Key Laboratory of Nano-minerals and Pollution Control of Anhui Higher Education Institutes, Hefei University of Technology, Hefei, 230009, China.
Institute of Environmental Minerals and Materials, School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China.
Environ Sci Pollut Res Int. 2020 Apr;27(11):12376-12385. doi: 10.1007/s11356-020-07829-x. Epub 2020 Jan 28.
Siderite is a naturally occurring mineral that can be found extensively in coal. The structural evolution of siderite in the process of coaling and its performance in the transformation of NO in the presence of NH were investigated in this work. In addition, the effects of the coexisting component, including vapor, SO, and the alkali metal K, were also discussed. Heat treatment was performed at 450, 500, 550, 600, and 700 °C to obtain siderite-derived α-FeO, which was then evaluated in de-NO via the selective catalytic reduction (SCR) of NO with NH in a fixed bed. The X-ray diffraction (XRD), the X-ray fluorescence spectrometer (XRF), N adsorption-desorption (BET), the X-ray photoelectron spectrometer (XPS), the scanning electron microscope (SEM), and the transmission electron microscope (TEM) were used to investigate the variations in the morphology and structure of the thermally treated siderite. The results showed that siderite was gradually oxidized and decomposed into α-FeO with a nanoporous structure and large surface area of 27.27 m g after calcination under an air atmosphere. The α-FeO derived from siderite at 500 °C (H500) exhibited an excellent SCR performance, where the NO conversion rate was great than 90% between 250 and 300 °C due to the pore structure and high specific surface area, additional adsorbed oxygen states, abundant oligomeric Fe oxide clusters, and large amount of acid sites. Regardless of the vapor content, SO concentration, and reaction temperature, the α-FeO derived from siderite at 500 °C (H500) still favored the conversion of NO. When the reaction temperature was lower than 350 °C, H500 favored the conversion of NO even in the presence of an alkali metal (K). The experimental data demonstrated the positive effect of siderite-derived α-FeO in SCR technology and provided insight into NO behavior in coaling flue gas after NH injection.
菱铁矿是一种广泛存在于煤炭中的天然矿物。本工作研究了菱铁矿在成煤过程中的结构演变及其在 NH 存在下 NO 转化中的性能，同时还讨论了共存组分（包括蒸汽、SO 和碱金属 K）的影响。在 450、500、550、600 和 700°C 下进行热处理以获得菱铁矿衍生的α-FeO，然后在固定床中通过 NH 选择性催化还原（SCR）来评估其脱 NO 性能。采用 X 射线衍射（XRD）、X 射线荧光光谱仪（XRF）、N 吸附-脱附（BET）、X 射线光电子能谱仪（XPS）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究了热处理菱铁矿的形貌和结构变化。结果表明，在空气气氛下煅烧后，菱铁矿逐渐氧化分解为具有纳米多孔结构和大表面积（27.27 m²/g）的α-FeO。在 500°C 下由菱铁矿衍生的α-FeO（H500）表现出优异的 SCR 性能，由于其孔结构和高比表面积、额外的吸附氧态、丰富的低聚氧化铁簇和大量的酸位，在 250-300°C 之间，NO 转化率大于 90%。无论蒸汽含量、SO 浓度和反应温度如何，500°C 下由菱铁矿衍生的α-FeO（H500）仍然有利于 NO 的转化。当反应温度低于 350°C 时，即使存在碱金属（K），H500 也有利于 NO 的转化。实验数据证明了菱铁矿衍生的α-FeO 在 SCR 技术中的积极作用，并为 NH 注入后成煤烟气中 NO 的行为提供了深入了解。
