TYPES OF WOOD STOVES
The purpose of this section is to define some of the wood stoves available. It is not our intention to favor one type or brand over another. It is important to note that home-made stoves may pose a serious fire threat and may make your home fire insurance invalid.
CATALYTIC COMBUSTION HEATERS
Corning Glass Works has developed a catalytic afterburner for wood stoves that may increase the efficiency and decrease air emissions. It is intended to be built into stoves by the manufacturer and it is in the form of a ceramic honeycomb, coated with a metallic catalyst. The catalyst burner lowers the ignition point of smoke from 1300 oF to about 500 oF, allowing more of the smoke to burn before it leaves the stove. By burning the smoke, there is more complete combustion and less pollution. This catalyst is available only to stove manufacturers who design their stoves with a bypass around the catalyst in case it becomes plugged. Certain materials capable of clogging this catalyst include metallic paper and foil, manufactured logs with chemical binders and coal. The catalytic combustor has been introduced by a number of wood stove manufacturers and is now commercially available. Also catalytic inserts for wood stove flue pipes are available.
TWO-CHAMBER COMBUSTION SYSTEMS
Wood heaters which incorporate two separate combustion chambers within the same unit are available. The purpose of this two-chamber arrangement is to provide optimal conditions for the complete combustion of gases and charcoal formed during pyrolysis. Each chamber is fire- bricked lined and has separate air inlets for primary and secondary combustion air. Wood combustion occurs in the bottom chamber, with primary combustion air being introduced underneath the grate and toward the back of the unit. This causes the wood to burn from back to front. The volatile gases produced during the pyrolysis process flow to the upper chamber where a high-speed stream of preheated air along with high temperatures (2000 oF) cause combustion of the gases.
A recent development for the home market is the pellet stove. This type of stove has been in use for 60 years by industrial users and now the design has been made small enough for home use. The basic principle is that stored, dry wood pellets are fed a few at a time into a burning chamber where, with forced air, they are burned at high temperatures. This gives the most efficient combustion for the wood used and results in very little smoke discharge. The stove does require electricity to operate and the pellets are more expensive than cordwood. The stove is considered the most fire safe.
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