Screen Inclination Research Articles

Investigation of Impact Contact Force Testing and Damage Analysis on Potatoes

To investigate the influencing factors and intrinsic relationships between potato impact force and impact damage during potato soil separation, a testing system for potato impact force was established. The impact force test system is composed of a base, a height adjustment device, a simple separation screen, a soil storage tank, an impact force sensor, and so on. By allowing potatoes to fall freely to simulate the collision process, impact force data are collected, and a high-speed camera is used to locate the impact position and analyze the degree of damage. Through the response surface analysis method, the influencing factors and laws of the impact force and impact damage during the collision process between potatoes and rods under soil and no-soil conditions were studied. The results of the response surface analysis indicate that when the screen inclination is within the range of 14.12° to 14.77°, falling height ranges from 453.83 mm to 500 mm, screen rod spacing falls within 36.50 mm to 40 mm, and the screen rod material is rubber. Potatoes can still be at a relatively low damage level when enduring a large impact force. This study has significant implications for reducing potato impact damage during harvesting, enhancing economic benefits in the potato industry, and advancing the technical level of potato harvesting equipment. In the future, based on the results of this study, further exploration can be made to optimize the design of potato harvesting equipment so as to better reduce the damage to potatoes during harvesting and subsequent processing processes and promote the sustainable development of the potato industry.

Study on the wet dust collection mechanism of metal-based filter screens and the effect of its inclination angle on dust removal performance

The wet filter dust collector (WFDC) is widely used in dust control in various industries, but its dust collection mechanism is unclear, and the influence of the metal-based filter screen (MBFS) inclination angle on the dust removal performance is still uncertain. In this paper, the liquid film crushing and collecting dust mechanism of MBFS and the influence of its inclination angle on the dust removal performance of WFDC are studied. The results show that with the increase of inclination angle (30° to 150°), the average pressure drop of WFDC first decreases and then increases, the average dust concentration first increases and then decreases, and the MBFS dust removal performance is optimal at 90°. The optimized WFDC was applied on-site in a coal preparation plant, which exceeded the dust suppression efficiencies of 91 % and 88 % for total dust and respirable dust, respectively. The research results are expected to provide theoretical guidance for WFDC design and improvement.

Simulation and Experiment of Sieving Process of Sieving Device for Tiger Nut Harvester

In order to realize mechanized and efficient harvesting of tiger nuts, study the efficient screening technology of beans and soil in a mechanized harvesting operation and improve the harvesting operation efficiency of crawler-type tiger nut harvesters, a theoretical analysis of the motion process of detritus particles on a sieve surface was conducted to determine the main factors affecting the motion of the particles on the sieve surface. A numerical simulation of the sieving process using the discrete element method was conducted to improve the screening efficiency of tiger nuts. The transport law of the debris particle population was analyzed from different perspectives, such as the average velocity of particle motion, particle distribution rate, screening efficiency and loss rate. The effects of factors such as screen amplitude (SA), vibration frequency (VF) and inclination angle (IA) on the sieving performance of the tiger nut threshing and screening device were investigated. The results show that sieving performance evaluation indexes, such as the average speed of particle movement, particle distribution rate, screening efficiency and loss rate, are non-linearly related to the factors of screen amplitude, vibration frequency and screen inclination angle; the effects of amplitude and frequency on the distribution particle size are consistent and show a gradual increase, with the distribution particle size reaching 3.32 mm at an amplitude of 14 mm and 3.46 mm at a frequency of 22 Hz. In the sieving process, the average velocity of the particle population decreases gradually along the direction of motion, and the influence of each factor on the average velocity of the particle population in the motion of the detritus is similar, all showing an increasing trend. This study can provide a reference for exploring the transport law of particles and the efficient screening technology of tiger nuts. Field harvesting tests showed that the screening efficiency and loss rate were 92.87% and 0.83%, respectively, at a screen amplitude of 14 mm, a vibration frequency of 10 Hz and an inclination angle of 2°, and the test results corresponded to the simulation results and met the design requirements of the tiger nut harvester. This study can provide reference for the investigation of the particle transport law and efficient screening technology for tiger nuts.

Research on the distribution law of spatio-temporal permeability screening and adaptation characteristics of banana-type equal-thickness classification of coal gangues

ABSTRACT Screening is an important technological challenge to alleviate environmental contamination and resource waste and enhance the large-scale synthesis of coal gangue solid waste resources. Single inclination vibrating screen for coal gangue grading process can easily cause concentrated accumulation of materials at the infeed end, loosening and stratification difficulties, and deterioration of grading effect. This study replaces a single inclination screen surface with a variable inclination (banana-type) for coal gangues classification and separation. After studying the spatio-temporal permeability distribution characteristics of the screen surface with variable and single inclination, it is found that the integrated optical density (IOD) of gangue on the screen surface with variable inclination is 1.5 times of single inclination, and the gangue under the screen with variable inclination is 2.5 times that of a single inclination. The particle penetration position on the variable inclination’s screen surface is in the middle, while the penetration is significant. Moreover, the screening performance and the whole mismatch content are increased by 2.24 and 1.74% points compared with the single inclination, respectively. At the same time, the distribution size is closer to 6 mm. In addition, the range and screen inclination angle adaptation characteristics are studied. When >6 mm, gangue accounts for 55%, a smaller screen inclination gradient should be selected, such as 3° and 4°, matching the productivity of 18t/h, achieving the best screening performance and processing capacity.

Numerical simulation of particle screening efficiency of large multi-layer vibrating screen based on discrete element method

With the increasing requirements for energy conservation and environmental protection, multi-layer vibrating screens have become hot issues. Compared with single-layer vibrating screens, multi-layer vibrating screens has much better performance in terms of processing effect, treatment capacity, and environmental protection. The research on the physical parameters of the multi-layer vibrating screen is of great significance to the actual production. However, analysis and simulation studies of multi-layer vibrating screens are limited. In this paper, the screening process of wet particles on a multi-layer vibrating screen was simulated by using the discrete element method. The characteristics and application scope of the two vibration modes were analyzed. The particle penetration rate, the number of collisions, and the distribution of the particles under 23 combinations of structures and vibration parameters were investigated. The influence of different parameters on screening performance was analyzed. Several optimal combinations of frequency, amplitude and screen inclination angle under different working conditions were obtained. The screening efficiency of the balanced elliptic motion is higher than that of the linear motion. The best combination of the three parameters is 4 mm amplitude, 20 Hz frequency, and 3° inclination angle. The efficiency is higher when the particles follow a distribution of arithmetic on the screen. This study provides a reference for the efficient operation and optimal design of large multi-layer screening equipment.

Optimization of parameters of open-pit screening and dumping stations

Introduction. The mining and geological features of a number of deposits lead to the fact that during the development of the massif under the influence of drilling and blasting operations, the degree of crushing of a mineral depends on the content of useful components in it, and the chemical composition of the ore is differentiated by size classes. The determined relationship between the quality of the ore mass and its size can be used to increase the efficiency of the ore preparation technology through the use of screening and dumping stations (SDS) in open pits. The implementation of the ore preparation technology based on the SDS will allow to reduce the costs of enrichment and transportation of the ore mass by separating its substandard part directly in the open pit and excluding it from the traffic flow at the processing plant, where the efficient operation of SDS is possible by optimizing a number of parameters as mining transport equipment serving SDS and a screener itself. Results. To determine the main parameters of SDS the characteristics of the initial movement of the rock mass along the inclined surface of the screen were determined, such as the productivity of unloading the vehicle onto the surface, the initial thickness of the layer for feeding and the speed of movement of the rock mass along the slope of the screener. Based on the presented algorithm, the main characteristics of the screening process are calculated: the size of the material flow layer in the i-th screener section; the speed of movement of the bulk mass along the screener; the average size of a piece in the starting material and the output of the material into screen throughs. The parameters of the screening process were determined on the basis of a given relative content of the size class of the material supplied to the surface of the screener, subject to its uniform distribution within the class. The optimized parameters of SDS were selected: the angle of inclination of the screener and the linear dimensions of the unloading platform, depending on the dimensions of the dump truck. Determination of the optimal parameters of SDS was carried out by constructing a generalized desirability function for two optimized criteria: the material yield to screen throughs and the oversize of the screener. Based on results of the calculation, optimization graphs of the dependence of the optimization function on the angle of inclination of the surface of the screener and the carrying capacity of the dump truck unloaded onto the screener were constructed. Conclusions. The optimal angle of inclination of SDS screen is 40° –42° and does not depend on the grain size distribution of the feedstock supplied to screening.

ОПТИМИЗАЦИЯ КОНСТРУКТИВНЫХ ПАРАМЕТРОВ БУНКЕРНОГО УСТРОЙСТВА

Based on previous theoretical studies, the main design parameters of the device were established, such as angle of installation of wire screens, the number of wire screens in hopper, the location of wire screens in hopper, and the minimum size of the gap and bridge in wire screens. It is established that in order to determine the optimal width of the gap in the wire screen, it is necessary to know the height of bulk material layer passing through the gap of the hopper device element and speed of bulk material on the second bridge. To ensure optimal operation of the element (wire screen) of the device for controlling technological process of loading, storage and unloading, it is necessary that loaded material passes evenly through the wire screen that is throughput capacity of each slot of the device is the same. The obtained equations allow us to determine the minimum gap width depending on the radius of bulk material particle, falling speed of the material on the screen, coefficient of friction and width of crossbar of the screen. For experimental research, a laboratory model of a bunker-type device was created and tested. The model allows you to quickly change parameters such as the angle of inclination of wire screen, gap width in the wire screen, the length of the wire screen, the distance between the wire screens and the height of the loaded layer. At the same time, it was found that the loading process is influenced by the coefficients of uniformity of distribution of bulk material over the entire cross-section of container, as well as the coefficient of material segregation when filling the loading device. The method of conducting experiments included determining the parameters of developed hopper device: the angle of inclination of the wire screen, the length of the wire screen, gap width in the screen and the interval between the sieves. The initial levels were selected based on analysis of previous studies of the bulk material loading process. The results of these studies identified the optimal values of main parameters of the developed device depending on the downloadable material: the angle of inclination of wire screen - 36...38°; length of wire screen...0,19 0,28 m; the distance between screens - 2,3...2,8 m. The obtained numerical values of parameters can be used in the design of bunkers or silos for similar purposes.

Evaluation of the residual moisture content in pilot scale vibrating screening operating with pressure reduction in the screen drying region

To study the aspects of solid-liquid separation in vibrating screening operations, experiments were carried out with a 3k experimental design, analyzing the following independent variables: g-force, angle of inclination of the screen, and volumetric concentration of solids in the feed. The influence of a reduction of the pressure on the dewatering process was also taken into account. The results obtained for the screening operation without pressure reduction indicate that the minimum residual moisture content was reached with a g-force of 3.0, screen inclination of 1.5°, and volumetric concentration of 6.0%. Additionally, the use of pressure reduction with a sieve allows for the lowest residual moisture content with a g-force of 3.0, 3.0° screen inclination, and 6.0% volumetric concentration. The major influence of pressure reduction in the residual moisture content was observed for the experiments with 2.0% of volumetric concentration, the lowest level adopted for this variable in the experimental design.

Vibration screening: A detailed study using image analysis techniques to characterize the bed behavior in solid–liquid separation

Particulate suspensions systems are present in various industrial sectors, vibrating screens being some of the most versatile pieces of equipment for the separation of these two phases. This paper presents a study of the dynamics of the mixture on the screen during solid–liquid separation using vibration screening. The independent variables studied were g-force, volumetric concentration of solids in the feed, feed flow rate and inclination of the screen. The equipment used was a vibrating screen of 175 mesh with 95 μm aperture size. The evaluated response variables were the residual moisture content of the retained solids, the screen area occupied by the liquid, the transport velocity of the retained solids and the screen area occupied by the retained solids. The solid material used was sand with a density of 2.67 g/cm3 and a Sauter mean diameter of 373 μm, and the liquid phase was composed of water containing 0.1% xanthan gum. A central composite design was applied to the experiments and the results for each response were analyzed statistically. It was possible to verify that the increase in the g-force and screen inclination variables increased the operational capacity, since the areas occupied by the liquid and the retained solids were reduced. It was also found that higher volumetric concentrations of solids in the feed favored a reduction in the moisture content of the retained solids and their transport on the screen, since larger particulate material conglomerates were formed, which had a more uniform displacement path.

Screening Efficiency Analysis of Vibrosieves with the Circular Vibrations

Abstract The analysis of influence of factors that depend on construction characteristics of the vibrosieves with circular vibrations on screening efficiency is presented in this paper. The dependence of the screening efficiency on the aperture size, length and inclination of the screen, as well as on vibration amplitude, is considered. Based on obtained results, one can see that the screening efficiency increases with vibration amplitude and the screen length increase. Further, increases of the screen inclination and aperture size are causing an initial increase of the screening efficiency, which is later decreasing.

ДИНАМИКА ЖИДКОСТИ В ПОДВИЖНОМ СОСУДЕ С НАКЛОННЫМИ РЕШЕТКАМИ

Forced oscillations of a rectangular tank p artially filled with liquid are considered in this work. Two inclined screens are located in the tank as inserts. The system of Reynolds–averaged Navier–Stokes equations is solved numerically with the SST k - ω turbulence model. The volume of fluid (VOF) method is taken for simulation of gas–liquid interface. The problem is solved in two-dimensional statement. Unstructured triangular mesh converted to a fine structured rectangular mesh is used near the screens. A comparison of two turbulence models with experimental data is carried out, and the optimal model for the pressure loss coefficient calculation is chosen. The effect of the inserts inclination angle on the pressure loss coefficient is investigated at different values of the oscillation amplitude of the tank and different heights of the screen slats. It is obtained that the pressure loss coefficient dependence on the inclination angle at small Keulegan–Carpenter number has the local maximum depending on the oscillation amplitude and the geometric parameters of the screens. Comparison with the known analytical dependence of the pressure loss coefficient dependence on the inclination angle that obtained for the stationary flow through the inclined screen is conducted. It is found that this dependence needs to be verified for the case of oscillation tank at big screen inclination angle and small Keulegan–Carpenter number.

Empirical study on the effects of screen inclination and feed loading on size classification of solids by gravity

This study explored the insights into the theory of dry solids classification, in particular the classical dynamics aspects related to the mass loading of particles, deck inclination of the screen, and resulting measures of flowability. Prototype screening equipment was fabricated and experiments were carried out with ideal rounded mono-shaped glass beads. The overall performance of the prototype was assessed in relation to two screen design variables, the tilt angle of inclination and the mass throughput of the feed, which affects particles flow. Mathematical models relating to the classification process were developed, simulated and compared to the results obtained from the experiments. Important parameter ranges within which equipment may be operated with minimal malfunctioning were approximated from the models. Screen loading, bulk flow velocity, and screen inclination angles determine flowability of powders and particles in gravity classification; these parameters were used in this study to assess how well the particles flowed over the screens. A close correlation was found between theory, simulation models and the experimental results, which facilitated development of empirical models that may be used to predict and estimate the classification rates, efficiencies and flowability for such systems. Dense screen loading improved the classification rates, but hampered flowability, and consequently the efficiency. Increase in deck inclinations improved flowability and efficiency, but only to a certain optimum point after which it led to excessive overflow.

Modeling of Screening Processes with the Discrete Element Method Involving Non‐Spherical Particles

AbstractPhenomena related to sieving of non‐spherical particles are investigated numerically in two batch apparatuses and on a horizontally aligned continuous sieve by particle‐based simulation approaches in the framework of the discrete element method. The feed material is approximated by complex‐shaped particles composed of clustered spheres. Comparisons are made with regard to the passage through the screen as well as the segregation and transportation on the screen. Results for passage are compared to data from literature, where simulations with spherical particles were performed of a laboratory‐scale sieve operated with non‐spherical quarry rock particles. Additionally, variations in screen inclination are investigated. Experimental results are matched by the simulations. A distinctive influence of particle shape on flow rates and residence times is identified.

An experimental study on fish-friendly trashracks – Part 1. Inclined trashracks

Experimental results are presented for trashracks placed in an open water channel with different bar shapes, spaces between bars and screen inclination angles. The numerous configurations provided results on head losses and on changes in velocity along the rack for a large range of situations, including fish-friendly trashracks. A new head-loss equation is proposed that takes into account the effect of the different tested parameters and demonstrates the need to separate the effect of the trashrack bars, which is directly related to the inclination of the trashrack, from the effect of the transversal elements such as spacer rows whose effect on the flow is not altered by rack inclination. Velocity measurements also adduce rules for efficient water intakes complying with fish-friendly criteria.

Screening efficiency and screen length of a linear vibrating screen using DEM 3D simulation

The effect of screen length on the screening efficiency of particles is studied under various single parameter conditions including frequency, amplitude, vibration angle, and screen inclination. The Discrete Element Method (DEM) has been used to simulate the screening process. A functional relationship between screening efficiency and screen length is established. It is shown that screening efficiency and screen length have a complicated exponential relationship. Relationships between them are profoundly discussed and conclusions are easily drawn: low values of the parameters do not benefit screening; screening efficiency generally increases with screen length; screening efficiency reaches a plateau when these parameters are in range frequently encountered in practical applications.

ENGINEERING STUDIES ON THE FACTORS AFFECTING THE PERFORMANCE OF SHELLING AND GRADING CORN MACHINE

The performance of an Italian made combined machine was tested and evaluated for shelling and grading two different Egyptian corn crop varieties. Whereas, the optimum design, and operating parameters were determined in order to increase the mechanical shelling and grading efficiency and machine productivity. The crop was feed at a constant rate of 25 kg and at the grains recommended moisture content range of 12-14% (d.b). The shelling unit of the machine was deduced at four different drum speed levels (from 370 up to 820 rpm, those corresponding drum linear speeds from 4.84, up to 10.74 m/s). Also, shelling unit was tested under three concave clearance levels (32, 42 and 52mm). While, the grading unit deduced at different cylindrical screen speed levels (from 55, up to 95 rpm corresponding to linear cylinder speeds from 1.38, up to 2.39 m/s). The grading unit was also tested versus different cylindrical screen inclination angle up to 9 degrees. The tested machine performances were evaluated in terms of the grading and cleaning efficiency. In addition, costs per unit weight of production and energy unit requirements were estimated and compared with the traditional shelling and grading methods of corn crop. The obtained results revealed the following important points: The optimum parameter levels for the mechanical shelling operation were drum speed of 670 rpm (8.77 m/s) and concave clearance of 42 mm. These parameters levels were recommended to match the performance of the grading unit. The promising parameters levels for operating the grading both tested crop varieties were 80rpm (2.00 m/s) for cylindrical screen speed and 3 degrees for inclination angle.As operating at the optimum parameter levels the highest values of grading efficiency (83.68 and 82.84 %), grading cleanliness (77.78 and 77.18 %), and machine capacity (0.51 and 0.47 ton/h) were achieved. for both tested corn varieties, SC10 and TC310 respectively. Also, the lowest values of specific energy consumption (25.94 and 29.29 kW.h/Mg) and cost (76.12 and 78.28 LE/ton) for both tested corn varieties, SC10 and TC310, respectively.

Comparison of measured and simulated flow through screens: Effects of screen inclination and porosity

The use of screens to reduce insect entry into greenhouses has become a common practice. Screens act as mechanical barriers that prevent migratory insects from reaching the plants. However, they impede ventilation thereby increasing air temperature and humidity within the enclosures. In an attempt to explore ways by which ventilation can be improved, the effect of screen inclination on flow parameters downstream the screen was investigated experimentally and by computational fluid dynamics (CFD) simulations. Experiments were done in a wind tunnel and CFD simulations were conducted by using the ANSYS-CFX 11 software package. The CFD code was first validated by comparing between the numerical and experimental velocity profiles downstream inclined screens with different porosities. In the validation stage the screens were inclined at 45°, 90° and 135°, (angle measured between the floor upstream and the screen plane). The validated code was used to determine the effect of screen inclination on mass flow rate through the screen and on airflow-induced forces that act on the screen. The effect of screen porosity was examined by using screens of different porosities (0.4, 0.52 and 0.62). The experimental and CFD results were in good agreement with respect to the velocity magnitude for a screen placed at 90°. Fair agreement was observed with an inclined screen that is placed at either 45° or 135°. However, at both 45° and 135° the agreement with respect to trends in air velocity vertical distribution downstream the screen was good. When the screen was placed at 90° to the floor, the air velocity downstream the screen was almost constant with height. With inclined screens the velocity increased with height for 45° and decreased with height for 135° inclination. A wider range of inclinations (30–150°) was used in the simulations to systematically study the effect of inclination on the mass flow rate through the screens and on the forces on the screens. The CFD results show that for all porosities the mass flow rate through screens that are inclined 45° was higher than through screens inclined at 135°. The higher mass flow rate at 45° was associated with larger force acting on the screen. The force acting at 45° was always greater than at 135°.

수산폐기물 전처리 용 스크린기술 개발

수산폐기물을 방류기준에 맞추어 효과적으로 분리 처리하기 위하여, 고형물을 함유한 폐수로부터 고체와 액체를 분리해내는 전처리 공정이 필요하다. 또한, 전처리 공정효율이 극대화될수록 후속처리공정의 처리용량향상, 처리시설 규모축소, 경비절감 등의 효과도 커진다. 이를 위해 이 논문에서는 진동형 역경사식 스크린 기술을 제안하고, 최적의 고액분리를 위해 적정 진동주파수 및 기진각을 검출하였다. 진동발생기는 스크린 몸체에 대해 일정한 각도(<TEX>$0^{\circ}$</TEX>,<TEX>$30^{\circ}$</TEX>,<TEX>$45^{\circ}$</TEX>,<TEX>$90^{\circ}$</TEX>)로 각각 두었으며, 진동주파수는 진동에 의한 스크린의 손상을 고려하여 35-60Hz 범위 내에서 5Hz 단위로 가변하면서 고액분리효율을 측정하였다. 스크린 경사각은 예비실험을 통해 <TEX>$3^{\circ}{\sim}5^{\circ}$</TEX>로 설정하고, 여과장치는 직사각형과 정사각형 2종류로 제작하였다. 실험결과 장치의 형태와 관계없이 대체적으로 <TEX>$0^{\circ}$</TEX>의 기진각과 60Hz의 진동주파수에서 우수한 여과효율이 나타났다. 그리고 여과 전후의 부유물질(SS)의 양을 비교하여 제안한 기술의 유효성을 검증하였다. In order to effectively isolate the marine wastes with an effluent standard, the pretreatment process is required to isolate solid materials from the liquid-solid mixed wastes. The more effective the pretreatment becomes, the more processing capacity of posttreatment will be improved and process facilities will be downsized. In this paper, we suggested the vibrating reverse-slant screen, investigated the optimal vibration frequency and vibrator installation angle for the separation of the liquid solid mixed wastes. Several experiments for separation efficiency were conducted under the condition of various vibration frequency(<TEX>$35{\sim}60Hz$</TEX>, 5Hz interval) and vibrator angle(<TEX>$0^{\circ}$</TEX>, <TEX>$30^{\circ}$</TEX>, <TEX>$45^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>) considering the crack of screen. The screen inclination angle is set up the gradient as <TEX>$3^{\circ}{\sim}5^{\circ}$</TEX> through the preliminary experiments. Also, we made two types of screen(respectively rectangle and square screen). The separation device has shown the optimum efficiency at vibrator angle <TEX>$0^{\circ}$</TEX> and vibration frequency 60Hz, and has no relation with the shape of screen. And the proposed technology is verified by comparing with quantity of suspended solids before and after filtration.

VDT Screen Height and Inclination Effects on Visual and Musculoskeletal Discomfort for Chinese Wheelchair Users with Spinal Cord Injuries

This study investigated the visual fatigue and musculoskeletal discomfort for wheelchair users in a VDT data entry task. Eight Chinese male wheelchair users were recruited as participants to perform 9 different experimental combinations. Three screen heights and three screen inclinations were evaluated. Visual fatigue was measured using the change in critical fusion frequency (CFF), near point accommodation (NPA) and a visual complaint questionnaire. Musculoskeletal discomfort was estimated using the rating of perceived exertion (RPE). Each participant performed a data-entry task within a 30 min period using random orders. All participants during the data-entry operation used the upright posture with the participant's lower and upper arms forming right angles. The results showed that the screen height and screen inclination significantly affected visual fatigue and musculoskeletal discomfort. On average, the optimal screen height choice for wheelchair users was at eye-level height or 5 cm below eye level with a vertical screen inclination.

Free‐Surface Flow Through Screen

A prediction model is developed for the headloss through a screen that is placed in an open channel. For a given approach‐flow condition, screen inclination, and screen characteristics (i.e., flow contraction and deflection caused by a screen), values of the headloss coefficient can be predicted by the model. The result shows that there is an optimal inclination angle to minimize the headloss. The predicted values of the headloss are found to be in good agreement with the measured values in the experiments.