needed not only of what those stoves are actually today, but
what they were in the pre-1985 period.

We will gladly acknowledge prior-art (so far, nothing before 1985), or truly
independent development (as is the case with Paal Wendelbo's Peko Pe), but
only when the evidence is in hand.

We are all busy, and I do not expect a fully researched response
immediately, so in the mean time let's not propagate rumors or incomplete
analyses.

Note:  The defining characteristic of the TLUD gasifiers is the "migrating
pyrolysis front" (could be called the MPZ), and not the fact that some stove
has upward moving air (most do) and the initial fire is at the top of the
fuel pile (as could be done in many common stove devices, but with poor
results on emissions).

--
Paul S. Anderson, PhD
Known to some as:  Dr. TLUD    Doc    Professor
Phone (USA): 309-452-7072   SKYPE: paultlud   Email: psanders at ilstu.edu

> On Jan 18, 2011, at 7:03 PM, Crispin Pemberton-Pigott wrote:
>
>> There is a company in Turkey called SILVER that makes TLUD stoves  
>> and has been doing so since 1958. I am in fact reprocessing a test  
>> done in December on one of them, not the smallest version. It peaks  
>> three times at 24 kW during the burn. It behaves badly and needs  
>> better secondary air which I found easy to add. They it was really  
>> good.  I think they had never had a test done before, certainly not  
>> one with gases and PM.  Lots of potential with small modifications.
>>
>> So TLUD is not all that new I guess. It keeps getting rediscovered  
>> because it is a good system at least for some applications.

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