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Intrepid II Woodburning Stove
30003840
Appendix: Catalytic Combustor
In any chemical reaction, including the combustion
process, there are certain conditions which must be
met before the reaction can take place. For example, a
reaction may require a certain temperature, or a certain
concentration of the reactants (the combustion gases
and oxygen), or a certain amount of time. Catalysts,
though not changed themselves during the reaction,
have the ability to act at a molecular level to change
these requirements. In the Intrepid II’s secondary
combustion chamber the catalyst reduces the tempera-
ture at which secondary combustion can start from the
540 - 650° C (1000 - 1200° F) range to the 260 - 315° C
(500 - 600° F) range, increasing efficiency, and reduc-
ing creosote and emissions.
The catalytic reaction, though advantageous, does
have some limitations of its own. Primary among these
it that the reactants (the gases) come into close physi-
cal contact with the catalyst itself.
To ensure the necessary contact, the catalytic element
in your Intrepid II is composed of a ceramic base in the
shape of a honeycomb. On each of the honeycomb’s
many surfaces a coating of the catalyst (usually a
noble metal such as platinum or palladium) is applied.
The large surface area exposed in this configuration
ensures that the combustion gases have the greatest
opportunity to come in contact with the catalyst.
Loss of catalytic activity will be apparent in several
ways. First you may notice an increase in fuel con-
sumption. Second, there will be a visible increase in the
rate at which creosote builds up in your chimney con-
nector system. You may also notice a heavy discharge
of smoke from the chimney. A number of catalytic
problems which can cause loss of activity are described
below:
Blockage
While the honeycomb pattern ensures good contact, it
also increases the resistance to flow of the combustion
gases, and, because of the many surfaces, provides
more places for creosote and fly ash to deposit. It is
important to follow the operating instructions in order
to minimize these deposits, and to periodically inspect
your catalyst for signs of blockage.
Masking and Poisoning
While the catalyst itself does not enter into the combus-
tion process, it is possible for certain elements, such
as lead and sulfur, to attach to the active sites on the
surface of the honeycomb. Though the catalyst is still
there, it is covered, or masked, by the contaminant, and
cannot function. To avoid this situation, it is important
not to burn anything in your Intrepid II that is a source
of these contaminants. Particularly avoid painted or
treated wood, coal, household trash, colored papers,
metal foils, or plastics. Chemical chimney cleaners may
also contain harmful elements. The safest approach is
to burn only untreated, natural wood.
Flame Impingement
The catalytic element is not designed for exposure to
direct flame. If you continually overfire your Intrepid
II, the chemistry of the catalyst coating may be altered,
inhibiting the combustion process. A glowing stove part
at the back of the firebox is a sign of over-firing.
Thermal degradation of the ceramic base may also oc-
cur, causing the element to disintegrate. Stay within the
recommended guidelines of the Operation section.
Mechanical Damage
If the element is mishandled, damage may occur.
Always treat the element carefully. Remember the
catalyst is made of a ceramic material; treat it as you
would fine china. Hairline cracks will not affect the
performance of the catalyst, as long as the steel sleeve
holds the element in the proper position.
Peeling
Peeling of the surface coat may occur if the catalytic
element is frequently subjected to excessive tempera-
tures. Follow the operating instructions carefully to
avoid this type of damage.
Every CFM Corporation product is equipped with either
a Corning “Long-Life”
®
or a Technical Glass Products
“Honeycomb”
®
. The products are equivalent. If for any
reason you must ship your catalytic element, remem-
ber its fragile nature. Place the element in a plastic
bag, and package it with a generous amount of shock
absorbing material.