含锌尘泥金属化球团还原特性及动力学研究

Research on reduction characteristics and kinetics of metallized pellets containing zinc dust and mud

作为一种新型高炉原料,含锌尘泥金属化球团(下称金属化球团)在高炉冶炼过程中的行为对其推广应用至关重要。实验室模拟金属化球团在高炉内的气固还原过程并结合微观检测手段研究金属化球团的还原特性和还原动力学,结果表明:金属化球团内铁氧化物均匀分散及疏松多孔结构有利于气固还原反应的发生,还原反应以间接还原为主,还原率在还原之初就快速增加,在1000℃时还原率达93.51%;金属化球团中有害元素Zn在850~900℃时快速被还原气化,此温度略低于其沸点,而有害元素S在温度低于1000℃没有表现出还原行为,残碳含量变化与锌含量变化表现出一定相关性;在时间小于3000 s时界面化学反应为金属化球团气固还原的限制性环节,随后限制性环节转换为气体内扩散,这与金属化球团内金属铁逐渐增加并集聚、渣相填充孔隙造成的球团致密度不断增加有关,2种限制性环节的表观活化能分别为23.76和74.20 kJ/mol,金属化球团气固还原反应较易进行。

The behavior of metallized pellets containing zinc dust and mud(hereinafter referred to as metallized pellets)in the smelting process of a blast furnace is crucial for its widespread application as a new type of blast furnace raw material.The gas-solid reduction process of metallized pellets in a blast furnace were simulated in laboratory combined with microscopic detection methods to research the reduction characteristics and kinetics of metallized pellets.The results indicate that the uniform dispersion of iron oxides within the metallized pellets and its loose porous structure are favorable for the gas-solid reduction reaction.The reduction reaction is mainly indirect reduction,and the reduction rate increases rapidly at the beginning of the reduction process,the reduction rate is 93.51% at 1000℃.The harmful element Zn in the metallized pellets is rapidly reduced and gasified at 850-900℃,this temperature is slightly below its boiling point.However,harmful element S does not exhibit reduction behavior at temperatures below 1000℃.There is a certain correlation between changes in residual carbon content and changes in zinc content;in less than 3000 seconds,the interfacial chemical reaction becomes a limiting link in the gas-solid reduction of metallized pellets,which then transforms into gas diffusion.This is related to the gradual increase and agglomeration of metal iron in the metallized pellets,and the continuous increase in pellet density caused by the filling of pores with slag phase.The apparent activation energies for the two limiting steps are 23.76 kJ/mol and 74.20 kJ/mol,respectively,the gas-solid reduction reaction in the metallized pellets is more favorable and easily proceeds.