搅拌磨DEM-CFD耦合仿真研究及搅拌器强度分析

为了研究具有自主知识产权的大型立式螺旋搅拌磨机结构强度与动力匹配,在立式螺旋搅拌磨机试验台进行了试验研究,建立立式搅拌试验磨机的离散元(DEM)-计算流体动力学(CFD)多学科耦合模型,进行搅拌器动态分析,搅拌器阻力矩仿真与试验吻合,搅拌磨DEM-CFD多学科耦合建模及仿真方法,对搅拌磨动力学分析是有效的。为评价320 t立式螺旋搅拌磨机的结构强度与动力性能,建立了320 t级立式螺旋搅拌磨机离散元模型和有限元模型,分析了搅拌器启动和运行的阻力矩,分析了启动速度和钢球尺寸对搅拌器阻力矩的影响,可为搅拌磨动力匹配提供设计依据,分析了搅拌器启动与运行过程中的结构强度,结果表明搅拌器结构强度可靠,现场测试结果验证了数值模拟结果。     

新型卧式超细搅拌磨机的结构原理研究与中试应用

介绍一种新型超细搅拌磨机,阐明该磨机的结构特点、工作原理、性能特点及磨介的选取,并对结构进行分析,分别论述磨机各组成部分的技术特点及应用,最后分析此搅拌磨机的机械参数和非机械参数对研磨效果的影响。     

立式搅拌磨机磨矿机理研究进展

立式搅拌磨机是一种高效率、低能耗的细磨和超细磨磨矿设备,相对于卧式球磨机,立式搅拌磨机在节省能量消耗方面具有显著的优越性,被广泛应用于矿山领域的精矿再磨和第二、第三段磨矿作业。为了促进立式搅拌磨机的优化与开发,本文介绍了立式搅拌磨机的运行工作原理,系统总结了立式搅拌磨机研磨理论和磨矿介质运动状态研究成果,综述了搅拌器转速、介质填充率、磨矿介质属性、搅拌器属性等工作参数与结构参数对立式搅拌磨机磨矿过程和研磨效果的影响,分析了立式搅拌磨机关键技术参数的选择条件,为立式搅拌磨机的机理研究与发展提供参考。     

典型石墨再磨设备的应用进展

着重叙述了球磨机和搅拌磨机等应用较为广泛的石墨再磨设备,对搅拌磨机的基本结构和种类做了较详细的介绍,并对石墨再磨设备的选型方法和原则进行了分析。     

GJM型石墨用搅拌磨机的研制与应用

介绍了GJM型搅拌磨机基本结构和工作原理,分析了设计中的主要因素,如搅拌装置、槽体结构和耐磨材料等;针对大鳞片石墨的特性开发了GJM型石墨专用搅拌磨机,着重介绍其在国内外石墨选厂的工业应用情况。结果表明,GJM型石墨用搅拌磨机可显著提高石墨产品的质量等级,为生产企业创造了巨大经济效益。     

卧式超细搅拌磨机分散盘的结构改进及试验研究

针对现有卧式超细介质搅拌磨机分散盘结构中存在的不足,在优化分析的基础上,提出了一种新型的分散盘结构形式。结合RNGκ-ε湍流模型和SIMPLEC算法,分别建立了现有分散盘和新型分散盘结构的仿真分析模型,通过对卧式介质搅拌磨机研磨腔内流场进行仿真分析,分别得到了研磨腔内流场速度、湍流强度、剪切率和黏性耗散率的分布规律。结果显示,使用新型分散盘结构的搅拌磨机具有更高的研磨性能。同时通过对试验样机的测试表明,使用新型分散盘结构的搅拌磨机的研磨效率显著提高,且在相同的研磨时间内,浆料粒径明显减少。     

几种典型搅拌磨机在金属矿山的应用进展

搅拌磨机是近年来金属矿细磨和再磨作业的重要装备,具有高能量输入密度、高效率、高强度等特点,解决了细粒嵌布难分选的难题,典型的金属矿细磨搅拌磨机有Isa磨机、立式螺旋搅拌磨机(VTM)、SMD磨机。笔者介绍了几种典型搅拌磨机的研究现状和发展趋势、结构特点和工作原理、主要的应用进展等。     

KLM型立式螺旋搅拌磨机的研究与应用

根据立磨机结构和工作原理,结合细磨作业立式螺旋搅拌磨机设计要求,选择KLM系列立磨机主要结构参数,通过对筒体、螺旋搅拌机构等关键部件的结构设计解决大型立磨机研制中的关键技术问题。介绍KLM系列立磨机在铁矿和铜钼矿选矿再磨中的应用情况。     

基于离散单元法立式螺旋搅拌磨机内介质运动学研究进展

阐述了立式螺旋搅拌磨机的结构组成及工作原理、离散单元法的基本原理和最新发展情况,国内外基于离散单元法对搅拌磨机内介质运动学的研究进展,浅析了存在问题及发展方向。     

微细粒矿用搅拌磨机的研究和发展

详细介绍了国内外矿用搅拌磨机的结构特点及应用,综述了矿山细磨设备的研究情况,评述了搅拌磨机的发展和应用前景.超细搅拌磨机具有能量密度高、细磨效率高、产品粒度分布均匀和选择性磨矿等特点,其推广应用将有效促进矿山金属资源的综合利用和节能降耗.     

The effect of particle breakage mechanisms during regrinding on the subsequent cleaner flotation

Stirred mills have been widely used for regrinding, and are acknowledged to be more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms during grinding. In this study, the effect of regrinding by both mills on surface properties and subsequent mineral flotation was studied, using chalcocite as the mineral example. A rod mill and a stirred mill with the same stainless steel media were used to regrind rougher flotation concentrates. Different chalcocite flotation recovery was achieved in the cleaner stage after regrinding in tumbling and stirred mills. The factors contributing to the different recovery included particle size, the amount of created fresh surfaces, surface oxidation and the redistribution of collector carried from rougher flotation. All the factors were examined. It was determined that the predominating factor was the different distribution of collector resulting from different particle breakage mechanisms in the stirred and tumbling mills, in line with ToF-SIMS analysis. In the tumbling mill, the impact particle breakage mechanism predominates, causing the collector to remain on the surface of newly produced particles. In the stirred mill, the attrition breakage removes collector from the surface, and decreases particle floatability. Furthermore, the type of grinding media in the stirred mill also influences the subsequent flotation, again due to the change of particle breakage mechanisms. The results of this study demonstrate that the selection of regrinding mills and grinding media should not only depend on the required energy efficiency, but also on the properties of the surfaces produced for subsequent flotation.     

Comparison of energy efficiency between ball mills and stirred mills in coarse grinding

Stirred mills are primarily used for fine and ultra-fine grinding. They dominate these grinding applications because greater stress intensity can be delivered in stirred mills and they can achieve better energy efficiency than ball mills in fine and ultra-fine grinding. Investigations were conducted on whether the greater performance of stirred mills over ball mills in fine grinding can be extended to coarse grinding applications. Four different laboratory ball mills and stirred mills have been tested to grind seven ore samples with feed sizes ranging from 3.35 mm to 150 μm. A case study on full scale operations of a 2.6 MW IsaMill replacing the existing 4 MW regrind ball mill at Kumtor Gold Mine in Kyrgyzstan is also included. This paper summarizes the major findings from these investigations.     

Product size distribution in stirred media mills

A study on the control of particle size distribution (PSD) of the ground carbonate product in stirred media mills (wet Drais stirred bead mill and dry Sala Agitated Mill) is presented in this paper. The results indicated that the slope of product size distribution can be controlled by altering some operating parameters, such as size of grinding media and tip or peripheral speed. The profile of product size distribution from the stirred media mills was found to follow most closely the Rosin-Rammler-Bennett (RRB) model.     

Analysis of stirred mill performance using DEM simulation: Part 1– Media motion, energy consumption and collisional environment

Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. Media flow patterns and energy absorption rates and distributions are analysed here. In the second part of this paper, coherent flow structures, equipment wear and mixing and transport efficiency are analysed.     

The effect of regrind mills on the separation of chalcopyrite from pyrite in cleaner flotation

Stirred mills have been widely used for regrinding and are more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms and redox environments during grinding. In this study, the effect of regrinding with these two types of mills on the separation of chalcopyrite from pyrite in the cleaner stage was studied. A laboratory rod mill and a laboratory stirred mill were used to regrind rougher flotation concentrates. It was found that chalcopyrite and pyrite exhibited different flotation behavior after regrinding with the rod mill and the stirred mill, resulting in different separability of chalcopyrite from pyrite. The mechanism underpinning this phenomenon was investigated by a range of techniques including dissolved oxygen demand measurements, X-ray photoelectron spectroscopy (XPS) and Time of flight secondary ion mass spectrometry (ToF-SIMS). It was found that the two mills produced different surface oxidation and pyrite activation by copper ions which determined the separation of chalcopyrite from pyrite. This study demonstrates that the selection of a regrind mill should not only depend on its energy efficiency but also the property of surfaces produced for subsequent flotation.     

Is media shape important for grinding performance in stirred mills?

Models for understanding the basic concepts of fine grinding and how they apply to the design of stirred media mills have not yet matured. While spherical media in tower mills has previously been studied, real grinding media shape in stirred mills can range from spherical (steel/ceramic balls) to highly non-spherical (sand or slag) resulting in very different media and grinding dynamics. Handling the contact mechanics of non-spherical particles is a challenge for numerical models, and very few studies dealing with non-spherical particle shape exist in the literature. Discrete Element Method (DEM) simulations of dry media flow in a pilot-scale tower mill are performed for four cases with different shaped grinding media, in order to understand how flow and energy utilisation within a stirred mill depend on media shape. Differences in media transport, stress distribution, energy dissipation, and liner wear were observed in the tower mill for the spherical and non-spherical cases. A significant departure from sphericity of the media leads to strong dilation of the bed, reduced bulk density, and a reduction in active volume and collisional power levels leading to a reduction in power draw for the mill. In addition, highly non-spherical media tend to pack tightly near the mill walls forming a near solid layer around the inside of the mill shell which results in poorer transport and mixing, as well as increased wear rates on the screw impeller. Grinding performance in stirred mills appears to deteriorate strongly when using highly non-spherical media.     

Analysis of stirred mill performance using DEM simulation: Part 2 – Coherent flow structures, liner stress and wear, mixing and transport

Stirred Mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot scale tower mills and pin mills are carried out in order to investigate the relative performance of these stirred mills. In the first part of this paper, media flow patterns and energy absorption rates and distributions were analysed to provide a good understanding of the media flow and the collisional environment in these mills. In this second part we analyse steady state coherent flow structures, liner stress and wear by impact and abrasion. We also examine mixing and transport efficiency. Together these provide a comprehensive understanding of all the key processes operating in these mills and a clear understanding of the relative performance issues.     

Generalizing a shear–volume power model for stirred mill power prediction

A stirred milling model, based on the concept of shear–volume power, was developed and applied to geometries typically found in mineral processing systems. Generalising this model permits its use to model more complex mill geometries, such as those describing a tapered disk mill and the CoBal mill. Due to the additive property of the shear–volume power, the calculation of the power of complex mills is possible through geometric decomposition. This approach is supported by the calculation of the shear–volume power of a number of simple geometries commonly found in mills, and is used in the calculation of the shear–volume power of a tapered disk mill and the CoBal mill. Finally, by incorporating a breakage model, an equation that offers some usefulness in the design, operation and optimization of stirred mills is presented.     

The application of a simplified approach to modelling tumbling mills,stirred media mills and HPGR’s

Most modern population balance models for comminution invoke the concept of a specific breakage rate function and a breakage distribution function to describe breakage kinetics. One of the difficulties of this approach is that these functions are very difficult to measure directly. Consequently, it is usual to assume that these functions can be represented by simple equations with parameters that can easily be estimated from test data using back-calculation techniques. However, these estimates can be very sensitive to small measurement errors and are usually subject to very large variances. This paper presents a simplified approach to modelling comminution processes that invoke the concept of an energy-based cumulative breakage rate function to describe breakage kinetics. This function can be estimated directly from plant data and is well-suited to multi-component modelling of individual rock types and mineral species. Examples of the application of this simplified modelling approach are described for the treatment of platinum ores using ball mills, AG/SAG mills, HPGR’s and stirred media mills.     

鞍钢脱硫扒渣选铁后尾渣超细粉磨试验研究

为使鞍钢脱硫扒渣选别后的尾矿能够用于代替部分水泥制备高强混凝土,采用普通球磨机和搅拌磨分别进行了脱硫扒渣尾渣的超细磨试验。通过条件实验,分别研究了普通球磨机和搅拌磨的球料比、矿浆浓度两个主要操作参数及磨矿时间对超细粉磨扒渣尾渣效果的影响规律,并分析了产生这种影响的原因。