Investigation of the process of grinding reduced sponge iron and development of the technology of producing iron powders of different bulk density

Summary The following grinding technology is recommended for the purpose of increasing the fine-fraction yield of powder: a) grinding of reduced briquets in a hammer mill and the sifting of powder into coarse and fine fractions; b) grinding of the coarse fraction in a ball mill over a period of 16 h and the sifting of powder by means of a vibrating screen; c) mixing of the fine fractions obtained in the first and the second screenings.In order to increase the bulk density of the powder, it is recommended to perform triple grinding of the powder in a hammer mill or to grind it in a ball mill.     

湿法球磨工艺参数对硅酸锆平均粒度的影响

对锆英砂湿法球磨加工中存在的问题进行了概述和分析,研究了湿法球磨中的球磨机转速、研磨时间、浆料浓度、填充率、球料比等工艺参数对硅酸锆的平均粒度的影响规律。研究结果表明,增加球磨机的转速,延长球磨时间,都会使研磨出的硅酸锆粒度变得更小,且硅酸锆平均粒度变化曲线都呈初期变化大,超过拐点后变化减缓的趋势。填充率和浆料浓度对硅酸锆平均粒度的影响类似,随着填充率或浆料浓度的不断增加,研磨出来的硅酸锆粒度越小,但总体上下降幅度不大,其变化幅度的差别主要来自于罐中水和空气的比例不同。球料比对硅酸锆的平均粒度影响显著,当球料比在2∶1到6∶1的范围内变化时,随着球料比增大,研磨出来的硅酸锆的平均粒度由6.55μm下降到1.82μm。     

球磨机介质配比方法的试验研究

对生产中简单实用的主要介质配比方法进行了试验比较。结果表明,确定适宜介质配比的方法是：根据给料粒度组成,先确定各主要窄给别对应的最佳介质尺寸,然后各直径球介质占球荷总质量的百分率等于给料中相应窄级别的产率确定介质配比;如果给料中粗粒级含量低,磨矿时间较长,磨机矿浆粘度较大,可按照各尺寸介质等质量百分比法计算介质配比,以适当增加大球介质的比例,提高磨矿效率。该研究结构对实际生产具有重要的指导意义。     

Ball-Mill Grinding Kinetics of Cement Clinker Comminuted in the High-Pressure Roll Mill

The use of high-pressure grinding rolls (HPGR) prior to ball mills has become a common practice in cement clinker grinding due to significant energy savings in comparison to ball milling alone. The energy savings has been attributed to higher energy efficiency of HPGR at low reduction ratios, smaller particle top sizes in the ball mill feed, and the weakening of particles resulting from compression of particle bed by HPGR. This study attempts to show how the weakening effect changes the kinetic breakage parameters of the HPGR-treated clinker. For this purpose, batch ball mill experiments were conducted with three narrow-size fractions (?3.35 + 2.36, ?1.70 + 1.18, and ?0.85 + 0.60 mm) of the feed and product samples of an industrial HPGR, and the breakage rate and breakage distribution parameters of the samples were compared. The results show that the weakening effect leads to nonlinear breakage rates for all sizes, coupled with abnormal breakage at the two coarsest sizes. The weakening effect leads to increased breakage rates of the HPGR product relative to particles of the HPGR feed. The increased breakage rates are accompanied by coarser progeny distributions for the two coarsest size ranges relative to that of the HPGR feed. The progeny distribution of the finest size of the HPGR product, however, is finer than that of the HPGR feed. Ball milling of size-distributed feeds prepared from the HPGR product and feed samples for the same grinding time produces self-similar size distributions when the size is normalized with respect to the median size.     

溢流型球磨机进料口密封装置的改进

分析了溢流型球磨机进料口矿浆泄漏的原因以及泄漏后给球磨机润滑系统和环境所带来的危害。通过对溢流型球磨机进料口密封装置的改进,减少和杜绝了矿浆泄漏,改善了球磨机运行环境,延长了润滑油使用周期、提高了球磨机有效作业率,降低了球磨机运行成本。     

A survey on troubleshooting of closed-circuit grinding system

An industrial ball mill operating in closed-circuit with hydrocyclones was studied by five sampling surveys. The aim of the present study was to optimise operating parameters (i.e. charge volume, make-up ball size regime, slurry mean residence time, number of hydrocyclones in operation and hydrocyclone’s feed solids content (S_f)) with respect to increasing throughout from 225 to 300 tons per hour (tph). The obtained results showed that increasing charge volume from 32 to 39% led to producing approximately 9% finer product size (P₈₀). Binary ball size regime rather than using mono-sized balls resulted in reduction of the P₈₀ relatively 5%. The S_f was identified as the most effective parameter on grinding efficiency. The cut-size plunged dramatically from 130 to 90?μm by reduction of S_f from 54 to 48%. Finally, it was concluded that the capacity of grinding circuit could be practically increased to 300?tph if all relevant parameters fell into the optimised ranges.     

半自磨机排矿速度及粒度优化研究

半自磨机磨矿介质由钢球和矿石自身组成,随着矿石硬度及块度的增加,造成半自磨机排矿速度偏慢及排矿粒度组成不合理,影响系统台效及电力、钢球等消耗。半自磨机为强制排矿碎磨设备,可通过改变排料端设计,将直形排料端改为弧形结构,优化半自磨机的排矿速度及粒度组成,达到提高半自磨系统磨矿效率的目的。     

焦家金矿磨矿介质配比优化试验研究与应用

针对焦家金矿选矿厂球磨机单位球耗高、磨机效率偏低和磨矿产品粒度组成不均匀等问题,基于矿石力学性质和磨矿循环产品粒度分布,采用段氏球径半理论公式计算得到推荐方案介质配比,并建立对照方案进行实验室磨矿对比试验,最终确定初装球方案为:Φ90:Φ70:Φ50:Φ40:Φ30=15:25:20:15:25.2016年10月26日...     

八道河铁矿运用长筒型球磨机的生产实践

通过采用长筒型球磨机技术改造的生产实践, 证明该球磨机作为细磨磨矿设备, 具有占地面积小、投资省、能量材料消耗低、新生细粒含量高等优点。解决了八道河铁矿选矿厂原用于细磨的球磨机磨矿效果差的问题。     

昆钢大红山提高8.53×4.27m半自磨机处理量实践

通过对半自磨机给料粒度合理搭配;调整半自磨机钢球尺寸;调整半自磨钢球补加量来控制磨机合适的充填率;格子衬板改造;排矿直线筛筛孔改造;半自磨机给矿自动化控制等改变了半自磨工艺,提高了处理量并降低了半自磨机的钢耗和电耗,达到了很好的效果。     

The effect of the mill speed on the comminution of zircon sand

Abstract

The effect of mill speeds on energy consumption and size reduction of zircon in a ball mill was investigated by comminution tests. Optimum grinding conditions, except mill speed, were determined prior to the investigation for the effect of mill speed.

The experimental results indicate that the most efficient grinding of hard minerals, such as zircon, occurs at around the critical speed of the mill when it is completely filled with zircon, balls and water in the proportion of 1:1:1 by apparent volume.

It is also found that the size-distribution parameter α and the energy-size parameter β of the product ground at around the critical speed of the mill are nearly equal, where abrasion and chipping rather than impact may be the predominant comminution mechanism.

Résumé

Par des essais de comminution, l'effet de la vitesse d'un broyeur à boulet, sur la consommation d'energie et la réduction de taille de la zircone ont été étudies. Avant ces essais les conditions optimales de broyage, sauf la vitesse, ont été determinées.

Les résultats expérimentaux indiquent que Ie broyage le plus efficace pour un minerai dur comme la zircone se produit pour une vitesse voisine de la vitesse critique du broyeur et quand it est complétement rempli de zircone, de boulets et d'eau dans une proportion volumétrique apparente de 1:1:1.

Il apparaît également que le parametré de granulométrie α et la paramétre déceivant l'énergie et la taille βdu produit broyé à une vitesse voisine de la vitesse critique sont sensiblement égaux; agrave; ce moment, les principaux mécanismes de comminution sont l'abrasion et l'écaillement plutôt que le choc.     

艾砂磨机在遂昌金矿的试验应用

遂昌金矿二段球磨闭路的磨矿产品细度已经达到极限,致使尾矿中金、银品位难以进一步降低。对艾砂磨机与二段球磨机的磨矿效果及产品的氰化浸出效果进行了对比,并介绍了艾砂磨机在选冶车间二段磨矿中所进行的工业试验。结果表明:采用艾砂磨机开路磨矿替代原二段球磨闭路磨矿,其磨矿产品-74μm从75%提高到95%,氰化尾渣金品位从0.35 g/t降低到0.12 g/t,银品位从13.17 g/t降低到7.4 g/t,指标较好,经济效益显著。     

铜精炼炉渣磨矿流程优化

采用闭路磨矿—压滤干排的方式处理铜精炼炉渣,会导致球磨机的台时能力降低。通过引入高频振动脱水筛,与旋流器和压滤机一起构成新的干排系统,使粗粒、细粒级进行了单独脱水,解决了球磨机排矿的脱水问题,实现了铜精炼炉渣的开路磨矿,既提高了球磨机的处理量,又降低了矿粉水分。     

顽石作为磨矿介质在含金铜硫分离中的试验研究

半自磨机排出的顽石硬度大、球形度高,具有磨矿介质特征。针对某铜硫金矿选矿厂分级机沉砂样,以顽石与钢球混合配比作为粗磨磨矿介质、全顽石作为粗精矿再磨介质,采用“铜硫混合浮选-粗精矿再磨-铜硫分离”工艺流程进行了浮选试验。在最佳条件试验的基础上进行闭路试验,最终可获得铜品位为18.45%、铜回收率为86.89%,金品位为16.68×10-6、金回收率为55.78%的铜精矿,高于工业生产实际指标。试验证实了顽石作为磨矿介质,在粗精矿细磨领域具有非常好的应用前景。     

Application of Artificial Neural Networks for Evaluating Pressure Filtration of Coal Refuse Slurries

Bench-scale pressure filtration testing was performed to evaluate the dewatering characteristics of two coal refuse slurries, which were collected from thickener underflow streams of two coal preparation plants. Pressure filtration provides an opportunity to produce drier solids (filter cake) that can be stacked or mixed with the coarse refuse and improved water (filtrate) recovery that can be reused in the plant. This paper examines the effects of some of the major influencing variables such as pressure, slurry pH, feed solids concentration, fines fraction of solids in the slurry, filtration time, and temperature on dewatering thickener underflow slurry. Experimental results indicated that the overall filtrate flux increased with increase in pressure and temperature while it decreased with increase in fines fraction, pH, filtration time, and solids concentration. A total of 82 experimental results were used to develop a feed forward back-propagating artificial neural network (ANN) model. The model had R² values over 0.9 for both the training and the testing datasets, indicating the goodness of fit. Sensitivity analysis performed using the ANN model indicated that filtration time and pH were the most significant variables influencing filtrate flux.     

易门铜业Φ2.4×3.6 m球磨机磨矿介质配比优化研究

针对易门铜业Φ2.4×3.6 m球磨机装补球制度不合理、磨矿产品细度低、分级机效率偏低及循环负荷偏高等问题,基于矿石的力学性质及粒度组成分布情况,采用段氏球径半理论公式对推荐初装介质配比进行计算,最终确定初装球方案为Φ80 mm∶Φ60 mm∶Φ50 mm∶Φ40 mm=30%∶25%∶25%∶20%。将推荐钢球配比方案与现场方案进行实验室磨矿对比试验,结果表明：与现场方案相比,推荐方案的过粗级别+0.150 mm产率降低了2.38个百分点,磨矿细度（-0.074 mm占比）提高了5.14个百分点,中间级别-0.150+0.010 mm产率提高了1.08个百分点,磨矿技术效率增长了3.39个百分点。由此可见,采用推荐初装钢球配比作为易门铜业Φ2.4×3.6 m球磨机磨矿介质,其优化效果明显。     

Investigation on grinding wear behaviour of austempered ductile iron as media material during comminution of iron ore in ball mills

An attempt has been made to assess the grinding wear behaviour of austempered ductile iron (ADI) as media material in comminution of Kudremukh haematite iron ore in a ball mill. Spheroidal graphite (S.G) iron balls were austenitised at 900°C for one hour and austempered at 280°C and 380°C for different time durations. These materials were characterized by measuring hardness, carrying out X-ray diffraction analysis, studying microstructures using scanning electron microscope (SEM). Grinding wear behaviour of ADI was assessed during wet grinding at different pH of the mineral slurry. The wear resistance of ADI was compared with that of forged En 31 steel balls under similar grinding conditions. It was found that ADI balls austempered at 280°C for 30 minutes which contains lower bainite registered superior wear resistance. It was also noted that the wear resistance of ADI was more at higher pH range of the slurry.     

钢球直径对磨矿的影响

从实验室小型试验和工业试验说明不同球径对磨矿的影响。磨矿时 ,选用合适的球径 ,可提高球磨机的处理能力 ,增加球磨机排矿的新生粒级产出量 ,以及降低钢球的消耗量 ,为浮选作业奠定良好的基础     

半自磨机顽石作为实验室立磨机介质的磨损与磨矿研究

随着半自磨流程在国内大型矿山的日益普及, 对如何处理半自磨机磨矿过程中产生的顽石, 各选厂采用的方式不尽相同.利用半自磨机顽石充当立磨机磨矿介质处理这类顽石并对此开展顽石的磨矿条件试验研究, 包括:磨矿时间、充填率、磨矿浓度和磨矿处理量等条件试验, 以及顽石、钢球磨矿介质对比试验.试验结果表明:半自磨机顽石可以作为磨矿介质在立磨机内使用, 其损耗量相比较于传统钢球的损耗量 (大约0.05 %) 是较大的, 一般在1 %~2 %之间.在磨矿时间3 min、填充率60 %、磨矿浓度65 %、磨矿量5 kg时可获得满足浮选要求的磨矿产品.在磨矿时间3 min、立磨机转速210 r/min、磨矿浓度65 %、磨矿量5 kg、磨矿介质直径10~20 mm、充填率60 %的条件下进行顽石和钢球磨矿介质的磨矿对比试验, 结果表明, 钢球磨矿产品的细度比顽石磨矿高16.72 %, 过粉碎粒级产率高2.35 %, 钢球的磨矿效率大于顽石, 但顽石磨矿产品中0.045~0.038 mm的产率高于钢球磨矿, 说明顽石充当磨矿介质时易使被磨矿物磨细到嵌布粒度的大小, 会使产品粒度分布更合理.      

Influence of cobalt on the attritor milling efficiency of WC-Co powder blends

This work investigates the effect of Co content on the energy-specific WC surface area relationship in attritor milling for slurries in which a constant 22 vol % solids is maintained. It is shown that increases in the Co level result in decreased milling efficiency, although the effect is less pronounced than might be anticipated, particularly at the highest Co concentrations (up to 24 wt %). Comparisons to a recent study on attritor milled WC-Co blends in which a constant 85 wt % solids (22–26 vol %) was maintained show that increased vol % solids also results in decreased milling efficiency. Increases in the Co level and/or the extent of grinding are shown to cause an increase in the apparent viscosity of the slurry. Changes in the vol % solids of the slurry are demonstrated to have an exponential effect on the apparent viscosity. It is expected that the vol % solids will have a dominant effect on viscosity for concentrations greater than about 24 vol %.