Abstract:
Some hazardous trace elements in coal, bottom ash, fly ash and fine fly ash from a circulating fluidized bed (CFB) boiler in a power plant were examined. The distribution, enrichment and partitioning behavior of Be, Zn, Hg, V, Cr, Mn, Co, Ni, Cu, As, Se, Cd and Pb were analyzed. The results show that the distribution and enrichment characteristics of trace elements are greatly affected by the temperature of CFB. According to the relative enrichment factor (
ER), Be, V, Co and Se trend toward fly ash; Zn and Mn show a tendency into bottom ash. Some volatile trace elements like Cd,Pb,Ni and Cu show low enrichment in both bottom ash and fly ash. The element of As is affected by calcium oxide, and its volatility is not obvious. Hg is more likely discharged with flue gas. Hg, As, Se, V, Cr, Mn, Co, Ni, Cu, Zn and Pb all have an enrichment tendency toward fine particles. On the basis of
ER and behaviors of the 13 trace elements in CFB boiler, these elements are divided into 3 categories: A(
ER<0.1), Hg mainly volatilizes into the atmosphere; B(0.1<
ER≤0.85), As, Be, Ni, Cu, Se, Cd, Pb, Co and V are more easily volatilization; C(
ER>0.85), Zn, Mn and Cr mostly stay in solid residues.