Reduction of gaseous and particulate emissions from small-scale wood combustion with a catalytic combustor

In this study, a catalytic combustor was used on a wood stove as a secondary emission reduction measure. An experimental comparison of emissions was done from combustion experiments with and without the catalyst. Samples were collected from gasification and burn out phases and from the whole combustion cycle (from start-up to burn out). Concentrations of carbon monoxide (CO), carbon dioxide (CO₂), oxygen (O₂) and organic gaseous carbon (OGC), temperature and pressure were measured online directly from the flue gas stack. With the catalyst, the O₂ concentration in the flue gas was lower and the temperature higher than without the catalyst, due to the large amount of unburnt compounds which were oxidized by the catalyst. Reductions of 21% for CO and 14% for OGC were achieved during the whole combustion cycle. During the burn out phase, a reduction as high as 80% was achieved for CO. PM₁ (particle mass below aerodynamic size of 1 μm) was reduced by 30% during the whole combustion cycle. During gasification, a 44% reduction of PM₁ was achieved but there was no reduction during burn out. The organic and elemental carbon analyzed from PM₁ had reduced also only during gasification by 56% and 37%, respectively. The particle emission reductions were notable and it can be concluded that the catalyst affects the particles through oxidation of condensable organic vapors and oxidation of soot particles. The catalyst has potential as a secondary emission reduction method but in order to achieve low emissions, also improved combustion technology for emission reduction needs to be developed.