Vibratory Screening Research Articles

Dynamics of a vibratory screening conveyor equipped with a controllable centrifugal exciter

Vibratory screening, sieving, and conveying processes are widely used in various industries. Among a great variety of vibration exciters, the unbalanced rotors are the most reliable, simple, and widespread ones. Due to the changeable operating conditions of vibratory equipment, in some cases, there occurs a necessity to control the disturbance (excitation) parameters of the corresponding drives. The primary purpose of this study is to substantiate the design parameters and analyze the dynamic characteristics of the vibratory screening conveyor based on the single-mass oscillatory system, and equipped with the controllable centrifugal exciter. The research methodology consists of several basic stages: developing the conveyor’s dynamic diagram and deducing the differential equations of the system’s motion; designing the machine’s 3D-model and defining its main geometrical and inertial parameters; numerical modeling of the system’s oscillations in the Mathematica software; simulating the conveyor’s operation in the SolidWorks software. The research results present the time dependencies of the conveyor’s working member kinematic parameters at different eccentricities of the unbalanced mass. The main scientific novelty of this research is substantiating the idea and possibilities of implementing the enhanced controllable centrifugal exciter for changing the disturbance (excitation) conditions of the vibratory screening and conveying machines. The proposed ideas and obtained results can be used by researchers and designers of similar equipment while developing control systems for regulating its operational efficiency (performance) in accordance with the changeable loading conditions or technological requirements.

Methodological substantiation of the choice for optimal modes of equipment operation during the stage-wise concentrate removal in iron ores beneficiation

The urgent task of improving the quality of iron ore concentrates was studied. We propose to use the stage-wise removal of the concentrate by combining fine screening, regrinding, and magnetic-gravity separation. Exemplified by magnetite ore from the Stoilensky GOK, a scientific and methodological approach to the search for optimal separation parameters and modes was substantiated. It includes several stages: studying the particle size distribution and release of useful components in the feed product to select classification parameters; a series of experiments on grinding oversize products to diverse sizes; beneficiation of the obtained products by MG separation. To select the optimal parameters of ore preparation, an analysis of the beneficiation efficiency was used, which is calculated according to the Hancock – Luyken criterion. The results of the research are experimental dependences that connect the process parameters of beneficiation with those of fine vibratory screening. For the studied ferruginous quartzite ore processed at the Stoilensky GOK, the obtained dependences can be described by a second-order polynomial with a high accuracy of approximation. The best performance is achieved with a particle size of 0.1 mm: Fetot content in the concentrate is 69.7 %, recovery is 85 %, classification efficiency is 80.4 %. The top size of the product in this case is 0.076 mm, which corresponds to 70-73 % grinding size of –0.045 class.

On the dynamic behavior of an asymmetric self-regulated planetary-type vibration exciter

The problems of studying the dynamic behavior and improving the operational efficiency of various vibratory equipment are currently of significant interest. Special attention is paid to the possibilities of developing the enhanced designs of the planetary-type vibration exciters for the conveying, screening, and sieving machines. The novelty of the present research consists in providing the changeable inertial parameters of the improved planetary-type vibration exciter in order to adjust its operational conditions in accordance with the technological requirements. The mathematical model of the single-mass vibratory screening conveyor equipped with the proposed exciter is developed using the Lagrange-d’Alembert principle. The simulation of the system kinematic and dynamic characteristics under different operational conditions is carried out in the Mathematica software using the integrated Runge-Kutta methods.

Аналіз технічних рішень для зневоднення та класифікації за крупністю мінеральної сировини при тонкому і надтонкому вібраційному грохоченні

The article is aimed at studying new technical solutions for dehydration and size classification in the case of fine and ultrafine vibratory screening of mineral raw materials. It is shown that the moisture content in many products is limited by GOST or temporary regulations. Water is the ballast in their transportation. An excessive amount of water contributes to the freezing of raw materials in winter conditions and causes great difficulties in unloading them from wagons. Traditional methods make it possible to effectively separate only materials with a particle size of more than 1 mm, and reduce the moisture content of the finished product to 18-22%, depending on the size, which does not meet the required standards. It is necessary to reduce moisture to 8-10% or less. In addition, the processing of various raw materials in most cases requires, simultaneously with dehydration, the separation of products of a wide range of sizes. To overcome the adhesion forces between wet particles, different excitations are used, one of which is a combined excitation that provides intensive movement of the liquid and particles relative to each other. Combined means excitation with various combinations of polyfrequency, impulse dynamic effects, and additional effects of various physical fields are also possible. The use of polyfrequency and impulse dynamic (“single impacts”) impacts on the MVG2.0 vibrating polyfrequency screen makes it possible to effectively separate the solid phase from the liquid when treating recycled water with a particle size of 20 microns. At the same time, the residual moisture in the oversize product is no more than 17%. The method of complex dehydration of wet mineral raw materials, combining three dehydration mechanisms (vibration, electrokinetic and vacuum), concentrated in one device, allows, at different initial moisture content of the raw material, to reduce the moisture content from 30 to 16%, from 20 to 14% and from 10 to 6%, t .e. reduce the humidity from 30 to 6% in several stages. These results were obtained for narrow size classes of 0.25÷0.63 mm. The use of modes with "double impacts" and disintegrating elements in the new vibro-impact screen made it possible to reduce the humidity from 30% to 8-10%. The separation efficiency of the +0–0.1 mm class was up to 65–70%. When using an activator, the moisture content of the material is reduced from 30% to 7-9%, and the separation efficiency of the +0-0.1 mm class is increased to 70-75%. Due to the use of a disintegrator over the activator, the moisture content of the oversize product was reduced to 6–8%, while the separation efficiency of the +0–0.1 mm class increased to 75–80%. Experimental method on the model of a vibro-impact screen for different fineness classes determined the conditions under which the maximum extraction of the class +0–0.1 mm and the decrease in humidity are determined. Currently, work is underway aimed at creating a vibro-impact screen, which will implement: expanding the range of impact on the processed material, increasing the life of the screen, the possibility of operational automatic control, increasing the stability of work and, at the same time, simplicity of design.

Experimental study on mechanical property and microstructure of cement mortar reinforced with elaborately recycled GFRP fiber

Mechanically recycled glass fiber reinforced polymer (GFRP) has increasingly been reused in concrete, while its physicochemical properties need to be tailored for achieving effective reinforcement. To this end, fibers were carefully separated from three sources of GFRP recyclates via a process consisting of vibratory screening, followed by hydraulic selection and aerodynamic separation. The influence of the elaborate fiber selection on the physical-mechanical properties and microstructures of mortars were investigated with mechanical testing, X-ray micro-CT and Scanning Electron Microscopy (SEM) analysis. Results indicated that the fine selected GFRP fibers apparently enhanced the mechanical properties and reduced the shrinkage of mortars, with the highest compressive and flexural strength of 47.3 MPa and 9.83 MPa, respectively. The reinforcement mechanisms were mainly attributed to (i) the porosity of mortar ameliorated by the modified fiber uniformity; (ii) the increased fiber-cement adhesion thanks to the rough and hydrophilic surface of recycled GFRP fibers; and (iii) the protective resin coating of recycled GFRP fibers against alkali corrosion.

PREPARATION OF TUFF IN THE DUMPS OF BASALT QUARRIES FOR VIBRATION SCREENING

The article presents the current development of an integrated technology for the processing of tuff in the dumps of basalt pits to highlight the valuable metal fraction and silicate masses. In order to prepare tuff for processing, it is proposed to use the effect of moisture absorption and reduce the strength of tuff when moistened with water, since it has a porous structure and is relatively easy to absorb moisture. This operation, followed by vibratory screening in a small class of -2.5 + 2.0 mm, is promising for the selective extraction of tuff from dumps of basalt quarries, where, unlike other rocks, tuff is a water-absorbing mineral. The article presents the results of experimental studies and the development of mathematical models of the process of softening tuff with water. The objective of the research was to determine the degree of change in the strength of tuff under the influence of moisture and to establish the dependence of humidity and strength to predict the process of softening of tuff when wet. Experimental studies were carried out on various samples of tuffs of the Rafalovsky basalt quarry, while the exposure time of the sample in water was recorded, humidity, indenter indentation pressure on the press or contact load and compressive strength or contact stress during indenter penetration were determined. It was found that when moistening tuff during the day, humidity increases on average by 9%, strength decreases from 120.5 to 10.6 MPa and is 9.2% of the strength of the feedstock. Humidity of tuff in time increases according to the law of a quadratic parabola with a complex argument, the force of indentation of the indenter from moisture and wetting time changes according to the logarithmic law, strength from humidity and time - according to the law of the quadratic parabola. Also, the article proposes an algorithm for calculating humidity and strength characteristics during wetting during the day. It is advisable to use this technology of softening tuff with water as an ore preparation operation with the integrated technology of tuff processing.

Promising Dissociation Technologies for Preparation of Minerals to Flotation

Milling of minerals and middlings is studied in ultra-fine bead mills, Vertimill fine milling machines and in hydropercussion-and-cavitation machines (rotary-pulsating type). Fine and ultra-fine milling provides the wanted rate of dissociation of sulphide minerals and host rocks as compared with ball milling, while hydropercussion-and-cavitation milling improves selectivity of dissociation at equal grain size composition of products from the rotary-pulsating machines and ball mills. Possible improvement of ore quality by fine hydraulic vibratory screening before deep concentration is examined. It is shown that as against hydrocyclones in pre-treatment circuits, fine hydraulic vibratory screens reduce circulation of fines with oversize flow, decrease overgrinding and increase mass fraction of optimal sizes for subsequent flotation.

Mineral coal thermal modification effect upon its vibratory screening efficiency

Mineral coal thermal modification effect upon its vibratory screening efficiency

Recycling of a fine, heavy fluff automobile shredder residue by density and differential fragmentation

A compilation of the physical properties of materials which might typically occur in automobile shredder residue and an analysis of their suitability for the separation of materials in fine (<15mm) heavy fluff ASR (fhf-ASR) is presented. Differences in density and resistance to crushing of fhf-ASR materials were identified as potentially the most suitable low cost, technologically simple means for the separating this waste into its three principal components – metals, minerals (glass/stones) and organics (plastics).Results presented of laboratory scale tests demonstrate that fhf-ASR can in large part be separated into three principal components. Tests were conducted with 0.63–2.0mm and 2–10mm fractions. Recovery of plastics by density separations were conducted with water only jigs for the 2–10mm fraction and shaker tables for the 0.63–2mm fraction. Comparisons are presented of the separations of glass and stones from metals obtained by linear screening and vibratory screening of roller mill and impact mill crushing products of the high density 2–10mm fraction. Equipment used for these tests are of a laboratory or demonstrative scale. It is reasonable to anticipate that industrial scale processing would produce significantly better results.The 2–15mm fraction was found to constitute 91.6% of the fhf-ASR sampled. The metals content of the 2–10mm portion of this fraction was upgraded from 2.5% to 31% and 76.9% with recoveries varying inversely with grade from 91.9% to 40.1%. From 63.6% to 17.1% with a recovery of 93.5% of the organic materials. A residual product of fine sand of crushed glass/stones of 99.4% purity recovered 71.3% of these.

DEM simulation of a 3D vertical vibratory screening process: The study of a simulated woven‐mesh structure

AbstractA discrete‐element method (DEM) was applied to analyze the complicated phenomena of granular screening using different plate‐, bead‐, and woven‐mesh structures. In the past, mesh structures have often been simplified as plate or bead structures in screening‐process simulations, resulting in large differences between the simulated and experimental sieving rate. Here, a mesh‐type, 3D woven structure was accurately modeled, and the simulated sieving process yielded results more closely resembling the experimental process. The woven‐mesh model constructed of sine and cosine functions was also used to assess the effect of the structures on the sieving rate and mesh‐blocking phenomena, i.e., cohesionless particles plugging the mesh. By monitoring the in situ blocking conditions in the discrete‐element method simulation, cohesionless particles with diameters of 1.1w (where w is the size of the aperture) were found to block the most mesh apertures. The large difference in sieving rates observed when separating particles with sizes of 0.7w and 1.1w and those of 0.9w and 1.1w resulted from the differing degree of freedom for the smaller particles to move to the bottom of the bed. The 0.7w particles were more able to move downward in the bed and be sieved out, leading to a higher sieving rate as compared to those with 0.9w diameters. The significant factors and phenomena of the sieving process, such as particle–mesh and particle–particle interactions, instantaneous mesh‐blocking, and the intrinsic motion of the granular bed, which cannot be observed experimentally, can be modeled by the DEM simulation using our 3D woven‐mesh model. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Probabilistic simulation of vibratory screening under high loading conditions

An integral criterion, based on the concept of a probability flow, is proposed to characterize the effect of segregation and sieving in a simulated process of screening.

OPTIMIZATION OF AN AERATED STABILIZATION BASIN PRETREATMENT SYSTEM AT A CORN AND POTATO CHIP PROCESSING PLANT

OPTIMIZATION OF AN AERATED STABILIZATION BASIN PRETREATMENT SYSTEM AT A CORN AND POTATO CHIP PROCESSING PLANTTom's Foods Inc. operates a corn and potato chip processing plant outside of Dallas, Texas. In order to meet pretreatment limitations, they operate an aerated stabilization basin (ASB) with preliminary treatment of food solids using vibratory screening and oil and grease (O&G) using a gravity separator. Recently, after increases in production, the ASB has had instances of elevated fixed...Author(s)Tom SandyInan BeydilliMike LucikRay SummersJack WardenSourceProceedings of the Water Environment FederationSubjectSession 3 Application of Membranes in IndustrialDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2003ISSN1938-6478SICI1938-6478(20030101)2003:2L.211;1-DOI10.2175/193864703784343875Volume / Issue2003 / 2Content sourceWEF EventFirst / last page(s)211 - 220Copyright2003Word count311

COMPARISON OF MULTIPLE FREQUENCY VIBROMETRY TESTING AND SENSORY NERVE CONDUCTION MEASURES IN SCREENING FOR CARPAL TUNNEL SYNDROME IN AN INDUSTRIAL SETTING

The value of vibrometry in the evaluation of carpal tunnel syndrome is controversial. Several investigators have suggested that vibrometry screening with multiple frequencies would improve the correlation and increase the sensitivity when screening for carpal tunnel syndrome. One hundred sixty-nine industrial workers from two manufacturing plants in southern Michigan were screened for median nerve impairment using both vibrometry (seven frequencies, 8-500 Hz) and electrophysiologic testing in each hand. The vibratory threshold at each frequency, as well as composite measures-Jetzer index and negative sums, were compared with electrophysiologic measures of amplitude and latency. The individual frequencies and the Jetzer index correlated with median sensory latency, but the relationships were weak (r = 0.22 to 0.32). Only at the lower frequencies (8, 16, and 32 Hz) did the vibratory threshold correlate with sensory amplitude; correlation ranged from 0.187 to 0.303. Vibration threshold sensation is most closely related to axonal loss or conduction block, but the earliest finding in carpal tunnel syndrome is that of demyelination; thus we would not expect an abnormal vibratory threshold with mild carpal tunnel syndrome. These results support this interpretation and suggest that vibratory screening for early carpal tunnel syndrome is not effective.

Vibratory screening or diagnostic systems

A method of (and apparatus for) diagnosing a patient to measure sensory disturbances of the patient that includes the steps of applying normalized vibrator forces to a body portion or part (e.g., the finger) of the patient; automatically effecting discrete, but variable, vibrations of the body portion over a wide range of frequencies and at various vibratory amplitude levels at each vibration frequency; and noting the onset of sensory perception by the patient on an up-cycle at each vibration frequency and correlating the information, so derived, with the physical condition of the body portion or part. The method contemplates, once the onset of vibratory perception is achieved, in an up-cycle, decreasing the amplitude of vibration at each vibration frequency until the patient ceases or fails to sense the vibration and, in part, correlating the lower level of sensory perception to the condition of the body portion or part.

Treatment of municipal solid wastes by steam classification for recycling and biomass utilization

A patented method of steam classification (the Holloway Process) and a prototype process unit have been investigated. The process treats municipal solid wastes (MSW) with steam and pressure to yield sterilized recyclable metals, glass, and plastics and a cellulosic pulp. After processing, the components of the mixture are separated into three sizes by vibratory screening. The recyclable materials must be subsequently separated from the screened fractions. Process conditions have been optimized to maximize the yield of a sterile cellulosic fraction that has a variety of possible end uses, such as compost, combustion fuel, and feedstock for conversion to fuels and chemicals.

A Study of Vibratory Screening of Drilling Fluids

This work presents results of an experimental and theoretical study ofvibratory screening of bentonite/water drilling fluids containing amedium-fine fracturing sand to simulate granular drilled solids. Satisfactory solids conveyance off the screen can be obtained for flat decks if the vibrator is placed to yield proper phasing between the normal and tangential acceleration components at all points on the vibrating deck. Introduction Drilling fluids returning from a well during drilling are passed serially through a number of solid/liquid separation devices to maximize removal of drilledsolids from the fluid before reuse. The vibratingscreen or shale shaker, the first device to process thefluid, removes the largest particles. Othersolids-separation equipment in the surface mud system can operate efficiently only if the shale shaker is performing properly. Consequently, it often is considered the most important solids-control device on a drilling rig. Most, if not all, of the various shaker designs now available have evolved from vibrating screens used in other industries, primarily the mining industry. Because of its obvious importance in such industries, vibratory screening has been the subject of numerous studies and investigations. On the other hand, very little investigative work has been published on vibratory screening of drilling fluids. The essential difference between this type of screening and that in other industries is that most of the material processed by a drilling fluid screen is liquid, rather than solid. For example, a well-maintained drilling fluid could have less than 10% tool solids by volume. Consequently, much of the existingtechnology for vibratory screening of dry solids, or even very wet slurries, does not apply toscreening of drilling fluids. The importance of this problem has been recognized by the IADC, which recently sponsored a conference on vibrating screen separators. Because the screen cloth itself is critical in determining the amount and size of solids removed by a shale shaker, the API has published a recommended practice for designating shale shaker screen cloth. More recently, Cagle and Wilder reported results of an experimental comparison between two commercially available shakers, primarily to evaluate a new design in screening cloth. Beyond this study, however, comprehensive investigations of the problem apparently have not been published. JPT P. 1889＾

Size Classifying of Granular Particles in a Vibratory Screening System

Size Classifying of Granular Particles in a Vibratory Screening System