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。     

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。     

高压辊磨机选型试验的研究现状

结合高压辊磨机中物料粉碎机理,介绍了影响高压辊磨机粉碎效果的关键因素,评述了高压辊磨机设备选型试验的研究现状。高压辊磨机粉碎物料的效果主要受物料性质、辊压机工作参数及粉碎工艺等的影响。通过小型及半工业型高压辊磨机粉碎试验能够为高压辊磨机的设备选型和流程设计提供依据,但试验过程相对复杂。颗粒床活塞压载试验和数学建模尽管能够对矿石料层粉碎的工作压力、比能耗、产品粒度分布等进行有效预测,但和高压辊磨机设备选型的经验公式一样均需要对其适用性进行验证。指出高压辊磨机未来的研究方向为粉碎过程中能量传递模型、矿石碎磨特性及对分选工艺影响等的理论基础研究,以及高压辊磨机在选矿流程中的数值模拟研究。     

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.     

Flowsheet considerations for optimal use of high pressure grinding rolls

High pressure grinding roll (“HPGR”) technology is very rapidly gaining a wide acceptance within the mineral processing industry. Benefits, including a superior energy efficiency and a lower overall operating cost of an HPGR based circuit compared to alternative technologies have been demonstrated at a number of operations throughout the world. Increasing numbers of units are presently being installed in the minerals industry world-wide. This trend is an excellent reflection of the confidence now placed in the technology by new and existing users.This paper summarizes basic principles of the equipment and of various options how to include an HPRG in the grinding circuit for most efficient use. Case studies demonstrate the application of HPGR’s in different grinding circuit set-ups and for the comminution of different ore types. Benefits of the options of open circuit grinding, closed circuit grinding incorporating wet and dry screening as well as the option of achieving a finer grind by recirculating part of the HPGR product using a mechanical splitter are discussed.From a processing point of view the effects of partial product recycle are detailed and some guidance for selection of cut size between HPGR and ball mill is provided.     

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.     

高压辊磨机挤满给料控制系统开发与应用

为了提高高压辊磨机的设备利用效率,减少空转率,本文提出了一套完整的高压辊磨机给矿控制策略。该控制策略以挤满给料专家控制算法为核心,加之对整个高压辊磨机作业回路进行故障监测与诊断,保证了高压辊磨机给料的持续和稳定性,提高了作业回路的生产效率和安全性。     

The effect of using different comminution procedures on the flotation of sphalerite

High Pressure Grinding Rollers (HPGR) are known to reduce energy consumption and wear costs and improve the throughput in the circuit. It has been suggested that they can also modify the liberation characteristics of the ore. In the present study the effect of using conventional crushing as opposed to HPGR in combination with either dry or wet milling was investigated using a base metal sulphide, viz. sphalerite, in order to determine whether there may be an improvement in flotation performance following the use of different comminution procedures. It was found that, irrespective of the crushing procedure (HPGR or conventional), dry milling resulted in the highest grades and recoveries of zinc. These were typically 94% recovery at 40% grade. In order to gain an insight into the effect which these comminution procedures had on the ore, samples of feed and product were investigated using surface analytical techniques. Mineralogical analyses showed no differences in the liberation characteristics of sphalerite irrespective of the comminution procedures used. However, dry milling produced a lower d50. The paper proposes possible reasons to explain these observations.     

The effect of using different comminution procedures on the flotation of Platinum-Group Minerals

The use of High Pressure Grinding Rollers (HPGR) has been widely reported to have major benefits in the treatment of minerals such as iron ore and diamonds. To date there have been few investigations into its use in the treatment of ores containing Platinum-Group Minerals (PGMs). HPGRs are known to reduce energy consumption and wear costs and improve the throughput in the circuit. In the present investigation the effect of the comparative use of HPGR and conventional crushing in combination with either dry or wet rod milling on the flotation of PGMs was studied using batch flotation. Previous studies of a base metal sulphide had shown that either HPGR or conventional crushing followed by dry milling produced the highest grades and recoveries (Palm et al., 2010). However in the present study it was observed that a similar treatment of Platinum-Group Minerals produced the poorest results and the highest grades and recoveries were obtained for the case of conventional crushing in combination with wet milling. The HPGR showed no advantages in terms of flotation performance and dry milling produced particularly poor flotation results.The results were investigated further using various surface characterization techniques in order to determine the reason for the decrease in grades and recoveries of platinum when using dry milling and HPGR as opposed to the case for base metal sulphides. The feed and product samples were analysed using ToF-SIMS, XPS and MLA. The paper will propose reasons to explain the different flotation behaviour of the two ore types following the various comminution processes focusing on the surface characteristics of the ores, the particle size distribution and the pulp chemistry.     

Predicting the overall specific energy requirement of crushing,high pressure grinding roll and tumbling mill circuits

In a previous paper [Morrell, S. 2008a. A method for predicting the specific energy requirement of comminution circuits and assessing their energy utilisation efficiency. Minerals Engineering 21(3), 5–9] an approach was described which enabled the specific energy of tumbling mills such as Autogenous (AG), Semi-autogenous (SAG) and ball mills to be estimated from laboratory-derived ore characterisation data. The following paper extends this approach to encompass jaw, gyratory and cone crushers as well as High Pressure Grinding Rolls (HPGR). The technique is applied to three different comminution circuits and their overall specific energies are compared. All of the calculations involved are described in detail in an appendix.     

A preliminary investigation into the feasibility of a novel HPGR-based circuit for hard,weathered ores containing clayish material

The paper reports the progress of a research project using rock samples from a large copper–gold mining project. The orebody contains a mixture of hard rock, softer material, and clays (sericite), in proportions that are expected to vary throughout the mine-life. The feasibility of a novel comminution circuit, using an autogenous (AG) mill/scrubber and parallel trains of cone crushers and high-pressure grinding rolls (HPGR) is being investigated. The process enables the application of energy-efficient HPGR to base and precious metal hard-ores containing clay, which are usually processed using SAG mill circuits.The work presented in this paper involved laboratory testwork including pilot HPGR testing, and modelling and simulation of both the HPGR-based circuit and an equivalent SAG-based circuit. The preliminary analysis reported herein includes a comparison of the energy consumption of both circuits; complete operating and capital cost comparisons will be reported in a future paper.     

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.     

Effect of High Pressure Grinding Rolls (HPGR) pre-grinding and ball mill intermediate diaphragm grate design on grinding capacity of an industrial scale two-compartment cement ball mill classification circuit

Effect of High Pressure Grinding Rolls (HPGR) pre-grinding and two-compartment ball mill intermediate diaphragm grate design on grinding capacity of an industrial scale conventional two-compartment ball mill cement grinding and classification circuit was investigated. For this purpose, cement clinker was crushed in an industrial scale HPGR in open circuit and fed to a Polysius® two-compartment ball mill and air classifier closed circuit. Two-compartment ball mill intermediate diaphragm middle grate design was changed when HPGR crushed clinker was fed to the circuit to obtain optimum flow of material from the first compartment into the second compartment. Modifications on the diaphragm design were required due to the increased throughput when processing HPGR product. Two sampling campaigns were performed at the steady state conditions of the circuit. Raw clinker (uncrushed clinker) was fed to the conventional two-compartment ball mill air classifier circuit in sampling campaign-1 whereas HPGR crushed clinker was fed to the same circuit with modifications on the intermediate diaphragm middle grate design in sampling campaign-2. Mass balanced tonnage and particle size distributions were estimated by using JKSimMet Steady State Mineral Processing Simulator in both sampling campaigns. Polysius® two-compartment ball mill was modeled by using perfect mixing modeling approach (Whiten, 1974). Specific discharge and breakage rates in the grinding compartments were estimated by using the two-compartment ball mill model structure proposed by Genç and Benzer (2015). Specific discharge rates were found to increase at coarse size ranges when raw clinker was fed to the circuit in compartment-1. However, specific discharge rates of particles were increased slightly at coarse size ranges in the second compartment at higher mill capacity condition. Specific breakage rates were increased when the circuit was fed with HPGR crushed clinker. Modifications in the circuit and the ball mill intermediate diaphragm grate design enabled the optimization of the grinding capacity of the conventional two-compartment ball mill cement grinding and classification circuit. Ball mill grinding and classification circuit capacity was increased by 10% and specific energy consumption of the ball mill was decreased by 9.1%.     

Investigation of particles with high crack density produced by HPGR and its effect on the redistribution of the particle size fraction in heaps

The application of comminution technology such as the high-pressure grinding rolls (HPGRs), which is able to generate a high density of cracks in the ore particles, is favourable for leaching processes. Extraction of metallic values by the heap leach process, can take place on the particles with partial exposure of mineral grains, if it can provide sufficient surface front for chemical attack by leaching solution. The aim of this study was to assess the benefits of high crack density in the ore particles produced using the HPGR and how it could diminish due to inadequate percolation of the leaching agent.A zinc ore was comminuted using HPGR at three different pressure settings and with a cone crusher for the control experiment. Subsamples from the (+23/−25, +14/−16, +5.25/−6.75 mm) size fractions were characterized and packed into leach reactors. The reactors were stopped from time to time to investigate the progress of crack and micro-crack growth and its effect on metal extraction using the X-ray computed tomography (CT). The results are validated with those obtained using traditional techniques such as SEM and QEMSCAN. Investigation of the leach reactors residue indicated significant changes in the particle size distribution (PSD) of initial feed toward the fine size fraction. The residues from the reactors leaching the material prepared using the HPGR product contained more fine particles than the reactors, which were fed by cone crusher product. These differences were up to 10.3%.     

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%。     

关于矿石粉碎特性参数及其测定方法

从粉碎工艺设计应用的角度,综述各种表征矿石粉碎特性的物料参数及其测定方法,包括用于传统碎磨设备选型计算的物料参数及其测定方法、用于自磨/半自磨流程设计的物料参数及其测定方法,以及用于高压辊磨流程设计的粉碎试验方法。     

基于生产数据的高压辊磨机粉碎建模与模拟

根据工业流程考查数据对凹山选厂超细碎工段的高压辊磨机粉碎进行了数学建模。利用所建粉碎模型以及以分配曲线形式表示的分级模型对高压辊磨机与3 mm筛分作业构成的闭路粉碎流程进行了模拟计算。计算结果证明了这种高压辊磨机模型及建模方法的有效性和实用性。     

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.     

高压辊磨机在金属矿选矿与球团预处理领域的工艺和操作参数

高压辊磨机能量利用率高,目前已在水泥行业、金属矿山、冶金球团等领域广泛应用。结合当前研究成果及工业现场数据,本文对比了高压辊磨机在金属矿山和球团预处理行业中的工艺流程,以及辊面比压力、辊面线速度、辊缝几个工艺参数,为高压辊磨机在金属矿山和球团预处理应用中工艺参数的选择提供参考。