Understanding the generation and removal of primary particulate matter: insights from diesel, biomass, and metal emissions

The removal of condensable particulate matter (CPM) poses a significant challenge in air pollution control due to its complex formation mechanisms and diverse physicochemical properties. This study investigates the generation, characteristics, and removal efficiency of primary particulate matter (PM), with a focus on CPM from three representative emission sources: diesel, biomass, and metal. Diesel combustion primarily produces carbon-rich particles, with CPM predominantly formed through heterogeneous condensation. In contrast, oil heating generates organic-rich particles, while metal fume results in metal-rich particles, formed by the condensation of metals’ vapors during high-temperature processes followed by rapid cooling. We evaluated the filtration performance of two control devices: electrostatic precipitators (EP) and fabric filters (FF). Our results indicate that FF outperforms EP, particularly in sub-100 nm range, due to its diffusion-based removal mechanism. However, FF exhibited reduced efficiency over time when controlling oil mist, suggesting that EP may be more suitable for capturing liquid-phase particles. Additionally, the study highlights pressure drop issues associated with FF, which can lead to clogging and the re-emission of particles during long-term operations. These findings highlight the necessity for standardized testing protocols to assess the removal efficiency of different types of primary PM, emphasizing the importance of well-defined size distribution on air quality management.