基于压力场-剪切力场-温度场耦合作用的不锈钢渣熔融改质新工艺的基础研究

Stainless steel slag is classified as a hazardous waste, because some toxic Cr-bearing substances could be released from it causing harm to the human being and living organisms. Therefore, a pollution-free disposal for stainless steel slag before it be discharged to the environment or be reused as a secondary resource is of greatest importance. Spinel, one of the major phases in stainless steel slag, is confirmed to be the most suitable phase for stabilizing chromium since its excellent stability even in harsh conditions. A considerable amount of research has been devoted on promoting the chromium migration to the stable spinel, but some key issues remain unsolved. The Cr-bearing spinel crystals grow slowly and randomly distribute in the matrix, which is unfavorable for the chromium stabilization and the subsequent Cr-bearing spinel recycling. By investigating the research achievements of the geochemistry, genetic mineralogy, and experimental petrology on the metallogenic mechanisms of natural chromite, a novel pressure field-shear stress field-temperature field coupled melting modification method is proposed and will be intensively studied in this project to promote the crystallization and aggregation behaviors of the Cr-bearing spinel crystals. A series of melting modification tests will be carried out under various pressure, shear stress and temperature conditions, and the variation on phase, structure, and chemical composition will be determined using diversified detection means and analytical methods. The multi-field coupling effects on the nucleation and growth behaviors of Cr-bearing spinel crystals will be illuminated, and their movement and aggregation mechanism induced by the shear stress will be clarified. Moreover, the structural evolution of the melt during the melting modification process and the resulting property changes will be revealed. Based on these findings, the mutual relations between the modification conditions, silicate structure, physicochemical properties of melt, and crystallization behavior of Cr-bearing spinel can be disclosed, and Cr-bearing spinel aggregates with a large grain size is expected to be formed by the multi-field coupled melting modification treatment. For the purpose of recycling chromium resource from modified slags, an extraction study for Cr-bearing spinel will be carried out using modern beneficiation technologies, and a toxicity evaluation on the tailings will be performed. The expected research achievements are to provide a theoretical foundation and a technical support for the improvement of the pollution-free disposal and the comprehensive utilization of stainless steel slag.

不锈钢渣是不锈钢冶炼过程中产生的含铬废渣，直接排放会造成严重的资源浪费和环境污染。采用熔融改质工艺可将不锈钢渣中的铬富集在稳定的尖晶石相中，有效降低铬的氧化溶出风险。然而铬尖晶石生长缓慢、分布弥散，极大影响了铬的稳定化效率和铬尖晶石的选择性分离能力。为解决此难题，本项目借鉴地球化学、成因矿物学和实验岩石学相关成果，开展基于压力场-剪切力场-温度场耦合作用的不锈钢渣熔融改质实验研究，解析单一/复合外场作用下铬尖晶石的形核、生长机理，探讨剪切力诱导作用下的尖晶石运动、聚集机制，研究改质条件-熔体结构-理化性质-结晶行为的内在关系，探索有利于大尺寸尖晶石聚集体形成的熔融改质方法，以实现铬尖晶石的强化生长与区域富集。本项目还将采用现代选矿工艺对铬尖晶石进行分离提取，评价提铬尾渣中铬的稳定化水平，形成基于铬资源高效回收的不锈钢渣处理新方法。项目的顺利实施对于我国钢铁工业的绿色发展具有重要的推动作用。

不锈钢渣是一种典型的高污染含铬固体废弃物，其无害化处理与资源化利用的根本难题在于提升铬的稳定化水平。如何实现铬元素在尖晶石相中的快速定向富集是解决此问题的关键所在。本项目基于地球化学、成因矿物学和实验岩石学相关成果，将外场作用引入到高温不锈钢渣的熔融改质过程，开展了基于多场协同耦合作用的熔融改质实验研究。通过研究，阐明了外场作用下铬尖晶石的形核、生长机理，构建了尖晶石的结晶动力学模型，揭示了剪切力诱导作用下的尖晶石运动、聚集机制，明确了外场作用对熔体结构的影响行为，建立了改质条件—熔体结构—理化性质—结晶行为的内在关系，形成了有利于大尺寸尖晶石聚集体形成的不锈钢渣熔融改质新方法，实现了铬元素的定向富集与尖晶石晶体的强化生长。对改质渣中铬的溶出风险进行了综合分析，提出了基于铬强稳定化控制的不锈钢渣综合利用新方法，为不锈钢渣污染的源头阻断与高水平资源化利用奠定了理论基础。项目执行期内，发表了SCI论文20篇，申请了国家发明专利4项（已授权1项），培养了研究生5人。在此基础上，进一步挖掘与凝练出了新的科学问题，形成了面向不锈钢渣铬污染控制与其碳捕集应用的矿相结晶行为精确调控新思路，申请并成功获批了2020年国家自然科学基金面上项目。