Grinding process within vertical roller mills: experiment and simulation

Based on screening analysis, laser size analysis, grindability and rigidity tests of samples collected on line from a cement and a power plant, a simulation of the grinding process in vertical roller mills was carried out. The simulation calculation used a breakage function, B. The results indicate that the breakage function, B, and the selection function, S, in the form of a matrix, can be used to express the probability of the material breaking during the grinding process. This allows the size distribution of the product to be numerically estimated. The simulation results also show that the simulated size distribution curves fit the actual experimental product curves quite well. The model provides a good starting point for simulation of the grinding process. Further research is needed to determine the proper breakage function and the matrix value of the selection function.

Research on new beneficiation process of low-grade magnesite using vertical roller mill

We investigated whether the vertical roller mill can be efficiently used in the beneficiation of low-grade magnesite and whether it can improve upon the separation indices achieved by the ball mill.We conducted experiments involving the reverse flotation and positive flotation of low-grade magnesite to determine the optimum process parameters,and then performed closed-circuit beneficiation experiments using the vertical roller mill and ball mill.The results show that the optimum process parameters for the vertical roller mill are as follows:a grinding fineness of 81.6wt%of particles less than 0.074 mm,a dodecyl amine(DDA)dosage in magnesite reverse flotation of 100 g·t?1,and dosages of Na2CO3,(NaPO3)6,and NaOL in the positive flotation section of 1000,100,and 1000 g·t?1,respectively.Compared with the ball mill,the use of the vertical roller mill in the beneficiation of low-grade magnesite resulted in a 1.28%increase in the concentrate grade of MgO and a 5.88%increase in the recovery of MgO.The results of our causation mechanism analysis show that a higher specific surface area and greater surface roughness are the main reasons for the better flotation performance of particles ground by the vertical roller mill in the beneficiation of lowgrade magnesite.

Roller Screw and Threaded Chain Speed Reducer: An Experimental Evaluation

We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.

Remaining Useful Life Prediction for a Roller in a Hot Strip Mill Based on Deep Recurrent Neural Networks

Accurate estimation of the remaining useful life(RUL)and health state for rollers is of great significance to hot rolling production.It can provide decision support for roller management so as to improve the productivity of the hot rolling process.In addition,the RUL prediction for rollers is helpful in transitioning from the current regular maintenance strategy to conditional-based maintenance.Therefore,a new method that can extract coarse-grained and fine-grained features from batch data to predict the RUL of the rollers is proposed in this paper.Firstly,a new deep learning network architecture based on recurrent neural networks that can make full use of the extracted coarsegrained fine-grained features to estimate the heath indicator(HI)is developed,where the HI is able to indicate the health state of the roller.Following that,a state-space model is constructed to describe the HI,and the probabilistic distribution of RUL can be estimated by extrapolating the HI degradation model to a predefined failure threshold.Finally,application to a hot strip mill is given to verify the effectiveness of the proposed methods using data collected from an industrial site,and the relatively low RMSE and MAE values demonstrate its advantages compared with some other popular deep learning methods.

Model Building of Backup Roller Diameter Effect Rate in 4-High Mill

Software for calculating the strip profile in 4-high hot rolling mill was developed using influence coefficient method. Regularity of backup roller diameter effect rate was studied systematically using the software. The results show that backup roller diameter effect rates decrease versus the increase of strip width, increase significantly versus the increase of backup roller diameter and obscurely increase versus the increase of reduction. The difference between backup roller diameter effect rate and it is reference value increases versus strip width increasing. When backup rollers diameter is set to be 1.64 m and strip width is 1.85 m, the error of strip profile calculated using the model of backup roller diameter effect rate reference value will be 3.55μm. Based on the results, reference values of roller diameter effect rate and six power polynomial fitting coefficients of modification coefficients were determined considering coherent parameters. The high precision model of backup roller diameter effect rate was established. When the model is used to predict strip profile, the accuracy is less than 5.0 μm.

Analysis of Dynamic Characteristics of Forced and Free Vibrations of Mill Roll System Based on Fractional Order Theory

In this paper,the main researches are focused on the horizontal nonlinear vibration characteristics of roll systems for rolling mill,mainly including the study of forced vibration and free vibration of the roller.Firstly,the nonlinear damping parameters and nonlinear stiffness parameters within interface of the rolling mill are both considered,and a fractional-order differential term is also introduced to model the horizontal nonlinear vibration.Secondly,the averaging method is introduced to solve the forced vibration system of the mill roll system,and the amplitude-frequency characteristic curves of the system are obtained for different orders,external excitation amplitudes,stiffness and fractional order coefficients.Thirdly,the amplitude-frequency and phasefrequency characteristics of the free vibration of the mill roll system are investigated at different fractional orders.Then,the accuracy of the averaging method for solving the dynamic characteristics of the system is verified by numerical analysis,and the effect of the fractional differential term coefficients and order on the dynamic characteristics of the roll system are investigated.Finally,the time-frequency characteristics and phase-frequency characteristics of free vibration systems at different fractional orders are studied.The validity of the theoretical study is also verified through experiments.

Optimal Design of Tapered Roller Bearings Based on Multi⁃Physics Objectives Using Evolutionary Algorithms

Rolling element bearing is the most common machine element in rotating machinery.An extended life is among the foremost imperative standards in the optimal design of rolling element bearings,which confide on the fatigue failure,wear,and thermal conditions of bearings.To fill the gap,in the current work,all three objectives of a tapered roller bearing have been innovatively considered respectively,which are the dynamic capacity,elasto-hydrodynamic lubrication(EHL)minimum film⁃thickness,and maximum bearing temperature.These objective function formulations are presented,associated design variables are identified,and constraints are discussed.To solve complex non⁃linear constrained optimization formulations,a best⁃practice design procedure was investigated using the Artificial Bee Colony(ABC)algorithms.A sensitivity analysis of several geometric design variables was conducted to observe the difference in all three objectives.An excellent enhancement was found in the bearing designs that have been optimized as compared with bearing standards and previously published works.The present study will definitely add to the present experience based design followed in bearing industries to save time and obtain assessment of bearing performance before manufacturing.To verify the improvement,an experimental investigation is worthwhile conducting.

Discussion on Lightning Protection Design of "Feilongzaitian" Roller Coaster of Fangte in Zigong

The lightning protection design of "Feilongzaitian" roller coaster of Fangte in Zigong was discussed, and the lightning protection measures of "Feilongzaitian" roller coaster were analyzed from the aspects of direct lightning protection, grounding and lightning electromagnetic impulse protection.

Analysis of Vibrations of Roller of the Polymer Composite Coating Equipment on Stitches of Tarpaulin Materials

The article presents a structural diagram and the principle of operation of the installation of a sewing machine for applying a polymer composition to the stitch lines of tarpaulin materials. The calculation schemes and the mathematical model of oscillations of the axis of the composite roller during the application of the polymer composition along the lines of tarpaulin materials are presented. Based on the numerical solution of the problem, the regularities of roller oscillations are presented. The main parameters of the system are substantiated.

基于板带厚度误差PI反馈的轧机辊缝调节方法

针对轧机刚度系数未知波动影响板带厚度控制精度的问题,提出了基于板带厚度误差PI反馈的轧机辊缝调节方法。首先,建立轧机弹跳方程、液压辊缝调节动态方程,以及从辊缝设定值到板带出口厚度的动态方程;其次通过测厚仪和测压计,获取轧机出口处的板带厚度,以及轧机施加的轧制压力;然后设计基于板带厚度误差量PI反馈的辊缝大小的设定值,同时引入比例反馈增益系数与积分反馈增益系数的单参数化设计;最后将辊缝大小的设定值输入轧机液压辊缝调节系统进行辊缝调节,最终形成一套完整的轧机辊缝调节方法。该方法提高了轧制参数的预设定精度,大大减小了轧机刚度系数波动对板带厚度控制精度的影响,从而提高了板带厚度精度。

Roller转子密炼机聚合物流体的混沌混合特性

建立了Roller转子密炼机二维有限元模型,利用网格重叠技术,对密炼机流体的流动过程进行了数值模拟。利用粒子示踪技术,采用4阶Runge-Kutta法计算了不同转数和不同流体粒子释放位置的密炼机Poincaré截面、平均对数线拉伸及Lyapunov指数等混沌混合参数。从非线性混沌理论的视角研究了Roller转子密炼机的混沌混合机理。结果表明,在双转子周期性扰动的作用下,聚合物流体在密炼机内被反复地拉伸、折叠,且啮合区的Poincaré截面出现了典型的"马蹄形"混沌结构。随着混合周期的增加,平均线拉伸以指数形式增长,且Lyapunov指数大于零。Roller转子密炼机流体具有混沌对流的特征。

安徽某镜铁矿石磨前辊压—预选抛废工艺研究

安徽某低硫磷酸性镜铁矿石中主要有用成分为Fe,主要脉石成分为SiO2,以镜铁矿形式存在的铁占总铁的96.11%,铁矿物呈稠密、中等稠密、稀疏—星散等不同密集程度的浸染条带状嵌布,部分解离较容易。为解决细粒尾矿产生量过大对尾矿库库容的过快消耗,并降低选矿生产成本,对原入磨前矿石进行了高压辊磨机闭路辊压—强磁选抛废可行性研究。结果表明,立环脉动高梯度磁选机2次粗选抛废,可抛出产率22.33%的废石,得到铁品位42.99%、铁回收率96.03%的预选粗精矿;预选尾矿中隔出的粗粒(+0.3 mm)可作为建筑用砂出售。在原磨矿前增设高压辊磨机闭路辊压—立环脉动高梯度磁选机湿式粗粒预选抛废—废石捞砂流程,不仅可以显著减少入磨矿量,降低入磨粒度,提高入磨品位,减少细粒尾矿产生量,还可以获得大量的建筑用砂,增加企业的经济效益。

磨粉机磨辊表面磨损特征提取与识别

目的:预测磨粉机喷砂辊使用寿命。方法:通过搭建的图像采集系统对磨辊表面的磨损图像进行采集,基于灰度共生矩阵算法,获得磨辊磨损周期内的二阶矩、熵值、对比度和相关性等纹理参数,将获得的纹理特征参数输入构建的基于粒子群算法(PSO)的LS-SVM模型,最终对喷砂辊的磨损寿命进行预测。结果:粒子群算法可以很好地优化LS-SVM的惩罚因子和核参数,PSO-LS-SVM算法要远远优于LS-SVM算法模型,采用PSO-LS-SVM算法可以准确地识别磨粉机喷砂辊表面的磨损状态。结论:该系统可以准确地预测喷砂辊的使用寿命。

高压辊磨技术在铜冶炼渣选矿中的应用研究与探索

采用磨矿浮选工艺回收铜冶炼渣中有价金属元素时普遍存在磨矿能耗偏高、磨矿细度偏低、浮选尾矿有价金属含量偏高的问题。高压辊磨技术利用层压理论,物料在辊压时使矿物沿解离面产生裂纹,能够降低磨矿功指数,提高矿石的可磨性。国内外关于高压辊磨技术在铜冶炼渣选矿中的应用开展具体试验研究的较少。通过对某铜冶炼企业的冶炼熔炼渣开展高压辊磨试验,结果表明,高压辊磨设备能明显降低碎磨物料的粒度、增加入磨物料细粒级含量,物料邦德功指数下降幅度达到20.26%,物料可磨性得到较大改善。在此基础上又进行了磨矿、浮选试验,对试验进行对比,高压辊磨后的物料较常规破碎物料在相同磨矿条件下磨矿细度提高8.68个百分点,有价元素金、铜浮选回收率比常规破碎磨矿浮选分别提高了1.80、1.23个百分点,回收率提高显著。研究表明,高压辊磨技术在铜冶炼渣选矿中具有较好的应用价值。

Young Chinese Baker Rocks “Bread Olympics”

A young Chinese baker became a world champion by pursuing his passion and working hard to overcome challenges.Adancing lion,giant panda,roller coaster,and a merry-go-round in eye-popping shapes-when these elements are grouped together,what kind of magic can happen?Winning magic if you are Gong Xin,a Gen Z baker from China who made a one-meter-high artistic creation using all of these elements.He won the ninth World Bread Competition(Mondial du Pain)as a result.Many Chinese found it hard to believe what he had done after seeing pictures.“This is virtually a work of art,”and“it is equivalent to a foreigner taking first place in a dumpling-making contest in China,”were some of the many online comments.As the host of the competition,France,famous for its bread-making techniques,was beaten into second place,leaving the French media shocked that a Chinese baker had won the famous world bread contest.

安徽某铁矿高压辊磨系统优化试验

安徽某选厂为提高处理量,以全铁品位35.17%的中碎产品为试样,进行了2种不同方案的高压辊磨系统优化试验研究。中碎产品全部预先筛分—筛上干选—辊磨试验不同筛孔尺寸预先筛分试验结果表明:给矿中细粒级越少,越有利于新生成-5 mm粒级产品,预先筛分筛孔尺寸为5 mm时,新生成的-5 mm粒级含量最多,达57.99%。中碎产品部分预先筛分—筛上产品干选合并未筛分给矿高压辊磨试验结果表明:随着中碎产品分矿比例的降低,辊压给矿中-5 mm粒级含量降低,新生成-5 mm粒级含量增加;当分矿比为3∶1时,新生成的-5 mm粒级含量最高,为45.36%。试验结果对比表明,采用全部预先筛分—筛上干选—辊磨试验方案指标最好,较中碎产品直接进行高压辊磨,新生成-5 mm粒级含量提高25.47个百分点。

白象山选矿厂提高产能优化实践

白象山选矿厂为了进一步提高生产效率和产能,针对精矿产品质量、生产作业率等指标进行了生产流程优化,提高设备利用率,采用先进生产设备等研究。通过循环使用淘洗机尾矿溢流水,减轻了尾矿大井负荷,提高了磁选机的选别效果,同时优化湿式筛分预选工艺筛孔尺寸,提高了选厂处理能力;通过优化高压辊辊缝及频率等参数,使用新型侧挡板,延长了高压辊辊面的使用寿命,提高了设备利用率;通过使用凿岩台车、深孔钻机等智能采矿设备,改善了选厂给矿状况。现场生产实践表明,通过上述措施优化,有效提高了白象山选厂的产能。

内蒙古某铁矿石选矿试验研究

为了高效开发利用内蒙古某铁矿石资源,在矿石工艺矿物学性质研究的基础上开展了高压辊磨—湿式磁选抛尾—塔磨—磁选全流程试验研究。结果表明:原矿经高压辊磨制得-1mm粒级粉矿,在400mT磁场条件下湿式磁选抛尾,获得了全铁品位36.63%、磁性铁品位为31.31%的湿式预选精矿,湿式预选精矿经塔磨磨至-0.030mm占95%,经1粗1精磁选获得了铁品位为65.78%、回收率为66.22%的铁精矿,试验结果可以为该铁矿石选别流程确定提供依据。

内蒙古某低品位铁矿选铁工艺试验

内蒙古某低品位铁矿全铁品位为20.33%、磁性铁品位为13.05%,为开发利用该铁矿石并确定合理的选铁工艺流程,在矿石性质研究的基础上,进行了原矿高压辊磨预选—预选精矿阶段磨矿—单一磁选工艺,高压辊磨预选—预选精矿阶段磨矿—磁选淘洗联合工艺,高压辊磨预选—预选精矿阶段磨矿—磁选浮选联合工艺3种工艺方案的试验研究对比。试验结果表明:3种工艺方案均可获得铁品位65%以上的铁精矿,前2种方案的选矿指标相当,且远优于方案3,而方案2较方案1可明显放粗二段磨矿细度,因此确定采用原矿高压辊磨预选—预选精矿阶段磨矿—磁选淘洗联合工艺作为该矿选铁的最佳工艺,最终获得了铁精矿产率19.07%、全铁品位65.50%、铁回收率61.50%的选别指标。

一种液驱冷轧机辊热凸度动态SVR预测模型

辊热凸度是当轧件发生变形或因摩擦作用生成热量而引起轧辊温度上升并由此产生轧辊外形尺寸改变的现象。为了降低液驱冷带轧机辊随温度的变化影响,综合分析了辊热凸度因素引起的变形效果差异性。选择液驱轧机作为测试对象,从热凸度作用原理方面考虑,同时根据实际获得的监测参数探讨了辊热凸度情况受到外部因素的影响程度。建立基于支持向量机的液驱冷带轧机辊热凸度动态预测模型,该模型结构较简单,并且可以获得优异的性能。对于辊热凸度的预测表现出了明显的优势。利用SVR模型以及交叉验证的方式确定参数,结果形成了一致的变化趋势与周期性特征。拟合优度与均方根误差分别为0.84与0.0153,获得了较理想的预测性能。该研究对提高板材的控制精度以及轧机节能具有较好的实际指导意义。