Real-time detection of vehicle-originated condensable particulate matter through thermodenuder integrated aerosol measurement method at tailpipes

Rethinking primary particulate matter: Integrating filterable and condensable particulate matter in measurement and analysis

The current definition of primary particulate matter (PM) encompasses filterable PM (FPM) and condensable PM (CPM), which are evaluated using two distinct conventional measurement methods: cooling and dilution. While the cooling method exclusively considers the homogenous formation of CPM, the dilution method, closer to real-world conditions, neglects FPM characterization. To overcome this limitation, we propose a doubled-dilution system that enables the parallel characterization of both FPM and primary PM without diverting FPM from the CPM formation pathway. The doubled-dilution system has been investigated from a laboratory scale to a full-scale coal-fired power plant to facilitate simultaneous, real-time measurements of primary PM and FPM size distributions. Moreover, the formation rates of homogeneous and heterogeneous nucleation were compared. The evolution of the primary PM size revealed a bimodal distribution, and the filter-based mass concentration results demonstrated a pronounced preference for heterogeneous reactions (17.6 times higher than homogeneous nucleation). In particular, primary PM emissions were underestimated by up to 65.3 % when only homogeneous CPM formation was considered, underscoring the importance of including FPM during primary PM measurements. Considering these results, we advocate adopting the term "primary PM" over "CPM."

An assessment of inorganic components in condensable particulate matter as a function of surface aggregation, spatial suspension state and particle size

Experimental studies assessed the removal efficiency and fine-size distribution of CPM coupled with compositional analysis across air pollution control device systems (APCDs) at an ultra-low emission (ULE) power plant. The findings indicated total CPM emissions were reduced to a minimum of 0.418 mg/m3 at the Wet Electrostatic Precipitator (WESP). The Wet Flue Gas Desulfurization (WFGD) showed the highest removal efficiency (98%) across all particle sizes, notably in the ultra-micron range. Selective Catalytic Reduction (SCR) demonstrated a mere 34% overall efficiency, with a negative removal rate in the ultra-fine particle range. The WESP effectively removed CPM only in sub-micron and ultra-micron sizes, but significantly increased water-soluble ions formation in ultra-fine spatially suspended CPM (CPMspa), leading to overall negative efficiency. Thus, the removal efficiency of the ultra-fine particle range was most affected among the three particle size ranges when the flue gas went through the APCDs. Major metal elements and water-soluble ions were more readily removed by APCDs due to their surface aggregation, while the removal of trace elements like Hg and Se was limited. Reducing SO42-/NH4+ formation in SCR, and optimizing WESP spray system operations based on flue gas components are essential steps in controlling CPM concentration in ULE power plants.

Emission characteristics of condensable particulate matter during the production of solid waste-based sulfoaluminate cement: Compositions, heavy metals, and preparation impacts

Recycling solid waste for preparing sulfoaluminate cementitious materials (SACM) represents a promising approach for low-carbon development. There are drastic physical-chemical reactions during SACM calcination. However, there is a lack of research on the flue gas pollutants emissions from this process. Condensable particulate matter (CPM) has been found to constitute the majority of the primary PM emitted from various fuel combustion. In this study, the emission characteristics of CPM during the calcination of SACM were determined using tests in both a real-operated kiln and laboratory experiments. The mass concentration of CPM reached 96.6 mg/Nm3 and occupied 87% of total PM emission from the SACM kiln. Additionally, the mass proportion of SO42- in the CPM reached 93.8%, thus indicating that large quantities of sulfuric acid mist or SO3 were emitted. CaSO4 was one key component for the formation of main mineral ye'elimite (3CaO·3Al2O3·CaSO4), and its decomposition probably led to the high SO42- emission. Furthermore, the use of CaSO4 as a calcium source led to SO42- emission factor much higher than conventional calcium sources. Higher calcination temperature and more residence time also increased SO42- emission. The most abundant heavy metal in kiln flue gas and CPM was Zn. However, the total condensation ratio of heavy metals detected was only 40.5%. CPM particles with diameters below 2.5 μm and 4-20 μm were both clearly observed, and components such as Na2SO4 and NaCl were conformed. This work contributes to the understanding of CPM emissions and the establishment of pollutant reduction strategies for waste collaborative disposal in cement industry.