Emission characteristics of air pollutants from coal-fired power generation units coupled with sludge combustion
To clarify the emission characteristics of air pollutants from coal-fired power generation units coupled with sludge,experimental research was conducted on three typical ultra-low emission coal-fired units with sludge co-firing.The results indicated that under the condition of a low proportion of sludge co-firing(≤6.0%),the emission concentrations of conventional pollutants(SO2,NOx,and particle)from coal-fired units remain essentially unchanged compared to the blank condition without co-firing,meeting the requirements for ultra-low emissions.Since the content of trace elements in sludge was much higher than that in coal,even if the co-firing ratio was not high,the concentration of trace elements in the flue gas usually increased significantly after co-firing,up to 17.1 times that of the blank condition,but it still met the requirement of the current emission control standards.The order of emissions for the 11 trace elements(Hg,Cd,Pb,Cr,Be,Ba,Ni,Ag,As,Se,Sb)in the flue gas before and after co-firing with sludge did not change significantly.The element with the highest concentration was usually Ba,followed by Cr,Pb,or Hg.After co-firing sludge,the dioxin emission concentration was 1.1 to 2.0 times that of the blank condition,meeting the current national standard,but not all complied with the more stringent Shanghai local standard.The migration distribution rules of trace elements before and after co-firing sludge did not show significant changes.For trace elements other than Hg,As,and Se,85%of their total content migrated to fly ash and bottom ash,with the majority being found in the fly ash.Due to their volatile nature,Hg,As,and Se had a significantly higher migration proportion in desulfurization gypsum than other elements.Under the collaborative control of the ultra-low emission full-process flue gas purification facilities,the proportion of various trace elements finally emitting from the chimney was generally less than 5.0%.
coal-fired unitssludge co-firingair pollutantemission concentrationmigration distribution
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