Experimental study on mercury removal of coal-fired flue gas over Co-doped iron-based oxide sorbent

In this paper, the citric acid method was used to prepare the Co-doped iron-based oxide sorbent. The mercury removal performance of the FeCo sorbent was investigated by a fixed-bed mercury removal experimental device system, and the characterization methods of the specific surface area (BET), X-ray diffraction (XRD), H₂-temperature programmed reduction (H₂-TPR), Fourier infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) were performed to analyze the physical and chemical characteristics of the sorbent. The results of the study indicate that the specific surface area and pore structure characteristics are improved after the addition of Co into α -Fe₂O₃, and the redox performance of α -Fe₂O₃ is also improved. The maximum mercury removal efficiency of FeCo sorbent is obtained at 200-250 ℃ at the value of about 97%. The presence of O₂ and NO in the gas benefits the removal of Hg⁰ over FeCo sorbent, while SO₂ and H₂O inhibit the removal of Hg⁰ over FeCo sorbent. The presence of NO can weaken the inhibitory effect of SO₂ on mercury removal performance over FeCo. During the mercury removal process, the active components Fe³⁺, Co³⁺, and O^* on the surface of the FeCo sorbent are consumed, particitate in the Hg⁰ oxidation process, and HgO is formed on the surface of the sorbent. After the mercury removal reaction in the atmosphere containing SO₂, the sulfation of the sorbent surface is occurred, which weakens the mercury removal performance of the adsorbent.