• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Fundamental Improvement in the Tribocharging Separation Process for Upgrading Coal
【24h】

Fundamental Improvement in the Tribocharging Separation Process for Upgrading Coal

机译：磨煤提质分离工艺的根本改进

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Triboelectrostatic separation is a physical separation technique that is based on surface electronic property differences among minerals to achieve a separation. Minerals have different surface conductivities and electron affinities. They are charged differently in quantity and/or polarity after a tribocharging process. Particles with different surface charges move discretely under external electric field produce a separation. Electrostatic separation is a dry mineral processing method that does not require any water or chemical reagents. It can greatly simplify the processing circuit and reduce operating cost. Additionally, problems caused by water in conventional wet mineral processing such as water freezing, dewatering, water pollution and water treatment are eliminated. Electrostatic separation has great potential as a fine particle separator (i.e. < 1mm) in industrial minerals processing application, especially in arid areas where water supply is limited.;In the current study, particle tribocharging kinetics was evaluated using a model system comprised of copper, pure coal, silica and ceramic. The results of the tribocharging process were recorded and analyzed using an oscilloscope and a signal processing technique. Charge exchange, charge separation and charge relaxation corresponding to tribocharging processes were studied using the generated pulsing signals. The signals provided a method to quantify the charge penetration into the conductor bulk during tribocharging. A new method to measure the particle surface charge using the pulsing was proposed and assessed, which was extremely useful for subtle surface charge measurements which effectively eliminated environmental noise. The interactive forces at the contacting interface, relative displacement, material electronic properties and ambient relative humidity were found to impact particle surface charge. The silica surface sites are 69 times more chargeable than the coal surface, which provides a fundamental explanation for upgrading that is achievable for silica-rich coal using triboelectrostatic separation. The influences of operating and environmental parameters were quantified and compared using an environment controlled chamber. Energy consumption at the interface was found to be positively correlated with the particle charge. Relative humidity has dual effects on the particle tribocharging, excessively low or high humidity levels do not favor particle tribocharging. Finally, a semi-empirical mathematical model of particle tribocharging was developed from the basic tribocharging compression model utilizing the parametric experiment study results. The model provides a more accurate method to predict particle surface charge under exact tribocharging conditions.;A novel rotary triboelectrostatic separator (RTS) using the tribocharging mechanism was tested for upgrading fine coal. The particle size influencing the RTS tribocharging and separation process is investigated. A practical method to quantify the particle charging distribution was developed based on the direct particle charge measurement and a Gaussian distribution assumption. The smaller particles were found to have a higher average surface charge and wider surface charge distribution, which provided an opportunity to separate the high grade and the low grade coal particles. However, particles that are too small have weak particle-charger tribocharging effect that reduces particle tribocharging efficiency. The particle separation process was analyzed considering the exact experimental hydrodynamic separating conditions. Smaller particles were found to be more sensitive to the airflow that used to transport the particles as a result of the effect on residence time in the separation chamber. A method combining mathematical and statistical analysis was proposed to theoretically predict RTS separation efficiency based on the particle charging conditions and particle separation conditions. The particle horizontal displacement probability distribution was ultimately derived from this method. The model predictions indicate that a wider horizontal displacement distribution provides improved separation efficiency for the RTS unit. The theoretical analysis indicates that a particle size range between 0.105 and 0.21 mm has widest horizontal displacement distribution and thus represents an optimum particle size range which is in agreement with experimental results.;The influences of the RTS operating parameters on separation performance achieved on a pure coal-silica mixture were investigated using a parametric study. The optimum operating conditions were identified. Using the optimum conditions, a five-stage separation process was conducted using the RTS unit to obtain the necessary data for the development of an ideal performance curve. Two stages of RTS separation were found to generate good quality clean coal with acceptable recovery. Particle tribocharging tests were performed using pure coal, pure silica and the coal-silica mixture as model feed materials. The test result found that mixing the pure coal with the sand reduced the particle charge distribution of the coal while increasing the charge distribution of the pure silica particle. The finding explains the inability to produce clean coal products containing ultra-low ash contents. However, the rejection of silica to the tailings stream is very high.
机译：摩擦静电分离是一种物理分离技术，其基于矿物之间的表面电子特性差异来实现分离。矿物具有不同的表面电导率和电子亲和力。在摩擦充电过程之后，它们的数量和/或极性不同。具有不同表面电荷的粒子在外部电场下离散运动，产生分离。静电分离是一种干燥的矿物加工方法，不需要任何水或化学试剂。它可以大大简化处理电路并降低运行成本。另外，消除了常规湿矿物加工中由水引起的问题，例如水冻结，脱水，水污染和水处理。静电分离作为工业矿物加工应用中的细颗粒分离器（即<1mm）具有巨大潜力，尤其是在供水受限的干旱地区。；在当前的研究中，使用由铜组成的模型系统评估了颗粒摩擦充电动力学，纯煤，二氧化硅和陶瓷。记录摩擦充电过程的结果，并使用示波器和信号处理技术进行分析。使用产生的脉冲信号研究了与摩擦充电过程相对应的电荷交换，电荷分离和电荷弛豫。这些信号提供了一种在摩擦充电过程中量化电荷渗透到导体主体中的方法。提出并评估了一种使用脉冲测量颗粒表面电荷的新方法，该方法对于有效消除环境噪声的细微表面电荷测量非常有用。发现在接触界面处的相互作用力，相对位移，材料电子特性和环境相对湿度会影响颗粒表面电荷。二氧化硅表面的电荷是煤表面的69倍，这为使用摩擦静电分离技术对富含二氧化硅的煤进行提质提供了基本解释。使用环境控制室对操作和环境参数的影响进行了量化和比较。发现界面处的能量消耗与粒子电荷呈正相关。相对湿度对摩擦带电有双重影响，过低或过高的湿度都不利于摩擦带电。最后，利用参数化的实验研究结果，从基本的摩擦充电压缩模型建立了颗粒摩擦充电的半经验数学模型。该模型为在精确的摩擦装料条件下预测颗粒表面电荷提供了一种更准确的方法。研究了影响RTS摩擦充电和分离过程的粒径。基于直接粒子电荷测量和高斯分布假设，开发了一种量化粒子电荷分布的实用方法。发现较小的颗粒具有较高的平均表面电荷和较宽的表面电荷分布，这提供了分离高品位和低品位煤颗粒的机会。然而，太小的颗粒具有弱的颗粒充电器摩擦充电效果，这降低了颗粒摩擦充电效率。考虑到精确的实验流体动力学分离条件，对颗粒分离过程进行了分析。由于对分离室中停留时间的影响，发现较小的颗粒对用于输送颗粒的气流更敏感。提出了一种将数学和统计分析相结合的方法，以基于颗粒充电条件和颗粒分离条件从理论上预测RTS分离效率。该方法最终推导了粒子水平位移概率分布。模型预测表明，更宽的水平位移分布为RTS单元提供了改进的分离效率。理论分析表明，粒径范围为0.105至0.21 mm的颗粒具有最宽的水平位移分布，因此代表了最佳粒径范围，与实验结果吻合。RTS操作参数对纯净分离性能的影响使用参数研究对煤-二氧化硅混合物进行了研究。确定了最佳操作条件。在最佳条件下，使用RTS装置进行了五个阶段的分离过程，以获取开发理想性能曲线所需的数据。发现RTS分离分为两个阶段，可产生合格回收率的优质清洁煤。使用纯煤进行颗粒摩擦充电测试，纯二氧化硅和煤-二氧化硅混合物作为模型进料。测试结果发现，将纯煤与沙子混合降低了煤的颗粒电荷分布，同时增加了纯二氧化硅颗粒的电荷分布。该发现解释了无法生产含超低灰分的清洁煤产品的原因。但是，二氧化硅对尾矿流的排斥率很高。

著录项

  • 作者

    Chen, Jinxiang.;

  • 作者单位

    University of Kentucky.;

  • 授予单位 University of Kentucky.;
  • 学科 Mining engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 150 p.
  • 总页数 150
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号