Effect of air staging on fine particle, dust and gaseous emissions from masonry heaters

There is a need to decrease the detrimental particle and gaseous emissions from residential wood combustion appliances. One encouraging alternative is to stage the air supply which improves the combustion conditions in small appliances. In this study, two types of combustion technologies were studied in conventional masonry heaters (CMH) and modern masonry heaters (MMH). Air staging in the MMHs considerably reduced the particle and gas emissions. The greatest reduction was observed in gaseous and particulate organic emissions. Methane emissions were reduced by 74%-91% and carbon monoxide by 26%-81%. The reduction of fine particle mass (PM1) was 14%-58%. Elemental carbon (EC, i.e. soot) emission increased in small combustion appliances but declined in large appliances. In addition, dust (TSP, Total Suspended Particulate matter i.e. Dust) emissions from hot flue gas were compared with the fine particle mass emissions from diluted sample. PM1 emissions measured from diluted flue gas were 1.1-4.4-fold as compared to TSP collected from hot flue gas. This may be attributable to the fact that organic vapors partially had penetrated into the TSP filter in a gaseous form whereas when they were diluted, semivolatile species condensed on the particles. It can be concluded that air staging is an effective way to reduce gaseous and organic emissions from batch combustion appliances. Particle emission measured from diluted flue gas represents a more realistic results than TSP (hot sampling), because in dilution, also the organic fraction of the particle emissions is taken into account.