Kinetic mechanism on elemental mercury adsorption by brominated petroleum coke in simulated flue gas

Abstract

A waste byproduct of petroleum coke was obtained as a precursor modified with bromine for elemental mercury capture from simulated flue gas on a bench scale fixed-bed reactor. The reaction temperature, the initial inlet elemental mercury concentration and the individual flue gas components of O₂, NO, SO₂ and HCl were determined to explore their influence on elemental mercury capture by the brominated petroleum coke. Results indicate that high initial inlet mercury concentration can enhance initial mercury accumulation and the optimal temperature for elemental mercury capture by brominated petroleum coke is about 150 °C. Kinetic models reveal that the pseudo-second order and Elovich models are best fitted to the mercury adsorption process, indicating that chemisorption is the control step with the intra-particle diffusion and external mass transfer taking place simultaneously. The kinetic parameters demonstrate that the initial mercury adsorption rate (h or a) and the equilibrium adsorption quantity (Q_e) increase remarkably, when higher concentrations of O₂ or NO exist in N₂ atmosphere. On the contrary, Q_e decreases with the presence of high SO₂ or HCl, which indicates a two-sided effect on the performance of mercury adsorption owing to their concentrations.