Testing the validity of the spherical DEM model in simulating real granular screening processes
Testing the validity of the spherical DEM model in simulating real granular screening processes
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DOI：
10.1016/j.ces.2011.09.029
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发表时间：
2012-01
影响因子：
4.7
通讯作者：
Geoff P. Delaney;P. Cleary;M. Hilden;R. Morrison
中科院分区：
文献类型：
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作者：
Geoff P. Delaney;P. Cleary;M. Hilden;R. Morrison
我们研究了颗粒状物质在水平振动筛上的流动。我们使用离散元方法(DEM)在实验室规模的实验和模拟之间进行了跨越一系列操作条件的直接定量比较。我们测试了通常使用的颗粒为球形的DEM近似对模型真实再现工业筛选系统行为的能力的影响程度，在工业筛选系统中，颗粒通常为非球形。模拟几何形状和输入粒度分布被设置为与实验系统完全匹配，该实验系统包括一个带有金属网布的水平筛网，采石场岩石以一系列输入流量输送到该筛网上。筛子振动，使颗粒床在甲板上流动，并与通过筛子的更细的物质垂直分层，在那里它们被收集在沿筛子长度的一系列垃圾桶中。通过分析每个收集箱的内容物，找到了流经筛网每一段的物料的尺寸分布。在模拟和实验中，在极低的流速下，绝大多数小于孔径大小的物质进入屏幕后都会被迅速捕获，这一点是最好的。在较高的流速下，对于接近格栅大小的颗粒，对通过筛网的流速的过度预测存在显著的定量误差。这归因于通过床层的更高的渗流速率和更容易被球形材料的筛面捕获。接近孔径大小的球形颗粒也显示出非常强烈的钉住屏幕的倾向，被困在屏幕开口中，并限制了进一步通过屏幕这些部分的流动。因此，在振动筛的DEM模拟中使用球形颗粒不足以模拟实际不是球形的颗粒的真实流动和分离。
We investigate the flow of a granular material over a vibrated horizontal screen. We perform a direct quantitative comparison, across a range of operating conditions, between laboratory scale experiments and simulations using the discrete element method (DEM). We test the extent to which the commonly employed DEM approximation of particles being spherical affects the ability of the model to realistically reproduce the behaviour of industrial screening systems where the particles are generally non-spherical in shape. The simulation geometry and input particle size distribution are set up to exactly match the experimental system, which consists of a horizontal screen with a wire mesh cloth onto which quarry rock is fed at a series of input flow rates. The screen is vibrated, causing the granular bed to flow over the deck and vertically stratify with finer material passing through the screen, where it is collected in a series of bins located along the length of the screen. The size distribution of the material flowing through each section of the screen is found by analyzing the contents of each collection bin. The best agreement is found for very low flow rates, where the vast majority of the below aperture size material is rapidly captured just after it enters the screen in both the simulation and experiment. At higher flow rates, significant quantitative errors are found with the over-prediction of the flow rate through the screen for near grate sized particles. This is attributed to the higher rate of percolation through the bed and the easier capture by the screen surface of the spherical shaped material. The near aperture sized spherical particles also show a very strong tendency to peg the screen, becoming trapped in the screen openings and limiting further flow through those parts the screen. The use of spherical particles in the DEM simulation of vibrating screens is therefore found to be inadequate for modelling realistic flow and separation of particles that are not actually spherical.