[Stoves] New kind of Sawdust stove

Tue Oct 25 15:27:16 CDT 2016

All,

This is a good contribution to the list. It is a challenging device to 
define. For me the real value of defining the type of a stove is that it helps me to think 
through how the stove works. Some things that I note are:

It seems that it could burn most any fuel, saw dust, rice husks, wood chips, 
wood sticks and logs, pellets, coal... It would burn all of these down to 
ash.  A version might also be able to burn liquid fuels.

The primary air in the pipe is moving downward, and there is no primary air moving up through the fuel. The flame receives it's air from above rather than below so it is more like an open fire than a gasifying stove.  A difference is this fire receives air from the center instead of the sides like an open fire.  There is no pyrolysis front, the fire is just simply burning down through the fuel.  Also the primary air is not limited as in a low oxygen pyrolyzing environment.  There is a lot of primary air, enough to burn a large portion of the gas, so actually the primary air enters together with secondary air.  There is more secondary air added later, but it does not look very efficiently introduced.  The stove probably produces lots of particulates.  

There is no mechanical forcing of any pyrolysis front.  There is pyrolysis just as there is pyrolysis in an open fire, that is how wood burns.  But there is no migratory pyrolytic front in a low oxygen atmosphere with the specific intent of producing wood gas to be burned elsewhere.  

A shorter cook stove design need not have a moving pipe, a short length of pipe will do to direct the air down to the fuel.  Attached is a sketch of a stove that I used while living on Long Island, NY.  A short length of pipe is all that was needed to make this stove burn without smoke.  The counter current flow of the secondary air produced a very good mix.

All the gasses in any natural draft stove end up comming out at the top.  Even in the type of stove called down draft, it is the up draft of the gasses in the chimney part of the stove that powers the gasses to move downward in the pyrolysis part of the stove.  The primary air in a down draft stove moves down until it hits the burning fuel, then the pyrolysis gasses mix with the secondary air, and then the flame gasses go sideways, finally to rise in the chimney section.  This is similar to what is happening in this stove.  The primary air moves downward till it hits the burning fuel, then the flame gasses move sideways to the chimney area and begin to rise.  The major difference is that the secondary air is added with the primary air and again later in the chimney.  To me this stove more closely resembles the stove called a down draft stove than a TLUD.  I see it as a stove that uses down drafted air to fan the fire.  

The stove keeps the surface char red hot, so two things: First it burns the 
char to ash and second this is one of the techniques for turn-down, so it may have good 
turn-down capability.  After a while ash will build up on the fuel surface, which might influence the power output or how long it can burn.

This is a very interesting design which has some good qualities.  

Kirk H.

----- Original Message ----- 
From: "Andrew Heggie" <aj.heggie at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Monday, October 24, 2016 2:15 PM
Subject: Re: [Stoves] New kind of Sawdust stove

> On 24 October 2016 at 19:57, Paul Anderson <psanders at ilstu.edu> wrote:
>> Crispin, Andrew, and all,
>>
>> I am glad that it works, and I am not totally sure what type of 
>> combustion
>> method it uses, except that it does not fit the description of a TLUD 
>> stove,
>> which is characterized by a migrating pyrolytic front (MPF).
>
> I think the TLUD with pyrolysis of some of the fuel is a special case,
> because if primary air is unrestricted it also provides sufficient
> oxygen to burn out any nascent char to CO2 and CO which mix with any
> pyrolysis offgas to be further burned out in the secondary flame
>
> AJH
>
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  ----- Original Message ----- 
  From: Ronald Hongsermeier 
  To: Discussion of biomass cooking stoves 
  Sent: Tuesday, October 25, 2016 12:14 AM
  Subject: Re: [Stoves] New kind of Sawdust stove

  Paul,

  I publicly apologize _here_ because you're making the big deal about it, while Crispin is actually trying to keep a clear taxonomy, which, due to your predilection for _geography_ is kind of like the difference between rocky or sandy or grassy coastlines. 

  It is quite clearly a TLUD. 

  Primary air comes down the pipe connecting the handle to the top, which acts as a holder for the mechanical forcing of the migrating flame front. My apology has to do with my initial understanding/confusion as to the placement of the secondary air holes, which I thought were being fed by the central tube, allowing airflow into the part of the migrating part below its "lid". However, in actual fact the secondary air comes from holes in the outer container, which also acts as a chimney with all gas flow ending at the top, which clearly makes it an up draught. 

  I agree with Crispin, (with apologies to everyone but you on this point) that it doesn't matter where the primary air comes from and agree with you that the migratory front is (kind of) part of the general definition, but only for those stoves in actuality that are not robust enough in terms of fuel variability to go beyond simple batch loading. If you put fuel in the top, it's "TL" that's why Crispin is asking for the "pyrolytic" variable in the taxonomy. 

  regards,

  Ronald von gesternwarfönbayern

  On 25.10.2016 03:01, Paul Anderson wrote:

    Crispin,      (with apologies to everyone else.)

    Come on Crispin, get off it.  You are just causing confusion regarding the estabilished terminology!!!   It is easy to mis-use words and descriptive acronyms, but you of all people should know better about what TLUD signifies.   Do not put yourself down with such silly talk!!

    Besides, in your next message (addressed to Andrew and the Listserv), YOU wrote: 
      It looks and acts like a TLUD but has zero air coming from below. 

    How can you imply that "zero air coming from below" is somehow an "up draft"?   And then to call it a TLUD?

    You are a friend and very talented, but get real.  Please stop confusing the terminology that is getting accepted and understood.  

    There can be up draft stoves and top lit stoves.   But the acronym "TLUD" is something quite specific, and the migratory pyrolytic front (MPF) is its very distinctive characteristic.  If MPF is not clearly evident, a stove should not be called a TLUD.

    Enough.   I hope there is silence about this subject.  But do go ahead and talk about the new kind of Sawdust stove.

    Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.comOn 10/24/2016 4:23 PM, Crispin Pemberton-Pigott wrote:

      Dear Paul
      It is definitely a TLUD but it is not a TLUD pyrolyser which is a subset of all things top lit and updraft. 
      Perhaps the TLUD builders have slipped into using the shorter form of the name.  
      Couldn't you have:TLUDTLUD gasifierTLUD pyrolyser (with various levels of carbon gasification)‎?
      I have not tested it yet with a meter to see how well it burns but it definitely works. 
      It is replacing a huge square, almost cubic steel TLUD loaded with coal which seemed to have no secondary air and no flame space. They said it worked for a long time on a load of fuel but was 'very smoky'. It didn't even look like a stove. I thought it was a storage bin. 
      RegardsCrispin 

      Crispin, Andrew, and all,

      I am glad that it works, and I am not totally sure what type of combustion method it uses, except that it does not fit the description of a TLUD stove, which is characterized by a migrating pyrolytic front (MPF).  And a TLUD does not have "primary air supplied from above."

      Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype:   paultlud    Phone: +1-309-452-7072
Website:  www.drtlud.comOn 10/24/2016 1:28 PM, Andrew Heggie wrote:

        On 24 October 2016 at 09:57, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:

          Summary: It is a TLUD with primary and secondary air supplied from above.  The stove is used to heat the office of the welding shop.

          Crispin

        Unless I have misread your description I would say this is a Top Lit Cross Draught.

        It's similar to a device I made to burn stumps out of the ground using a ford tractor wheel but I used an old vacuum cleaner to Blast the air in.

        AJH 

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