Distribution of the existence forms of condensable particulate matter during condensation: The surface collection and the space suspension forms.

Condensable particulate matter (CPM), as an air pollutant that has received wide attention in recent years, has a high emission concentration compared to filterable particulate matter (FPM), and there is not yet a well-developed removal method. Air pollution control devices (APCDs) with a condensation process have a certain effect on CPM removal, which inspired us to study the condensation behavior of CPM. During the condensation process, the condensed CPM may exist in two final forms: one was to be collected by the cold surface that causes the condensation; the other was to convert to fine particles and suspend in the space of the flue. In a sense, the surface collection form can reflect the removal of CPM, while the CPM in the space suspension form should be further separated with the aim of removal. In this work, we adopted a CPM sampling system based on EPA Method 202 to reveal the distribution of the condensation behavior of CPM. In this sampling system, the CPM collected by all the cooling surfaces, including the cooling coil and impingers, can be counted as the surface collection form, and that collected by the terminal CPM filter can be regarded as the space suspension form. It was found that about 75 % of CPM was collected by the cooling surfaces, which suggested that CPM preferred to be in the surface collection form than the space suspension form. This preference characteristic also could be observed in the inorganic (CPMi ) and organic components of the CPM (CPMo ). Among the CPMi , almost all NH4 + and SO4 2- condensed in the form of surface collection. The preference characteristics in CPM's (and its components') condensation behavior are similar under every temperature reduction condition. In this work, the interference of CPM measurement error was resolved by the statistical method of ANOVA.