Vermont Casting 2160 - Manual (Page 28)

28
Dutchwest Sequoia
2001049
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 require-
ments. In the secondary combustion chamber of the
Sequoia, the catalyst reduces the temperature at which
secondary combustion can start from the 1000 - 1200
°
F.
(540 - 650
°
C) range to the 500 - 600
°
F. (260 - 315
°
C)
range, increasing efficiency, and reducing creosote and
emissions.
Though it is advantageous, the catalytic reaction does
have some limitations of its own. Primary among these is
that the reactants (the gases) come into close physical
contact with the catalyst itself.
To ensure the necessary contact, the catalytic element in
your Sequoia 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 consumption.
Second, there will be a visible increase in the rate at
which creosote builds up in your chimney connector
system. You may also notice a heavy discharge of
smoke from the chimney. There are a number of catalytic
problems which can cause loss of activity:
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 Sequoia 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 Sequoia, the
chemistry of the catalyst coating may be altered, inhibit-
ing the combustion process.
Thermal degradation of the ceramic base may also occur,
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 Dutchwest 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, remember
its fragile nature. Place the element in a plastic bag, and
package it with a generous amount of shock absorbing
material.
Catalytic Combustor