Ball Load Research Articles

Stabilization of residual mercury from gold mining as metacinnabar and cinnabar in ball mills on a pilot scale

Waste liquid mercury generated as a by-product of the Merrill–Crowe process in gold mining and recovered from mercury-containing waste must be stabilized for secure storage or disposal. This study developed a procedure for mercury stabilization. A ball mill with a 0.5 m3 capacity and a rotational speed of 43 rpm was used to stabilize the residual mercury with sulfur. The treatments were conducted for 30, 60, and 90 min at mercury: sulfur molar ratios of 1.0, 0.8, and 0.67. The ball loading ratio was 7.0 with residual mercury, and the temperature was below 40 °C. The treatment efficiency was evaluated by measuring the concentrations of mercury and other metals using the Toxicity Characteristic Leaching Procedure (TCLP), examining the stabilized residual mercury by X-ray diffraction, and conducting bioassays on Daphnia magna and Lactuca sativa. Principal component analysis (PCA) was performed on the aforementioned variables. The 90-min treatment, with a mercury-to-sulfur molar ratio of 0.67, stabilized mercury mainly as cinnabar compared with the other treatments and presented leachate mercury values below the detection limit <0.003. The leachate from the treatments also showed values of 21.28–38.44 toxic units, classified as very toxic, and generated toxicity, particularly for D. magna, because of the presence of other metals such as Al, Ba, B, Ca, Cu, Cr, Fe, Mn, Ni, and Zn. The variability of the residues in the PCA analysis was explained by the treatment effect and the presence of other metals in the residual mercury. The stabilized residual mercury obtained was classified as non-hazardous and could be stored or disposed of as ordinary waste in a security landfill.

The influence of different load distribution considering geometric error on the fatigue life of ball screw

The ball screw pair is a precision drive component that converts rotary motion into linear motion. In practical applications, because the feed system usually has rotational torque and geometric errors, it may increase the contact load of the ball screw pair and reduce the fatigue life. In order to study the influence of different loads and geometric errors on the maximum contact load and fatigue life of ball screw pairs, the following research work was carried out. Firstly, based on the composite load and rotational torque, the ball load distribution model is established, and the accuracy of the model is verified by finite element modeling analysis. Then, the influence of different composite loads, rotation times and geometric errors (including ball size error, lead error and raceway tooth profile error) on the ball load distribution is analyzed. Finally, the influence of compound load, rotating torque and geometric error on the fatigue life of ball screw pairs is studied. The results show that the rotational torque and lead error have a great influence on the load distribution and fatigue life of the ball, and the influence of lead error on load distribution is greater than that of dimension error and tooth profile error. The fatigue life of the ball screw pair with non-uniform load distribution is shorter than that of the ball screw pair with uniform load distribution.

Surface modification of micronized calcite (CaCO3) with stearic acid via mechanical dry coating

In this study, the surface coating (modification) of micronized calcite (CaCO3, d50=135 μm) in a stirred media (bead) mill with stearic acid was investigated. As a result of 15 min grinding and 5 min coating experiments, a product with d50=2.15 μm and specific surface area of 3.21 m2/cm3 was obtained. The activation rate of this final product as an indicator of coating rate was 97.7%. According to the optimum coating results, the stearic acid rate was determined as 1%, the modification time was 7.5 min, the ball load was 900 g and the stirring speed was 600 rpm.

An efficiency calculation model for ball screws by accounting for lead errors

Transmission efficiency is a pivotal indicator, providing a comprehensive view of the overall performance of a ball screw. While extensive research has predominantly focused on computing transmission efficiency across various operating conditions, the factors influencing the variability have often been overlooked. This study introduces an innovative method for computing transmission efficiency, which considers lead error, drawing on deformation coordination theory and load distribution. Multiple ball screws of varying precision grades underwent rigorous testing to quantify lead errors. Subsequently, each screw was matched with an identical set of nuts to measure the respective transmission efficiencies. Experimental results reveal a linear correlation between lead error and transmission efficiency when both lead error and uneven ball load distribution in ball screws are considered. The relative error between the calculated transmission efficiency results and experimental values for ball screws of different precision grades falls within the range of 0 % to 7.42 %, confirming the validity of the proposed model in this paper.

Analysis of failure characteristics and mechanical mechanisms of sandstone during spherical indenter intrusion based on acoustic emission experiment

This paper aims to investigate the effects of steel ball diameter on failure characteristics and mechanical mechanisms of sandstone during the spherical indenter intrusion process. By using equipment such as acoustic emission (AE), the process of spherical indenter intrusion into sandstone was monitored and recorded for analysis of the fracture characteristics, load-depth relationship, and specific energy of sandstone under spherical indenters with different diameters. The results showed that as the diameter of the spherical indenter increased, the peak load of the sandstone increased continuously, and the failure mode transitioned from “jump-type” to plastic, with the acoustic emission count exhibiting a staged variation characteristic. During this process, the accumulated acoustic emission count, intrusion coefficient, and specific energy of intrusion all exhibited a “parabolic” law of first decreasing and then increasing, all of which reached minimum values when the ratio of the diameter of indenter to sandstone was close to 1.0. This indicated that as the diameter of the indenter approaches that of the sandstone, the intrusion process becomes more facile and efficient. Finally, the study revealed the formation mechanism of dense core and crack inside the sandstone during intrusion, and discussed the law of the crushing rate in ball milling from the perspective of compression. The conclusions contribute to revealing the fragmentation mechanics of rocks in the ball milling process and aid in determining the ball loading parameters in the milling process based on rock properties, aiming to achieve energy-saving and cost reduction.

Effect of wet ball milling on copper ore flotation by fractal geometry

ABSTRACT One of the important parameters in mineral processing is particles morphology, which is a function of the comminution mechanism. Particles morphology has considerable impacts in flotation process. Variations in particles morphology have been studied by different methods, including fractal geometry. This study aims to investigate the ball milling effect on particles flotation using fractal dimension, in which the calculations in the particles morphology has been made using the step-length method. The ore sample of under-investigation was a copper ore. The examined parameters include grinding time, ball load, and solid weight percentage. The collected fractal dimensions for particles ranged from 1 to 2, which is according to the principle of fractal geometry. Based on the results, low (30 minute) or high (50 minute) grinding time reduces fractal dimension and recovery because low grinding time is resulted in a coarse grain product while high grinding time is resulted in fine particles with spherical shapes. If balls load is high (8710 gr), predominant comminution force turns to an abrasive force are resulted in fine and spherical particles due to an increase in the accumulation volume. When the ball load decreased (4690 gr), the coarse particles were produced. Fractal dimensions and recovery are decreased in both cases. Low (40%) and high (60%) solid weight percentages are resulted in ineffective comminution, producing a coarse grain product. As a result, fractal dimensions and recovery are decreased. There is a direct correlation between recovery and fractal dimension.

Control of ball mill operation depending on ball load and ore properties

Ball mills are used for the second stage of ore grinding in mining operations by proportioning ore piles. Controlling the operating conditions of ball mills is one of the key factors for optimal mill perform and high mill load turnover. One of the factors affecting the efficiency of the ball mill is the loading of the balls. Optimum distribution of ores according to the size of the mill, increasing the efficiency of the grinding process and reducing energy consumption are achieved. In addition, the ore properties are one of the important parameters for the optimal utilizing of the ball mill. Ore can have various properties, such as hardness, density, moisture content, etc., which can affect the ore’s productivity and grinding efficiency

Application of Attainable Region Technique to Optimize Copper Slag’s Desired Size Class

Copper slag is a hard material produced from smelting copper-bearing ores. Over the years, research has prioritized utilizing slag as a secondary source of base metals. This paper focuses on the grinding/milling of copper slag collected from the BCL Mine in Botswana to obtain a maximum amount of material in the desired size class with minimal energy consumption. This will then be followed by an integrated flotation and leaching approach of the desired size class material to recover copper. Our objectives are to determine the grinding time, ball loading, mill filling and desired size class for maximum recovery of copper mineral. The attainable region technique is an equipment-independent optimization tool employed here to determine the optimal specifications of our experimentally manipulated variables to satisfy the set objective function.

Load analysis of thin-walled flexible bearing in harmonic reducer considering assembly with flexspline and cam

As a critical component of the harmonic reducer, the fatigue fracture, vibration, and noise of the thin-walled flexible bearing seriously affect the service performance of the harmonic reducer. Thus the study of load distribution of thin-walled flexible bearing is necessary. By considering the taper and axial deformation of the bearing outer race after assembling with the flexspline and cam, a static analysis model of ball load for the thin-walled flexible bearing is established. Then the influences of maximum radial deformation, diametral clearance, and geometric defects on the load distribution of flexible bearing are studied. Results show that the proposed model is consistent with the finite element analysis in calculating the ball load. The relationship between ball load and maximum radial deformation of the flexible bearing is approximately linear, and the angle of load distribution decreases with the increase of diameter clearance. The effects of ball size deviation, raceway waviness, and raceway surface spalling on the load distribution of flexible bearings are also revealed. The research results can provide a reference for the structural optimization and stress analysis of thin-walled flexible bearings.

Preparation of one-part alkali-activated nickel slag binder using an optimal ball milling process

The effects of ball milling processes on specific surface area, particle size distribution, and compressive strength at different curing ages of one-part alkali-activated nickel slag mortar (AASBM) were investigated. Results show that the influence of impact efficiency on nickel slag from mechanical and chemical interaction differs with ball milling process. Reducing ball loading rate and increasing ball material ratio has the highest energy efficiency for improving specific surface area and improving the strength of 28 d of AASBM, respectively. With the extension of ball milling time, the specific surface area of cement can be improved but the strength increase amplitude of the mortar will decrease accordingly. When the ball loading rate is 30%, the ball material ratio is 15, and the undisturbed nickel slag is milled with high speed for 2 h then mixed with solid alkali, the compressive strength of AASBM is optimal.

EFFECT OF GRINDING MEDIA ON THE MILLING EFFICIENCY OF A BALL MILL

The size of grinding media is the primary factor that affects the overall milling efficiency of a ball mill (e.g. power consumption and particle size breakage). This article tackles the lack of a design tool that could help choose the ball loading composition in mills. Such a tool enables the maximization of the exposed surface area per unit energy (cm2/J). The effect of ball load composition, by varying the grinding media size distribution (e.g. alternatively by mixing four groups of 19.5, 38 mm; 19.5, 50 mm; 38, 50 mm and 19.5, 38, 50 mm), on the milling efficiency of a laboratory scale ball mill has been investigated in this article concerning ball number, total surface area, and ball weight. The results reveal that the amount of required energy is close in values, per each ball loading mixture, concerning three characteristic parameters. The amount of required energy varies between 3.22 kWh/st &amp; 3.65 kWh/st. Moreover, the new surface area per unit energy (e.g. cm2/J) significantly influences milling efficiency. In contrast, the ball weight has a minor effect. This study would be helpful in industries in which comminution is part of the process, such as mining and cement industries.

A modeling method for predicting the precision loss of the preload double-nut ball screw induced by raceway wear based on fractal theory

Precision double-nut ball screws are key functional parts in machine tools. The positioning accuracy of a ball screw can directly affect the machining accuracy of a machine tools. During actual use, the preload degradation and the large axial clearance of the double-nut ball screw are caused by the contact wear, which directly affects the transmission positioning accuracy. The contact wear is focused on the ball and the rough raceway surface of the ball screw. Therefore, a novel method is proposed in this paper to characterize the rough spherical morphology of raceways for ball screws based on fractal theory, and the fractal parameters of the screw and nut raceways are identified. A fractal contact model of the asperity on the raceway surface is established. By introducing contact parameters to modify the contact area, an area distribution function suitable for the coordinated contact is obtained. A mathematical model for calculating the normal contact load of the ball screw in three states is established by considering the friction factor. A precision loss model of the ball screw is established based on the full ball load distribution model and the multiscale contact load model, and the proposed model is verified by experiments. The surface contact coefficient of the inner and outer raceways is discussed. The influence of raceway fractal parameters on the wear rate is analyzed, and coupling research on precision loss and preload degradation for the ball screw is carried out. The initial wear rate under different axial load is discussed, and the change trend of wear rate with time is analyzed. The precision loss model of the preload double-nut ball screw based on fractal theory provides a new theoretical basis for accurately predicting the precision degradation and provides method support for establishing the wear life prediction of a ball screw.

DEM Analysis of Single-Particle Crushing Considering the Inhomogeneity of Material Properties

Crushing characteristics of single particles are the basis of granular material simulation with discrete element method (DEM). To improve the universality and precision of crushable DEM model, inhomogeneous stiffness and strength properties are introduced into the bonded particle method, with which the Weibull distribution and size effect of particle strength can be reproduced without deleting elementary balls. The issues of particle strength and carrying capacity under complex contact conditions are investigated in this work by symmetric loading tests, asymmetric loading tests, and ball–ball loading tests. Results of numerical experiments indicate that particle carrying capacity is significantly influenced by coordination numbers, the symmetry of contact points, as well as the relative size of its neighbors. Contact conditions also show impact on single-particle crushing categories and the origin position of inner particle cracks. The existing stress indexes and assumptions of particle crushing criterion are proved to be inappropriate for general loading cases. Both the inherent inhomogeneity and contact conditions of particles should be taken into consideration in the simulation of granular materials.

Ball Throwing Machine Design To Develop Footballers’ Technical Attributes

For a football player to perform well in football, it is necessary to improve his technical and tactical skills. Improving these skills is enabled with repetition of the same positions that the football player has the ball. The repetitions of these same positions can be performed with the aid of a machine. In this study, a football throwing machine design which can provide direction and velocity for the ball in a repeatable and controllable manner is generated in order for fully educational evaluation. Ball loading canister on the ball throwing machine enabled to use many balls. There are a couple of ball throwing wheels both are made of polyurethane material and have concave surface. These wheels are mounted on a body for axial rotation on a common ground. Each wheel’s rotation speed can be adjusted individually. In order to determine horizontal-vertical direction of movement of the ball, two linear actuator are used. Ball’s velocity, direction, orbit and throwing laps are controlled electronically. All controls concerning ball throwing are carried out via Delta PLC (Programmable Logic Controller) and HMI (Human Machine Interface) panel. A user interface is developed for controls made via PLC. Owing to interface, different training plans are designed by handler or trainer via operator panel and footballer is provided to train in various density. In order to prevent toppling tripod system, and to carry easily a towing arm is used. Machine can work with an accumulator or feed directly from grid circuit.

Comparing strategies for grinding itabirite iron ores in autogenous and semi-autogenous pilot-scale mills

High grade iron ore resources are becoming depleted in Brazil, with relatively low-grade ores requiring more intensive comminution for proper liberation of iron minerals, followed by upgrading. Comminution circuits that have been frequently used in the Brazilian iron ore industry in preparation of high-grade iron ores consist of multiple crushing stages followed by ball milling and are known for being highly complex and capital-intensive installations. This work assesses the potential suitability of autogenous (AG) and semi-autogenous (SAG) milling through an extensive pilot plant campaign carried out with itabirite iron ores. The effects of ore type, feed size distribution, circuit configuration (open or closed-circuit and two-stage or single-stage), mode of grinding (AG or SAG), ball load, use of pebble crushing as well as of full secondary pre-crushing have been investigated. The results demonstrate both the technical feasibility and energy efficiency of such an alternative for itabirite comminution circuits.

Investigation of classification alternatives for grinding circuits

ABSTRACT In the present work, the performance of a silica sand grinding circuit was evaluated. Detailed classification tests were performed using a laboratory scale teetered bed separator (TBS) in a grinding circuit to evaluate the possibilities of using one instead of a cyclone. Mathematical models were used to simulate and compare size classification efficiencies of an actual cyclone and a TBS. According to simulation results, TBS gave a better separation efficiency and lower bypass. Significant decrease in circulating load was achieved to obtain very similar product quality. Mill ball load can be reduced from 35 per cent to 30 per cent according to simulation results. This modification reduces specific energy consumption of the ball mill by approximately 10%. The TBS can be used as an alternative and more efficient classifier to further improve the classification efficiency of close circuit grinding operations.

Using DEM to investigate how shell liner can induce ball segregation in a ball mill

Sometimes it is desirable to segregate the ball load in a mill so as to allow for the possibility of larger balls dealing with coarser particles at the feed end and finer product being ground more efficiently at the discharge end. The Hardinge mill with cylindrical and conical sections has been used to achieve segregation quite effectively. The cylindrical section tends to retain the biggest balls while the smaller balls drift to the conical section. However, this is a complex design and we use the discrete element method (DEM) model to investigate if simply altering liner configuration on an ordinary cylindrical mill can lead to similar success. The study involves simulating a mill with 4 sections. Each section can be configured with distinct liner profiles. Three ball size classes are tracked for evidence of segregation at 75% and 60% of critical mill rotation speed. The ball distributions in the various segments at the end of 80 mill revolutions suggest that varying axial liner profile configuration can affect ball segregation, particularly for the mill running at 75% of critical speed. The convenience of using computer simulations to avoid costly plant trials is highlighted.

Usage of discrete element method in the research of vibrating mills with circular vibrations of the grinding chamber

The paper reviewed the application of the discrete element method for researching the motion of the ball load in vibration mills with circular vibrations of the grinding chamber at different amplitude-frequency characteristics. Vibration mills are actively used in various industries, in particular for road construction in the production of bitumen or mineral components. The paper presents the model of the vibration mill used in numerical calculation, the main indicators of the load’s kinematics providing the efficiency of the vibration mill, presents and analyzes the results of numerical experiments, determines the rational mode of operation of the machine.

Determination of granulometrical composition of the clinker by grinding in a ball mill to determine the specific consumption of additional energy

This paper presents results regarding the grinding behaviour of two batches of material (clinker) in a ball mill with its own two-step grinding process: the first one with a ball load, the second with a load of cylindrical metal bodies. The first step was performed until the residue R009has reached aprox.35%, and the second stage until Blaine's specific surface was over 3800 cm2/g. Periodically, at 10-minute intervals, the fineness of the clinker and the specific energy consumption were determined. These consumptions are quantified from the first determination and relates to the weight of the material subjected to grinding (20 kg clinker / from a source), determining the grinding ability of the material.

Modeling and Analysis of Full Ball Load Distribution of Ball Screw with the Combined Load

Modeling and Analysis of Full Ball Load Distribution of Ball Screw with the Combined Load