Study Of The Generation Mechanism Of The Major Components Of Condensable Particulate Matter

Condensable Particulate Matter(CPM)is a material that is vapor phase at stack conditions but which condenses and/or reacts upon cooling and dilution in the ambient air to form solid or liquid PM immediately after discharge from the stack.As an air pollutant that has received wide attention in recent years,CPM is featured with high emission concentration,small size of formed particles,and complex composition.CPM can be divided into inorganic and organic components,of which the inorganic component mainly consists of water-soluble anions and metal elements,while the organic component is too diverse to be quantified accurately.For the inorganic components of CPM,SO42-and NH4+ are the most abundant,and the origin of these two ions has not yet been determined by the academic community.For the organic components of CPM,the more toxic Polycyclic Aromatic Hydrocarbons(PAHs)and the more abundant Normal alkanes(n-alkanes)have been investigated.Exploring the generation mechanism of the main components of CPM is an objective need to deeply understand the characteristics of CPM and to develop CPM control strategies.Therefore,this paper focuses on the generation mechanism of the main components of CPM in coal combustion flue gas.The specific objects of the study include inorganic and organic components of CPM.For the inorganic components of CPM,the study includes the generation mechanisms and interactions of SO42-and NH4+,and explores the generation mechanisms of SO42-and NH4+inorganic components of CPM through both simulated flue gas experiments and real flue gas experiments.The organic fraction of CPM was investigated by gas chromatography to quantify PAHs and n-alkanes,and the effects of flue gas oxygen content and flue gas sampling temperature on the organic fraction of CPM were investigated on a real flue gas experiment bench.Regarding the CPM inorganic components,first,for SO42-:SO42-in CPM is more predominantly contributed by SO3/H2SO4 in the flue gas than the various sulfates.For NH3 and SO2,if either or both of them increase in the flue gas.the NH4+and SO42-in CPM will also increase at the same time.SO2 in the flue gas causes a positive bias in EPA Method 202 measurements of the CPM,and this positive bias increases with increasing SO2 concentration.Nitrogen purging can mitigate,but cannot perfectly solve the SO2 interference problem.Second,for NH4+:NH3 is an important source of NH4+in the inorganic fraction of CPM,and NH4HSO4,(NH4)2SO4 and NH4Cl contribute to NH4+ in the inorganic fraction of CPM.Regarding the organic fraction of CPM,the PAHs in the organic fraction of CPM were mainly concentrated in the 4-rings and 5-rings,and the PAHs of other rings accounted for a smaller proportion.The analysis of Toxic Equivalent Quantities(TEQ)showed that 5-rings PAHs contributed the most to TEQ,followed by 4-rings and 6-rings PAHs.In addition,the distribution of n-alkanes was more concentrated,mainly in C22 and later n-alkanes with higher carbon content.The n-alkanes showed an increasing trend with the decrease of flue gas sampling temperature and the decrease of oxygen content in the flue gas.