Effect of Atmosphere and Additive on Enrichment Characteristics of Trace Elements during Fluidized Bed Coal Combustion

Abstract

The enrichment characteristics of trace elements (Cr, Mn, Co, Ni, Cd, Pb, Hg, As, Se) were investigated under air and O2/CO2 atmosphere during fluidized bed coal combustion. Results showed that Co, Ni, Cd, Pb, Hg, As, Se were more volatile than Cr and Mn. The increase of temperature promoted Mn, Co, Ni, Cd and Pb to migration from bottom ash to fly ash, and contributed Hg, As and Se to vapor phase. Cr, Mn, Co, Cd, Se tended to decrease in bottom ash and increase in fly ash during oxy combustion, while 21%O2/79%CO2 atmosphere led to the emission of gaseous As and the enrichment of Ni, Pb in both bottom ash and fly ash. With the increase in O2 concentration, the relative enrichment of all the trace elements except As increased, suggesting that their volatility were inhibited. Adding limestone and mixture of limestone and kaolinite had an inhibiting effect on volatilization of trace elements (especially Mn, Cd, Pb, Hg, As, Se) and the inhibiting behavior was strengthened under the oxy atmosphere.