[Stoves] Stove comparison/ PM

[Paul S. Anderson]

Crispin and Alex and all,

One clarification about this comment from Crispin:
>> As you know, the
>> essence of the biomass gasifier stove claim is that it is the gasification
>> process that creates a clean burning gas, by leaving the PM producing carbon
>> behind

I believe there are two (probably more?) sources of PM.  One is from  
the NON-combustion of the volatiles, which is the case IF the fire  
goes out at the upper combustion of the gases from the TLUD.  And Alex  
stated that also below.

The second source is the point of confusion with the comment from  
Crispin.  In the TLUD when char is created, the carbon even when very  
free from volatiles is also holding much of the ASH that is in the raw  
fuel.  When the char/carbon is burner (char gasification), that ash is  
being released and some (the smallest particles?) is able to be  
carried upward by the air currents, giving the PM reading.  The carbon  
does not produce the PM.  It was just holding the matter that could  
escape as PM in some circumstances.

Note that the PM from TLUDs is lowest when the char is note  
char-gasifier, is higher when the TLUD combusts everything down to  
only ash remaining, and both of those amounts of PM are LOWER than  
what is the PM from a charcoal burning stove (when compared by the  
WBT:  The data are in my graph of CO and PM emissions that reports  
data from WB tests at Aprovecho.

But the vast majority of potential for PM is from "smoke" that is not  
combusted, and a proper burner (such as the concentrator lid) on a  
TLUD does a very good job of getting that smoke combusted.

I do NOT have specific scientific tests to support the above  
statements about ash in char.  Maybe someone else (those working on  
charcoal stoves?) has such data or would conduct the tests.

Paul
-- 
Paul S. Anderson, PhD
Known to some as:  Dr. TLUD    Doc    Professor
Phone (USA): 309-452-7072   SKYPE: paultlud   Email: psanders at ilstu.edu
www.gtz.de/de/dokumente/giz2011-en-micro-gasification.pdf   (Best ref.)


Quoting Alex English <english at kingston.net>:

> Crispin,
>
> Glad to know there are still mysteries to be probed.
>
>
>>
>> Agreed. I am becoming more convinced that temperature has more to do with it
>> than perfectly balanced air supply. I am seeing some unexpected things. One
>> is a very low PM level from a TLUD stove with 0.5% excess air.
>
> I assume this is with coal. Do you have this data logged to share?   
> Are you doing PM testing with wood fuel?
>>
>
>>
>> Interesting, eh? Burn cleanly the volatiles then burn even more cleanly the
>> carbon. Perfect for biomass stoves. To put a number on it, stoves with
>> nearly no non-carbon in the fuel pile are consistently produces only a few
>> microgrammes of PM over a period of several hours. It is in the non-carbon
>> gasification phase that the PM is produced (potentially). As you know, the
>> essence of the biomass gasifier stove claim is that it is the gasification
>> process that creates a clean burning gas, by leaving the PM producing carbon
>> behind. It is not supported by observations that include real-time
>> monitoring of the PM (i.e. watching when it is produced and when not).
>
> Snuff a biomass fueled TLUD and its a PM cloud. So its the burner  
> that matters. If PM shows up above the flame then it is likely  
> sneekage due to insufficient mixing and/or too large a space for the  
> flame PM laden gasses slipping by in the outside lane.
>
> Good wood pellet stoves have low PM without being gasifiers. Low  
> moisture helps. What role does the flue particle size and  
> distribution and depth on the grate play? Your coal is pea sized, I  
> think? Have you found any  differences with large sized fuel?
>
> Alex
>
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