我国振动筛理论研究及技术应用进展

鉴于振动筛在我国现代矿物加工行业中的重要性,结合近年来我国振动筛理论研究及技术应用进展,概述了我国振动筛振动理论研究热点,阐述了我国振动筛筛分机理与筛分方法研究现状,总结了我国振动筛技术研究的创新成果,介绍了各种先进技术在振动筛上的应用情况,同时针对我国振动筛理论研究及技术应用过程中存在的各种亟待解决的问题,提出了相应的对策和建议。最后结合我国振动筛行业面临的新形势,对其未来发展方向进行了展望。     

全密度聚乙烯装置振动筛堵孔机理与解决对策

目前,潮湿细粒物料的堵塞筛孔是筛分作业中经常遇到的难题,造成筛孔堵塞的因素有很多。本文论述了国内线性低密度聚乙烯装置挤压机组中振动筛在实际筛分过程中经常出现的多种问题,主要针对筛孔堵塞这一问题作出了详细的分析,由于物料特性、物料表面水分的含量以及筛网结构等原因造成筛分过程中物料容易黏附在筛网上或者一些筛孔被粒径大或形状不规则的物料颗粒堵塞,导致筛分效率下降,甚至有时候需要停机进行清理,严重影响了筛分作业的顺利进行。为了解决这一问题,对振动筛筛网结构进行优化设计,通过提高振动筛的振动强度来减缓筛网的堵塞情况,提高筛分效率,同时采用弹簧装置降低振动筛带来的噪声,体现了环保要求。并指出了标准化、系列化、通用化、低噪声是细粒难筛物料筛分机械的发展趋势。     

单层振动筛优化改造为双层振动筛

重型振动筛原设计为单层筛,通过在筛框内加装一层上筛板,并增加振幅,从而实现能够筛分不同物料与粒径的振动筛。对改进修理方法,进行探讨。     

旋转振动筛在活性炭筛分中的应用

筛分是活性炭生产过程中一道重要的工序。筛分设备性能的好坏对颗粒活性炭的质量和得率有很大影响。目前国内采用的筛分设备主要有滚筒筛、摇动筛、往复式振动筛、电磁筛等。这些振动筛的运动规律一般都只是水平和垂直方向运动的合成,其中以往复式振动筛效果较好,因此应用较多。     

振动筛使用须注意的几个问题

正筛分是复合肥生产工艺过程中不可或缺的一道工序。筛分可利用的机械设备种类很多,在线生产应用较为常见的大致有两种,一种是回转筛,另一种是电动振动筛(简称振动筛)。目前,常见的振动筛是在电机出轴端装有偏心块,运行中产生离心力,使筛体产生振动。这种振动电机安装斜度一般控制在10°~18°。振动筛运行受多方面影响,存在如下问题:(1)依承着重力推让原理,即质量小的让位于质量大的,小颗粒让位于大颗粒,筛分过程中存在挤压、碎坏、磨琢现象;(2)振动筛服务于复合肥在线生     

尿素筛分装置改型总结

尿素筛分装置原采用振动筛进行筛分小颗粒和粉尘尿素,由于振动筛振动频率高,对粒子强度要求高,以及因过筛量较大,料层厚度过高等原因造成筛分效果不理想。为此,将振动筛改型为双层摇摆筛,扩大过筛面积,降低料层厚度,提高筛分效果,以提升尿素产品外观质量。     

2SBH2665型振动筛技术改造

马钢焦化新筛运焦系统采用2SBH2665型振动筛筛分混合焦,两座筛贮焦楼各安装两台振动筛,一开一备,要求每台振动筛焦炭处理量300t/h,筛分效率不小于90%。由于2SBH2665型振动筛设备设计不合理,造成振动筛故障频繁：振动筛箱体多处开焊、倾斜,激振器轴承损坏,走行万向联轴节断裂,走行轨道基础松动等。此外,由于振动筛下层筛板材质选用不合理,磨损快,导致焦炭筛分不合格。     

燃煤电厂应用筛面振动筛的理论探讨

根据概率筛分，且经单层和多层筛面煤粒筛分理论论证后而设计的筛箱固定，筛面振动的筛面振动筛，符合一般的振动筛运动学和运动学原理，这种筛大大减小了掺振质量，减轻了振动载荷和对基础的冲击，降低了噪音，节省了功率，可采用小型振动筛技术制造大型振动筛从而解决了大型振动筛的诸多技术难题，是一种有发展前途的方向性系列化产品。     

晋宁磷矿筛分工艺优化改造研究

晋宁磷矿近年生产的磷矿石含泥量大,筛分时易堵塞筛孔,筛分效率低,生产出的黄磷矿产率仅为4.96%;为了提高黄磷矿产率,对筛分工艺流程中的格筛和直线振动筛进行了改造,提高了筛分效率和有效筛分面积,黄磷矿的产率提高到了12.27%。对类似选厂直线振动筛的工艺参数优化及改造具有一定的借鉴作用。     

复混肥生产中振网筛结构的改进

探讨复混肥生产筛分设备的选型与结构的改进。对传统筛分设备(偏心振动筛)与单轴惯性振网筛性能进行对比;对新型振网筛使用中存在的结构缺陷进行研究与改进。使用振网筛后,筛分设备的故障减少,备件费用与电费降低。     

Separation of ultrasonic contributions and energy utilization characteristics of ultrasonic regeneration

The method of applying ultrasound to silica gel regeneration process has been proved to be able to improve regeneration efficiency and reduce regeneration temperature. The average regeneration rate can be increased by 10% and the benefits should owe to the special “vibration effect” and “heating effect” induced by ultrasound. In this article, a dynamic one‐dimensional mathematical model, validated by experiments, has been developed. It is then used to investigate energy utilization efficiency of the ultrasonic regeneration and respective contribution ratio of the two ultrasonic effects. The results show that the contribution ratio of vibration effect dominates and the energy utilization efficiency of silica gel regeneration with ultrasound can be 1% higher. The ultrasonic regeneration is more energy‐saving when the contribution ratio of vibration effect is greater. The results also show that the enhancement of regeneration brought by ultrasound is not a simple sum of their respective contribution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1843–1853, 2014     

ISB智能振网弧形筛应用

弧形筛的筛分效果直接影响最终产品的质量、产率以及筛下水的后续处理。邢台矿选煤厂为取得良好的使用效果,从筛分效率、平均分配误差及总错配物含量等方面,对击打弧形筛和新型的ISB智能振网弧形筛进行了比较。结果表明,智能振网弧形筛具有更好的筛分效果。     

Flow properties of polymer melt in longitudinal ultrasonic‐assisted microinjection molding

Microplastic parts are usually fabricated by microinjection molding (µIM) which is an effective and low cost method. But the defects, such as short shot, often appear during fabricating plastic parts with high aspect ratio structures or complex shapes. a longitudinal ultrasonic‐assisted microinjection molding (LUµIM) method effectively improve the molding quality. In the paper, the mechanism that the ultrasonic vibration impacts on the polymer melt is investigated. Considering from the point view of energy effect, mechanical energy transmission, and mechanical energy conversion, which are divided from the energy of ultrasonic vibration, are analyzed. The model of energy transmission and a new rheological equation including the parameters of ultrasonic vibration are established to describe the rheological behavior of polymer melt in microcavity. The simulation results show that the ultrasonic vibration improves the viscosity field and the velocity field in complex shaped microcavity, and leads to a better filling capability and uniformity of the polymer melt. This research achievement can be used to guide the process flow and parameter selection of LUµIM. POLYM. ENG. SCI., 57:797–805, 2017. © 2016 Society of Plastics Engineers     

Influence of ultrasound on the processing and structure of polypropylene during extrusion

The effects of ultrasonic irradiation on extrusion processing and crystallization behavior of polypropylene (PP) are examined. The results show that appropriate irradiation intensity can prominently decrease die pressure and apparent viscosity, increase output, reduce extrudate swell, and improve apparent quality of PP. DSC and WAXD analysis demonstrate that the crystalline structure of PP is changed and the content of the β crystalline increases through ultrasonic vibration. Special effects can be induced by ultrasound, such as strong stress, shatter and vibration, which alter the growth of PP crystals and may favor a special crystal transformation (α → β).     

Study on ultrasonic vibration-assisted adhesive bonding of CFRP joints

As adhesive bonding does not disrupt the continuity of the fiber integral, it has become an important bonding method of CFRP (carbon fiber-reinforced plastics) joints. Regarding the quality problems in the traditional adhesive bonding process, i.e. the low and unstable adhesion strength, a novel ultrasonic vibration-assisted adhesive bonding method for CFRP joints is proposed. In this method, extra force caused by ultrasonic vibration is introduced into the bonding process to reinforce it. The strengthening mechanism is then analyzed. According to our study, it is found that: (1) ultrasonic vibration can improve the adhesion strength and stability by 52 and 66% in the test. (2) The strengthening mechanism is summarized as: high-frequency vibration contact between adhesive and wall is produced under ultrasonic vibration, which forms better contact; adhesive is driven to penetrate into the surface roughness of the bonding area under ultrasonic vibration, which increases the effective bonding area.     

Ultrasonic-Assisted Convective Drying of Apple Slices

A promising approach for the application of ultrasound to assist in convective food drying was developed and tested in this study. The application of ultrasound is based on the transmission of ultrasonic energy as a combination of airborne contacts and through a series of solid contacts between the ultrasound element and the product tray as the ultrasonic vibration transmitting surface. A computer-based ultrasonic drying setup was built to allow continuous recording of the process variables in real time and enabled simulation of dehydration to be accomplished under controlled conditions over a range of drying parameters. Apple slices were dried using the drying setup to study the influence of ultrasound in combination with conventional hot air drying on drying kinetics and product quality.

The results from this work indicate that ultrasound can simultaneously be applied to accelerate the processing time (i.e., reduce energy consumption and increase production throughput) in conventional hot air drying without compromising product quality. It appears that the magnitude of influence of ultrasound to enhance the air-drying process depends on the process variables employed. In particular, the ability of ultrasound to improve the efficiency of the convective drying process appears to be maximized when using low temperature and high ultrasonic power level. This finding maybe very useful when there is a need to effectively dehydrate heat-sensitive products or when shorter drying times are required in order to achieve better retention of the functional and nutritional properties of the product.     

分子筛清洁交换工艺的开发与应用

分子筛交换工艺是利用铵盐对分子筛改性的重要工序。排放的废液含有大量的氨氮,即增加了分子筛的生产成本,同时对废液要进行处理,也增加了装置废水排放压力。通过生产污水对NaY分子筛预交换的探讨,结合装置生产的工艺情况,摸索适合分子筛生产的新型清洁化交换工艺,减少了30%的铵盐使用量,降低分子筛生产过程中高氨氮废液排放量,提高装置清洁化水平。     

Experimental study on laser assisted ultrasonic elliptical vibration turning (LA-UEVT) of 70% SiCp/Al composites

SiC_p/Al composites are more and more used in aerospace, military industry and other industries. However, the surface integrity of materials is poor, and the cutting force is large as the anisotropy of materials in the traditional machining (TM) process, which hinders the application of ceramic particle reinforced metal matrix composites. With the requirement of high dimensional accuracy, high efficiency and low damage for materials in these fields, non-traditional machining technology has become a research hotspot. Laser assisted machining (LAM) is a non-contact special machining method. Its advantages in machining SiC_p/Al composites have been proved by experiments, but there are still processing defects such as thermal cracks. Therefore, to further improve the machining quality of 70% SiC_p/Al composites with high volume fraction, a new machining method combining ultrasonic elliptical vibration turning (UEVT) and laser heating assisted turning (LAT) is proposed. High frequency intermittent machining and the adjustment of laser temperature influence on materials can be realized by adjusting the ultrasonic amplitude. Combining the characteristics of the two processing techniques, the feasibility study of the new machining method was studied by turning experiments. In this paper, compared with TM and LAT, the removal mechanism of materials and the effects of different laser heating temperatures and ultrasonic vibration on cutting force, surface quality, subsurface damage and chip morphology are explored. The results show that LA-UEVT can effectively reduce the cutting force and surface roughness, improve the plastic removal ability, and inhibit surface and subsurface damage. And the material removal process is mainly in the form of small particle crushing and particle pressing, which improves the stability of cutting force in the cutting process.     

Machinability improvement in three-dimensional (3D) ultrasonic vibration assisted diamond wire sawing of SiC

Ultrasonic vibration assisted (UVA) cutting has been proven to be an effective method for improving machining behavior in processing hard and brittle materials. However, there is no investigation on three-dimensional (3D) UVA diamond wire sawing (DWS). In this paper, a novel 3D vibration assisted DWS system is developed. A theoretical model is established for predicating sawing forces. Experiments have been carried out on DWS of silicon carbide (SiC) ceramics. The effects of ultrasonic vibration assistance, input vibration direction and cutting parameters on sawing forces, surface morphologies and tool wear are studied respectively. The simulation results indicate that elliptical motion in 3D space can be obtained for the diamond abrasive. The experimental results reveal that the proposed model has sufficient accuracy to predict sawing forces. It is demonstrated that sawing forces can be reduced by ultrasonic vibration assistance either in vertical direction or in longitudinal direction. However, 3D ultrasonic vibration condition provides the lowest sawing force because of the combined advantages. Due to intermittent cutting mode, sawing forces are decreased by 31%, 40% and 29.8% in X, Y and Z direction, respectively. Because debris can be removed more easily from the contact surface and large ductile smooth area can be obtained, 3D ultrasonic vibration assistance generates higher surface integrity than that of traditional sawing process. Moreover, the wear of diamond wire saw can be effectively decreased.     

Ultrasonic vibration-assisted laser engineering net shaping of ZrO2-Al2O3 bulk parts: Effects on crack suppression,microstructure, and mechanical properties

Laser additive manufactured zirconia-alumina ceramic (ZrO₂-Al₂O₃) parts demonstrate severe problems resulting from cracking and inhomogeneous material dispersion. To reduce these problems, we propose a novel ultrasonic vibration-assisted laser engineered net shaping (LENS) process for fabrication of bulk ZrO₂-Al₂O₃ parts. Results showed that the initiation of cracks and the crack propagation were suppressed in the parts fabricated by LENS process with ultrasonic vibration. For the parts fabricated without ultrasonic vibration, the sizes of cracks decreased with the increase of laser power. Scanning electron microscope analyses proved that the introduction of ultrasonic vibration was beneficial for grain refinement and uniform material dispersion. Due to the suppressed cracking, refined grains, and homogenized material dispersion, the parts fabricated with ultrasonic vibration demonstrated better mechanical properties (including higher microhardness, higher wear resistance, and better compressive properties), compared with the parts fabricated without ultrasonic vibration.