[Stoves] Clinker Formation - Oorja and forced air

[Michael N Trevor]

Here in the Marshalls we had a similar problem when people left the fan running on the charcoal in the bottom of the XL woodgas stove too.
The burned out the bottom. Force draft on coals is good for blacksmithing bot not stoves.
Michael N Trevor
Majuro
From: Paul Anderson 
Sent: Sunday, May 18, 2014 12:15 PM
To: Discussion of biomass cooking stoves 
Subject: Re: [Stoves] Clinker Formation - Oorja and forced air

All,

I like Tom's comments.    And I remind Otto and others that there is a major difference between the TLUD pyrolysis stage in an Oorja and the carbon-burning stage in the same stove that is operated after the Migratory Pyrolytic Front (MPF) has reached the  bottom.   THAT is why the Oorja has the cast iron cup at the bottom, to protect the regular metal from the forge-heats of air blowing on hot char.   With the FORCED air onto that hot char, the cup glows red hot.   And with the forced air the fine particles can be elevated out of the cup and out of the stove, and into the room, as Otto has described.   

Otto wrote: 
  To avoid clinker formation, we just removed the char [from a TLUD stove] , before it starts glowing, namely biochar.......problem solved?
I agree.   But point out that such a solution is equally possible if the TLUD has Force Air (FA).

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 5/18/2014 12:08 PM, Tom Miles wrote:

  Otto,

   

  The TLUD should be the perfect device for high ash fuels. Jock Gill has burned a lot of grass pellets in TLUDS so that should be  good indication. Paul W had burned bundles of grass as you, Otto, probably have. Just as you have described the temperature in the carbon should be well below sintering temperatures low until you reach the char burning stage. At that point you will be oxidizing he carbon at well above 1000C which will melt most ash and you will get clinkers.

   

  The fine carbon burnout will only be as efficient as the gas burning portion of the TLUD even so it should be very good. I agree with Dean that the carbon burnout in a forced draft stove might be an issue. On the other hand you can have low velocities at the grate and higher velocities above the grate burnout should be very good. The challenge is doing that in stoves that operate at low power, poor air control, and burns with very high excess air. It would be difficult to recirculate flue gas in as small stove. Even then you need lower oxygen in the recirculating gas than you can get in a stove. 

   

  Tom    

   

  From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin Pemberton-Pigott
  Sent: Sunday, May 18, 2014 2:48 AM
  To: stoves at lists.bioenergylists.org
  Subject: Re: [Stoves] Clinker Formation

   

  Otto that straw pellet test will be important because it may have all its Cl and K in it so the melting temp will be lowered. 

   

  If processed agri-wastes are to be an important fuel they will have to be accommodated by the designer. 

   

  Regards 

  Crispin 

   

  BBM 2B567C3

        From: Otto Formo

        Sent: Sunday, May 18, 2014 16:39

        To: Stoves Bioenergylist

        Reply To: Discussion of biomass cooking stoves

        Subject: Re: [Stoves] Clinker Formation
       

   

  Dean Still,
  According to Crispin and to our experience, the flames reaching the cooler pot, instantly create char or black carbon - insufficient combustion create more PM and black carbon........!?
   
  The fan driven Oorja, was tested here with woodpellets, four years ago.
  At full blast the "room" was soon covered in a thin layer of soot and ash.
  The cast iron combustion "chamber" was glowing instantly- around 1000 - 1100 C.
  What about ultra fine particles......?? 
   
  Natural Draft gasifiers, are the way forward................
   
  We will soon test the Peko Pe with staw pellets and see the effects of clinker formation.
   
  Using Corn colbs  (agri-waste) as fuel, we noticed a temperature of 450 - 550 C at the top of the flame and around 350 -400 C at the pyrolysis front.
  At the end of the burn, when most gases are utillized and the char starts glowing, we can raech the temperature arond 900 - 1000 C.
   
  To avoid clinker formation, we just removed the char , before it starts glowing, namely biochar.......problem solved?
   
  Otto






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