KR脱硫渣高温矿物组成及含硫相的析出行为

 KR脱硫渣是KR铁水预处理脱硫工艺的副产品,其磁选后尾渣中CaO质量分数大于50%。可将其用作优质造渣原料返回到转炉炼钢工艺中,降低转炉炼钢的原料消耗。但KR脱硫渣中的硫(w((S))=1.0%～2.5%)成为转炉冶炼循环利用的障碍,直接将其用于转炉冶炼会使钢中的硫含量增加。因此,根据工业KR脱硫渣的化学成分,以合成渣的形式对KR脱硫渣中矿物组成及含硫相的析出行为进行研究,旨在明确KR脱硫渣中各矿物相组成及炉渣中硫的析出行为和赋存状态,为后续通过氧化性气氛有效脱除KR脱硫渣中的硫提供理论参考。采用热力学数据库FactSage 8.0的Equilib模块对CaO-SiO₂-CaS-CaF₂基熔渣的凝固过程进行模拟,利用XRD、SEM-EDS对合成渣样品的矿物组成及微观形貌进行分析、检测。热力学计算结果表明,CaS的析晶温度为1 320 ℃,低于MeO#1相、MeO#2相及2CaO·SiO₂相的析晶温度。炉渣样品的面扫描分析结果表明,在实际凝固过程中,受残余液相黏度增大的影响炉渣中少量硫未能析出形成CaS晶体,则以非晶态的形式赋存在基质相中。KR脱硫渣主要由C₃S相、MeO#1相(CaO固溶体)、MeO#2相(MgO固溶体)、基质相和CaS相等矿物组成。炉渣中的硫主要以游离态CaS晶体形式赋存,少量以非晶态硫的形式赋存。炉渣中CaS晶粒主要沿着先析出的高熔点硅酸盐(C₃S)相边界析出。

Mineral composition of KR desulfurization slag and precipitation behavior of sulfur-containing phases

KR desulfurization slag is a by-product of the desulfurization pretreatment process about hot metal, in which the mass percent of CaO in the tailings after magnetic separation is more than 50%. It can be used as a slag-making material by recharging to converter steelmaking process to reduce the economic cost of converter steelmaking. However, the sulfur in the KR desulfurization slag (w((S))=1.0%-2.5%) has become an obstacle to the recycling of converter smelting, and its direct use in converter smelting will increase the sulfur content in the steel. Therefore, according to the chemical composition of industrial KR desulfurization slag, the mineral composition and precipitation behavior of sulfur-containing phase in KR desulfurization slag were investigated in the form of synthetic slag. The purpose is to clarify the mineral phase composition of KR desulfurization slag, the precipitation behavior and occurrence state of sulfur in slag, so as to provide theoretical reference for the subsequent effective removal of sulfur in KR desulfurization slag through oxidizing atmosphere. FactSage 8.0 was adopted to simulate the solidification process of CaO-SiO₂-CaS-CaF₂-based slag, and XRD and SEM-EDS were employed to analyze the mineral composition and microscopic morphology respectively. The thermodynamic calculation results show that the crystallization temperature of CaS is 1 320 ℃, which is lower than that of MeO#1 phase, MeO#2 phase and 2CaO·SiO₂phase. The results of surface scanning analysis of slag samples show that a small amount of sulfur in slag did not precipitate to form CaS crystal due to the increase of residual liquid viscosity during the actual solidification, and it exists in the matrix phase in the form of amorphous state. KR desulfurization slag mainly composes of C₃S, MeO#1 (based on CaO), MeO#2 (based on MgO), matrix and CaS. The sulfur element mainly precipitates along the boundary of the silicate (C₃S) phases.