Résumé

In order to reduce pollutant emissions, a commercial wood log stove with staged combustion was fitted with an exhaust gas after treatment device based on a metal-based oxidation catalyst coated with platinum and palladium followed by a sintered metal particle filter (both used on diesel internal combustion engines) and a regulated exhaust gas fan for draft control. The tests were performed with standardised logs (wood species, size and humidity) precisely positioned in the furnace. Further, an exhaust gas draft control based on the pressure at the stove outlet enabled achievement of better operating stability than draft control based on the temperature. Regarding the exhaust gas emissions, the use of a catalyst lead to a complete (i.e. 100%) carbon monoxide (CO) oxidation, independently of both its internal structure and length, as well as the draft control parameter (pressure or temperature). In the case of draft control by pressure, the catalyst resulted in a significant reduction of polycyclic aromatic hydrocarbons (PAH) by 65 to 90 %, increasing with the cell density. The addition of a particle filter downstream had the same influence on particles emission as an increase in cell density. On the other hand, the exhaust gas temperature at the level of the catalyst was too low to permit significant methane (CH₄) oxidation and reduction of nitrogen oxides (NOx). The use of a particle filter enabled a minimum of 90 % reduction of the mass emitted. However, this also lead to an important increase of the pressure losses between the stove and the fan inlet, resulting in higher electricity consumption. Globally, an active combustion control by draft regulation combined to an exhaust gas after treatment based on oxidation catalyst and particle filter appears to be a promising solution to reduce wood log stove exhaust gas emissions and should be further studied.

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