基于磁介质设计实现下游捕收强化弱磁性矿物分选效率及其机理研究

Increasing the utilization of weakly magnetic mineral resources is of great significance for ensuring the raw material supply demanded for industrial development of China. Although the vertical ring pulsating magnetic separators are widely applied in the processing of weakly magnetic minerals, the mineral particles are mainly captured at the upstream side of the matrices and serious mechanical entrainment still occurs, resulting in the low separation efficiency. That is a key factor restricting the utilization of weakly magnetic minerals. Increasing the slurry velocity can realize the downstream capture of the matrices and enhance selectivity, but the recovery of the magnetic minerals will decrease dramatically. In this project, based on the fact that the capture of magnetic particles by the downstream side of the matrices in the longitudinal configuration of high gradient magnetic separation (HGMS) can significantly increase selectivity, enhanced downstream capture under low slurry velocity (normal velocity) is to be realized to significantly decrease the mechanical entrainment of gangue minerals and enhance the capture of fine magnetic minerals through matrix’s material combination and structure design, utilizing the drainage and space hindrance effect of the nonmagnetic part and the magnetic capture effect of the magnetic part. Concerning the matrix design and separation mechanism of downstream capture, single wire design for decreasing and eliminating the particle capture at the upstream side of the matrix, single wire design for enhancing the particle capture at the downstream side of the matrix, theoretical analyses of the particle capture by the downstream side of the matrix and particle buildup at the downstream side of the matrix, the magnetic separation tests and parameter optimization of downstream capture of multi matrices are to be investigated through finite element simulation, theoretical derivation and experimental research. The aim of this project is to significantly increase the separation efficiency of weakly magnetic minerals and at the same time, to provide new mentality and approach for the efficient utilization of weakly magnetic minerals.

提高我国弱磁性矿产资源利用效率，对保障国家工业发展所需原料供应具有重要意义。立环脉动高梯度磁选设备在弱磁性矿物的分选中应用广泛，但由于主要采用介质上游捕收，机械夹杂仍较严重。提高给矿速度实现介质下游捕收能够提高选择性，但矿物回收率会急剧降低。基于磁介质下游捕收能够大幅度减少机械夹杂的事实，本项目通过磁介质材质组合和结构设计，利用非磁性部分的引流及空间阻碍作用和磁性部分的磁捕收作用，以介质设计方法和矿物分选机理为研究对象，结合仿真分析、理论计算和试验研究等方法，进行单根介质设计消除磁性颗粒在介质上游的累积和强化磁性颗粒在介质下游的累积、磁性颗粒捕集行为和累积行为理论分析以及多根介质的下游捕收磁选效果及参数优化等研究，实现低给矿流速（常规流速）下介质下游的强化捕收，大幅度减少机械夹杂的同时强化细粒磁性矿物的捕收效率，解决高梯度磁选分选效率低的问题，为弱磁性矿物的高效加工利用提供新思路和新途径。

弱磁性矿产主要包括赤铁矿、褐铁矿、镜铁矿、菱铁矿、钛铁矿、锰矿、黑钨矿和钽铌稀土矿等。我国弱磁性矿产资源储量大，但资源禀赋差，利用率低，对外依存度居高不下。高梯度磁选是处理弱磁性矿物经济有效的手段，但因其较低的选择性而通常用于弱磁性矿物的粗选中，后续仍需采用离心、浮选或磁化焙烧等工艺获得合格精矿产品，导致流程复杂，生产成本高。提高高梯度磁选的选择性是实现弱磁性矿物清洁高效利用的关键。非磁性脉石的机械夹杂和磁性脉石的竞争捕集是造成高梯度磁选选择性低的两大主因。本项目提出采用组合材质磁介质实现下游捕收来减少进而消除非磁性脉石的机械夹杂。采用剥离磁介质上下游累积物的方法对高梯度磁选中非磁性脉石机械夹杂的系统研究发现，磁介质下游捕收较上游捕收具有更优的选择性，而重力在非磁性脉石的机械夹杂中具有较大的促进作用。采用石英（比重2.65）、重晶石（比重4.39）和黄铜（比重8.09）三种不同密度的非磁性颗粒作为脉石矿物，与赤铁矿的人工混合矿的实验结果表明非磁性脉石的机械夹杂程度随着脉石密度的增大而加剧，轻密度脉石的机械夹杂能够通过增大给矿流速或脉动强度得到有效消除，而重密度脉石的机械夹杂难以消除，即使采用较大给矿流速或脉动强度。通过对上下部分分别为非磁性材料和磁性材料的组合材质磁介质的优化设计和实验研究，成功实现了组合材质磁介质的下游捕收。组合材质磁介质实现的下游捕收对消除非磁性脉石的机械夹杂具有显著效果，即使是重密度脉石。但是采用组合材质磁介质分选攀西钛铁矿等实际难选弱磁性矿物时的效果仍不佳。主要原因是组合材质磁介质对引起选择性低的另一因素，即磁性脉石的竞争捕集作用很有限，消除磁性脉石的竞争捕集是下一步需要重点解决的关键难题。项目资助下，发表SCI检索论文14篇，出版专著一部，申请或授权发明专利11项。