不同价态离子置换过程稀土矿体孔隙结构空间演化机制及渗流特性研究

In-situ leaching method has been successfully applied in southern ion-type rare-earth mines, due to its prominent advantages in reducing the cost of mining and protecting the surface environment. However, during the promotion process, there have been many problems such as low recovery rates of mining and slip of poured slope. These outstanding technical problems are related to the seepage, and the evolution of the pore structure of the rare earth ore body during the leaching process is the key factor for the good migration and infiltration of the leaching solution. According to the literature reviewed at home and abroad, many researches attributed the changes of pore structure in solution seepage process to the physical and mechanical factors such as the decrease of effective stress in matrix and the migration of seepage matrix particles, but neglected the "secondary porosity structure" caused by the strong chemical exchange between the ions. Therefore, based on the in situ leaching process, the project intends to study the mechanism and dynamic evolution of ion exchange on the pore structure of rare earth ore bodies, and a seepage mathematical model of ionic rare earth orebodies based on the change of porosity will be established. At the same time, the influence of valence change on the seepage porosity during chemical substitution was studied, and the optimal valence of ions is obtained from the existing cations that can theoretically displace. It can provide the basic research basis on improve the leaching process and enhance the leaching efficiency.

原地浸矿法因其在降低回采成本、保护地表环境等方面的突出优势，在南方离子型稀土矿山推广应用。但在推广过程中出现了采矿回收率低、注液边坡滑移等诸多问题，这些突出问题均与浸矿液在母体中的渗流密切相关，而浸矿过程稀土矿体孔隙结构演化成为浸矿液良好运移渗透的关键所在。但查阅国内外相关研究文献发现，众多研究将溶液渗流过程孔隙结构变化归因于介质骨架有效应力降低和渗流母体颗粒运移等物理力学因素，却忽略了由于离子间强烈化学交换而引发的“次生孔隙结构”。本项目正是基于这一问题，立足于原地浸矿工艺过程，拟通过试验的方法研究离子置换对稀土矿体孔隙结构的作用机理及动态演化规律，建立基于孔隙率变化的离子型稀土矿体渗流数学模型。同时，掌握离子价态对化学置换过程渗流孔隙的影响，在现有理论上可置换的阳离子中，选择有利于浸矿液渗流的最优离子价态。为改进浸矿工艺和提升浸矿效果提供基础研究依据。

原地浸矿法因其在降低回采成本、保护地表环境等方面的突出优势，在南方离子型稀土矿山推广应用。但在推广过程中出现了采矿回收率低、注液边坡滑移等诸多问题，这些突出问题均与浸矿液在母体中的渗流密切相关，而浸矿过程稀土矿体孔隙结构演化成为浸矿液良好运移渗透的关键所在。本项目正是基于这一问题，立足于原地浸矿工艺过程，通过试验的方法研究离子置换对稀土矿体孔隙结构的作用机理及微观结构动态演化规律。结论表明，不同价态阳离子浸矿，矿体渗透性降低，渗流速率与阳离子价态呈现负相关。不同价态阳离子与稀土阳离子置换使得浸矿母液离子强度和pH发生变化，改变浸出率和浸出速率，最佳浸出速率为1+价态铵离子，最佳浸出率为2+价态的镁离子。对比试验结果得到最优浸矿剂为2+价态的硫酸镁溶液。综合考虑不同价态浸矿导致矿体导水率与基质吸力变化，构建了浸矿液非饱和入渗数学模型，改变了传统饱和入渗模型的缺陷，误差率由11.3%降至5%。研究结果为改进浸矿工艺和提升浸矿效果提供了详实基础研究依据。