高压辊磨机粉碎行为研究进展

高压辊磨机粉碎原理为层压粉碎，具有处理量大、节能高效等特点。与传统破碎方式相比，高压辊磨机粉碎产品细粒级含量高、微裂纹发育、矿物解离度高、邦德球磨功指数低，还有助于下游选别或浸出作业。随着辊面抗压强度和抗磨蚀性能不断增强，高压辊磨机已经广泛应用于冶金矿山领域，如金刚石与围岩解离、球团原料铁精矿预处理、金属矿磨前（超）细碎，（半）自磨工艺顽石破碎等。高压辊磨机的成功应用与其粉碎行为密切相关。文章依次从高压辊磨机的研发背景、工作原理、辊面压力分布、宏观粉碎过程、料床应力响应、粉碎产品特性等方面系统评述了高压辊磨机的粉碎行为，并分析了边缘效应和辊面磨损的产生机理、负面影响及其应对措施，旨在全面地阐述高压辊磨机粉碎行为。     

Sample requirements for HPGR testing procedure

Green field projects demand relatively large amounts of sample from drill-cores. Besides chemical analysis, samples are required for mineralogy and liberation characterization, physical characterization, concentration tests and a number of tests for crushing and grinding parameters. If the project’s process route includes a possible HPGR grinding stage, lab-scale tests for scale-up and variability analysis are required. HPGR grinding characterization can be carried out in a small diameter roll HPGR, such as the LABWAL. Some commercial labs recommend 20–30 kg samples for steady-state tests, but this is a rather large sample from the point of view of a green field project campaign. The question that is being assessed here is how much sample is really required? Surely, the more material that is available the more reliable will be the test results. However, when the sample mass size is reduced, what is the impact on the data that is produced? In this work, six phlogopitite samples weighing 20 kg were tested in the LABWAL HPGR using six initial hydraulic pressures, 10, 20, 30, 40, 50 and 60 BAR. The specific capacity and specific power factors were determined, as well as the critical angle of nip, and the critical gap. Size distributions were measured and size-mass balance parameters were determined for the Austin model under the range of grinding pressures that were produced. With the data, a hypothetical industrial HPGR for the phlogopitite was designed for a standard capacity of 100 t/h and operating at 2 N/mm² specific grinding force. The work was then repeated using 10 kg samples and 5 kg samples. Results show that, under the conditions that were chosen, samples weighing 5 kg are sufficient for characterization in the LABWAL HPGR.     

Some benefits of using studded surfaces in high pressure grinding rolls

High pressure grinding rolls (HPGR) with studded or profiled surfaces are being promoted as new advancements to address the wear problem apparent with the grinding of harder materials. This study examines the performance of studded rolls in comparison with smooth rolls in terms of energy consumption, throughput, product size and slip between the compressed particles and particle bed. The experiments were performed on the CSIRO HPGR with studded roll tyres. The results indicate that the use of studs will increase throughput while wear is expected to be reduced, however, it is at the cost of higher energy consumption and grinding forces.     

The effect of feed moisture on the comminution efficiency of HPGR circuits

The comminution efficiency of high-pressure-grinding-rolls (HPGRs) is a well described function of a number of feed parameters including grindability, abrasion index, granulometric composition, top size and particle size distribution. Far less studied is the effect of feed moisture. This paper investigates both the overall and the specific comminution efficiency of a circuit consisting of a pilot HPGR unit followed by a batch ball mill as a function of the moisture level in the HPGR feed. Forsterite olivine sand (−7 mm) supplied by Sibelco Nordic was used as feed material. The results showed that the relationship between moisture and crushing efficiency for both the HPGR and the circuit can be described successfully by means of a parabolic function. Dry material, as well as that with the highest moisture content, showed the lowest particle size reduction ratios irrespective of the specific grinding force level. The paper also analyses the phenomenon of flake generation and shows that the feed moisture influences the flake content in the coarser size fractions of the HPGR product.     

Modeling the contribution of specific grinding pressure for the calculation of HPGR product size distribution

Vale, one of the largest mining companies in the world, has prioritized the development of HPGR technology for practical application in its current projects. An existing model for the HPGR, capable of predicting product size distributions, has been evaluated under distinct grinding conditions for one feed material. The effect of grinding pressure and feed size distribution were investigated. The model response showed a clear dependency of product size distribution with specific grinding pressure. As a result, specific grinding pressure was incorporated into the model, allowing for predicting product size distribution at practical values of this important process parameter. Based on this result, a characterization procedure was envisaged so as to produce parameters for the model. The procedure does not require complex experimental procedures, and all of the testing can be carried out in an expedited form in an instrumented bench-scale HPGR, using small samples of about 10 kg. The only analyses required are size distributions. The model was implemented in the Modsim? plant-wide simulator, with facilities to predict product size distribution for any roll diameter, length and speed of an HPGR machine.     

Improvement of energy efficiency of rock comminution through reduction of thermal losses

The principal objective of this work was to develop a thermal imaging technique to measure the radiant heat coming from rock particles during or immediately after crushing, with the purpose of minimising energy losses while maintaining the efficiency of rock crushing. The main goal of the work was energy optimization of crushing in High Pressure Grinding Rolls (HPGR). We were able to perform reproducible measurements of the temperature increase that occurs during transient events such as dynamic rock breakage and HPGR crushing. Results obtained show that with an increase of energy introduced, there is an increase in the maximum temperature along the fractured surface as well as increases in the overall amount of thermal energy.Results obtained during HPGR testing clearly indicate that there is an optimum intensity of pressure to which rock needs to be exposed. Any further increase in pressure, results in only a marginal increase in fragmentation and a significant increase in unproductive heating of rock. We were also concerned about the effect of the size of particles coming into the HPGR. The fraction of new fine material (fines) produced during HPGR crushing is much higher in the case of feed with a narrow size distribution, i.e. without pre-existing fines. Significantly, improved performance is achieved with a reduced amount of net comminution energy.Observed relative crushing inefficiency of feed with a wide fragment size distribution (containing fines and coarse particles), is due to a large amount of pre-exiting fines, which clog the pore space between coarser fragments. In the compressed zone of the HPGR this creates approximately hydrostatic compressive loading conditions, which require much higher pressure (i.e. energy) to cause breakage of coarser particles. Experimental results indicate that up to 40% of energy can be saved through optimization of the applied pressure and modification of feed fragments size distribution.     

Comparison of open and closed circuit HPGR application on dry grinding circuit performance

A conventional cement grinding circuit is composed of a two compartment tube mill, a mill filter which collects the fine material inside the mill and a dynamic air separator where final product with required fineness is collected. In general the material fed to the circuit has a top size of 50 mm which is very coarse for the ball mill. For this purpose, later in 1980s, high pressure grinding rolls (HPGR) has found applications as a pregrinder which increased throughput of the grinding circuit at the same fineness.In early applications, HPGR was operated in open circuit. But later as the operating principle of the equipment based on the compression, some portion of the HPGR discharge recycled back to improve efficiency of the mill or operated closed circuit with classifiers. Within this study effect of open and closed circuit HPGR applications on dry grinding circuit performance was examined. For this purpose sampling studies around three different cement grinding circuit were completed. In the first study, a circuit including open circuit HPGR, ball mill and air separator was sampled and chosen as the basic condition. As the final product size distribution is important for grinding circuit, model structure of each equipment was developed. The second and third surveys were carried out around closed circuit HPGR operation with V and VSK separator to develop models for the separators. Finally the separator models were used in basic condition to simulate closed circuit HPGR application.It was understood from the studies that closed circuit HPGR operation improved the overall circuit efficiency at the same final product fineness by reducing the specific energy consumption.     

不同破碎方式下产品磨矿特性的对比研究

对西藏墨竹工卡邦铺钼铜矿进行了高压辊磨和传统破碎,然后对两种产品进行了分批磨矿试验,应用磨矿动力学原理,并借助MATLAB 7.1软件分析了高压辊磨产品和传统破碎产品磨矿过程中各个粒级的磨矿速度。结果表明:在磨矿初期,高压辊磨产品的磨矿速度大于传统破碎产品的磨矿速度;在粗级别(-3.2+0.105 mm)中,高压辊磨产品磨矿速度的最大值高于传统破碎产品,而且粒度越粗,磨矿速度的最大值相差越大;随着磨矿时间的继续增加,磨机中粗粒级的含量越来越少,磨矿概率迅速降低,从而导致高压辊磨产品的磨矿速度小于传统破碎产品的磨矿速度,对于粗粒级(-3.2+0.105 mm)这种现象尤为明显;针对上述现象提出"高压辊磨—粗粒选择性快速磨矿"这一概念。     

齐大山铁矿石高压辊磨产品磨矿及解离特性研究

以齐大山铁矿细碎矿石为对象,考察其高压辊磨机粉碎产品的磨矿特性和单体解离特性,并与实验室颚式破碎机粉碎产品进行比较,结果表明：当目标粒度分别为0.074和0.280 mm时,辊压产品的邦德球磨功指数分别比颚破产品的降低13.96%和28.23%;在-0.074 mm占80%磨矿细度下,-3.2和3.2~0.074 mm辊压产品与对应颚破产品的相对可磨度分别为0.83和0.86;辊压产品与颚破产品相比,-0.5 mm粒级中铁矿物的单体解离度高15.16个百分点,不同磨矿细度下的磨矿产物中铁矿物的单体解离度高5.55~0.98个百分点;辊压产品磨矿产物中的连生体属于二次磨矿时易于解离的连生体,而颚破产品磨矿产物中的连生体属于二次磨矿时难以完全解离的连生体。     

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.     

Predicting the specific energy required for size reduction of relatively coarse feeds in conventional crushers and high pressure grinding rolls

In a previous paper (Morrell, 2009. Predicting the overall specific energy requirement of crushing, high pressure grinding roll and tumbling mill circuits. Minerals Engineering 22 (6), 544–549), an approach was described to predict the specific energy of a range of tumbling mill and crushing/high pressure grinding rolls (HPGR) circuits. In the case of crushing and HPGR circuits, recently acquired data have enabled this approach to be extended to coarser particle size reduction situations. This is achieved through the use of a size-dependent hardness parameter. Crushing and HPGR conditions are described where the use of this parameter should improve the accuracy of specific energy predictions. A worked example is also given.     

破碎方式对邦铺钼铜矿石可磨性及钼浮选的影响

分别采用高压辊磨工艺和传统破碎工艺将西藏墨竹工卡县邦铺钼铜矿石破碎到-3.2 mm,分析了两种破碎产品的粒度特性,测定了两种破碎方式下矿石的 Bond球磨功指数,考察了两种破碎方式对后续球磨-钼浮选的影响。结果表明：高压辊磨产品比传统破碎产品细粒级含量多且粒度分布更均匀;高压辊磨产品在不同目标粒度下的Bond 球磨功指数比传统破碎产品至少降低9.05%;高压辊磨产品和传统破碎产品浮选钼的最佳磨矿细度分别为-0.074 mm占65%和75%,相应地,前者的Bond球磨功指数比后者降低10.87%,但浮钼回收率减少2.32个百分点。     

不同破碎方式对鞍山式赤铁矿石磨矿特性的影响

高压辊磨破碎是基于料层粉碎的一种新型破碎方式,不仅本作业破碎效率高、能耗低、粉矿量大,而且破碎产品颗粒内部丰富的微裂纹也有利于后续磨矿作业节能。为了定量评价高压辊磨破碎对后续磨矿的影响,以鞍山式某赤铁矿石为试样,进行了磨矿技术效率和Bond球磨功指数试验。结果表明：由于高压辊磨产品中小于指定粒度（-0.074 mm）的物料产率明显较高,因而在较粗磨矿细度下,高压辊磨产品的磨矿技术效率均略低于颚式破碎产品,但随着磨矿细度的提高,二者的差距越来越小,当-0.074 mm占85%时,二者的磨矿技术效率相当,超过该磨矿细度,则磨矿效率开始小幅反超;目标粒度为280、150、105、74 μm时,高压辊磨产品的Bond球磨功指数比颚式破碎产品分别低9.41%、7.70%、4.97%和4.28%,降低的幅度随目标粒度的降低而减小,表明高压辊磨破碎对一段磨矿有显著的节能效果。     

High pressure grinding rolls (HPGR) applications in the cement industry

In this study, the performance evaluation studies in five cement grinding circuits, in which HPGR is used in various configurations, were presented. Sampling surveys were performed around the circuits followed by the determination of the size distribution of the samples down to 1.8 μm using a combination of sieving and laser sizing methods. The results showed that the specific energy consumption of the circuit decreases as the size reduction achieved by the HPGR increases. As given in the case studies when the size reduction ratio (F₈₀/P₈₀) changed from 308.2 to 4.4, the specific energy consumption of the HPGR was 8.02 and 4.05 kWh/ton, respectively. Since various configurations offer rather different ball mill feeds, the best usage of HPGR could be attained by optimization of operating parameters of both ball mills and air classifiers.     

高压辊磨机粉碎工艺国外应用进展与发展趋势

基于层压粉碎原理,高压辊磨机具有处理量大、能量利用率高、粉碎产品粒度细等特性,已经广泛应用 于冶金矿山领域,且节能降耗效果显著。 文章总结了开路粉碎、边料返回半闭路粉碎和筛分(包括干法筛分和湿法筛 分)全闭路粉碎三种粉碎工艺的选择依据。 结合高压辊磨机在金刚石解离、铁矿球团原料预处理、(半)自磨顽石破碎 和金属矿磨前粉碎领域的典型应用案例,重点阐述了高压辊磨机的粉碎工艺流程、设备型号、操作参数及应用效果。 不断提高粉碎效率、降低粉碎成本仍是高压辊磨机粉碎工艺的发展方向。 虽然多台高压辊磨机串联配置、高压辊磨 机与风力分级设备配置、高压辊磨机与搅拌磨机直接配置等新工艺发展不够成熟,但节能降耗优势明显,有望为冶金 矿山物料高效粉碎提供新的解决方案。     

马坑磁铁矿石高压辊磨—湿式中磁预选—阶段磨选工艺试验

为探索采用高效碎磨工艺处理福建马坑铁矿石的可行性,进行了高压辊磨—湿式中磁预选—阶段磨选工艺流程试验。结果表明:较常规碎矿工艺,高压辊磨破碎获得的产品细粒级含量显著提高,能够满足湿式中磁预选的粒度要求;磨矿条件相同时,高压辊磨产品相对传统颚式破碎产品新生成-0.074 mm粒级含量高,相对可磨度高;高压辊磨产品(-5 mm)经湿式中磁预选—两阶段磨矿弱磁选,可在磨前抛出38.88%的合格尾矿,并可获得铁品位为66.75%、磁性铁品位为65.95%、铁回收率为80.21%、磁性铁回收率为96.25%的铁精矿,精矿铁品位较现场提高了2.66个百分点、铁回收率提高了0.30个百分点,可作为马坑铁矿节能降耗、提质增效改造设计的依据。     

Analysis of grinding media effect on specific breakage rate function of particles in a full-scale open circuit three-compartment cement ball mill

A full-scale three-compartment FLSmidth® cement grinding ball mill with dimensions of Ø3.5 × L10 operating in open circuit was sampled to analyse the grinding media effect on specific breakage rate function of particles. Size reduction performance of the ball mill was evaluated with respect to the applied grinding media size. Samples from the circuit and inside the mill were collected. Mass balance of the circuit was done using JKSimMet Steady State Mineral Processing Simulator. Specific discharge and breakage rate functions of particles were estimated using perfect mixing modeling approach (Whiten, 1972) on the basis of the proposed open circuit three-compartment ball mill model structure (Genç and Benzer, 2015). Maximum specific breakage rate was related to maximum grinding media size in the grinding compartments. An exponential correlation was found to exist between maximum grinding media size and maximum specific breakage rate. Relationship between maximum grinding media size and maximum particle size was also fitted to an exponential function. Findings indicated that, grinding performance of cylpebs applied in the third compartment did not improved the size reduction performance as compared to the grinding performance of the first and second compartment.     

Effects of grinding on the preg-robbing potential of quartz in an acidic chloride medium

The effect of high-energy milling on the surface properties of quartz is examined with regard to its preg-robbing behavior towards gold. A standard ring mill is used to process dry quartz samples, and the changes in the morphology of the particles, structural deformations and surface chemistry are investigated to explain the increased preg-robbing ability of quartz in acidic chloride solutions. The transition from fine grinding to mechanochemical activation of quartz can be observed from changes in the morphology of the particles, as well as the types of structural deformations. The transition occurs between 1 and 5 min of grinding in the mill used, corresponding to particle sizes around 0.55 μm. Structural studies differentiate two stages of fine grinding: particle breakage with limited structural disruption, and structural disturbance by mechanochemical alteration, which occurs after particles reach their grinding limits. Quartz keeps its structural order to some degree even after 30 min of aggressive grinding. The surface chemistry of ground quartz demonstrates generation of point defects including low valence silicon and non-bridging oxygen centers. These defect sites play an important role in the surface reactivity of the quartz, and influence the extent of gold loss during preg-robbing.     

罗河铁矿复合铁矿石高压辊磨工艺应用研究

为了解高压辊磨破碎对罗河铁矿选矿厂细碎产品可磨性的影响,对现场细碎产品进行了开路辊压破碎、边料返回闭路辊压破碎试验,边料返回闭路辊压破碎产品与现场细碎产品相对可磨度测定试验,样品和高压辊磨机边料返回闭路破碎产品球磨功指数测定试验,以及增设高压辊磨工艺后一段球磨扩能效果分析。结果表明：①高压辊磨作业可大幅度提高产品中细粒级含量,边料返回闭路破碎试验产品-3 mm粒级含量由辊磨前的56.73%提高至85.30%,提高28.57个百分点;-5 mm粒级含量由辊磨前的67.79%提高至92.65%,提高24.86个百分点;单位处理量为252 ts/（hm3）。②高压辊磨作业可显著改善入磨矿石的磨矿性能,当磨矿细度为-0.075 mm占60%时,与样品相比,高压辊磨机边料返回闭路破碎产品的相对可磨度为1.294;样品经高压辊磨破碎后,其球磨邦德功指数由16.15 kWh/t降至13.75 kWh/t,降幅为14.86%。③选矿厂增设高压辊磨边料返回超细碎作业后,由于入磨矿石可磨性的改善,一段球磨的产能可提高35.41%。     

Value adding limestone to filler grade through an ultra-fine grinding process in jet mill for use in plastic industries

In this study, ultra-fine grinding of limestone was carried out in jet mill using four levels of classifier rotational speed and grinding pressure. The holdup amount was determined during the grinding process, while the feed rate was kept constant at 8 kg/h. The ground product was characterized for its particle size and shape. In addition, the mechanochemical effect on the ground product was characterized through XRD. The particles size of the ground product ranged from 2.21 μm to 7.29 μm, demonstrating various particle shapes such as cubical, angular, and elongated. The degree of crystallinity of the ground product ranged from 54.5% to 93.7%. Afterwards, the ground product was incorporated as filler in polypropylene (PP), and its performance was characterized for mechanical properties. After conducting the test work, we find that the PP filled with ground limestone exhibited excellent thermal and mechanical properties. The composite flexural modulus, impact strength, tensile strength, and elongation at break were 2.1 GPa, 42 kJ/m², 22.75 MPa, and 21%, respectively, when loaded up to 20%. It likewise exhibited CTE value of 57.2 ppm/°C.