Effects of an electrostatic precipitator on particle mass, composition, and number size distributions in residential wood combustion emissions

Abstract

Residential wood combustion (RWC) is an increasingly dominant source of particulate matter (PM) pollution in Europe. Electrostatic precipitators (ESPs) are a promising technology for controlling particle mass emissions from RWC appliances, but their influence on particle number concentrations (PNC) is highly variable, as they may occasionally increase PNC. In this study, we evaluated the effect of an ESP on PM1, black carbon (BC), elemental carbon (EC), organic carbon (OC), and particle number size distributions in emissions from wood-fueled stoves commonly used in Finland, under conditions spanning a wide range of upstream emission loads. Experiments were conducted in a state-of-the-art small-scale combustion simulation and measurement facility. The emission reduction efficiencies of the ESP were 75.7% ± 4.7% for PM1, 83.2% ± 14.2% for EC, and 70.1% ± 12.6% for OC. The operation of ESP not only reduced PM1 concentrations but also influenced particle composition and optical properties with its differential collection efficiencies for EC and OC. Moreover, it reduced PNC within the size range of 0.13–2.5 μm, but nucleation-mode PNC occasionally increased, suggesting possible new particle formation. Additionally, the combustion conditions that showed negative efficiencies for PNC had higher upstream organic gaseous carbon concentrations and higher OC:EC ratios compared to those with positive efficiencies, suggesting that organics-rich flue gas may contribute to increased PNC when ESPs are used. These findings highlight the importance of controlling organic emissions to improve the overall emission reduction performance of ESPs.