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Abstract:
In this work, magnetic Cu-Fe binary oxide (CF) sorbents synthesized by sol − gel method are modified by oxygen non-thermal plasma for efficient removal of elemental mercury (Hg0) from coal-fired flue gas. Sample characterization indicates that plasma treatment has very little impact on the physical properties, magnetization characteristics, and crystalline phases of CF sorbents. But the content of Fe3+, Cu2+, and lattice oxygen in CF sorbents are significantly improved after plasma treatment. Mercury adsorption experiments suggest that the modified sorbents show higher Hg0 removal efficiency in comparison with raw sorbents, and longer treatment time leads to higher Hg0 removal efficiency. The effect of plasma discharge power (32–96 VA), discharge atmosphere (N2, air, 50% N2 + 50% O2, and O2), and reaction temperature (50–350 °C) on mercury removal performance are also explored in a fixed-bed reactor. The presence of O2, NO, and HCl promote Hg0 removal. SO2 and H2O suppress Hg0 removal, but O2 addition can obviously weaken such inhibitory effects. Both experimental results and kinetic model indicate that chemisorption is the decisive factor for Hg0 removal over CF sorbents. Moreover, the mechanism of Hg0 removal over the modified CF sorbents is also investigated. The results indicate that Fe2O3 and CuO serving as active sites are greatly consumed in Hg0 removal process. The multiple regeneration cycles testify that the combination of thermal desorption and non-thermal plasma treatment can realize the efficient regeneration of CF sorbents.
