Optimization of a fully air-swept dry grinding cement raw meal ball mill closed circuit capacity with the aid of simulation

Production capacity of a fully air-swept industrial scale two-compartment KHD Humboldt Wedag® cement ball mill was optimized with the aid of simulation. It was proposed to operate the mill as a single compartment by eliminating the pre-drying compartment. In this respect, grinding performance of the air-swept ball mill was evaluated and modelled as a perfectly mixed single tank using the perfect mixing ball mill modelling approach (Whiten, 1974). Static separator was modelled by efficiency curve model (Whiten, 1966). The empirical breakage function required in the estimation of average specific breakage rates was measured by drop-weight technique. The full scale model parameters were used to simulate the raw meal mill grinding circuit with the aid of JKSimMet Steady State Mineral Processing Simulator. Simulation results indicated 23% production capacity increase in cement throughput in case the pre-drying compartment was used in grinding.     

Economic optimisation of a flotation plant through grinding circuit tuning

The paper describes a procedure to tune a grinding circuit in order to maximise the economic efficiency of the flotation plant. The optimisation process is performed using a plant simulator based on phenomenological models of grinding and flotation and an empirical model for predicting the minerals size distribution from the ore size distribution of the grinding circuit product. The economic efficiency of the plant is assessed either by the net smelter return per ton of ore or the net revenue of the concentrator. The approach is illustrated for a lead silver gold plant located in Mexico and shows that the economic efficiency of this plant could be increased by 10 to 20%.     

JKsimMet软件对某钨选矿厂磨矿-分级回路建模与粒度控制

描述了计算机软件JKsimMet 6.1中文版(简称JK 6.1)应用于某37 t/h钨矿选矿厂的磨矿回路优化研究。该软件可模拟和控制优化选矿厂的磨矿-分级回路,有效减少过粗和过细颗粒的产生,保证磨矿系统处理量的最大化。采用JK 6.1软件模拟的结果应用于生产中的结果表明,沉砂中WO3品位的累积减少了0.17%;在细度相近的情况下,溢流中-10μm粒级产率降低1.16%;沉砂中-10μm粒级产率降低0.63%;同时溢流产品的细度P80从78μm增大至82μm;钢球单耗降低7.69%;电能消耗减少4.77%。     

Statistical monitoring of a grinding circuit: An industrial case study

With the increasing availability of large amounts of real-time process data and a better fundamental understanding of the operation of mineral processing units, statistical monitoring of mineral processing plants is becoming increasingly widespread. Process plants are typically too complex to model from first principles and therefore models based on historical process data are used instead. Multivariate methods such as principal component analysis are indispensable in these analyses and in this paper, it is shown how the statistical analysis of process data from a grinding circuit and a sound fundamental knowledge of the operation of mineral processing plants complement one another. For this purpose a philosophy for the statistical monitoring and cause and effect analysis of a process was outlined. It was shown how a well defined process hierarchy with complementing performance measures can effectively be used to detect a shift in the operation of a mineral processing plant and find the root cause of the shift. Visualisation of the results was found fundamental in communicating the findings of the statistical analysis to the processing plant. This resulted in the requirement for multidimensional visualisation of the process for which principal component analysis plots and process performance graphs in the form of two-dimensional histogram plots and parallel plots were found to be the most effective. Data availability, process variable selection, process hierarchy definition and performance measure selection were also found to be critical factors directly impacting on the success of statistically monitoring a process.     

微波-酸浸方法助磨鲕状赤铁矿研究

以鄂西鲕状赤铁为研究对象,在考察微波预处理提高鲕状赤铁矿磨矿效率的基础上,研究微波后酸浸对其磨矿的影响,并对作用机理进行分析。结果表明,在酸用量为5%(酸与矿石质量比),酸浸时间为50min,矿浆浓度为50%的条件下,磨矿产品-0.038 mm粒级含量可提升19.3%,磨矿效率得到提高。经过简单的磁选流程,可获得品位60.44%、磷含量0.19%的铁精矿,证明鲕状赤铁矿得到有效解离。     

Self-optimization of an autogenous grinding circuit

This paper deals with the optimization of an autogenous grinding circuit using a random search technique. This technique is based on a hierarchical structure of learning automata operating in a random environment constituted by the autogenous circuit to be optimized. The ore feed rate to the mill is considered as the control variable while the mass flow rate of the concentrate of the subsequent separation process constitutes the controlled variable.The variation domain of the manipulated variables is discretized into a set of regions which are associated to the actions of the automata of the last level of the hierarchical learning system. A probability is associated to each action (region). The learning system selects one of the available actions and, based on the response of the environment, modifies the strategy (the probabilities associated to the set of actions) using an adaptation procedure called reinforcement scheme.Numerical results illustrate the feasibility and the performance of this self-adjusting optimization algorithm.     

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%.     

Efficiency of grinding stabilizers in cement clinker processing

Stabilizers are commonly used in the production of very finely ground particulate materials. Doping with such additives is an absolutely essential process step in the production of ultra-fine and nano-fine solids; in all cases, the additives work as inhibitors that prevent the re-agglomeration of fine particles. Such additives, which are well known in both dry grinding and wet grinding processes, help to decrease the enormous energy consumption of cement production. This paper describes the essential features of stabilizers used in Portland clinker grinding processes. The results of milling experiments employing twelve commercially used and experimental additives are described. Their effectiveness in producing ultrafine (0–30 μm) particles varied widely. Novel acrylate-based grinding stabilizers showed considerable promise for the production of very fine cement clinkers.     

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.     

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.     

The interaction of flash flotation with closed circuit grinding

Flash flotation is an important unit operation within many grinding circuits. It provides an opportunity for the valuable mineral to be recovered as early as possible in the processing plant. This prevents liberated valuable mineral from building up in the recirculating load of the mill, and reduces the occurrence of overgrinding. Overgrinding can place a significant limitation on overall recovery, because it causes the production of valuable fines that are difficult to recover by flotation.The flash flotation cell is fed by the cyclone underflow in a closed grinding circuit. This feed stream represents the optimal particle size distributions of valuable mineral and gangue for flotation kinetics, selectivity and grade. The flash cell treats the recirculating load of the ball mill, and therefore influences the performance of both the mill and the hydrocyclone classifier. The effect of a flash cell in the grinding circuit is difficult to determine since flash cells in Australia are introduced at the design stage and so no plant data is available before and after the introduction of the flash flotation unit. By establishing a computer simulation of the closed-circuit grinding with flash flotation, the interaction of flash flotation with grinding can be estimated. The models can be used to predict the effect of various changes to the operating conditions on circuit performance as well as the expected grinding performance in the absence of flash flotation. This enables the effect of flash flotation and any possible benefits to be evaluated.The model was developed from unit models of the ball milling, hydrocyclone classification and flash flotation processes. An empirical model was used for the flash cell, and generic models were fitted to the ball mill and hydrocyclone based on the matrix model and the Plitt model respectively. The data required for the development of the models was obtained from plant surveys of the Kanowna Belle gold mine and laboratory batch grinding and flotation tests.The model accurately represents the plant grinding and flash flotation circuit while operating under normal conditions. Simulation of the circuit using the model enabled the effect of variations to flash cell operating conditions on the flash concentrate, recirculating load and cyclone overflow to be determined.     

Optimisation of the grinding circuit at arafertil,Brazil

Arafertil's regrinding circuit is responsible for the recovery of apatite with a low degree of liberation, representing approximately 11% of the overall apatite concentrate production. Low grinding capacity prevented an ideal size distribution of product for maximum recovery in the subsequent flotation stage, as shown in a liberation study.This work was aimed at attaining the required increase in regrinding capacity, using process simulation by computer mathematical modelling, with the objective of implementing an optimised grinding and classification circuit.The ball mill and hydrocyclones models were calibrated, and their equations were defined, from industrial data acquired in the old concentrator configuration and results from laboratory grinding tests with power consumption measurements.The model was validated by means of comparison between the results predicted by simulation and those achieved in the plant after refurbishment. The apatite flotation recovery increased from 31.5% to 48.0%, in agreement with the previous apatite liberation study.     

IPM斩波轻型智能充电装置研究

分析了利用IPM斩波的轻型智能充电装置的特点及工作原理,给出了软硬件设计和完善的抗干扰措施。     

微波辅助磨矿对煤岩组分解离的影响

在自制的微波搅拌球磨机中研究了微波与机械力联合作用对煤岩组分解离的影响,揭示了微波-机械力作用下丝炭和镜煤的破碎特征。通过浮选方法对煤岩组分解离效果进行了检验,探讨了球磨过程中微波辐射时间对煤岩组分浮选分离效果的影响。结果表明,微波辐射对丝炭的影响较镜煤显著,致使微波场中煤岩组分的破碎具有差异性和选择性;微波辐射时间为2 min时,浮选分离后镜质组和惰质组的富集率最高,分别由57.7%增至92.6%,37.6%增至57.7%。     

自动化在磨矿分级控制中的应用

磨矿分级自动控制系统是利用先进的模糊控制,在满足选别工艺和精矿品位的前提下稳定分级溢流粒度,提高系统磨矿台时处理能力,提高磨机效率,减少或避免机电故障,减轻操作工人的工作强度,降低水、电、钢球、衬板等的消耗,为企业创造效益。     

Application of model predictive control in ball mill grinding circuit

Grinding circuit needs to be stably controlled for high recovery rate of mineral ore and significant reduction of production cost in concentrator plants. Ball mill grinding circuit is essentially a multi-input–multi-output (MIMO) system with strong coupling among process variables. Simplified model with multi-loop decoupled PID control usually cannot maintain a long-time stable control in real practice. The response tests between four controlled variables (namely, product particle size, mill solids concentration, sump level and circulating load) and four manipulated variables (namely, fresh ore feed rate, mill feed water flow rate, pump speed and dilution water flow rate) are carried out to construct a four-input–four-output model of grinding circuit. Based on this modeling, constrained model predictive control (MPC) is adopted to handle such strong coupling system and evaluated in an iron ore concentrator plant. The variables are controlled around their set-points and a long-term stable operation of the grinding circuit close to their optimum operating conditions is achieved. More than three years’ operation in industry demonstrates the effectiveness and practicality of this control strategy.     

碎磨流程智能化改造提升的路径分析

碎磨流程是矿产资源开发过程中的关键环节和能耗大头,也是如今智能化浪潮下很多选矿厂最先着手进行优化的地方。从三个角度详细阐述了碎磨流程智能化改造提升领域的技术和运用现状,希望能为该领域提供一些思路和借鉴。装备升级方面,介绍了智能碎磨设备功能和传统碎磨设备改造的现状,以及碎磨设备的研发、试验、优化环节中各类软件工具的运用情况;工艺优化方面,描述了仿真模拟技术和优化算法与碎磨流程数据相结合后,在工艺回路设计、设备选型、工艺参数优化方面的辅助功效;生产控制方面,分述了实时检测、故障诊断和过程控制方面的多种技术在碎磨流程中的应用效果和适用条件。     

提升行业科技期刊编辑业务能力的途径

认为随着新媒体时代到来,对行业科技期刊的编辑人员提出了新的更高的要求.从提高编辑人员的职业道德素养、提升专业知识水平、创建学习型编辑部3个方面就如何提高编辑业务能力提出了对策.     

某冶炼厂制酸系统开路除氟实验研究

本文对某冶炼厂制酸系统稀酸主要成分重点是氟的含量进行了分析,以硫酸铝作除氟试剂进行了试验,研究了pH值、药剂投加量、放置时间、过滤条件等因素对除氟效果的影响,确定了最佳的实验参数。     

Effect of grinding media on zinc depression in a lead cleaner circuit

Laboratory testwork, investigating the effect of high chrome grinding media in a lead regrind application has on subsequent metallurgical performance, was conducted at a large silver–lead–zinc operation in Australia. The initial data showed that the use of a more inert grinding media could have increased zinc losses to the lead cleaner concentrate if careful attention was not paid to alloy selection.Diagnostic tests showed that iron hydroxide surface coatings generated by grinding media corrosion reactions are an effective depressant for sphalerite in this ore body, even though it is known that an excess of these coatings could depress both galena and sphalerite flotation. These tests demonstrated that a 1% chrome alloy produced the desired pulp chemical conditions to yield an increase in lead concentrate grade through the rejection of sphalerite from the lead circuit.A plant trial was conducted in one of the two parallel grinding/flotation trains, and data collected for statistical analysis. During the plant trial, pulp chemical surveys of the regrind circuit were also taken to compare the effect of grinding media on the cleaner one feed slurry pulp potentials, dissolved oxygen, pH, temperature and EDTA extractable iron.The statistical analysis showed clearly that the change to 1% chrome grinding media had a significant positive impact on improving galena/sphalerite selectivity during lead cleaner flotation and improved the lead concentrate grade. The improved metallurgical performance is explained in terms of modified pulp chemistry.