Stoves and furnaces – Fireplaces or accessories
Reexamination Certificate
1999-08-05
2001-05-29
Yeung, James C. (Department: 3743)
Stoves and furnaces
Fireplaces or accessories
C126S30700R, C126S312000, C110S203000, C110S210000, C422S177000
Reexamination Certificate
active
06237587
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to the maintenance of air quality, and more particularly to the reduction of air pollutants from woodburning fireplace emissions.
2. Description of the Prior Art
In recent years the quality of the air has received major consideration. Clean air has become more than a phrase. Significant efforts have been expended to minimize pollutants in the air we breath. Some examples of these efforts are: emission standards have been imposed on automobile exhausts, incinerators in apartment houses have been shut down, and large garbage burning incinerators must meet established standards or be shut down.
Several of the compounds produced during the combustion of wood are of great concern to environmentalists and to environmental organizations, such as the Federal Government's Environmental Protection Agency (EPA), interested in maintaining, or in some cases establishing, clean air. The problem of air pollution caused by the compounds produced when wood burns has been recognized by many, and a growing number of state and local environmental agencies are considering the regulation of wood burning devices.
Emission standards for a majority of combustion processes have been established by the EPA. Though acceptable emission levels for wood burning stoves have been set, there are, however, no federal emission standards for wood burning fireplaces. The lack of standards for a wood burning fireplace is attributable to the fact that, presently, no device exists which can significantly reduce the pollutants emitted from a fireplace when wood burns. These pollutants are varied and many. The primary pollutants being; particles of organic compounds, carbon monoxide, volatile organic compounds, and nitrous oxides.
This lack of emission reduction devices for fireplaces has prompted regulatory agencies, in areas of the country where emissions from wood burning fireplaces are restricted, to ban their use in times of air pollution alerts. Overall, the number of days during which the operation of wood burning fire places are banned is increasing, as are the number of communities that ban their use.
One fireplace pollutant removal device of the prior art utilizes a filter, a fan, and a smoke detector. In operation, the filter is placed in the flue, the fan is positioned above the filter to draw the exhaust gases up through the filter, and the smoke detector is mounted in front of the fireplace. The smoke detector acts as a monitor of gases reflected from a clogged filter and provides an alarm when the filter needs cleaning. A method of removing the clogged filter provides a roll of thin filter-paper which is scrolled through the flue as segments of the filter-paper saturate with pollutants. Since the filter paper may be combustible, this pollutant removal device is a fire hazard and therefore, unacceptable. Assuming that a fire is not caused by over heating the filter paper, when the paper clogs smoke will be emitted from the fireplace into the area adjacent to the wood burning chamber, creating a smoke hazard.
Another fireplace pollutant filter of the prior art utilizes a ceramic fiber duct positioned, along the flow path of the combustion products, between the combustion chamber and the flue. A first duct portion promotes secondary combustion of unburned products of combustion and a second duct portion directs products of combustion from the front of the combustion chamber to the flue. Though some pollutants may be removed by this device by the secondary combustion, many may enter the atmosphere due to an incomplete removal by the secondary combustion and the lax of pollutant removal from the combustion products flowing through the second duct.
Although there are many catalytic devices designed to reduce pollutants in fluid streams, the backpressures created by these devices are too high to allow proper fireplace operation. The increased backpressure hinders the fireplace's draw, causing a variety of unacceptable consequences, including smoke escaping into the house instead of up the chimney.
SUMMARY OF THE INVENTION
The deficiencies of the prior art are overcome in the present invention by properly positioning a reticulated foam, having a ceramic substrate coated with catalytic material, in the fluid flow path of the exhaust from the burning wood. Reticulated foam is a three dimensional latticework of interconnected ligaments forming a porous, open-celled structure. Matter forming the structure covers only 5 to 10 percent of the overall volume. Thus, reticulated foam has an extremely large surface area per volume. Coating the surface area with catalytic material causes fluids flowing therethrough to be exposed to large surface areas of pollutant conversion material. In accordance with the invention, reticulated foam is configured for the location in the fluid flow path at which it is positioned. Heat from the exhaust of the burning wood maintain the catalyst at an efficient conversion temperature. Conversion of pollutants to harmless compounds while a fire is growing or smoldering, periods when the catalyst may not be operating efficiently due to the relatively low temperatures of the exhaust, is accomplished by embedding thermostatically controlled heaters in the reticulated foam. These heaters are activated when the temperature of the exhaust is below a predetermined temperature and are deactivated when the temperature is above the predetermined temperature. The temperature of the catalyst may also be maintained by coupling a thermostatically controlled electrical source directly to the catalyst. Current from the electrical source flowing through the catalyst, which is a poor conductor of electricity, creates heat, causing the temperature of the catalyst to rise.
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Busselle Lincoln D.
Grace Lance C.
Sparling Ralph C.
Levine Seymour
Temeku Technologies Inc.
Yeung James C.
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