Modelling of high voltage pulse breakage of ores

A high voltage pulse (HVP) breakage model was developed as a general modelling structure to represent the three HVP breakage indices: body breakage probability (the D₁-model), body breakage product fineness (the D₂-model), and body breakage product pre-weakening degree (the D₃-model). Relations between the HVP breakage indices and HVP pre-concentration characterisation curves were established. The preliminary result indicated that the HVP breakage model has the potential to predict the recovery of valuable metals from the calibrated model parameters. A t_n-family of curves (t_n is defined as cumulative percentage of product passing 1/n of the initial size) was used to describe the HVP breakage product size distribution. The t_n-family of curves can be employed to estimate the product size distribution from the predicted t₁₀ values by the D₂-model.     

Characterisation of superficial breakage using multi-size pilot mills

Low energy surface breakage has a high frequency of occurrence and thus plays a significant role in grinding processes. Yet this superficial breakage is poorly understood, measured and modelled – forming the focus of this work.Pilot mills of 0.8–1.8 m diameter, designed to provide a predominantly surface breakage environment with efficient removal of the resultant progeny, are utilised to characterise superficial breakage. A new rate, that of superficial breakage (1/(kW h/m²)), is introduced which measures fractional superficial breakage rate per energy provided to the surface of the material. This methodology is proposed as being suitable for understanding and characterising the surface breakage behaviour of ores.Tests were conducted on two ores with different hardness. Superficial breakage rates varied from 2 to 16 (1/(kW h/m²)) for the different ores and mill sizes, indicating a good sensitivity to ore type and the need to understand the applied stress – related to mill size. The results show that a single ‘surface breakage rate for use in mill modelling is incorrect as the rate of superficial breakage is dependent on the size of the mill and therefore the inter-particle stressing conditions.     

Ore particle breakage behaviour in a pilot scale high voltage pulse machine

SELFRAG AG has developed a flexible pilot scale Pre-Weakening Testing Station (PWTS) using high voltage pulses (HVP). This provides a unique opportunity to investigate the machine setting conditions on ore breakage behaviour. A joint campaign was undertaken by the Julius Kruttschnitt Mineral Research Centre and SELFRAG AG to investigate the breakage behaviour of two copper–gold ores and one iron ore in the PWTS. The effects of specific energy, pulse voltage, cumulative discharges, feed particle size and ore particle breakage pattern (body breakage or surface breakage) were investigated. The investigation revealed that the mass-specific energy of HVP was the most significant factor affecting the breakage behaviour in the PWTS. This effect was compounded with the effects of ore properties and particle size. Comparison between the PWTS and a laboratory HVP machine indicates that there is considerable scope for optimisation of HVP performance based on processing zone design.     

Comparison of different breakage mechanisms in terms of product particle size distribution and mineral liberation

The comminution process is still governed by a large number of factors that influence the liberation of the valuable components in the ore. A better understanding of these basic factors will provide more certainty about the design of equipment in order to achieve the best liberation and energy efficiency.Impact and bed breakage mechanisms were investigated as two distinctly different modes of breakage. Standard drop weight tests and hydraulic piston-die press tests were conducted with different energy intensities on samples.This paper describes the work carried out for the comparison of mineral liberation and particle size distribution in the particle bed breakage with impact breakage of two different copper ores. Ground products from these two different modes of breakage were screened into size fractions which were analyzed for the particle size distributions by sieve analysis and the degree of liberation by an image analysis system. The results of these analyses were statistically compared to make inferences in relation to the stated objective of the work. Test results indicated that compressive bed breakage mechanism gives finer product particle size distribution and provides better mineral liberation compared to impact breakage mechanism.     

Further study of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography procedures

The present work aims to verify the 3D quantitative analysis of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography. The breakage of single multiphase copper ore particles (6 mm cubic particles) by slow compression was examined. From XMT reconstructed images using the Marching Cube method, interfacial areas between copper mineral grains and host rock were determined for both parent particles and progeny particles. In this way, the specific interfacial area ratio was calculated as a metric for grain boundary fracture. Preferential grain boundary fracture only occurs at low energy dissipation rates and the current results confirm initial results for 3 mm cubes published previously by Garcia et al. (2009).     

宽粒级煤炭颗粒在三相流化床中的分选实验研究

拓宽浮选粒度上限是浮选领域挑战的难题之一。应用三相流化床技术,在上升水流中引入气泡流,对比有无气泡对煤炭颗粒床层膨胀度的影响,得出气泡流的引入能够加强低密度颗粒的流化。并在单独上升水流、上升水流+气泡流和上升水流+气泡流+捕收剂(煤油)3种水流条件下,进行煤炭分选实验。结果表明,气泡流的引入,能够大幅减少低密度级颗粒悬浮所需的上升水流速度,气泡流对低密度级颗粒的影响强于高密度级,气泡的存在强化了颗粒密度、弱化了粒度对分选的影响;在上升气泡流中添加捕收剂后,低密度级颗粒与气泡形成颗粒-气泡结合体,低密度级颗粒便能够在较低的上升水流速度下进行分选,低速上升水流稳流度较低,保证了大颗粒与气泡的稳定性。添加捕收剂后,各粒级颗粒分选所需上升水流速度较为接近,各粒级精煤灰分在10%左右。     

深部围岩分区破裂化模型试验研究

为研究深部巷道围岩破裂机理,在"深部巷道围岩破裂机理与支护技术模拟试验装置"进行了模型试验,系统研究了深部巷道围岩在最大初始开洞荷载与洞室轴线平行作用下直墙拱顶试验的破坏形态和机理。模型试验表明:当最大主应力与洞室轴线平行,在较大轴向压力作用下产生较大的朝洞内的膨胀变形,使得在围岩内产生较大的径向拉应变,其产生的拉伸断裂是出现分层破坏现象的关键,分布特点是随着轴向应力的增加其拉应变值增加,随距洞壁距离的增大其拉应变值减小。拉伸断裂面形成后,相当于在原来的介质内又形成了一个新的半径增大的洞室,洞室在较大的轴向压应力持续作用下,拉伸破坏过程不断重复出现,就会形成交替的破裂区域和未破裂区域,即分层破裂现象。     

八叉树矿体块状模型及其在三道庄露天矿的应用

矿体块状模型广泛应用于品位、储量计算,也可用于露天矿最终开采境界优化和开采计划优化。在研究了八叉树存储结构和基于分离轴的OBB相交测试理论的基础上,提出首先应用八叉树对矿体三维空间进行块状划分,将矿体用一系列的小单元块来逼近,然后利用OBB理论检测单元块与矿体边界的空间关系,对相交单元块进行细分,利用点在多面体内外判断确保块状模型约束在表面模型内,从而以最佳状态逼近矿体边界。最后运用该方法建立了三道庄露天矿矿体块状模型。该方法快速有效,能够满足矿山生产设计需求。     

薄基岩采动裂缝水砂流运移过程的模拟试验

在分析厚松散层薄基岩下开采水砂突涌工程地质模式的基础上,设计自制了水砂混合流运移及突涌模型。试验以0.05 MPa和0.10 MPa水压力条件下的不同水砂混合物成分、不同通道裂缝宽度为例,揭示了孔隙水压力在裂缝通道中不同位置的变化特征。通过设置的模型试验,定量化地研究水砂混合物运移及涌出的多种地质信息,获得不同模型试验水砂混合流运移通道中不同位置监测的水压力变化曲线,同时分析裂缝通道水砂流速度与通道宽度的关系,观测水砂流通道溢出口出砂量与时间的变化关系。