Effect of Oxidizing Honeycomb Catalysts Integrated in a Firewood Room Heater on Gaseous and Particulate Emissions, Including Polycyclic Aromatic Hydrocarbons (PAHs)

摘要

Residential wood combustion is linked to a significant extent of emissions of polycyclic aromatic hydrocarbons (PAHs), which represent highly toxic, semivolatile pollutants. The use of catalysts reveals an effective measure to reduce emissions, especially gaseous flue gas compounds (carbon monoxide (CO) and organic gaseous compounds (OGC)). Their effect on toxicologically relevant PAHs is not clarified yet. In this work, the impact of two commercially available oxidizing platinum/palladium catalysts with either metallic or ceramic honeycomb carriers was examined under real-life operating conditions of a firewood room heater. The catalytic effect on CO and OGC, total suspended particles (TSP), total carbon (TC), elemental carbon (EC), organic carbon (OC), and 19 different PAHs, including 16 EPA PAHs (PAHs defined by the Environmental Protection Agency as priority pollutants) was evaluated by parallel measurements of catalytically treated and untreated flue gas from firewood combustion. The metallic catalyst, having a reaction surface that is 3.5 times greater than the ceramic catalyst, leads to a more-pronounced impact. Both types, the ceramic and the metallic catalyst, led to distinct reductions of CO (-69%, -88%) and OGC (-27%, -39%). In the test with the metallic catalyst, TSP increased (+17%) and PAHs were clearly reduced (-63%). This reduction was exclusively related to the higher-molecular-weight PAHs, such as the particularly toxic benzo(a)pyrene. Carbonaceous fractions (TC, EC, and OC) were not affected significantly. The toxicity of emissions arising from EPA PAHs can be clearly reduced by catalytic treatment. Moreover, the increase of TSP opens new questions, which must be clarified before the investigated catalysts are recommended as suitable secondary measure for emission abatement.