Multiscale Understanding of the Mechanism of Mercury Removal by Acid–Chlorine-Modified Biomass Coke: Experiments and Simulations

Abstract

Coal-fired power plants are a significant source of mercury pollution, necessitating the development of inexpensive and efficient adsorbents for mercury removal. This work proposes the preparation of an adsorbent using acid-chlorine-modified rice straw coke for this purpose. The characterization of the adsorbent shows that the modification increases the surface pore structure and makes the surface carry abundant oxygen-containing functional groups, which is conducive to improving the mercury removal capacity of the adsorbent. This work studies the effects of the acid–chlorine ratio, mass ratio, inlet mercury concentration, and reaction temperature on the desorption performance of modified rice straw coke and investigates the mechanism of mercury removal by combining the kinetic model and density functional theory. The results demonstrate that the optimal effect of the combined acid–chlorine modification is achieved at an acid–chlorine ratio and mass ratio of 1:2. The reaction temperature has a significant effect on the efficiency of mercury removal, and the increase of the inlet mercury concentration can promote mercury removal. The mercury adsorption process is primarily controlled by surface mass transfer and chemisorption, with chemisorption being the critical control step. The introduction of Cl and O atoms through modification creates doped structures that are highly conducive to mercury adsorption. The Cl atom exhibits greater reactivity toward the Hg atom, facilitating the removal of mercury. The presence of O atoms not only increases the abundance of oxygen-containing functional groups on the surface, but also enhances the activity of the Cl atoms. These findings provide valuable theoretical support for the application of biomass coke in the field of mercury removal, addressing mercury pollution associated with coal-fired power plants.

Investigation of Mercury Removal Behavior by Modified Biomass Coke in Oxy-fuel Combustion Flue Gas

“…Quantum chemical simulation is a new method to study the process and mechanism of Hg removal nowadays. 22 The density functional theory (DFT) is a widely used method in quantum chemistry that helps to provide a reliable explanation of mercury adsorption behavior. 23 He et al 24 used DFT to simulate the adsorption process of HgCl and HgCl 2 on the surface of CeO 2 and found that oxygen vacancy was conducive to mercury oxidation, which better revealed the mechanism of mercury oxidation from the microscopic level.…”

“…Quantum chemical simulation is a new method to study the process and mechanism of Hg removal nowadays . The density functional theory (DFT) is a widely used method in quantum chemistry that helps to provide a reliable explanation of mercury adsorption behavior .…”