After-treatment of household wood-fired stove emissions: From catalyst formulation to full-scale system

Abstract

The development of a suitable after-treatment system for the abatement of the pollutant emissions contained in the flue gases of wood fired stoves, is the object of this work. All steps from powder catalyst synthesis, to the deposition of the selected catalyst on lab-scale monoliths, and finally the implementation of all developed concepts in a full-scale monolith, to be mounted in the chimney of a commercial stove to experience real working conditions, were tackled.A series of La–Cr perovskite catalysts was developed to undertake this task, from which La0.9Na0.1CrO3 demonstrated to be the best compromise in terms of CO, HC and soot oxidation. The addition of 2% of Au enhanced the CO oxidation activity of the catalyst.The selected catalyst was then deposited on a lab-scale structured monolith (200cpsi) to assess the best catalyst loading. It emerged that, at a 10% oxygen concentration and a GHSV of 3500h−1, a 6% loading (referred to the monolith weight) of La0.9Na0.1CrO3+2%Au completely removed all CO and HC from the gaseous flow around 400°C. This is a remarkable result since most of the wood combustion cycle produces an exhaust gas stream above this temperature.Finally, a full-scale monolith was mounted on the chimney of a stove, and was exposed to several wood loading cycles and different wood stacking protocols. The catalyzed monolith, with a 10wt% catalyst loading, but a much lower cell density (50cpsi), was able to abate all gaseous emissions throughout the entire wood combustion cycle, even at its lowest temperatures (around 200°C). This was possible because, after some repeated wood loading cycles, the monolith heated up and stayed at suitable thermal levels (thanks to its inertia) viable for CO and HC oxidation, due to the exotermicity of these reactions. The soot emissions were also reduced by more than order of magnitude, thanks to the above described reason, and the high levels of SOF, which confer both reactivity towards combustion and sticking enhancement at the monolith surface.The developed catalyzed filter proved also to be very stable in terms of performances, even after a severe aging protocol of 160h.