Performance of MnCl2 doped magnetic iron-carbon sorbent on mercury removal from flue gas: The effect of O2 and SO2
In order to get a more stable and efficient sorbent on mercury removal from flue gas, MnCl2 has been used to improve the sorption capacity of magnetic iron-carbon. BET and XRF tests have been conducted to demonstrate the characteristic properties of the obtained doped sorbents. Higher concentrations of impregnation solution lead to more MnCl2 loaded sorbents but these present worse physical properties. Experiments have been conducted under different conditions to investigate the effects of O2 and SO2. Mercury sorption capacity and SO2 resistance of modified magnetic carbon have been strengthened after doping with MnCl2. The presence of O2 in flue gas can further facilitate mercury oxidation and weaken the inhibition of SO2. The mechanism of mercury oxidation is closely related to the manganese in sorbent whenever oxygen is present. XPS test results reveal that O2 facilitates conversion of Mn to oxidation states, which can easily accept electrons from Hg0, thereby accelerating the oxidation of Hg0. In addition, HgO is confirmed as the main form of mercury compound after reactions when O2 was introduced. DFT calculation results also reveal the mercury oxidation mechanism in those reactions with oxygen participation.