低品位含钒资源高效利用的物理化学研究

Stone coal is a kind of abundant vanadium mineral resource in China, its reserve in terms of V2O5 accounts for 87% of China's total reserve of V2O5, i.e. 6.7 times of V2O5 reserved in vanadium titanium magnetite. At present, to leach the vanadium in stone coal, the V3+ existed in stone coal need to be oxidized into V4+ or V5+ by roasting firstly. But the pyrite and carbon in stone coal go against the oxidation of V3+, and lead to the low leaching rate of vanadium. In addition, due to the scattered distribution of vanadium in stone coal, the physical separation methods cannot effectively concentrate vanadium phase, leading to the useless acid consumption in the process of leaching, and serious environmental pollutions.. In view of the above problems, the stone coal is proposed to be reduced by using the carbon in the stone coal as the reductant in the present project. In the self-reduction process, the occurrence state of vanadium in stone coal will be changed and the vanadium will enrich in the phases that easy to be separated. Consequently, the following investigations will be carried out. The evolution of structures and compositions of the phases in stone coal will be revealed by combining the dynamic in situ means and fine static analysis methods, and the interaction mechanism between vanadium and carbon and the physical-chemical behaviors of vanadium during the self-reduction process will also clarified. Finally, the rules concerning the migration, enrichment and distribution of vanadium and other elements during the self-reduction process will be elucidated, and new technical directions for the clean utilization of stone coal will be designed, as well as the related theoretical basis will also be provided.

石煤是我国丰富的含钒资源，已探明石煤中钒储量以V2O5计算占我国V2O5总储量的87%，是钒钛磁铁矿V2O5储量的6.7倍。目前的石煤提钒工艺中，需经氧化焙烧将石煤中难以浸出的V3+氧化为容易浸出的V4+、V5+，但石煤中的黄铁矿和碳会抑制V3+的氧化，导致钒浸出率低。另外，由于石煤中钒分布分散，物理选矿方法无法有效富集含钒相，导致浸出过程中的无益酸耗、及严重的环境污染。. 针对上述问题，本项目拟利用石煤中的碳为还原剂，通过石煤的高温自还原改变钒的赋存状态、实现钒的富集和高效提取。通过动态原位手段与精细的静态分析方法相结合，揭示自还原过程中石煤的物相结构与组成演变规律，明晰钒、碳间的相互作用机理及钒在自还原过程中物理化学行为。最终明晰石煤自还原过程中，钒及其他有价其他元素的迁移、富集与分布规律，为石煤的清洁高效利用设计新的技术方向，并提供相关的理论依据。

为解决现有石煤提钒过程中存在的两大根本问题,第一、直接处理低品位原矿导致的能耗高、废弃物排放量大、环境污染风险高的问题，第二、现有氧化焙烧—湿法浸出工艺与石煤的本征还原特性不符而导致的V3+氧化不完全、浸出率低的问题，项目提出如下新思路：1）充分利用石煤的本征还原特性，通过自还原焙烧实现钒的重构与富集；2）物理分离富钒相获得高品位钒精矿；3）从钒精矿中直接浸出分离V3+，实现钒的清洁提取。为此，开展完成了以下工作：. I) 系统研究了多个含钒氧化物体系的相平衡关系和热力学性质、构建了相关体系的相图。所获得的基础数据填补了该领域的热力学数据空白，而且指导设计了适合V3+高效富集与分离的磁性尖晶石富钒相（Fe3-xVxO4）；. II) 巧妙地采用环境友好的Fe2O3作为钒的富集载体，研发出“含钒石煤中钒的自还原富集—磁选分离新方法”，成功将石煤中分散赋存的三价钒（V3+）重构为Fe3-xVxO4富钒相。新方法成功应用于湖北宜昌地区的含钒石煤（V含量约为0.7%），实现了钒的高效富集，磁选分离的钒精矿中钒含量达14%，钒品位提高了20倍，钒的回收率达92%。. III) 从尖晶石富钒相的结构特征出发，研发出“Fe粉协同草酸水热络合提钒及水热沉钒新方法”，实现了钒精矿中三价钒（V3+）的一步浸出和绿色沉淀分离。相比传统先氧化（V3+氧化为V5+）后浸出的两步提钒工艺，省去了氧化焙烧环节、大幅降低了能耗，避免了使用强酸强碱、从源头控制了污染。. 项目从基础研究到提出新的技术方向、再到具体可操作的新方法，为我国特色低品位钒资源的清洁高效利用提供了不同于前人的新的技术方向，也为更多低品位难处理钒资源的清洁高效利用提供了科学依据和新方向。