干式弱磁场气流悬浮磁选机的研制

【作者】 程坤；

【导师】 张宗华；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2007， 博士

【摘要】 磁选是在不均匀磁场中利用矿物之间的磁性差异而使不同矿物实现分离的一种选矿方法。由于磁选具有流程简单、经济、有效等特点,而被广泛应用于黑色金属矿石的选别:有色和稀有金属矿石的精选:重介质选矿中介质的回收:从非金属矿物原料中除去含铁杂质,保护破碎机和其它设备;从冶炼生产的钢渣中回收废钢以及从生产和生活污水中除去污染物等领域。磁选设备按照选分介质可分为干式磁选机和湿式磁选机。后者是目前应用最广泛的磁选设备。针对我国矿石具有“贫、细、杂”的特点,许多矿区地处干旱缺水或严寒地区,以及水资源日益短缺、环境保护越来越受到重视的情况,研制符合我国实情,能够选别细粒矿石、尽可能减轻对水资源污染破坏的新型干式磁选设备具有十分显著的经济社会意义。干式弱磁场气流悬浮磁选机是针对细粒入选物料,在下部给矿的方式下,使其在气流作用下进入分选空间,在矿粒处于松散状态下,因受力和运动轨迹不同而达到分选目的。设备主要由给矿系统、供风系统、管道系统、分选系统、动力及调节系统和排矿系统所组成。本文研究了悬浮于气流中的细粒矿石受力和运动的情况;分析了在垂直及弯曲管道中细粒矿石的运动状态;研究了磁性颗粒和非磁性矿粒(或弱磁性矿粒)在弱磁场作用下的受力情况,分析得出了其不同的运动轨迹;研制出了干式弱磁场气流悬浮磁选机的设备装置,并利用该设备进行了矿物试验,取得了较好的分选效果。从试验结果来看,干式弱磁场气流悬浮磁选机作为一种新的干式选别设备能够在矿物分选领域得到广泛的应用。1.在磁选过程中,矿粒主要受到磁力和机械力的作用,磁性不同的矿粒因受到不同的磁场力作用,沿着不同的路径运动。磁性矿粒和非磁性矿粒(或弱磁性矿粒)的运动路径由作用在这些矿粒上的磁力和所有机械力的比值来决定。2.钕铁硼永磁材料因磁性能高,机械性能良好,不含战略金属钴、镍,相对价格较低,而被广泛使用。本研究将其与价格更低廉的铁氧体进行合理配置,得到了磁场性能明显改善、能够满足选别要求的磁系。3.悬浮于气流中的细粒矿石所受到的力有气流对矿粒的曳引阻力、矿粒所受的重力、浮力、压力梯度力、Magnus效应升力、Saffman升力、虚假质量力、Basset力、接触点的力,在弯曲管道中还受到离心力作用。4.本文分析研究了入选矿粒在选别过程中三个阶段的受力情况。第一个为矿粒在气流中垂直运动的阶段,第二个为矿粒刚进入磁场有效范围的阶段,第三个为矿粒在磁场中的分选阶段。5.悬浮于气流中的细粒矿物因矿石本身的粒度、质量、形状、密度、体积的不同,矿粒间相互摩擦作用以及气流场中速度梯度的变化等因素影响,其运动轨迹各不相同,从而为分选提供了条件。6.本文对入选矿粒在设备中的运动进行了数值分析。推导出在无外加磁场作用下,悬浮于气流中的矿粒群在垂直管道中的运动轨迹方程,分析了单颗粒矿物在弯管内运动的受力情况,得到了颗粒由下往上至稳定段所需时间和上升距离的关系;研究了颗粒群在悬浮状态下由水平管道向垂直上升管道过渡的弯管部分,其速度随时间和距离的变化关系,得到了关系方程:研究了非磁性矿粒由水平管道向垂直管道运动时其颗粒群速度随时间、距离的变化关系。运用牛顿第二定律,在Lagrangian坐标系中建立起了颗粒在选别过程中的运动轨迹方程式。7.本文根据原理分析研制出了干式弱磁场气流悬浮磁选机,并对该设备的磁系材料选择、磁系磁场特性、磨矿设备的选择、管道的设计、分选区域的设计、转筒转速调节设备的选用及出矿系统的设计进行了分析,最终确定了各组成系统的设备及结构参数。8.本文利用研制的干式磁选设备进行了矿物分选实验。通过对入选物料粒度组成,供风系统风压、给矿量、磁选区域结构与分选效果的关系研究,确定了选别的最佳条件,并在最佳选别条件下对矿物进行了分选试验。9.本文利用干式弱磁场气流悬浮磁选机所进行的矿物试验与湿式筒式磁选试验进行了对比,得出了在入选物料粒级范围、给矿量、磁场强度等条件基本一致的情况下,悬浮磁选所得的精矿品位比湿式磁选低1.91%,精矿回收率高0.61%的结论。分析悬浮干式磁选与湿式磁选在选别上略有差异的原因,一是湿式磁选是以水作为分选介质,因此在湿式分选过程中入选物料在水流和磁性交替的磁系产生的变化磁场中进行磁翻滚运动,使得部分脉石矿物被清除出来,从而提高了精矿产品质量:而在悬浮干式磁选中虽然磁系也是极性交替使吸附矿粒群产生磁翻动,但气流的“清除”作用要低于水流的“清除”作用。二是在湿式磁选中非磁性矿物(或弱磁性矿物)是在水流和自身重力的作用下沉入槽体底部,然后排出,再次被夹带的几率较小;悬浮磁选过程中的非磁性矿物(或弱磁性矿物)在气流作用下向上运动,其自身重力方向向下,在湍流的作用下再次被夹带的几率较大,从而造成精矿指标的下降。更多还原

【Abstract】 Magnetic separation is one of mineral processing methods,which uses magnetic difference between different minerals in homogeneous to separate.Magnetic separation is easy to run,economical and effective,so was widely used in ferrous metal ore separation,non-ferrous and rare metal ore separation,medium recovery in heavy medium separation,remove iron impurities from non-metallic mineral to protect crusher and other equipment,scrap steel recovery from steel slag and remove pollutants form sewage of production and livelihood.Magnetic separator can be divided into dry and wet magnetic separator according to election media.The latter is the most extensive application of magnetic separator.Domestic ores are "poor,small,complex",many mines located in drought or cold areas,water resources shortage and more attention to environmental protection. In these conditions,develop a new type dry magnetic separator which in line with actual situation,can separate fine ore,minimize pollution damage to he water has economic and social significance.Dry weak magnetic field air suspension magnetic separator selected minerals for fine.In the way of feed ore in lower part and particles enter sorting room under the air, fine be separated because of force and move trails in dispersed state.The equipment composed by feeding,wind,plumb,separation,power and mining systems.This paper studied the force and motion state of fine suspended in air,analyzed the movement of fine in vertical and curved pipe,studied the force of magnetic and non-magnetic(or weakly magnetic)particles in magnetic field and got their trajectory. This paper developed the dry weak magnetic field air suspension magnetic separator, and used the device made mineral test.Test showed that the efficiency was good. According to the results,dry weak magnetic field air suspension magnetic separator as a new dry separator can be widely used in mineral separation.1.In the magnetic processing,the role mineral subjected was magnetic and mechanical,different magnetic particles along different paths due to different magnetic role.The movement trails of magnetic and non-magnetic(or weakly magnetic)particles was determined by the ratio of magnetic and all mechanical role on particles.2.NdFeB permanent magnetic materials was widely used because of high magnetic properties,good mechanical properties,lower prices,no strategic metal such as cobalt,nickel.This study made a reasonable distribution of NdFeB and ferrite, achieved a magnetic line which improved the magnetic properties significantly and meet sorting requires.3.The force of fine mineral suspended in the air suffered including dray resistance of air on the particles,gravity,buoyancy,pressure gradient force,Magnus effect lift,Saffman lift,quality of the false,Basset force,point of contact,and particles in the pipeline also suffered the centrifugal force.4.This paper studied the force state of particles in the separation.First stage was particles vertical moved in the air,second stage was particles entered in magnetic field initially,third stage was particles separated in magnetic field.5.Particles in suspended state made different movement trails because of their different size,quality,shape,density,volume,mutual friction role of mineral particles and changes of velocity gradient,so as to provide the conditions of separation.6.In this paper,the numerical analysis of particles movement in the equipment was made.This paper derived the trajectory equation of mineral group suspended in the air at vertical pipe in the absence of external magnetic field.Analyzed the force state of single particle move in the elbow,got the relationship of time and distance from the bottom-up to the stability.Studied the relationship of speed changes with the time and distance of the particles in the suspended state of from the level to vertical rise pipe,got the relationship equation.Studied the particles speed relation with the time and distance of non-magnetic ore tablets in the state of from level to vertical pipe. Established trajectory equation in the Lagrangian coordinates of particles in the processing using Newton’s second law. 7.This paper developed the suspension magnetic separator according to the principles,and analyzed the magnetic material selection,the magnetic properties of magnetic field,the selection of grinding equipment,the design of plumb and separation interval,the selection of equipment of rotor speed control and the design of mine system,and finally identified the components of the equipment and system structure parameters.8.In this paper,made the mineral separation experiments used the dry magnetic separator.Through studied the relationship of air pressure of air system,feed volume of mineral,magnetic separation regional structure and separation effect,determined the best conditions for the election,and in these conditions made a mineral separation test.9.This paper compared the mineral test results of suspension dry magnetic separator and wet drum separator,and made a conclusion.In the same conditions such as particles size range,the feed volume of ore and magnetic field strength,the suspension dry magnetic separate compared to wet magnetic separate,concentrate grade is lower 1.91%and concentrate recovery is higher 0.61%.It had two reasons for the test differences of suspended dry magnetic separate and wet magnetic separate. Firstly,water is wet magnetic separation medium,in the wet processing,the particles made a magnetic roller sports under the changed magnetic field of water and magnetic lines of magnetic turn,these made part of gangue minerals was cleared out,so enhanced the concentrate product quality.In suspended dry magnetic,the particles also made a magnetic roller sports under the magnetic lines of magnetic turn,but airstream’s "elimination" is below to the water’s "elimination".Secondly,in the wet magnetic separation,non-magnetic(or weakly magnetic)minerals under the influence of water and their own gravity into the bottom of the groove,and then drained,so less risk of being entrained again.In the suspension dry magnetic processing,the non-magnetic(or weakly magnetic)minerals was upward in the airflow,downward direction of its gravity,the more risk of being entrained again in effect of turbulence, so the concentrate indicators declined.更多还原