GAS-L: Checking out Catalytic burners - Part 3

[Peter Singfield <snkm@btl.net>]

Continuing along these lines:

(Peter Singfield / Belize)

 From:

 http://www.eren.doe.gov/consumerinfo/refbriefs/bb5.html

Catalytic Combustors in Wood-Burning Appliances 

If you are shopping for a wood-burning home heating appliance, the dealer
may offer you a unit with a catalytic combustor. Catalytic combustors are
similar to catalytic converters in automobiles. They are honeycomb-shaped
discs made of glass or ceramic with a rare-metal catalyst coating. They are
usually located across the exhaust vent of stoves. As smoke passes through
the combustor, the gases and particulates in the smoke react with the
catalyst. The reaction lowers the combustion temperature of the gases and
particulates, which causes them to burn up in the combustor. Catalytic
combustors decrease emissions and increase overall fuel efficiency by
25%-30%. New catalytic wood stoves and inserts advertise efficiencies of
70%-80%.

Maximizing the Performance of Catalytic Combustors

Catalytic combustors last from 1 to 10 years, depending on the stove, the
fuel used, and how often the stove is used. To help maximize the
performance and life of wood-burning appliances, manufacturers provide
guidelines in the owner’s manual for appliance operation, combustor
maintenance, and catalyst replacement.

To operate properly, a catalytic combustor has to reach at least 600o F
(316o C) and hold that temperature for 10 minutes. (Note that exposure to
direct flame can severely damage catalytic combustors. They should be
installed with a flame deflector plate or otherwise protected from direct
flame contact.) You can ensure that the combustor reaches its optimum
temperature by starting the fire with dry kindling and small pieces of
wood. You can then adjust the temperature of the fire for comfort without
affecting the combustor performance. Reloading the stove, however, may
lower the temperature of the exhaust gases, and decrease the effectiveness
of the combustor until it reaches its operating temperature. To avoid this
problem be sure to follow the manufacturer’s instructions for reloading
your stove.

The ceramic element of a catalytic combustor tends to deteriorate over
time, because of the repeated heating and cooling of normal stove use. You
should check the condition and performance of a combustor frequently. Most
catalytic stoves or inserts have a view window or thermometer to help you
check the combustor. The catalytic cell is removable and replaceable and
costs between $75 and $160.

Burning plastics, paint, colored paper, and other materials that contain
chemicals, such as lead or potassium, will ruin the catalyst. Warranties
will not cover damage to the combustor from burning trash in the stove. To
maximize the performance and life of a catalytic combustor, follow the
manufacturer’s instructions on the type of wood fuel recommended for the
stove.

Stoves with catalytic combustors are best for long-term use. They are most
appropriate for homeowners who use wood as their major heat source or for
those who wish to reduce air pollution from burning wood.

Retrofits

If you want to retrofit an existing non-catalytic wood-burning appliance
with a catalytic combustor, you can buy a catalytic damper. These are
available as kits and are usually installed in the flue collar. To monitor
the stove temperature after adding a catalytic combustor, you should also
install at least one heat sensor on the stove body or stove pipe. Several
manufacturers sell retrofit kits, and they may be available from woodstove
retailers. They are not appropriate for all types of stoves. Again, be sure
to follow the manufacturer’s installation and operating instructions.

For More Information

A free brochure Catalytic Woodstoves: Installation, Operation, and
Maintenance (Order Number: EPA450K92006 Source Name: OAR) is available from
the:
U.S. Environmental Protection Agency (EPA)
Office of Air And Radiation
1200 Pennsylvania Ave NW (6101)
Washington, DC 20460
Phone: (202) 260-0594; Fax: (202) 401-4761
World Wide Web: www.epa.gov/oar/oarhome.html
To view the document on-line, visit:
www.epa.gov/Region10/offices/air/catalyti.html




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This brief was updated in May 2001.

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