细粒煤流态化摩擦电选的基础研究

Triboelectric separation is a dry separation method for fine particles, and based on the tribocharge difference of particles to achieve separation in the electric field. It has a promising application in processing of coal, minerals, fly ash and waste plastics. Fluidization is an ideal tribocharging method, and tribocharge the particles oppositely through collision and rubbing in fluidized bed. A novel design triboelectric separation by using electric field fluidized bed is proposed to investigate. This novel design combines fluidization tribocharge and separation process in fluidized bed. The particles are pre-tribocharged in first fluidized bed, and then feed into another electric-field fluidized bed to achieve separation while continue to tribocharge by fluidization. This novel triboelectric separation would be high performance. Fine coal and minerals particles will be studied in this project. The main research contents of the project include the fluidization characteristics of one-component particle and hybrid particle of coal, quartz, calcite and pyrite samples, the effect and mechanism of fluidization causing tribocharge of particles in fluidized bed, the influence and regulation mechanism of electric field on the fluidization behavior of particles, the dynamic model of movement and transportation of tribocharged particle in electric field fluidized bed, establishing the lab fluidization triboelectric separation system to investigate the separation and enrichment pattern of particles tribocharged oppositely in electric field fluidized bed. The key fundamental problems in fluidization triboelectric separation would be resolved in this project, and the research achievements are theoretical guidance and positive to fluidization triboelectric separation of other particle martials.

摩擦电选是一种细颗粒干法分选方法，它根据不同颗粒摩擦荷电差异在静电场中实现分离。在煤炭、矿物、粉煤灰、废塑料等分选加工领域应用前景广阔。流态化方法是一种理想的颗粒摩擦荷电方法，能使不同颗粒间摩擦碰撞带上异性电荷。本课题提出采用电场流化床进行摩擦电选的新方法，将颗粒流态化摩擦荷电与分选结合在一起。颗粒预先流态化荷电后，进入电场流化床中分选并同时继续流态化摩擦荷电，实现高效分选。本项目以煤和伴生矿物颗粒为研究对象开展研究，主要研究煤、石英、方解石、黄铁矿单组分颗粒和混合颗粒的流态化特性，以及流态化行为对颗粒流态化摩擦荷电的作用机制；电场对颗粒流态化行为的影响规律及调控机制；荷电颗粒在电场流化床中迁移运动的动力学模型；建立流态化摩擦电选实验室系统，研究异性荷电颗粒在电场流化床的分选富集规律。项目研究将解决流态化摩擦电选的关键基础科学问题，研究成果对其他物料颗粒的流态化摩擦电选也具有理论指导意义。

颗粒流态化过程中伴随着不断的颗粒碰撞-分离行为，引起颗粒间的摩擦带电。本课题将流态化摩擦荷电与外加电场耦合，提出了一种外加电场流化床，使颗粒在流化床中摩擦荷电的同时实现静电分选，在干旱地区的细粒煤和矿物分选、城市矿产回收等方面应用前景广阔。课题以煤及其伴生矿物等颗粒为研究对象，分析了不同物料颗粒的组成及单组分和混合组分的流化特性，研究了流化特性对不同颗粒流态化摩擦荷电特性的影响规律；研究了外加电场对颗粒流化行为的作用机制及不同组分物料的富集特性和迁移规律，探讨了电场强度、流化气速和流化时间等因素对煤-石英混合颗粒的荷电强度和富集效果的调控机制，研究了细粒煤和伴生矿物反向迁移运动规律及动力学，实现了颗粒物料的摩擦荷电和富集分选。采用外加电场二维流化床研究了外加电场下气泡演变的行为机制，结果表明外加电场影响气泡的纵向分布，减小气泡直径，降低气泡上升速度，并使得气泡发生横向位移；而增加流化气速则影响气泡的横向分布，增大气泡直径和上升速度。据此提出了外加电场下流化床中荷电颗粒与气泡行为相互影响的作用机制，气泡在上升过程中裹挟颗粒，同时带电颗粒向两极板移动也导致气泡的横向迁移。借助原子力显微镜和开尔文探针力显微镜，研究了微观尺度下矿物表面电荷的产生和耗散机理，证实了表面水膜的存在会削弱材料之间的电荷转移，使得探针-水膜-样品之间的电荷转移更为复杂；提出了电荷耗散速率系数对电荷强度的依赖关系，并探讨了表面水膜对正/负电荷横向扩散过程中的作用机制，量化了高湿度条件下环境中水分子与固体表面水膜对电荷耗散的影响规律，并证实了电荷耗散是两者共同作用的结果。最后，建立了实验室流态化连续分选系统，建立了连续分选效果的综合评价机制，并开展了细粒煤分选、废弃线路板非金属组分、废旧塑料等颗粒物料的流态化摩擦电选实验，为流态化摩擦电选技术的工业应用奠定了基础。