[Stoves] Emissions from briquettes vs pine wood

[psanders at ilstu.edu]

Tim and all    (my questions/comments are below) (I am finally at home  
after several months with numerous trips.)

Quoting Timothy Roy Longwell <tlongwell at zamorano.edu>:

> Greetings,
>
> Has anyone else done emissions evaluations of briquettes? We have  
> found that briquettes made of a) sawdust, b) grass and c) pine  
> needles (with newspaper as the binding agent) have higher carbon  
> monoxide and dioxide and PM when compared with pine fire wood.

1.  Was this observed multiple  times?

2.  Having higher CO2 does not match up with higher CO and PM.
     Either:
      a.   The amount of fuel (energy value, not the weight) in the  
briquette is greater than the fuel of the pine wood.    or

      b.  The fire is more intense for the briquette, resulting in  
higher CO2 during a shorter period of time.    or

      c.  Something else that needs to be mentioned.

3.  For CO and PM to be higher than is the case for the pine wood,  
there could be some differences within the operation of the stove.  I  
assume that the stove was the same for both the briquettes and the  
pinewood.  (If not, that might be part of the explanation.)  (What  
stove type was it?)

If in the same stove, the difference could be in the placement of the  
fuels.  In comparison with the probable dimensions of the pinewood, a  
"standard" briquette (if there is a "standard") has a greater distance  
from the nearest edge to the half-way point of the thickness of the  
biomass.  (That is, "half of the shortest dimension of the fuel"  
impacts the time needed to pyrolyze to the center and also the time  
before char-gasification can occur in the center of the particle of  
biomass.)

Therefore, during the burning of the thicker briquette, there is more  
time when char is exposed to the incoming air, resulting in more  
char-gasification, therefore more CO that MIGHT somehow escape without  
being combusted by secondary air.

Also, the draft (air currents) throught the briquette fuels might be  
faster in smaller total area, pulling off more PM that rises with the  
emissions.  Also, the micro-structure of briquette particles is  
probably less ridged or firm than the stronger cellular structure of  
the pinewood.  (I believe the evidence is that pine-char will hold  
together much better than briquette-char, impacting how much PM can be  
swept up with the emissions currents.)

4.  You raise an interesting question that merits additional study.   
Perhaps you could make your briquette fuel to resemble the dimensions  
of the pinewood fuel.  If your stove were to be TLUD-type, smaller  
briquette pieces would be needed and the "problem" might be solved??

Paul    "Dr. TLUD"   Anderson      psanders at ilstu.edu
309-452-7072    Skype:  paultlud

******************************
>
> Regards,
>
> Ing. Timothy Roy Longwell
> Profesor Asociado de la Carrera de Desarrollo Socioeconómico y Ambiente,
> Jefe de la Empresa Universitaria Forestales
> E. A. P. El Zamorano
> Honduras, América Central
>

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