复杂熔渣体系中低品位有价组元强制析出的基础研究

The function of high magntic fields (HMFs) on the condensed state is the frontier of the discipiline of metallurgy and material and etc. However, most of studies focuses on the molten metal and its solidification. Our previous study has found that there exists a significant effect on the forced precipitation during the process of solidification of molten slag system under HMFs, and similar studies have not been reported. Based on urgent needs of effective recovery of valuable elements from metallugical solid waste, it is necessary to study the physical and chemical laws of precipitation in molten slags under HMFs. Therefore, stainless steel slag with a low content of Cr 1-5 wt% will be selected as the object of this study. High-temperature solidification process techniques, combining with modern material structure test technology, are used to explore the thermodynamic causes, dynamic mechanism during the process of forced precipitation of chromium in the slag system under external field. The law of interaction between chromium and other elements will be investigated in order to clarify the collaborative mechanisms and migration law. This study focuses on exploring the mechanism of forced precipitation behavior of the target element with or without external field, in order to acquire the general physicochemical principles and laws of forced precipitation of valuable element in complex slag systems. Then, theoretical model about forced precipitation will be established. Expected results can not only give a support for study in other slag system and will enrich the theoretical system of metallurgical physicochemistry in molten slag, but also provide a technical basis to recovery chromium from the stainless steel slag, and to eliminate its harmful influence to environment in the end.

以强磁场对凝聚态作用行为的研究，是冶金、材料等学科的前沿，但多以金属熔体为研究对象。申请者在前期研究中发现，强磁场对熔渣凝固过程中强制析出作用显著，而类似的研究未见报道。基于对冶金固废中有价组元有效利用的迫切需求，研究强磁作用下熔渣组元析出的物理化学规律，很有必要。为此，拟将含有低品位铬（w=1～5%）的模拟不锈钢熔渣作为研究体系，利用高温凝固和现代材料结构测试技术，研究在外场强制作用下，熔渣体系中有价组元铬强制析出的热力学成因、动力学机制；寻求场效应下，铬与伴随组分的共析及其析出相演化规律，及过程中组元之间相互作用机制和迁移规律。重点探寻：在外场强制作用下，目标组分迁移、强制析出的一般机制与规律，目标相生成的物理化学成因，进而建立相关的理论模型。预期成果不仅可为其它熔盐体系的相关研究提供理论借鉴，丰富冶金物理化学理论体系，而且可为不锈钢渣中铬的回收利用，消除其对环境危害提供技术基础。

含有价组元的熔渣体系很多，如含铬不锈钢渣、含钒钢渣等；其组分复杂，导致凝固析出的矿相组成存在较大的变化，因此，针对其冷却过程中析晶以及有价组元的析出与赋存行为已有广泛的研究。但是，在磁场作用下有价组元析出行为方面的研究尚较少涉及。本项目以含有低品位铬（w=0～9%）的模拟不锈钢熔渣作为研究体系，设计不同碱度（CaO/SiO2）、不同Cr2O3、FeO、Fe2O3含量以及添加成分CaF2、B2O3，研究熔渣体系的电导率，以及在无、有磁场作用下析晶规律以及有价组元走向，研究认为：（1）熔渣电导率随着Cr2O3含量的增大而减小；当Cr2O3含量保持不变时，熔渣电导率和活化能均随着碱度的增大而上升，但是电导率下降速度随温度下降反而愈快；（2）在无磁场作用下，低碱度、低Fe2O3、高FeO有助于含铬尖晶石 [(Mg,Fe)(Fe,Cr,Al)2O4]相析出；较高的析晶温度有利于含铬尖晶石中Cr2O3含量提高；（3）强磁场作用于含铬熔渣的凝固过程，析出的晶相组成不会因为磁场介入而改变；但是对于含有FeO的不锈钢熔渣体系，尖晶石晶粒随磁场作用方向呈条带状排列，且晶粒尺寸变小。对于目标相—含铬尖晶石相进行合成并研究其结构与磁学性能，研究发现：随Cr2O3含量增加，尖晶石结构的晶胞参数变小，晶粒尺寸变小，亚铁磁性转变为顺磁性。课题取得的成果不仅可为其它熔盐体系的相关研究提供理论借鉴，丰富冶金物理化学理论体系，而且可为不锈钢渣中铬的回收利用，消除其对环境危害提供技术基础。