[Stoves] Misuderstanding of TLUD stoves Re: Refuelable TLUD Coal Stove developed in Mongolia that is not a batch process.

[Paul S. Anderson]

Quoting Crispin Pemberton-Pigott <crispinpigott at gmail.com>:
     snipped
>
> A TLUD is just a down draft built upside down. They can be refuelled  
> continuously but if the desire is to get char out, that could be a  
> problem.
>
This is a very common misunderstanding that was even promoted by Tom  
Reed who initialy call it "inverted down draft" gasification.

In a true downdraft gasifier, there is a hot zone that stays at the  
bottom all the time, and the fuel moves downward to it, becomes char  
and is later subjected to char gasification.  The air flow is also  
downward.

In a TLUD, the hot zone starts at the top, but then the hot pyrolysis  
front migrates downward until reaching the bottom of the fuel pile.   
That is FUNDAMENTALLY DIFFERENT from the downdraft gasifiers.

Furthermore, after the pyrolysis front reaches the bottom, the air  
flow still continues to be updraft.  Placing a significant amount of  
fuel onto the top of the fuel bed can cause variations in the gases  
created (initially much water vapor while the fuel is drying, then the  
pyrolytic gases start later).

Note:  In the case of the Chip Energy Biomass Furnace  
(www.chipenergy.com) which is a true updraft gasifier with continuous  
operation (and the hot zone is at the bottom where the air is  
entering), the new fuel enters in small amounts, avoiding the problem  
mentioned in the above paragraph about water vapor.

I hope this helps explain what is happening in the TLUDs

Paul


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