[Stoves] Trials on TLUD Gas Burners - Counter Current Flow - Equivocal Results

[Julien Winter]

Hi Stovers;

I have made some additional observations on a 'counter current' burner
(CCB) on a 17 cm diameter natural draft, top-lit updraft gasifier, using
wood chips and wood pellets.  A more conventional burner with a ring of
holes in the chimney side-wall was also used.  Thermocouples measured bed
temperature (more on that later).

During Phase I pyrolysis of the fuel, the CCB maintained a temperature (ca.
650-700 °C) at the surface of the char/fuel bed, while the temperature for
the convention burner declined.

The CCB did not self regulate the volume of secondary air very well, so
that when primary air was cut back, the gas/air mixture became too lean,
and the flame went out.  A CCB would have to have some mechanism to
regulate secondary air.  That was not unexpected.

The CCB didn't have any special ability to maintain char gasification on
the top of the char bed as previously thought.  The flame at the top of the
char from wood chips also occurred with the conventional burner.  The flame
was a property of the fuel that formed a very open bed of char, and not the
burners.  No CO flame occurred on the top of a bed of wood pellet char.

While the CCB may be useful if one wants to keep the char bed hot
during Phase I pyrolysis, the need to regulate secondary air is a
complication that may not be desirable for stoves used by the public.  Like
many burners, the CCB will work on a stove running on high primary and good
fuel.

I am not continuing to work on this burner, unless circumstances change.

Cheers,
Julien.





-- 
Julien Winter
Cobourg, ON, CANADA
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