转炉熔渣低温气化脱磷行为

 在低温下脱磷转炉熔渣中的磷质量分数过高往往是限制转炉渣循环利用的重要因素,因此如何有效降低转炉熔渣中磷质量分数成为众多钢铁企业迫切需要解决的重点问题之一。基于此,从理论分析和工业试验角度,并结合XRD、SEM-EDS和拉曼光谱等试验手段进一步分析研究了理论热力学条件、转炉渣熔点、矿相结构和炉渣结构对低温气化脱磷的影响。通过理论分析表明,较高温度、较低的FeO含量和碱度有利于低温气化脱磷反应。工业试验结果表明,当终点温度为1 350～1 360 ℃、转炉渣FeO质量分数为25%～35%、碱度控制为1.2～2.5时,气化脱磷率可以达到30%以上。当炉渣碱度小于1.25、FeO质量分数小于35%时,适当地提高炉渣碱度和FeO含量能促进炉渣熔点降低,进而有利于低温气化脱磷反应的发生。XRD和SEM-EDS分析结果表明,转炉渣主要由富磷相、基体相和RO相组成,其中Si、P、Ca质量分数高的Ca₂SiO₄-Ca₃(PO₄)₂富磷相的存在不利于低温气化脱磷反应发生,Fe、Mn等金属氧化物质量分数高的RO相和基体相的存在有利于低温气化脱磷。通过转炉渣拉曼光谱分析表明,当转炉渣硅氧四面体结构Qn(n=1,2,3)相对含量较低时,渣中聚合度降低,且Ca₃Si₂O₇相含量较少,炉渣流动性较好,此种渣结构有利于低温气化脱磷。通过本研究可以为钢铁企业实现脱磷转炉渣的二次利用提供借鉴。

Dephosphorization behavior by low temperature gasification of converter slag

The high phosphorus content in the dephosphorization converter slag at low temperature limits the recycling of the converter slag. Therefore, how to effectively reduce the phosphorus content in the slag has become one of the key issues that many iron and steel enterprises urgently need to solve. Based on this, the effects of theoretical thermodynamic conditions, melting point of converter slag, mineral phase structure and microstructure of slag on low-temperature gasification dephosphorization were further analyzed and studied from the perspective of theoretical analysis and industrial experiment, combined with XRD, SEM-EDS and Raman spectroscopy. Theoretical analysis shows that higher temperature, lower FeO mass fraction and alkalinity are beneficial to the low temperature gasification dephosphorization reaction; the industrial test results show that the gasification dephosphorization rate can reach over 30% when the terminal temperature, mass percent of FeO and alkalinity of converter slag are controlled in the range of 1 350-1 360 ℃, 25%-35% and 1.2-2.5 respectively. When the basicity and mass percent of FeO of slag are lower than 1.25 and 35% respectively, properly increasing the basicity and mass percent of FeO of slag can promote the melting point of slag to decrease, which is conducive to the occurrence of low-temperature gasification dephosphorization reaction. XRD and SEM-EDS analysis results show that the converter slag is mainly composed of phosphorus-rich phase, matrix phase and RO phase. Among them, the existence of Ca₂SiO₄-Ca₃(PO₄)₂ phosphorus-rich phase with high mass fraction of Si, P and Ca is not conducive to low-temperature gasification dephosphorization, while the existence of RO phase and matrix phase with high mass fraction of metal oxides such as Fe and Mn is conducive to low-temperature gasification dephosphorization. The Raman spectrum analysis of converter slag shows that when the relative content of the silicon-oxygen tetrahedral structure Qn(n=1,2,3) in the converter slag is low, the degree of the polymerization in the slag decreases and the content of the Ca₃Si₂O₇ phase is less, so that the fluidity of converter slag is better. This slag structure is conducive to low temperature gasification dephosphorization. This study can provide reference for iron and steel enterprises to realize the secondary utilization of dephosphorization converter slag.