Research on Condensable Particulate Matter Emission Characteristics from Sewage Sludge Combustion

Combustion is an effective disposal method for sewage sludge (SS), but the corresponding condensable particulate matter (CPM) emission poses a big risk to the environment. To investigate the CPM characteristics from pelleted SS combustion, tests were conducted in a tube furnace experimental system, and the effects of combustion temperatures on CPM generation and the impacts of sampling temperatures on CPM migration were studied. Results showed that the inorganic components took up the majority (60.75–86.24%) of the total CPM. Significant PO 4 3− was first detected in CPM mainly due to the remarkable phosphorus content in SS. The CPM exhibited distinct acidity, and SO 4 2− was the primary water-soluble ion in CPM, followed by PO 4 3− and Cl − . Ca, Na, and K accounted for the vast majority of metal elements in CPM. Alkanes and esters were the predominant organic species of CPM. With the combustion temperature increasing, the inorganic CPM increased by the enhanced volatilization of relevant elements, and the organic CPM decreased owing to the improved combustion conditions. As the sampling temperature decreased, more CPM precursors converted to FPM, resulting in a decrease in both inorganic and organic components of CPM. Particularly, a drastic cooling process contributed to the enlargement of CPM by strengthening the heterogeneous condensation and agglomeration. CPM from SS incineration could do great harm to the environment and human health for its fine particle size and complex compositions, and combustion control and proper flue gas cooling devices would be conducive to CPM control.