碎磨功耗理论的发展与展望

矿山碎磨作业电力消耗占据全球总电力消耗的近2%,同时也是矿山生产中能耗最高的作业单元。碎磨流程能耗预测是碳排放和能源管理、矿山生产管理和数字矿山建设必不可少的重要环节。对基克、雷廷格和邦德等关于碎磨功耗的三大经典理论进行了回顾,着重介绍了邦德理论的发展历程并讨论了其在现代碎磨流程生产实践中应用的局限性。对上世纪70年代以来陆续提出的多种新的碎磨功耗理论进行了介绍,并讨论对比了邦德理论模型和新的理论模型对碎磨流程单位能耗的预测精度。总结了碎磨功耗理论模型在碎磨工艺流程设计与设备选型、碎磨流程运行效率评估与优化、金属矿山生产能力预测与管理以及金属矿山碎磨能耗碳评估模型等4个方面的应用价值。尽管该领域自主知识产权上的不足对我国数据安全和矿山生产造成了障碍,但随着国内矿山数字化智能化建设的飞速发展,我国碎磨功耗理论模型必将在较短时间内迎来显著的突破。

降低660MW机组深度负荷期间磨煤机电耗

景德镇电厂#1、#2机组在2011年分别投入运行,经过近几年运行和调整,机组安全性和经济性得到较大提高,由于电网峰谷负荷相差大,为提高在低负荷期间机组经济性,施行在低负荷时三台磨煤机运行,本文就三台制粉时的炉内稳燃、磨组运行方式、运行措施、经济性等进行探讨。希望对同类机组在低负荷期间,制粉系统优化调整有一定的参考和借鉴作用。

水泥熟料易磨性的估算

水泥熟料的易磨性是从测定粉磨熟料和石膏时使产品达到一定细度所需的功耗来求得。这一功耗值与工厂的结果相当吻合。作者已把由粉磨试验测得的单位功耗与显微测定结合普通熟料分析结果所得估算值建立了关系式。用熟料光片在普通光学显微镜上,很容易进行显微测定。不同工厂熟料的易磨性可以进行估算,但对某些熟料(估算时)要特别小心。

振动磨机操作参数的确定及粉磨功耗的计算

通过对振动磨机正常工作时介质运动状态的分析,建立一个简单的介质运动学模型,并根据所建立的模型确定振动磨机的一些重要参数,如磨简直径、振幅、介质填充率等最佳取值范围,从而使振动磨机获得最佳粉磨效果和降低能耗。

精浆机精浆机理的研究

精浆机是机械制浆系统中的重要设备 ,它直接影响着纸的品质和纸机的运转能力。本文通过对精浆效果各种影响因素的深入分析 ,阐明了精浆机的精浆机理为通过刀齿间有效缘角负荷及有效表面负荷 ,对纤维进行有效处理 ,从而达到精浆的目的 ;基于有效缘角负荷理论 ,给出了精浆机主要参数的确定方法 ;通过分析比较 。

好砚 集砚 说砚

吾少好弄翰,60年前,时墨膏、墨汁的生产尚属初生期,书画挥运无不以砚为用,以砚为基,作'人磨墨,墨磨人,磨墨人'之无尽止的耗磨时日。砚多为石,'石不能言最可人',这正是在这日转星移的悠悠岁月中,产生出的伴侣般的依恋情结。20世纪之前,中国文人讨生活是离不开砚的。'吾生无田食破砚',农之生计在于田,儒之生计在于砚。砚、田是等量齐观的。

Field investigation on effects of railway track geometric parameters on rail wear

Rail wear has dramatic impact on track performance, ride quality and maintenance costs. The amount of rail wear is influenced by various elements among which geometric parameters play an important role. The amount of wear in Iran’s railway lines and its imposed maintenance costs oblige us to make modifications on the various geometrical parameters. In order to ensure the effectiveness of these changes, it is necessary to investigate these parameters and their effects on the wear. This research is aimed at studying the effects of different track geometrical parameters on the vertical and lateral wear by conducting a three phase field investigation. The first phase was carried out at the switches of a station, the second phase at a straight line, and the third at a curved line out of the station. The results obtained are analyzed and the role of each track geometrical parameter in the rail wear is discussed. Recommendations for prevention or reduction of rail wear are presented.

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.

Numerical analysis of grinding power consumption of a vertical planetary mill

Planetary wheel rolling on a coal-bed was simplified as rigid wheel rolling on the coal-bed with a rigid base when a Ver- tical planetary mill(VPM)is running.Based on our analysis,we conclude that the Bekker formulation for computing rolling resis- tance is not applicable to calculate directly the rolling resistance of the wheel.According to the principle of the Bekker apparatus,pressure-sinkage curves were obtained by tests on a piece of mono-axial consolidation apparatus used in soil-mechanics.The de- formation modulus of the coal-bed was calculated using elastic mechanics.A finite element model of the planetary wheel coal-bed was built up by the use of a rigid and a Drucker-Prager material model in LS-DYNA.According to the simulation results,the wheel rolling resistance,the grinding power consumption and the motor power of the mill were calculated and the mistake in the initial design of the mill was modified.The simulation results agree well with the results of the semi-industrial tests.

Wheel wear comparison between motor car and trailer of intercity train

To analyze wheel wear discrepancy between motor car and trailer of an intercity train,a novel wheel wear rates calculation model was proposed,which was composed of the intercity train dynamics model,wheel-rail three-dimensional rolling contact FEM model and the wear model.The simulated results were contrasted with measured results in field test.The simulated results showed the motor car wheels had larger rotation rate and longitudinal creepage than the trailer wheels.Meanwhile,the motor car wheels encountered larger vertical forces and longitudinal forces from bogie because of the heavier car body and the impact of traction torque.The traction torque acting on motor car wheel could increase the slip rates in the rear part of wheel contact patch and weaken the spinning phenomenon of relative slip.Larger contact pressure and slip rates caused the higher wear rates of motor car wheel than those of trailer wheel.The overall trends of wheel wear depth in simulated and tested results were similar.And they both showed the motor car wheel encountered the more serious wear than the trailer wheel.These models can be used to study the effect of the traction characteristics curves on the wear of wheel.

Energy Consumption in Comminution of Mica with Cavitation Abrasive Water Jet

We have studied the efficiency of energy consumption in the comminution of mica powder with cavitation abrasive water jet technology. The energy required to create new surfaces in the comminution of mica powder with cavitation abrasive water jet was calculated,in order to estimate its efficiency of energy consumption. The particle size distribution and the specific surface area were measured by applying a JEM-200CX transmission electron microscope and an Autosorb-1 automatic surface area analyzer. The study results show that the efficiency of energy consumed in creating new surface areas is as high as 2.92%,or 4.94% with the aid of cavitation in the comminution of mica powder. This efficiency will decrease with an increase in the number of comminutions. After three comminutions,the efficien-cies will become 1.91% and 2.29% for comminution without cavitation and with cavitation,respectively. The abrasive water jet technology is an effective way for comminution of mica powder.

火力发电机组制粉系统经济优化调整分析

600MW机组是我国当前电厂的主力机组,磨煤机电耗是电厂经济调整中的重要指标之一。进行磨煤机的优化,对提高燃烧效率、稳定安全运行具有重要意义。本文针对景泰电厂600MW锅炉中速磨煤机的运行情况进行分析、试验,进而针对降低制粉系统、一次风机电耗,为锅炉经济运行提供参考。

Experimental study on expansion and contraction of unsaturated porous asphalt mixture exposed to freeze-thaw cycles

The expansion and contraction of an open-graded friction course(OGFC)with a nominal maximum aggregate size of 13.2 mm(OGFC-13)with three air void contents(AVCs)and six saturation degrees(SDs)exposed to freeze-thaw(FT)cycles were measured using strain gauges.Cantabro tests were conducted on OGFC-13 specimens before and after FT cycles to evaluate the degradation of raveling resistance.The effects of SD,AVC,and the number of FT cycles on the expansion and contraction of OGFC-13 and degradation of raveling resistance were analyzed.Results show that OGFC with low water saturation will contract to stability during the freezing process,whereas fully saturated OGFC will contract first and then expand to be stable.OGFC with a medium saturation experienced three stages,namely,contraction,expansion,and contraction,during the freezing process.For the OGFC with a low SD,the decrease in the void content can effectively reduce the low temperature shrinkage.By contrast,for the OGFC with a high SD,lower void content produces more temperature shrinkage at the beginning of freezing and less expansion at the end of freezing.The decreases in SD and AVC can effectively improve the raveling resistance of OGFCs exposed to FT cycles.

What if the ＂Gold Standard＂ Can＇t Be Realized？ Propensity Scoring to Adjust for Attrition in Random Experiments

When it comes to evaluating the effectiveness of interventions, the random experiment is considered the ＂gold standard＂. Randomization is considered the gold standard because it provides a way of decreasing the chance that systematic differences, other than type of intervention, will be obtained between treatment and control groups. What has received little attention in the literature, however, is the fact that even with random assignment researchers may end up facing problems similar to those faced with data from a study that did not use randomization. This is because attrition may result in the values of potentially confounding variables no longer being ＂balanced＂ between （or among） the groups under investigation. This means that in order to estimate the effect of the treatment, one must find some way of adjusting for these potential confounders. Although multiple regression modeling is the way social science researchers typically control for the effects of potentially confounding variables, this paper argues that a modification of multiple regression modeling that uses propensity scores, under some conditions, may provide more parsimonious and better fitting models.

A Takagi-Sugeno-Kang (TSK) Power Model Using Compressed-sensing Sampling

More and more information are needed in social life and commercial production, causing significant pressure on the sampling and too much time spent on signal sampling. Compressed sensing is one emerging hotspot in signal processing which employs a special sampling method to capture and represent compressible signals at a rate significantly below the Nyquist rate. In this paper, a Takagi-Sugeno-Kang (TSK) Model based on compressed-sensing sampling theorem is proposed for grinding power. It is further tested by using the actual production data, and the algorithm performance in grinding power model is also analyzed. The experiments show the validity and effectiveness of the proposed modeling method and its bright application foreground in other fields with similar features, such as power, metallurgy and so on.

Tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced PTFE-PPS composites in sliding system

Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al_2O_3-reinforced polytetrafluoroethylenepolyphenylene sulfide(PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads(100–300 N) at a high linear velocity(2 m/s) using a block-on-ring tester. Addition of the nano-Al_2O_3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al_2O_3 content was 3%(volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al_2O_3 content, independent of the normal load applied.

Development and validation of a model for predicting wheel wear in high-speed trains

In this paper, we present a comprehensive model for the prediction of the evolution of high-speed train wheel profiles due to wear. The model consists of four modules： a multi-body model implemented with the commercial multi-body software SIMPACK to evaluate the dynamic response of the vehicle and track; a local contact model based on Hertzian theory and a novel method, named FaStrip （Sichani et al., 2016）, to calculate the normal and tangential forces, respectively; a wear model proposed by the University of Sheffield （known as the USFD wear function） to estimate the amount of material removed and its distribution along the wheel profile; and a smoothing and updating strategy. A simulation of the wheel wear of the high-speed train CRH3 in service on the Wuhan-Guangzhou railway line was performed. A virtual railway line based on the statistics of the line was used to represent the entire real track. The model was validated using the wheel wear data of the CRH3 operating on the Wuhan- Guangzhou line, monitored by the authors＇ research group. The results of the predictions and measurements were in good agreement.

Experimental analysis of the mechanism of high-order polygonal wear of wheels of a high-speed train

This paper presents a detailed investigation, via field experiment, into the mechanism of high-order polygonal wear of wheels of a new type of high-speed train. The investigation was carried out during the performance acceptance test of the train and its initial commercial operation. The investigation covered the performance acceptance test of 150 000 km and the commercial operation of about 150 000 km. In the performance acceptance test of the first stage of about 70 000 km, at 200-250 km/h with full loading and sometimes overloading by 30%, the serious polygonal wear of 23-order took place on all the wheels of the train, and was measured and analyzed in detail. All the potygonized wheels were re-profiled because the polygonal wear had caused strong vibration and damage to the train parts. After re-profiling, the vibration of the train and track and the wear status of the wheels were measured and analyzed at different test mileages according to the polygonal wear situation of the wheels. The measured vibration of the train includes the accelerations at different positions of a motor car and a trail car. The vibration modes of the key parts of the bogies of the two cars were calculated. Meanwhile, the track resonant frequencies were investigated at the site. The purpose of the above tests and analysis is try to find the frequency of work mode matching the passing frequency of the high-order wheel polygon. The present investigation shows that one of the working models causes the formation and development of the high-order wheel polygonal wear. The growth of this wear was effectively reduced through the frequent changing of the running speed of the train operating on the way back and forth every day.

Effect of gauge corner lubrication on wheel/rail non-Hertzian contact and rail surface damage on the curves

Wheel/rail rolling contact is a highly nonlinear issue affected by the complicated operating environment(including adhesion conditions and motion attitude of train and track system),which is a fundamental topic for further insight into wheel/rail tread wear and rolling contact fatigue(RCF).The rail gauge corner lubrication(RGCL)devices have been installed on the metro outer rail to mitigate its wear on the curved tracks.This paper presents an investigation into the influence ofRGCL on wheel/rail nonHertzian contact and rail surface RCF on the curves through numerical analysis.To this end,a metro vehicle-slab track interaction dynamics model is extended,in which an accurate wheel/rail non-Hertzian contact algorithm is implemented.The influence of RGCL on wheel/rail creep,contact stress and adhesion-slip distributions and fatigue damage of rail surface are evaluated.The simulation results show that RGCL can markedly affect wheel/rail contact on the tight curves.It is further suggested that RGCL can reduce rail surface RCF on tight curves through the wheel/rail low-friction interactions.