Effect of entrainment in bubble load measurement on froth recovery estimation at industrial scale

Froth recovery was calculated in a 130 m³ mechanical cell of a rougher flotation circuit. This was done by bubble load determinations along with mass balance surveys. Valuable grade in the bubble load decreased in the −38 μm due to fine particles entrained to the chamber of the device. The effect of fine particle entrainment on froth recovery was evaluated. A comparison between results from the raw bubble load data (assuming all particles were transported by true flotation) with those from corrected bubble load information (subtracting fine particle entrainment) was carried out. Entrainment occurred due to hydraulic transport in the bubble rear, which corresponds to the worst case scenario for froth recovery estimation. Results showed that the relative error was less than 0.3%, which allowed validation of the bubble load measurement as an effective methodology for froth recovery estimation at industrial scale.     

The entrainment effect on the performance of iron ore reverse flotation

An iron ore mineral processing plant in Brazil treating Itabirite ore was assessed by sampling a circuit consisting of Wemco 144 mechanical cells, as part of the AMIRA P9P collaborative research project. This paper presents and discusses the results of entrainability, water recovery and quartz and hematite grades associated to hydrodynamic parameters. The results indicated strong correlation between water recovery and hematite losses which was intensified by the operating conditions of the circuit.A potential alternative to reduce the hematite losses through entrainment and to increase quartz removal was to modify the traditional circuit design to treat rougher and cleaner/recleaner tails in different stages. In addition, the scavenger residence time must be matched to the quartz floatability. Changes to design and operation of these circuits are needed to sustain concentrate recovery and grade as iron ores become finer.     

BPSM-III型粒度仪多模型建模在山东黄金某选矿厂的应用（增刊）

选矿流程中最重要的影响因素之一是磨矿的粒度。BPSM-III型在线粒度分析仪是由北京矿冶研究总院自主研发的基于直接接触式测量原理的粒度仪,由于采用直接接触式测量原理存在的局限性,导致在矿浆粒度及性质发生较大变化时,采用单一模型较难实现2%的模型精度。本文在山东黄金某选矿厂应用的BPSM-III型粒度仪上采用多模型进行建模,从而保证了粒度的测量精度,使得粒度仪可以更好的指导磨浮生产。     

The effect of breakage method on the shape properties of an iron-oxide hosted copper–gold ore

Using a mineral liberation analyser (MLA), the shape properties of an iron-oxide hosted copper–gold ore following comminution in either a hammer mill or a piston–die compression unit were examined. It was found that particle angularity distributions were able to be fitted to the beta distribution, providing a convenient way to quantify changes in particle shape properties as a function of the breakage method employed. Particles discharged from the hammer mill were less angular than particles discharged from the piston–die compression unit. This was attributed to attrition breakage mechanisms, whereby topographical features are chipped off parent particle surfaces. The results suggest that the quantification of shape properties is a convenient method for obtaining insight into the nature of breakage events that take place inside comminution devices.     

Optical analysis of particle size and chromite liberation from pulp samples of a UG2 ore regrinding circuit

Since the early seventies high chromite and low base metal sulphide (BMS) contents of the UG2 reef imposes technological challenges to mineral processors and extractive metallurgists. Forty years later, particle size distribution and size by size mineralogy are considered as key factors to the continuous improvement of the UG-2 ore metallurgy. With the successful development of ultra fine grinding technologies, a compromise has to be found between fine grinding to achieve platinum group minerals liberation and to avoid the overgrinding of gangue minerals, especially chromite gangue which is detrimental in smelting process. Indeed, fine chromite grains, despite of being naturally hydrophobic mineral, can be recovered in flotation concentrate by entrainment. In addition, overgrinding also increase liberation of naturally floatable gangue (talc) which contaminate the concentrate and need to be controlled during flotation.In this paper, innovative techniques of single particle image analysis from both dry and wet samples have been tentatively used to assess the chromite particle size distribution and the chromite grade of samples taken from a secondary milling circuit. Preliminary results demonstrate excellent potential for online particle imaging making use of both the particle geometry (size, shape) and the optical properties (translucency).     

半工业磨机中钢球尺寸对黑钨矿细度和形状影响研究

黑钨矿极易发生泥化现象,导致其有效浮选仍是一个难题。本研究在实验室球磨机中,探讨了不同尺寸的钢球作为介质对黑钨矿细度和形状的影响,在干磨条件下进行了6种不同球径(20、30、40、50、60、70 mm)的磨矿试验。结果如下所示：各磨矿条件下获得的产品粒径均随磨矿时间的增加而减小。以70 mm钢球为磨矿介质时,大颗粒含量最低,-10μm过磨颗粒含量最高。这些粒径比x80/x20随着产品尺寸的减小先增大后减小,每一个球的粒径都趋于平缓。中值粒径x50随球径的减小先减小后增大,其中40mm球径最小(0.06 mm);但当球直径小于40 mm时,破碎混合颗粒物料的粉碎能力减弱。在相同的磨矿时间下,粒径比x80/x20随球径的减小先增大后减小,其中40mm球的粒径比最大;对于40mm钢球,产品的细度和宽度不一致,因此选择钢球直径不容易。当球直径小于40 mm时,粒径比x90/x10越来越大。粒径比(x90-x10)/x50随着产品粒径的减小先增大后减小,减小趋势随着球径的减小而趋于平缓,在x50为0.075 mm-0.085 mm范围内达到最大;另一方面,20毫米球下,(x90-x10)/x50磨矿产品尺寸几乎是不变的,为20.66。当产品粒径小于1 mm时,产品颗粒的球形度急剧增加,且随着球直径的减小,球形度增加的更快。当产品粒径小于0.04 mm时,产品颗粒球形度的变化趋势趋于平缓,这可能是在磨机内表面和球表面形成粘附颗粒层。0.8 ~ 0.3 mm的球形度变化趋势小于0.3 mm以下的球形度变化趋势。     

超细草酸镍沉淀过程中颗粒大小及形貌控制

在以硫酸镍盐为原料、草酸铵为沉淀剂制备超细草酸镍粉末的过程中，对影响草酸镍颗粒大小及形貌的主要因素进行了研究．结果表明：加料方式及草酸铵溶液的初始pH对草酸镍形貌和大小的影响很大，而镍盐及分散剂的种类只对颗粒大小有一定的影响．当草酸铵溶液初始pH为4、硫酸镍浓度为0．5mol／L及在1L NiSO4溶液中分别添加分散剂PVP和PEG6．2g时，以草酸铵溶液向硫酸镍溶液中加入的方式，可制得呈类球形的、均匀分散的、粒径0．3～0．5μm的草酸镍粉末．     

PEPT studies of heavy particle flow within a spiral concentrator

Future improvements of gravity concentrators require an increased knowledge of the mechanics behind the separation, including the motion of the particles. This work details the investigation of particle motion through a spiral concentrator. The results of tracking the motion of individual particles using the positron emission particle tracking (PEPT) technique are described. Tracer particles of different sizes and density were tracked along the trough of a laboratory scale spiral. Multiple passes of one tracer through the spiral are combined to represent the bulk of flow of this particle type and size, with the position and time recorded to allow for the particle trajectory and speed to be determined. Finally, the use of PEPT will be shown to be a powerful method to visualise the behaviour of particles during the concentration process, providing data that will be used for the validation of new models of spiral concentrator performance.     

立式辊磨机与球磨机粉磨水泥熟料的颗粒形状研究

为了澄清业界对立式辊磨机粉磨水泥熟料的种种认识误区,对立式辊磨试验机和标准邦德功指数试验机粉磨水泥熟料产品进行了电镜分析。分析结果表明,采用不同粉磨设备,其产品颗粒形状差别很小,且粒度分布区间和粒度分布趋势均基本吻合,得出立式辊磨机完全可以替代球磨机的结论。     

CFD simulation of a centrifugal air classifier used in the aggregate industry

The aggregate industry in Sweden is investigating methods to improve the quality of manufactured sand (aggregate smaller than 2 mm produced by crushing rock) for concrete production. A common way to improve the shape of the particles is to use a vertical shaft impact (VSI) crusher. However, the crushing process creates a large amount of fines (particles smaller than 63 μm) that are not desirable in concrete mixes. The aggregate industry in Sweden is therefore investigating methods to reduce the amount of fines produced by the manufacturing of sand. One method being investigated is air classification.A centrifugal air classifier used in the aggregate industry was investigated using computational fluid dynamics (CFD) to improve the understanding of the influence of the geometric design of the classifier on the cut size and the resulting particle size distribution. Simulations were performed with a CFD model using an Euler–Lagrange approach. The simulation results show that the classification results are affected by air flow velocity, particle shape, particle size, the geometry of the air classifier and turbulence in the air flow.     

热处理对Cu-Zn-Al合金形状记忆效应的影响

为提高Cu-Al形状记忆合金在应用过程中的稳定性及使用寿命,研究了在SME(ShapeMemory Effect)法训练条件下,热处理过程中不同的淬火介质对Cu-Zn-Al形状记忆合金形状记忆效应的影响.研究结果表明:使用不同的淬火介质,Cu-Zn-Al合金具有不同的形状记忆效应和不同的马氏体形貌,当淬火介质为冷水、冷...     

The role of a flash flotation circuit in an industrial refractory gold concentrator

In order to determine the contribution of the flash flotation circuit to the overall plant performance of the Kanowna Belle concentrator, two survey campaigns both with and without the flash circuit in operation have been conducted on two distinctly different ore types: a very high grade ore, and a very low grade ore of higher hardness. Using two different ores with the same target valuable mineral species (gold and pyrite) through the same treatment route allows any trends in performance to be more easily identified. As both survey campaigns involved running the plant with and without the flash flotation circuit in operation, the significant contribution of the flash flotation cell to overall plant recovery and final concentrate grade is highlighted. The flash circuit on this plant may be considered as the primary rougher, contributing in excess of 42% of the valuable material that is recovered to the final concentrate stream, at a grade of approximately 35% sulphur; and in-so-doing reducing the overall plant footprint that would otherwise be required to achieve the same recoveries at the target concentrate grade.Mineralogical analysis of survey samples shows that the feed to the flash flotation cell (cyclone underflow) is of a much higher grade and contains a higher proportion of well liberated valuable material as compared to the conventional flotation circuit feed (cyclone overflow). Maximising the recovery of this material before it re-enters the milling circuit should be of paramount importance to optimising overall plant performance.When the flash flotation circuit is taken off-line the recovery of sulphur (and hence pyrite) is observed to decrease dramatically, and whilst the recovery of gold also decreases, it is to a much lesser extent. The difference in the recoveries of gold and pyrite that is observed without the flash flotation circuit in operation is most likely attributable to a change in the way the gold is being liberated as a function of the change in grinding circuit operation that is required when the flash circuit is taken off-line. The distribution of valuable material in the cyclone overflow stream (conventional flotation feed) undergoes a step change when the flash circuit is taken off-line with an increase in the amount of valuable fines being generated, which is further reflected in the flotation tails with a higher proportion of both pyrite and gold being present in the intermediate and fine size classes. This increase in the amount of pyrite fines in particular may have contributed to the loss in recovery that was observed when the flash flotation circuit was taken off-line.Pulp chemistry data from various points around the flotation circuit highlight the different processing conditions in the flash cell, compared to the conventional circuit, which will impact on the type of minerals able to be recovered by flotation, as well as reagent selection for this type of processing application.     

离心泵叶轮内颗粒轨迹与磨损的关系

通过对离心泵叶轮内颗粒轨迹影响因素的分析,得到了颗粒轨迹与磨损的关系。     

工业型煤机结构设计

对工业型煤机的结构设计提供了成型的改进方案     

An energy model on particle detachment in the turbulent field

A flotation detachment model is developed by considering energy balance in the process. Energies concerned are surface energy increment and kinetic energy supplied by turbulent liquid motion. Surface energy increment is the work of adhesion by surface forces which is reflected by surface tension and contact angle. What makes this model outstanding from other detachment models of energy balance perspective is more accurate account of kinetic energy supplied from turbulent liquid motion. Eddies in the same scale as attached particles are considered accountable for particle detachment in the close vicinity. In this way, detachment probability is written as a function of energy dissipation rate. Predictions from different models are compared to experimental results. It is demonstrated that previous models overestimate the influence from turbulent liquid motion. Notably, with more accurate account of eddies’ influence, the new model predicts particle detachment in accordance with experimental results.     

露天采矿矿坑形状与矿坑稳定性的研究

在露天采矿矿坑监测实践中发现了矿坑平面形状与矿坑稳定性的联系，给出了类椭圆形矿坑、类圆形矿坑、类矩形矿坑的应力与位移监测数据，以实测数据为依据，指出了类椭圆形矿坑、类圆形矿坑的优越性，得出了类椭圆形矿坑优于类圆形矿坑、类圆形矿坑优于类矩形矿坑的结论。介绍了矿坑监测采用的方法和监测过程。     

数控加工采煤机摆线轮齿形坐标点数的选取

以采煤机摆线轮为例 ,通过对摆线轮齿形加工选点数量的分析及计算机作图对比 ,得出齿形加工的坐标点数可以比原设计点数减少 3 / 4的结论。经验证 ,工艺程序简化 ,效率高     

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。     

Development of a pilot roller test machine for investigating the pulverizing performance of particle beds

Various types of pulverizers are commonly used in power plants for the purpose of breaking coal particles into fine powders to achieve optimum combustion for the boilers. To investigate the effects of factors that may influence the pulverizing efficiency, this study presents the development of a pilot roller test machine, which can significantly simplify the grinding conditions in actual pulverizers whilst the key variables involved in a rolling compression can be considered. The monitoring and data acquisition systems allow real-time monitoring of the pulverizing induced roller movements. Through parametric numerical analyses on an elastic feed bed of 5–30 mm in thickness and 500–1000 MPa in elastic modulus, it is found that the machine is capable of providing a maximum contact pressure stress in a range of 4.5–17.5 MPa. A series of fundamental tests have been conducted by the developed machine using a type of bituminous coal and typical bound values of roller weight and speed. The size reduction results as well as the measurements of roller movement demonstrate the capability of the machine as a suitable tool for testing grinding performance. Some discussions of the potential extension of the machine are also given in the final part.