Testing Creosote-Removing Devices

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Our current tests will, we hope, enable us to measure just how much less creosote can be expected in a chimney when a barometric draft regulator is used. In order to maximize the device's possible effect, we're adjusting it for the minimum draft setting that's consistent with the firing rate and heat output typically used in a home installation.

THE SMOKE CONSUMER

The Smoke Consumer consists of a knitted wire mesh filter mounted under a cast-iron plate. The assembly can be positioned either at a right angle or parallel to the smoke flow . . . just as can a simple stovepipe damper. When the filter is in the closed (across the flow) position, much of the flue gas moves through its passageways (of course a little smoke does flow around the device, in the space between the plate and the stovepipe wall). The manufacturer claims that the Smoke Consumer reduces creosote by filtering out particles. Consequently, the filter requires periodic cleaning: Maintenance includes a recommended "continuous burn reactor cycle" once a day—which involves running the stove hot enough to burn material off the filter—and manual cleaning of the mesh (by removing it from the unit) weekly.

THE SMOKE DRAGON

The Smoke Dragon is a catalytic afterburner and heat exchanger that's de signed to ignite any smoke that hasn't been burned in the stove itself. The Smoke Dragon's catalytic combuster—which is made by Corning Glass Works—is a ceramic honeycomb structure, about six inches in diameter and three inches long, coated with a very thin layer of a noble-metal catalyst (such as platinum and/or palladium).

Essentially, the catalyst lowers the ignition temperature of the smoke from around 1100 or 1200°F to about 400 to 600°F. Thus, if the gas is hot enough, and if it contains adequate oxygen, much of the material will be burned in and just above the catalyst. Furthermore, once the catalyst begins working, the smoke temperature can fall without ill effects . . . since the heat being generated by the burning gas in the catalyst will warm the incoming fumes enough so that they too will ignite. The Smoke Dragon has the potential for reducing creosote, cutting air-polluting emissions, and increasing the energy efficiency of the system with which it's used (much of the heat released in the combuster is recovered by the heat exchanger).

However, in practice it's difficult to predict the performance of catalytic devices. Factors that could influence the overall effectiveness of such a unit include smoke density, oxygen concentration, the degree of mixing of oxygen and smoke, flue gas temperature, and the amount of both intentional and unintentional smoke bypass. Thus, only through testing can the actual effectiveness of devices such as the Smoke Dragon be determined.

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