Energy & Fuels, Vol.31, No.1, 747-754, 2017
Migration Behavior of Trace Elements at a Coal-Fired Power Plant with Different Boiler Loads
Trace elements (TEs) emitted from coal-fired power plants have done great harm on the environment, which has caused widespread concern in the world. In this study, the effects of boiler loads (100 and 75% output) on the migration behaviors of TEs (including Cr, Mn, Co, Ni, Cu, Zn, As, Ba, and Pb) were conducted on a coal-fired power plant with selective catalytic reduction (SCR), electrostatic precipitator (ESP), wet flue gas desulfurization (WFGD), and wet electrostatic precipitator (WESP). Simultaneous sampling of coal, bottom and fly ash, flue gas, and the byproducts from WFGD and WESP was performed. It shows that mass balance rate of TEs at the two loads is in the acceptable range. TEs mainly distribute in bottom and ESP ash in the coal-fired power plant at the two loads. In comparison to the 100% load, the amount of TEs in bottom ash increases at the 75% load. The overall removal rates of TEs through the whole system at the two loads are higher than 99.9%. Except Co and Ba, the overall removal rate at the 100% load is more than that at the 75% load. The ability of the ESP to capture particulate TEs at the 75% load is lower than that at the 100% output, while it is adverse for the gaseous TEs, apart from As. WFGD and WESP have the synergistic effects to remove the total TEs. TEs may re-emit in the desulfurization process. There is little impact on the enrichment of TEs in ESP and bottom ash when the load changes. The concentration of TEs emitted to the atmosphere is in the range of 0.01-1.76 and 0.01-2.32 mu g/m(3) at the two loads in the gaseous form, which is extremely low. At last, the further work in the removal of TEs is proposed.