Extensive reduction of toxic gas emissions of firewood-fueled low power fireplaces by improved in situ gas sensorics and catalytic treatment of exhaust gas

High-temperature CO / HC gas sensors to optimize firewood combustion in low-power fireplaces

“…For complete combustion over a whole batch of combustion processes, the reaction kinetics for the complete oxidation of the flue gas components should be high enough, i.e. at temperatures higher than ∼ 700 • C, provided that the retention time in the post-combustion chamber is long enough (Butschbach et al, 2009). This means that in a batch firing process, complete combustion is possible only in the high-temperature (HT) combustion phase which follows the ignition phase (IP) and ends with a transition to the burnout phase (BOP).…”

“…This requires the implementation of proper automated and optimized combustion airstream control strategies. Further, an improvement in combustion quality can be achieved with catalytic support to the post-combustion process, even in the phases of lower combustion temperatures (Butschbach et al, 2009). It was reported that operational conditions, like the ignition technique (upside-down or bottom-up), fuel type and use of split or non-split firewood, also have a strong influence on the combustion quality (Vicente et al, 2015).…”

“…However, our previous investigations conducted at various fireplaces (Butschbach et al, 2009;Kohler et al, 2010) have shown that for the efficient operation of low-power fireplaces, it is not only essential to enable sufficient combustion air but also to avoid cooling effects in the post-combustion chamber by supplying excess air throughout the firing process. This means that the proper adjustment of the combustion air has to be defined by separate control of the airstreams into the primary and post-combustion chambers and cannot be based solely on Tc and ROC (this strategy is commonly adopted in gasoline-and diesel-fuelled combustion engines) due to the incomplete admixing of the pyrolysis gases with injected air.…”

“…However, the suitability of a CO / HC sensor for in situ application in the exhaust gases from firewood combustion processes is not well investigated. High-temperature gas sensors using mixed-potential electrochemical cells based on yttrium-stabilized zirconium oxide (Butschbach et al, 2009), chemoresistive metal oxide sensors (Eskilsson et al, 2004;, SiC-based field effect transistors (Andersson et al, 2013) and, perhaps, thermoelectric hydrocarbon sensors (Wiegärtner et al, 2015) are reported to be possible candidates for these applications.…”

“…This is accomplished by comparing the results of an automated firing experiment on a log-fuelled single-room heating furnace with those conducted in a hand-controlled furnace of the same type operated according to the instructions given by the manufacturer. The experimental details related to the aspects of the reproducibility of these experiments and to the concepts of airstream control are reported elsewhere (Butschbach et al, 2009;Kohler et al, 2013). The second and main part is directed toward an investigation of the characteristic performance of different types of CO / HC sensors, specifically mixed-potential (MP) and metal oxide (MO) gas sensors, suitable for high-temperature applications in the flue gas.…”