转底炉还原过程金属化球团强度变化规律

THE STRENGTH VARIATION OF METALLIZED PELLETS DURING THE REDUCTION PROCESS IN A ROTARY HEARTH FURNACE

钢铁冶金尘泥是钢铁工业生产过程中的主要固体废物,目前处理钢铁尘泥的主流工艺为转底炉直接还原工艺。转底炉金属化球团强度是影响球团成品率及其资源利用的重要指标之一,因此,对转底炉金属化球团的强度变化过程进行研究具有重要意义。本文以某钢铁厂冶炼生产的高炉布袋灰和转炉污泥为研究对象,通过对转底炉还原后的金属化球团进行抗压强度测试分析、扫描电子显微镜分析和X射线衍射分析,对还原过程中金属化球团强度的变化过程进行了研究。研究结果表明:随着还原温度的提高,球团强度脱离低强度区的时间越短,金属化球团抗压强度到达500 N、1000 N、1500 N的速率越快;金属化球团强度主要取决于金属Fe连晶状态,强度从高到低依次为:大片连晶>蠕虫状连晶>弥散分布。提高温度对铁氧化物还原、碳的气化反应及金属铁的聚集有促进作用,同时液态渣相的流动填充了球团内部的空隙使得球团内部结构更为紧密,在高温条件下还原获得的金属化球团抗压强度大于在低温条件下还原获得的金属化球团。

Steel metallurgical dust and sludge are the main solid waste in the production process of the steel industry.Currently,the mainstream process for treating steel dust and sludge is the direct reduction process using a rotary hearth furnace.The strength of metalized pellets is one of the important indicators that affect the yield of pellets and their resource utilization.Therefore,studying the strength variation process of rotary hearth furnace metalized pellets is of great significance.This article takes the blast furnace bag ash and converter sludge produced by a certain steel plant as the research objects.Through compressive strength testing and analysis,scanning electron microscopy analysis,and X-ray diffraction analysis of the reduced metalized pellets in the rotary hearth furnace,the changes in the strength of the metalized pellets during the reduction process were studied.The research results indicate that with the increase of reduction temperature,the time for the strength of the pellets to leave the low strength zone is shorter,and the rate at which the compressive strength of the metallized pellets reaches 500 N,1000 N,and 1500 N is faster.The strength of metalized pellets mainly depends on the state of metal Fe connected crystals,and the order of strength from high to low is large connected crystals>worm like connected crystals>dispersed distribution.Raising the temperature promotes the reduction of iron oxides,the gasification reaction of carbon,and the aggregation of metallic iron.At the same time,the flow of liquid slag phase fills the gaps inside the pellets,making the internal structure of the pellets more compact.The compressive strength of the metalized pellets obtained by reduction under high temperature conditions is greater than that obtained by reduction under low temperature conditions.