铁矿石尾矿制备催化剂催化还原氮氧化物实验研究
发布时间：2018-11-10 06:44
【摘要】：氮氧化物(NO_x)是一种主要的大气污染物,它会引起酸雨、光化学烟雾、臭氧层破坏等诸多环境问题,近年来日益受到人们的关注。目前,针对NO_x的脱除,应用最广泛且技术最成熟的方法是选择性催化还原法(SCR),其多采用过渡金属或贵金属催化剂。而铁矿石尾矿作为钢铁冶金行业的一种主要固体废弃物,其中仍含有大量未被利用的金属元素,如铁等,若将其制备成催化剂催化还原NO_x,不但可以实现冶金固废的综合利用,对于NO_x的减排也具有重要意义。以马钢南山矿铁矿石尾矿作为主要原料制备催化剂,NH_3为还原剂,进行催化还原NO的实验。建立了催化还原NO实验的电加热固定床反应装置,考察了催化剂粒径、反应温度、焙烧温度、NO初始浓度、O_2含量、空速、铁含量、添加MnO_2等因素对NO催化还原效率的影响。同时,对催化剂中的铁矿石尾矿进行LDPSA、XRF、BET、XRD、SEM、TGA等表征分析,并对催化还原NO进行失活测试及动力学分析。实验结果表明,铁矿石尾矿制备的催化剂对NO具有良好的催化还原性能。在气体流量为600m L/min,NO初始浓度为600ppm,NH3/NO=1,无O_2存在条件下,温度低于300℃时催化性能不是很理想,但随着温度升高,催化效率迅速升高,500℃时催化效率达到54.8%,550℃时催化效率达到85.4%,600℃时催化效率达到97.5%。催化剂粒径对催化还原效率有较大影响,平均粒径10μm催化剂催化效率比平均粒径300μm催化剂约高20%左右。实验发现对催化剂进行焙烧并不能显著提高其比表面积,450℃以上焙烧处理反而会使催化剂中的Fe_2O_3的衍射峰逐渐变得平缓直至消失,减小对NO的催化还原效率。NO的初始浓度和空速对NO催化效率均有一定的影响,随着NO初始浓度的升高,催化效率逐渐降低,但这种影响会随着反应温度的升高而逐渐减小。当气体总流量从600mL/min增加到800mL/min时,其催化还原效率下降约5%。O_2浓度对催化还原效率影响较大,温度较低时(350℃),O_2的加入促进了催化还原效率,无O_2时催化效率为3%,通入O_2时催化效率能达到10%以上,但当O_2浓度超过4%时对催化效率几乎无影响;温度较高时(500℃),O_2的加入会抑制反应的进行,无O_2时催化效率能达到55%左右,通入O_2时催化效率降低到40%以下。实验发现铁含量越高,催化还原效率越高,但铁含量越高,催化剂在石英砂表面的分散性越差,高温时容易粘结,影响了对NO的催化效果。铁矿石尾矿与MnO_2掺混制备的催化剂能有效提高对NO的催化还原效率,在相同温度时催化效率较高。对铁矿石尾矿制备的催化剂进行了失活测试,2.0g尾矿在600℃时初始效率达到98%,反应3h后仍达到95%,反应8h后仍能达到60%以上,反应13.5h后催化效率仍能保持在50%以上。对铁矿石尾矿制备的催化剂催化还原NO的动力学进行了分析,结果表明,进口NO浓度和O_2浓度对应的反应级数分别为0.876和0.248,而NH3的反应级数为零,该催化反应的反应活化能为87.76kJ/mol。
[Abstract]:Nitrogen oxide (NO_x) is a major atmospheric pollutant, which can cause many environmental problems, such as acid rain, photochemical smog, ozone layer destruction and so on, which has attracted more and more attention in recent years. At present, for the removal of NO_x, the most widely used and the most mature method is selective catalytic reduction method (SCR),). Transition metal or precious metal catalysts are mostly used in (SCR),. Iron ore tailings, as a major solid waste in iron and steel metallurgy industry, still contain a large number of unused metal elements, such as iron, if they are prepared into catalysts for catalytic reduction of NO_x, Not only the comprehensive utilization of metallurgical solid waste can be realized, but also the emission reduction of NO_x is of great significance. The experiment of catalytic reduction of NO was carried out using iron ore tailings of Nanshan Mine of Masteel as main raw material and NH_3 as reducing agent. An electrothermal fixed-bed reactor for catalytic reduction of NO was established. The particle size, reaction temperature, calcination temperature, initial concentration of NO, O _ 2 content, space velocity and iron content were investigated. The effect of adding MnO_2 and other factors on the catalytic reduction efficiency of NO. At the same time, the iron ore tailings in the catalyst were characterized by LDPSA,XRF,BET,XRD,SEM,TGA, and the deactivation test and kinetic analysis of the catalytic reduction NO were carried out. The experimental results show that the catalyst prepared by iron ore tailings has good catalytic reduction performance for NO. When the initial concentration of no is 600 ppm / min, the catalytic performance is not ideal when the temperature is lower than 300 鈩，
本文编号：2321656
[Abstract]:Nitrogen oxide (NO_x) is a major atmospheric pollutant, which can cause many environmental problems, such as acid rain, photochemical smog, ozone layer destruction and so on, which has attracted more and more attention in recent years. At present, for the removal of NO_x, the most widely used and the most mature method is selective catalytic reduction method (SCR),). Transition metal or precious metal catalysts are mostly used in (SCR),. Iron ore tailings, as a major solid waste in iron and steel metallurgy industry, still contain a large number of unused metal elements, such as iron, if they are prepared into catalysts for catalytic reduction of NO_x, Not only the comprehensive utilization of metallurgical solid waste can be realized, but also the emission reduction of NO_x is of great significance. The experiment of catalytic reduction of NO was carried out using iron ore tailings of Nanshan Mine of Masteel as main raw material and NH_3 as reducing agent. An electrothermal fixed-bed reactor for catalytic reduction of NO was established. The particle size, reaction temperature, calcination temperature, initial concentration of NO, O _ 2 content, space velocity and iron content were investigated. The effect of adding MnO_2 and other factors on the catalytic reduction efficiency of NO. At the same time, the iron ore tailings in the catalyst were characterized by LDPSA,XRF,BET,XRD,SEM,TGA, and the deactivation test and kinetic analysis of the catalytic reduction NO were carried out. The experimental results show that the catalyst prepared by iron ore tailings has good catalytic reduction performance for NO. When the initial concentration of no is 600 ppm / min, the catalytic performance is not ideal when the temperature is lower than 300 鈩，
本文编号：2321656
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