钒铬渣物相结构及尖晶石生长机制与调控的研究

Productive practices and existing studies have demonstrated that phase structure of vanadium slag affects its quality and thus the recovery rate of vanadium. From the study of crystallization behavior in vanadium slag, we found that the cooling parameter and slag composition have a significant effect on the phase structure of vanadium slag. Further experiments showed that the growth mechanism of spinels in vanadium slag differ significantly at different temperature zones. Thus, we propose the study on the phase structure of vanadium slag and the growth mechanism and regulation of spinels. Taking the vanadium-chromium slag (vanadium slag with high chromium content) as the research object, this project is to establish the crystallization rate models of different spinels, and using these models to calculate the precipitation order of different crystals and the optimal thermodynamic conditions for crystal growth. Image analysis method will be used in the study to investigate the isothermal and non-isothermal macroscopic crystallization kinetics, and explore the dominant mechanism and restriction of growth of spinels. A valence state calculation model is to be established and combine with experiment to quantitative study the valence state distribution and influencing factors of vanadium and chromium. This study aims to reveal the scientific issue of competitive crystallization behavior of spinels in complex molten vanadium-containing slag system. According to the requirement on the quality of vanadium-chromium slag in subsequent processes, the phase of vanadium-chromium slag and crystallization process can be regulated and controlled. This study is to establish control measures to provide more adequate scientific basis, and provide theoretical and technical support for the development and utilization of vanadium titano-magnetite with high chromium content represented by Hongge mine.

生产实践和现有研究已证明：钒渣物相结构影响其质量，进而影响钒回收率。我们在钒渣结晶行为研究中发现，不同的冷却制度和炉渣成分对钒渣物相结构有明显影响。进一步实验显示：不同温度区段下钒渣中尖晶石相的生长机理有所区别。由此，我们提出钒渣物相结构及尖晶石生长机制与调控研究。本项目以钒铬渣（高铬型钒渣）为研究对象，拟建立钒铬渣中尖晶石的结晶速率模型，计算不同晶体析出的顺序以及各自生长的最佳热力学条件；以图像分析法进行尖晶石相等温和非等温结晶宏观动力学分析，阐明尖晶石相生长的主导机制和限制性环节；建立价态计算模型，结合实验定量研究钒、铬的价态分布和影响因素。本研究旨在揭示多元复杂含钒熔渣体系下尖晶石竞争性结晶行为这一关键科学问题。根据后续工序对钒铬渣质量的要求，可对钒铬渣物相和结晶过程进行调控。本研究为确立调控措施提供更充分的科学依据，为以红格矿为代表的高铬型钒钛磁铁矿的开发利用提供理论和技术支撑。

针对钒铬渣物相结构影响其质量进而影响钒、铬回收率的问题，本项目提出钒铬渣物相结构及尖晶石生长机制与调控的研究。以钒铬渣为研究对象，建立了模拟钒铬渣中各物相形核与晶体长大行为的数学模型，研究了渣中不同物相的表观结晶速率，探讨了不同晶体析出的顺序以及各自的最佳生长温度区间，探明了组分、温度对钒铬渣中主要尖晶石形核和长大速率的影响规律，从本质上阐明了钒铬渣中尖晶石、橄榄石、辉石等物相结晶的最佳热力学条件，揭示了多元复杂含钒熔渣体系中尖晶石竞争性结晶行为这一关键科学问题。研究结果表明，钒铬渣中Cr2O3含量、Cr2O3/V2O3的增大或SiO2/FeO的减小有利于尖晶石生长；TiO2对尖晶石生长影响较小；钒铬渣中各晶体结晶能力顺序为：FeCr2O4>Mg2SiO4>FeV2O4>MgSiO3>Fe2TiO4>Mn2SiO4>MnSiO3> Fe2SiO4。以高温淬火-图像分析法研究了钒铬渣中尖晶石相等温结晶和非等温结晶宏观动力学，分析了温度、冷却制度等因素对钒铬渣中尖晶石相平均粒径和结晶面积的影响规律，基于晶体尺寸分布理论阐明了尖晶石相生长的主导机制和限制性环节。5 K/min的低冷速有利于尖晶石生长，从1873 K降至1473 K时尖晶石平均粒径达52.21 μm；当T>1773 K时，尖晶石生长受形核控制；当T<1773 K时，尖晶石生长受界面控制与扩散控制。降温至1523 K保温有利于尖晶石生长，保温100 min后其平均粒径可达60.34 μm，等温过程尖晶石生长受扩散控制。采用微区表征手段从微观角度研究了炉渣中钒、铬元素的赋存物相和分布规律，结合离子分子共存理论和化学计量平衡建立了炉渣中钒、铬价态计算的数学模型，结合实验研究了氧势、温度、炉渣成分等因素对钒、铬价态分布的影响规律。钒铬渣中铬主要存在形态为Cr3+，其次为Cr2+，有毒元素Cr6+最少；控制低氧压、低Cr2O3含量和低V2O3含量可减少Cr6+含量。本研究为确立钒铬渣物相结构的调控措施提供了充分的科学依据，可为以红格矿为代表的高铬型钒钛磁铁矿的开发利用提供理论和技术支撑。