Comprehensive understanding of the superior performance of Sm-modified Fe_(2)O_(3)catalysts with regard to NO conversion and H_(2)O/SO_(2)resistance in the NH_(3)-SCR reaction

Sm-doped Fe_(2)O_(3)catalysts,with a homogeneous distribution of Sm in Fe_(2)O_(3)nanoparticles,were synthesized using a citric acid-assisted sol-gel method.Kinetic studies show that the reaction rate for NO_(x)reduction using the optimal catalyst(0.06 mol%doping of Sm in Fe_(2)O_(3))was nearly 11 times higher than that for pure Fe_(2)O_(3),when calculated based on specific surface area.Furthermore,the Fe_(0.94)Sm_(0.06)O_(x)catalyst maintains>83%NO_(x)conversion for 168 h at a high space velocity in the presence of SO_(2)and H_(2)O at 250℃.A substantial amount of surface-adsorbed oxygen was generated on the surface of Fe_(0.94)Sm_(0.06)O_(x),which promoted NO oxidation and the subsequent fast reaction between NO_(x)and NH_(3).The adsorption and activation of NH_(3)was also enhanced by Sm doping.In addition,Sm doping facilitated the decomposition of NH_(4)HSO_(4)on the surface of Fe_(0.94)Sm_(0.06)O_(x),resulting in its high activity and stability in the presence of SO_(2)+H_(2)O.

真空下钢液中气泡析出尺寸分布特征的水模型研究

增氢析氢法是近年来提出的一种钢液中有效去除夹杂物的新技术。该技术利用析氢过程中生成的微小气泡将夹杂物粘附去除,达到净化钢液的目的,其中析出气泡的尺寸是影响该技术的关键因素。通过采用水/O_(2)体系模拟钢液/H_(2)体系,对不同溶气量、真空度以及溶液深度下的气泡尺寸进行研究,利用MATLAB软件对析气过程中气泡生长尺寸进行计算,得出不同因素下的气泡生长的规律。从理论角度对实验结果进行分析和讨论,结果表明:溶氧量增加、真空度降低以及溶液深度减小都会促进气泡生长,使统计得到的气泡尺寸增大。