Mercury removal from coal-fired flue gas of high-sulfur petroleum coke activated by pyrolysis and mechanochemical method

Abstract

With the signing of the Minamata Convention, the task of reducing mercury emission from coal-fired power plants is imminent. High-sulfur petroleum coke (PC), a by-product of the petrochemical industry, has the potential to prepare high-performance mercury removal adsorbents. The effects of activation parameters of pyrolysis, mechanochemistry, pyrolysis + mechanochemistry on the mercury removal ability of activated PC were systematically studied in this work. The TG, BET, FTIR, XPS and Hg-TPD were used to characterize physical and chemical properties, and adsorbed mercury compounds of some selected samples. The results show that pyrolysis, mechanochemistry, pyrolysis + mechanochemistry can enhance the mercury capture performance of Raw PC (RPC). PPC10-60–900, RPC-M-15 M, and PPC-M-15B have the best mercury removal rate of 29.15%, 25.68%, and 27.86%, respectively. Influence of pyrolysis parameters, mechanochemical activation parameters (Rbm, Rms) on mercury removal of activated RPC or pyrolyzed petroleum coke (PPC) are not regular, while final pyrolysis temperature plays a vital role on mercury capture for the PPC. At the fixed Rbm, mechanochemical activation with Rms = 1.08 g/cm2 (M) and 0.62 g/cm2(S) benefits for the pore structure improvement of RPC and PPC. The pyrolysis will make the C–H, C-O, C-O-C, and C = O disappear from PC, while mechanochemical activation almost has no effect on it. The conversion of sulfur forms occurs in both the pyrolysis and mechanochemical activation process. Sulfone acts an important role in the mercury removal of PC-based adsorbents. The mercury captured on the PPC, mechanochemically activated RPC (RPC-M) and PPC (PPC-M) mainly exists in the more stable form of HgS. Additional modifiers are needed to further improve the mercury removal performance of the PC-based adsorbent to facilitate its large-scale industrial application.