硫含量对KR脱硫渣中硫赋存状态的影响

 KR脱硫渣中的CaO是转炉冶炼工艺中重要的造渣原料,将其回用于钢铁冶炼工艺可降低冶金企业的CaO原料消耗,减少企业KR脱硫渣堆积量,节约企业冶炼的经济成本。KR脱硫渣中的2CaO·SiO₂(C2S)在转炉脱磷冶炼过程中可与炉渣中的磷形成稳定的2CaO·SiO₂-3CaO·P₂O₅固溶体,提高磷在渣中的稳定性。将KR脱硫渣代替活性石灰用作转炉造渣料,可促进转炉冶炼初期早化渣,提高转炉冶炼的脱磷效率。但由于KR脱硫渣中硫质量分数为1.0%～2.5%,将其直接用于转炉冶炼会导致钢水增硫。因此,采用FactSage8.0对炉渣中各物相凝固过程进行模拟,采用SEM-EDS、XRD对炉渣基本物相及微观形貌进行分析、检测,采用Image-ProPlus6.0对渣样中CaS平均晶粒面积进行分析,旨在明确硫含量对炉渣中硫赋存状态及析出行为的影响,为后续通过氧化性气氛脱除KR脱硫渣中的硫提供理论依据。热力学计算表明,硫质量分数为0.5%～2.5%时,炉渣中CaS析晶温度由1 240升高到1 390 ℃;当温度为1 600 ℃时,随着硫含量增加,炉渣中MeO#1相含量逐渐减少,炉渣黏度逐渐减小;硫质量分数为0.5%时,炉渣中硫以非晶态组织赋存;硫质量分数为1.0%～2.0%时,炉渣中硫主要以CaS形式赋存;硫质量分数为2.0%～2.5%时,炉渣中硫以CaS相和Ca₁₁(SiO₄)₄O₂S相赋存,Ca₁₁(SiO₄)₄O₂S主要赋存在硅酸盐相中。随着硫含量增加,炉渣中CaS晶粒长大速率逐渐增大,CaS平均晶粒面积逐渐增大,且炉渣中CaS晶粒逐渐由不规则结构演变为圆饼状结构。

Effect of sulfur content on occurrence state of sulfur in KR desulfurization slag

The CaO component in KR desulfurization slag is an important slagging raw material in converter smelting process. Its reuse in converter smelting can reduce the CaO raw material consumption as well as the accumulation of KR desulfurization slag for metallurgical enterprise, and save the economic cost of smelting. Moreover, 2CaO·SiO₂ (C2S) in the KR desulfurization slag can form stable C2S-C3P(2CaO·SiO₂-3CaO·P₂O₅) solid solution with phosphorus in the slag to improve the stability of phosphorus during converter dephosphorization smelting. Reusing KR desulfurization slag instead of activated lime as converter slag can promote early slagging in the initial stage of converter smelting and improve the dephosphorization efficiency. However, w((S)) in the KR desulfurization slag was 1.0%-2.5%, reusing it directly in converter smelting would lead to sulfur increase in molten steel. Therefore, in order to clarify the influence of sulfur content on occurrence state of sulfur in molten slag, and to provide a theoretical basis for subsequent effective removal of sulfur from KR desulfurization slag through oxidizing atmosphere,the solidification process of each phase in the molten slag was simulated by FactSage8.0, the basic phase and micro morphology of molten slag were analyzed and detected by SEM-EDS and XRD, and the average grain area of CaS in the slag sample was analyzed by Image-Proplus 6.0. Thermodynamic calculation showed that the crystallization temperature of CaS in molten slag increased from 1 240 to 1 390 ℃ when w((S)) was 0.5%-2.5% in the molten slag. In addition, the content of MeO#1 phase and the viscosity of slag gradually decreased in molten slag with the increase of sulfur content at 1 600 ℃. When w((S)) was 0.5%, the sulfur in the molten slag existed in amorphous structure, while w((S)) was 1.0%-2.0%, the sulfur mainly existed in the form of CaS. When w((S)) was 2.0%-2.5%, the sulfur existed in CaS phase and Ca₁₁ (SiO₄) ₄O₂S phase, and Ca₁₁ (SiO₄) ₄O₂S mainly existed in silicate phase. With the increase of sulfur content, the growth rate and average grain area of CaS in molten slag gradually increased, and the CaS grains gradually evolved from irregular structure to round structure.