Tim and all (my questions/comments are below) (I am finally at home
after several months with numerous trips.)
Quoting Timothy Roy Longwell <[email protected]>:
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 [email protected]
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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