Mercury Removal from Coal-Fired Flue Gas on Sulfur-Modified Petroleum Coke: Experiment and Simulation

High-sulfur petroleum coke is a common industrial byproduct generated during the petroleum refining process. This study aimed to investigate the influence of various factors, such as the alkali–coke ratio, activation temperature, and activation time, on the mercury removal performance of KOH-activated high-sulfur petroleum coke adsorbent. The optimal activation method was determined using KOH as the activator and elemental sulfur as the modifier. Subsequently, the effects of carbon-to-sulfur ratio, modification temperature, and modification time on the mercury removal performance were examined, leading to the development of a comprehensive preparation method for KOH-activated and sulfur-loaded modified high-sulfur petroleum coke mercury removal adsorbent. The experimental process involved the characterization of the adsorbent using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results revealed that KOH significantly enhanced the pore structure, while the sulfur-carrying modification introduced a substantial number of oxygen- and sulfur-containing functional groups. The XPS results suggest that S0/thiophene, S2–/sulfide, sulfoxide, and SO42– may all be involved in the mercury removal process. Elemental sulfur has a strong affinity for Hg0 and can directly react with Hg0 to form HgS. Related sulfur-containing compounds are transformed into sulfonates/sulfates, while Hg0 reacts to form HgS and HgSO4. In addition, density functional theory (DFT) simulations were conducted to investigate the adsorption process of mercury. It was observed that with the increase of the number of S atoms, the potential of Hg atoms in the adsorbed configuration gradually increased, and the reaction between adsorption and S atoms was enhanced, indicating that the adsorption energy of Hg atoms in the straight-chain carbon sulfide was greater with the increase of the number of S atoms. Moreover, the terminal S atom demonstrated a stronger adsorption effect on Hg compared with the nonterminal S atom when the S atom count is 2 or 3. This study provided valuable insights for the reuse of industrial byproducts and the development of efficient and cost-effective mercury removal adsorbents.