低品位高含水硅镁型红土镍矿干燥与预还原机理及协同机制

Low-grade and high water cut garnierite is a important nonferrous mineral resource, which has some characteristics as follows: large reserves, lower grade, difficult treatment. Based on pyrometallurgy process of garnierite, the cooperation mechanism and mechanisms of drying and pre-reduction of low-grade and high water cut garnierite are studied, constructing theoretical basis of drying and pre-reduction and high-efficient enriching valuable metal. Technological mineralogy of low-grade and high water cut garnierite is investigated and mineralogical structure property of garnierite is obtained; existing form and distribution law of water are analyzed, research method of drying mechanism of low-grade and high water cut garnierite is constructed, drying characteristics of different temperature ranges are found out and drying mechanism of low-grade and high water cut garnierite is determined; by thermodynamic analysis and optimizing experimental, the reduction behavior of nickel and iron is influenced at the different reduction conditions by some parameters, such as time, temperature, reductant content, additive content et al, the reduction laws of nickel and iron are found out, cooperation reduction mechanism of nickel and iron is explained and reduction mechanisms of nickel and iron are revealed in pre-reduction process; research system of cooperation mechanism of drying and pre-reduction is established, interactive coupling relationship of drying process and pre-reduction process is analyzed, the cooperation mechanism of drying and pre-reduction for low-grade and high water cut garnierite is explored. The theoretical guidance for pyrometallurgy process of garnierite is provided by the research.

低品位高含水硅镁型红土镍矿是一种重要的有色矿产资源，具有储量大、品位低、难处理的特点。本项目基于火法冶金过程，开展低品位高含水硅镁型红土镍矿干燥与预还原机理及协同机制的基础研究，构建干燥和预还原的理论基础，达到有价金属高效富集的目的。研究低品位高含水硅镁型红土镍矿工艺矿物学，获得矿物的矿相结构特性；分析矿物中水分存在形式及分布规律，构建干燥机理研究方法，找出不同温度区间干燥特征，阐明低品位高含水硅镁型红土镍矿干燥机理；通过热力学分析，系统及优化实验，研究不同预还原条件下时间、温度、还原剂用量、添加剂用量等参数对镍、铁还原行为的影响，找出镍、铁还原规律，阐释镍、铁协同还原机制，揭示预还原过程中镍、铁还原机理；建立干燥与预还原协同机制的研究体系，分析干燥过程与预还原过程交互耦合关系，探索低品位高含水硅镁型红土镍矿干燥与预还原协同机制。本项目的研究为硅镁型红土镍矿火法冶炼提供理论指导。

项目针对云南元江难处理的低品位高含水硅镁型红土镍矿，开展了硅镁型红土镍矿低温和高温干燥实验研究并分析了干燥特性和力学性能，研究了气体及固体还原剂作用下硅镁型红土镍矿中镍、铁的还原特性并揭示了预还原过程中镍、铁还原机理，同时探索了硅镁型红土镍矿干燥与预还原协同机制。研究结果表明：在低温干燥过程中，随着干燥温度的增加，红土镍矿的湿基含水量不断减小，红土镍矿低温干燥过程被分成两个阶段：升速干燥阶段、减速干燥阶段。红土镍矿湿基含水量降到平衡水分时，干燥过程结束，低温干燥过程的活化能为1.7 kJ·mol-1；在高温干燥过程的最佳干燥时间为30min。并且高温干燥后红土镍矿变成了不定型硅酸镁，随着干燥温度的继续升高，重新结晶形成(Mg,Fe)SiO4和Fe2O3；在预还原过程中，随着温度和还原剂量的增加，镍的还原率不断增加。对于气-固还原过程，延长还原时间和减小矿石粒径都会增加镍的还原率，但还原时间过长不利于FeO含量增加，因少部分FeO与SiO2生成了铁橄榄石，使FeO的含量有所降低，而粒径的减小则有利于FeO含量增加。对固－固还原过程，随着还原时间和CaO添加量的增加，金属镍还原率和FeO含量先增大后减小；在混合矿中铁镍比的增加，促进了镍铁还原，镍铁回收率都有所增加，添加三氧化二铁对镍的还原的有促进作用；随着干燥温度的升高，干燥阶段样品失重逐渐增加，而还原阶段样品失重逐渐减少，总体的质量损失几乎不变，还原样品经磁选后得到精矿中镍、铁的品位及回收率没有明显的变化；本项目获得了硅镁型红土镍矿干燥、预还原的关键技术参数，揭示了硅镁型红土镍矿干燥机理及镍、铁的预还原机理，初步探索了干燥与预还原协同机制，实现了硅镁型红土镍矿中有价金属的高效提取，对低品位高含水硅镁型红土镍矿干燥和预还原的工业化实践具有重要的指导意义。