Co掺杂铁基氧化物吸附剂燃煤烟气脱汞实验研究

使用柠檬酸法制备了Co掺杂的铁基氧化物(FeCo)吸附剂,通过固定床脱汞实验装置系统考察了FeCo吸附剂的脱汞性能,并利用比表面积(BET)、X射线衍射(XRD)、H_2-程序升温还原(H_2-TPR)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(XPS)等表征手段分析吸附剂的物理化学特性。结果表明,α-Fe_2O_3中掺入Co后,比表面积、孔结构特性均得到改善,且氧化还原性能也相应提升;FeCo吸附剂在200-250℃获得最高约97%的脱汞效率;烟气中O_2和NO的存在有助于FeCo吸附剂对Hg~0的脱除,而SO_2和H_2O则抑制FeCo吸附剂对Hg~0的脱除,同时NO能削弱SO_2对FeCo脱汞的抑制作用。在脱汞过程中,FeCo吸附剂表面的活性组分Fe~(3+)、Co~(3+)和O~*均消耗,参与了Hg~0氧化反应,且吸附剂表面生成了HgO。在含SO_2气氛中进行脱汞反应后,FeCo吸附剂表面发生硫酸盐化,从而削弱了吸附剂的脱汞性能,汞在吸附剂表面以HgO和HgSO_4形式存在。

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.