Using SPH one-way coupled to DEM to model wet industrial banana screens

Large banana screens with multiple decks are used extensively in the process separation of many valuable export commodities. They are high capacity vibrating screens with a curved profile. Discrete Element Method (DEM) modelling using non-spherical particles has previously provided significant insight into the operation of these dry industrial screens. Here we introduce the use of Smoothed Particle Hydrodynamics (SPH) to model the flow of slurry (water and fine material) through a double deck banana screen. This paper firstly reports on the underlying DEM model of the coarse particulate flow on a full-scale banana screen. We then use Smoothed Particle Hydrodynamics (SPH) to model the transport of fine particle slurry over and through the double deck banana screen. Finally, we combine the DEM with SPH models using a one-way coupling to simulate the effects of adding a slurry flow to coarse particulates on the banana screen. The key outcomes from this study are that; SPH is ideally suited for the high speeds and the high fragmented and filamentary nature of the fluid flow through the screen deck openings; the fluid only (SPH) model of slurry behaves similarly to the DEM approach in that more fluid is screened as the velocity slows, except near the earlier panels on the top deck; and, use of a porous media derived from DEM in one-way coupled approach with SPH produces clear and reasonable changes in fluid structure, separation and wetting of the screens consistent with slurry behaviour. Specifically, the fluid layer was much thicker in the coupled case, with slurry being trapped inside a coarse particle bed and which is sensitive to the fluid viscosity.     

Prediction of slurry transport in SAG mills using SPH fluid flow in a dynamic DEM based porous media

DEM modelling of the motion of coarse fractions of the charge inside SAG mills has now been well established for more than a decade. In these models the effect of slurry has broadly been ignored due to its complexity. Smoothed particle hydrodynamics (SPH) provides a particle based method for modelling complex free surface fluid flows and is well suited to modelling fluid flow in mills. Previous modelling has demonstrated the powerful ability of SPH to capture dynamic fluid flow effects such as lifters crashing into slurry pools, fluid draining from lifters, flow through grates and pulp lifter discharge. However, all these examples were limited by the ability to model only the slurry in the mill without the charge.In this paper, we represent the charge as a dynamic porous media through which the SPH fluid is then able to flow. The porous media properties (specifically the spatial distribution of porosity and velocity) are predicted by time averaging the mill charge predicted using a large scale DEM model. This allows prediction of transient and steady state slurry distributions in the mill and allows its variation with operating parameters, slurry viscosity and slurry volume, to be explored.     

Cone crusher modelling and simulation using DEM

Compressive crushing has been proven to be one of the most energy efficient principles for breaking rock particles (Schönert, 1979). In this paper the cone crusher, which utilizes this mechanism, is investigated using the discrete element method (DEM) and industrial scale experiments. The purpose of the work is to develop a virtual simulation environment that can be used to gain fundamental understanding regarding internal processes and operational responses. A virtual crushing platform can not only be used for understanding but also for development of new crushers and for optimisation purposes.Rock particles are modelled using the bonded particle model (BPM) and laboratory single particle breakage tests have been used for calibration. The industrial scale experiments have been conducted on a Svedala H6000 cone crusher operated as a secondary crushing stage. Two different close side settings have been included in the analysis and a high speed data acquisition system has been developed and used to sample control signals such as pressure and power draw in order to enable detailed comparison with simulation results. The crusher has been simulated as a quarter section with a batch of breakable feed particles large enough to achieve a short moment of steady state operation. Novel methods have been developed to estimate the product particle size distribution using cluster size image analysis. The results show a relatively good correspondence between simulated and experimental data, however further work would be need to identify and target the sources of observed variation and discrepancy between the experiments and simulations.     

A multiscale method for including fine particle effects in DEM models of grinding mills

A multiscale model for including interstitial powder or fine particles in DEM simulations of grinding mills is proposed. This consists of a traditional DEM model at the macroscale which includes only grinding media and potential coarser fractions of feed and product. Microscale models are embedded within this macroscale model. These can be sufficiently small that the fine powder can be included in a computationally affordable manner. The direct inclusion of the fine particles in the model allows predictions to be made of the effect of the local grinding environment on these fine particles. A shear cell is a good choice for the microscale model as it can well represent the local flow conditions at different points within the mill macroscale model. Averaging the macroscale flow allows the local collisional environments to be characterised and provides estimates of the shear rate and normal stress at each of the microscale locations which then controls the configuration of each microscale shear cell. A 1-way coupled implementation of this multiscale model is demonstrated for a simple cement ball mill. The relative importance of each region of the flow is determined with the toe region being the dominant contributor to the grinding. The grinding action produced by the shearing of thin layers of powder between adjacent layers of media flowing over each other is clearly demonstrated by the behaviour predicted in the microscale models. Methods for calculating power draw that include the effect of powder and for constructing collision energy spectra for the powder are described. Finally, the importance of the cushioning effect of high powder loads on the flow behaviour of the media is demonstrated.     

DEM modelling of non-spherical particle breakage and flow in an industrial scale cone crusher

Predictions of particle flow and compression breakage of non-round rock passing through an industrial scale cone crusher are presented. The DEM (Discrete Element Method) particle breakage model is generalised to allow non-round particles to be broken into non-round progeny. Particles are broken in this DEM model when the elastic energy of a contact is sufficiently high to initiate fracture. Progeny size distribution data from JKMRC Drop Weight Test (JKDWT) or JKMRC rotary breakage test (JKRBT) is used to generate the specific daughter fragments from each breakage event. This DEM model is able to predict the production of both coarser progeny which are resolved in the DEM model and finer progeny which are not. This allows the prediction of product down to very small sizes, limited only by the fineness of the fragments measured in the breakage characterisation. The predicted flow of material through the crusher, product size distribution and liner wear are discussed. The generalised breakage model demonstrated here is suitable for modelling all forms of crushers.     

非均质煤层瓦斯渗流的SPH方法模拟研究

应用光滑粒子流体动力学（smoothed particle hydrodynamics,SPH）方法对煤层瓦斯渗流进行模拟研究。针对非均质煤层瓦斯瞬态渗流问题,利用Fortran语言编制了变系数瓦斯渗流偏微分方程的求解程序,通过虚粒子法处理边界条件,构建了无网格性质的SPH瓦斯渗流模型。进行了不同原始瓦斯压力和透气性系数时常系数渗流方法下结果的误差分析,同时考虑透气性系数受矿山压力及Weibull分布影响的非均质煤层,分析了非均质煤层中瓦斯压力及涌出量的变化规律。模拟结果表明：应用SPH方法能很好的模拟煤层的瓦斯渗流;矿山压力影响以及透气性系数按Weibull分布赋值的非均质煤层都会导致瓦斯渗流的非线性。     

DEM在土地勘测定界中的应用

分析土地勘测定界工作中起伏地区地表面积与平面面积的差异,探讨地表面积计算的方法。从理论上分析空间平面投影到平面上的面积变形情况,指出利用DEM来实现地表表面积计算是可行的,并给出了在ArcGIS9.3制图软件中计算地表表面积的具体方法。     

非规则格网DEM数据采集综合取舍方法研究与实践

DEM数据已经被广泛应用在许多领域中,但目前国家出台的技术规范中,仅仅给出了DEM数据成果的精度要求,和规则格网DEM的采集间隔,对非规则格网的DEM数据没有明确其综合取舍的指标;而且国内外讨论的焦点也多在DEM数据成果的精度评价方法和规则格网DEM的综合取舍上,很少关注非规则格网DEM数据采集的综合取舍,致使出现采用非规则格网DEM数据成果或数据冗余或精度不能满足要求的情况,文中就此方面结合生产实际进行了探讨和研究,提出了非规则格网的DEM数据采集综合取舍方法。     

DEM、DOM的生产和质量控制

DEM、DOM是建立GIS系统的重要基础性资料,其质量的优劣直接影响到GIS系统的应用.为此,结合蚌埠市DEM、DOM的生产实例,阐述了DEM、DOM生产实施、质量控制的过程,并对与此相关的数字空三加密作了简要的介绍,最后对工作中遇到的一些相关技术问题进行了探讨.     

石台杵岭隧道DEM建立及其应用

以1∶2000的AUTOCAD地形图为基础,在MAPGIS软件中,建立了石台杵岭隧道地区的数字高程模型(DEM),并应用该DEM生成了杵岭隧道纵剖面和计算了工程量.结果表明,以AUTOCAD地形图为基础,建立DEM模型是简单可行的;应用DEM进行隧道纵剖面生成和工程方量计算是非常容易和精度较高的.根据以上结论,认为DEM引入到隧道和其他工程领域可行且非常有必要的.     

基于SPH方法的大块煤冲击破碎数值模拟

为研究大块煤在钎杆冲击下的破碎效果,引入RHT混凝土本构模型材料来模拟大块硬煤（压缩强度35 MPa）,并基于光滑质点流体动力学（SPH）方法建立了钎杆冲击大块煤的三维仿真模型。分析比较了大块在静压、纯冲击和冲压组合作用下的破坏程度,以及平头和圆锥形钎杆冲击效果的差异。仿真结果表明：平头钎杆在30 MPa压力、15 m/s速度或是其组合作用下,均无法使大块产生有效破坏;平头钎杆在200 m/s的超高速下可使大块产生彻体破坏,但实现钎杆高速运动困难;圆锥钎杆在30 MPa压力和15 m/s速度的冲压作用下,使大块产生了较大范围的锥形失效,远高于常规液压破碎锤的单次冲击破坏程度。锥形钎杆、高压高速是破碎硬质大块煤的一种有效方法,可在较少作用次数下实现破碎,验证了低频重载破碎大块的可行性。     

矿区DEM的时空模拟与反演方法及其应用研究

为了对矿区地表移动与变形的空间分布规律进行预计与"再现",文章提出了数字沉陷模型DSM的概念,分析了其与DTM和DEM的区别与联系,讨论了DSM的构建方法。在此基础上提出了矿区DEM反演的概念,讨论了反演分析原理及其实现方法。然后结合研究区实际例子进行了DSM计算和静态下沉等值曲线表达,最后采用动态移动过程模拟和时空反演模拟方法,根据常村矿矿井南部2002年的DEM构建了该区域2000,1997年的DEM。利用上述方法生成的DEM数据层可以与矿区对应时刻的生态数据图层一起进行GIS空间叠置运算,为分析矿区生态环境采动变化趋势提供数据方法。     

数字高程模型与等高线的三维一体化快速生成

介绍了三维虚拟环境中的数字高程模型与等高线一体化快速生成表达方法。首先讨论了基于移动拟合和移动加权平均两种算法快速生成数字高程模型的实现过程,提出在样点奇异区采用移动加权平均法替代移动拟合法插值可大大提高插值效率。论述了在三维可视化环境下数字高程模型与等高线一体化显示的原理和方法,重点对“三角面串序列法”进行了论述,并给出了其在流域治理规划应用中的实例。     

基于离散单元法的立磨机介质球运动规律研究

为查明立磨机磨矿介质球的运动规律,采用离散单元法进行了立磨机数值模拟,研究分析了介质球的受力、运动学参数、能量分布以及介质球之间的碰撞行为。研究结果表明,磨矿介质球的速度、动能在搅拌器螺旋叶片边缘达到最大值;其碰撞力、自转角速度、转动动能、碰撞能在搅拌器外缘达到最大值;环形区内介质球的碰撞力和速度梯度均较大,是重要的磨矿区域。通过分析碰撞力、碰撞能分布曲线,可以从微观角度剖析立磨机的磨矿行为,为强化立磨机的精确化磨矿和选择性磨矿提供了具体方向。     

基于DEM的振动参数对颗粒筛分分层与透筛的研究

应用离散单元法(DEM)模拟和分析筛分过程,研究了振动参数对颗粒筛分分层与透筛的影响。提出了分层和透筛细粒比的概念,拟合不同振动参数下分层和透筛区中细粒比与时间的变化曲线,得到了细粒比随时间变化的函数关系式。运用分层和透筛中细粒含量随时间的变化率来表示分层速率和透筛速率,量化了筛分中分层和透筛过程。进一步分析了分层速率和透筛速率与振动参数的关系,得到最佳分层和透筛速率下振动参数的取值。     

急倾斜水平分段放顶煤放煤规律的离散元模拟研究

提高水平分段高度是提高急倾斜水平分段放顶煤产量的有效途径,但顶煤分段高度提高后,其顶煤的放出工艺如何控制是影响其放出率的关键因素。对急倾斜水平分段放顶煤的放煤过程进行了离散元数值模拟,重点比较了在相同顶煤高度的条件下,顺序放煤与隔架放煤的特点,并在理论分析中给出了确定放煤轮数的具体公式,所得结论可供工程实际参考应用。     

我国长距离浆体管道输送系统的应用概况与展望

长距离浆体管道是一种高效、节能、环保的运输方式,拥有广阔的应用空间和发展前景。为了使我国浆体输送从业人员更加全面、及时地了解管道输送系统的现状和动态信息,以便进一步推动该技术在我国的应用和发展,着重介绍了国内浆体输送系统动力泵、管材和阀门的研发、制造水平,总结了管道输送系统主要设备和材料的应用概况及最新进展,并对未来浆体管道输送系统的发展趋势进行了展望。     

物料颗粒参数对大型矿用挖掘机挖掘阻力影响的仿真研究

为了探究离散元法应用中物料颗粒参数对大型矿用挖掘机挖掘阻力及仿真时间的影响,建立了WK-55型大型矿用挖掘机的挖掘仿真模型,从挖掘机挖掘的仿真时间、仿真结果的稳定性和挖掘阻力几个方面进行分析,分别探究了颗粒尺寸、密度、恢复系数、剪切模量、摩擦因数和表面能对挖掘仿真的影响,得到了各参数对挖掘阻力的影响规律。结果表明,适当地减小剪切模量可以在保证不影响挖掘阻力的前提下有效节约仿真时间,为后续的大型矿用挖掘机工作装置离散元仿真模型的简化提供了依据。     

On-stream and quantitative mineral identification of tailing slurries using LIBS technique

Mineral flotation processes are controlled by monitoring the grade of the present minerals. The performance of flotation can be greatly optimized by online assaying of the minerals in the slurry flows. However, online and quantitative mineral identification of the slurries is challenging. The major focus of this research is about measuring mineral contents from the elemental concentrations acquired by an on-stream slurry analyzer operating based on laser-induced breakdown spectroscopy (LIBS). A multivariate statistical method called partial least squares regression is employed to perform the elemental to mineral conversion. In this work, the samples under study come from an iron concentrator where knowledge about the grade of silicates and iron-oxides are important for controlling the flotation plant. In total, the concentrations of six out of ten minerals were successfully estimated. This accomplishment provides quantitative knowledge about mineral contents from the nearly real-time assay data without any modification on the measurement setup or further instrumentation. This can lead to many benefits such as rapid control of concentrate quality, enhanced recovery and savings in money, time, energy and manpower. The proposed technique is applicable to all types of slurry samples.     

基于DEM的振动筛筛孔形状对潮湿原煤筛分效果影响的研究

随着原煤含水量的增加,引起原煤颗粒间相互粘聚,影响振动筛筛分效率。基于离散元法,运用EDEM软件模拟了潮湿原煤颗粒在圆形筛孔、方形筛孔和矩形筛孔的筛分过程,并且以筛分效率和阻碍粒排出率为衡量指标,对振动筛筛孔形状影响潮湿煤筛分效果进行了研究。结果表明:在筛孔名义尺寸相同的情况下,潮湿煤在矩形筛孔筛面上的筛分效果最好,方形筛孔次之,圆形筛孔最差。