甲烷还原氧化球团过程中的渗碳行为

摘要

通过固定床热重反应器，利用X线衍射(XRD)、热重(TG)以及扫描电镜−能谱(SEM−EDS)等分析方法，研究纯CH 4气体还原球团过程中的渗碳行为。研究结果表明：甲烷还原铁氧化物依靠其裂化产生的H 2与吸附碳；CH 4还原5 min时，金属铁相产生，但由于吸附碳参与还原反应，故基本不存在积碳，由于金属铁层在球团颗粒表面逐渐增厚以及铁碳固溶体颗粒中碳质量分数逐渐增加，阻碍吸附碳的还原并抑制碳向固溶体颗粒内的进一步扩散，故积碳在还原5 min后出现，20 min后浮士体相消失且吸附碳质量分数逐渐增加；反应初期吸附碳对还原速率有一定促进作用，但当吸附碳大量沉积时，则阻碍还原气H2与还原产物H2O与CO的扩散，降低CH4还原速率。%With thermogravimetric fixed bed reactor, the analysis methods of X-ray diffraction (XRD), thermogravimetric (TG) and scanning electron microscopy (SEM) energy dispersive spectrometer (EDS) were used to investigate the carburization behavior in reduction of oxide pellets by CH4. The results show that CH4 reduction of iron oxide is mainly through the adsorption carbon and cracking H2. In 5 min, the metallic iron phase appears and since adsorption carbon takes part in the reduction, there is no carbon. However, with the metallic iron layer thickening gradually, it hinders the reduction and internal diffusion of adsorption carbon. Thus, deposition carbon appears after 5 min. After 20 min, FexO disappears and adsorption carbon increases gradually. The adsorption carbon can diffuse from the external of metallic iron particles to the center and produce iron carbon solid solution with metallic iron. The adsorption carbon has a positive effect on reduction rate at initial reduction stage. When large amounts of adsorption carbon deposits, it hinders the spread of reducing gas H2 and reduction product H2O and CO, which reduces the reduction rate of CH4.