THE STRENGTH VARIATION OF METALLIZED PELLETS DURING THE REDUCTION PROCESS IN A ROTARY HEARTH FURNACE
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,1 000 N,and 1 500 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.
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