Grinding Media Research Articles

Effect of grinding media shape on the particle size distribution of UG2 ore using the response surface methodology central composite design

In this study, the effects of truncated ellipsoids and cubes on the particle size distribution of a UG2 ore were compared to the spheres using the response surface methodology for experimental design, modeling, and optimization. The response surface methodology demonstrated that it can be useful in optimizing grinding operations. It provides lenses to see and analyze the behavior of the ball filling, interstitial filling, and % solids parameters which are complex and interactive, and their effects on the production of the desired product (−75 µm) for different grinding media. Spherical grinding media outperformed truncated ellipsoids and cubes, producing the highest amount of the desired size class (82.58%), followed by 80.41% for truncated ellipsoids and 77.07% for cubes. Spheres also consumed the least power followed by cubes and lastly truncated ellipsoids. The differences in optimal grinding conditions were attributed to different contact mechanisms, surface area, and load behavior of the grinding media.

Preparation of fine suspensions using stirred media bead mill

Preparation of fine suspensions using stirred media bead mill

Pt/Ni single-atom alloy boosts mechano-pyrolysis of alkane into hydrogen

Mechanochemistry approach was utilized to solve the carbon deposition during alkane pyrolysis process. Pt/Ni single-atom alloy (SAA) was constructed on Ni balls surface as catalyst and grinding medium simultaneously, and physical collision of metallic balls generated mechanical energy to remove the deposited carbon and accelerate reaction rates. XANES spectra proved Pt/Ni SAA structure on the Ni ball surface, and its turnover frequency (TOF) was 1530 h−1 under 1 atm and 450 °C without by-products. An extremely long lifetime of methane pyrolysis at least 350 h on stream has been obtained. This Pt/Ni SAA was also active for mechano-pyrolysis of ethane/propane, and DFT calculations confirmed that the improvement of catalytic efficiency originated from the d-band center up-shifting under mechanic stress on Pt/Ni SAA surface. This mechanical catalysis study provides an alternative route for clean hydrogen production and a strategy for deposited carbon removal under mechanical conditions.

Optimization of adaptive and sustainable gold ore grinding processes for better environmental and land conditions in the small-scale gold mining sector in Indonesia

The artisanal and small-scale gold mining (ASGM) sector largely relies on mercury in gold processing, posing potential environmental contamination, health issues, and land degradation. In the villages of Tatelu and Talawaan, ASGM operations, guided by local knowledge and resources, have transitioned to using cyanide leaching for gold processing sustainably. These operations utilize andesitic stones from river deposits as grinding media in the grinding process. However, the cyanide leaching results were not optimal, with a gold recovery below 60%. This leaves significant amounts of gold in the waste, necessitating further processing and the incomplete treatment of free cyanide waste. The suboptimal gold recovery in cyanide leaching is attributed to the inadequate grain size liberation during grinding. This study optimized grinding by comparing andesitic stone grinding media with steel balls and rods. The findings indicate that to achieve a grain size of 75% passing 74 um, grinding with andesitic stones takes 4 hours, while steel rods and balls take 3 hours. For a grain size of 75% passing 44 um, grinding with andesitic stones, steel balls, and rods requires 6 hours. With more precise process parameters, locally available andesitic stones can be an effective grinding medium to optimize gold recovery. In line with optimizing gold recovery, this will enhance ASGM's revenue, encouraging the adoption of waste management practices to alleviate environmental impact, health risks, and land degradation. This aligns with the promotion of sustainable practices within the ASGM sector.

Insights into metal wear and particle breakage using Bond's abrasiveness test

Nearly 80 years ago Fred Bond proposed his abrasiveness test, also known as Allis Chalmers abrasion test, together with empirical equations that have been used to predict the wear of mill and crusher liners, besides grinding media. Although those equations have been widely criticized over the years, in particular owing to the limited accuracy of the correlations originally proposed to predict wear, it remains the most widely used test to measure ore abrasiveness in the minerals industry. The work analyzes the test, through experiments conducted under conditions that differ from those originally proposed by Bond in order to gain insights on metal wear and particle breakage. The effects of particle size, ore competence, metal hardness and time of batch operation are analyzed. It is shown that initial particle size strongly affects the rate of wear, that the intensity of fragmentation varies with hardness of the paddle and that the size distribution from the ground material offers a valid proxy for ore competence that may be useful in geometallurgical studies.

Using Discrete Element Method to Analyse the Drop Ball Test

The drop ball test (DBT) is a common quality control procedure used in many grinding media manufacturing units to evaluate the quality of manufactured balls. Whilst DBTs have provided reasonable data over many years, the quantitative comparison of the energy that the balls are subjected to during the DBT and in high-impact loading environments such as semi-autogenous grinding (SAG) mills remains a grey area. To that end, DBT experiments were conducted, and the discrete element method (DEM) was used to assess the grinding media collision behaviour and the extent of ball impact loading to determine the impact energy spectra of the ball collisions. The impact energy spectra data obtained were used to quantify the energy that the grinding balls are exposed to in the DBT environment. The results showed that larger balls were exposed to relatively higher energy levels and had a higher probability of fracture than smaller balls. Furthermore, early ball breakage in a grinding environment is mostly attributed to the existence of imperfections or pre-existing defaults within the ball, whilst continuous wear is a gradual consequence that deplete balls in the mill.

Spontaneous room temperature reaction of titanium and its alloys with hydrogen during self-shearing reactive milling

Surface wear-activated spontaneous reactions of titanium and its alloys with hydrogen at room temperature are shown in this work. Titanium powder, intensively mixed under hydrogen pressure in a planetary mill, without any grinding media, reacts readily with hydrogen gas with the formation of stoichiometric titanium dihydride. The reaction, once initiated, proceeds spontaneously even without movement of the milling vial with a similar reaction rate. The moment of initiation of the reaction seems to be related to the removal of oxide impurities from the surface of the titanium particles and is strongly correlated with milling velocity. According to thermogravimetric measurements and X-ray diffraction (XRD) phase analysis, titanium is fully converted to TiH2. Titanium alloys were found to react in the same manner. Ti-5553 (β) reacts more easily than grade 5 Ti (Ti-Gd5) (α’), which is more reactive than grade 2 Ti (Ti-Gd2). The titanium alloy particles maintain their shape and coherency after hydrogenation. The method seems to be extremely cost-effective in the synthesis of titanium hydride and also allows the production of hydrogenated alloyed powders in spherical form, which can potentially be applied in the additive manufacturing of titanium foams. The results also show a significant risk of using titanium alloys in a hydrogen atmosphere at room temperature. It seems that after losing the protective oxide layer, parts made of pure titanium or its alloys may undergo catastrophic destruction after losing strength and ductility upon full conversion to hydride.

Influence of Galvanic Interaction between the Iron Grinding Medium and Chalcopyrite on Collectorless Flotation Behavior of Chalcopyrite: Experimental and Density Functional Theory Study.

The eco-friendly flotation process for chalcopyrite is economically significant and promotes sustainable development in mining. Collectorless flotation is a green and clean method for chalcopyrite utilization, but galvanic interactions during the grinding process can affect the surface structure, chemical composition, and electrochemical properties, impacting collectorless flotation recovery. This article uses a self-made device and flotation experiments to study galvanic interactions and their effects on surface oxidation and collectorless flotation behavior under different grinding conditions (including mineral particle size, slurry water content, pressure, and galvanic interaction time). The impact of galvanic interaction on the surface chemical composition and electrochemical properties of chalcopyrite is studied using high-performance liquid chromatography (HPLC), X-ray photoelectron spectroscopy (XPS), and electrochemical tests. Additionally, the effect of the galvanic interaction on the surface structure is analyzed with density functional theory. XPS and HPLC results show that iron grinding media contact with chalcopyrite, reducing elemental sulfur content of the chalcopyrite surface, improving hydrophilicity, and decreasing chalcopyrite collectorless flotation recovery. Grinding conditions, such as mineral particle size, slurry water content, and galvanic interaction time, significantly impact collectorless flotation and can be regulated to optimize results.

An innovatory approach for determining grinding media system to optimize fraction compositions of grinding products based on grinding dynamics principle

An innovatory approach for determining grinding media ratio and sizes to optimize fraction compositions of grinding products was created based on the principle of grinding dynamics by the single fraction tests, which were conducted with the ore from Yongping Copper mine (China) in a discontinuous conical ball mill (D × L 360 × 160 mm, China), and the results show that the optimal ball size for +8 mm fraction, −8 + 5 mm fraction, −5 + 0.45 mm fraction and −0.3 + 0.2 mm fraction are Φ70 mm, Φ60 mm, Φ50 mm and Φ30 mm, respectively. Furthermore this approach was supported from the point of view of collision energy between ore and media by discrete element method (DEM), wtih results illustrating that the materials are more active with the highest tangential collision energy with 2.23 J. In addition, the comparable tests of the full fraction feed were conducted with media system determined by this method, with the grinding technical efficiency 71.71%, being 7.61 and 1.63 percentage points higher than that under the scheme on site and the other scheme. Furthermore, applicability and feasibility were proved to be tremendously positive through the industrial tests, and results of industrial tests show that unit media consumption and unit energy consumption are reduced by 0.56 kW·h and 0.072 kg/t, respectively, what's more, not only the production capacity is promoted by 1.04 t/h, but also concentrate indexes are also improved with grade and recovery being increased by 1.01 and 2.61 percentage points compared with that before the test. This method is extremely promising and novel and could be used in most beneficiation plants to optimize the media system of ball mill to elevate indexes and promote production in all probability.

The effect of cathodic surface areas on galvanic interactions between grinding media, chalcocite and pyrite and subsequent mineral flotation

Sulphide mineral processing often involves grinding media and a number of types of sulphide minerals at various ratios of feed grades, but conventional studies on galvanic interactions for sulphide mineral processing often looked into dual-phase galvanic contacts with an equal surface area of anode and cathode. For the first time, this study investigated the galvanic interaction of a tri-phase galvanic system (GM-Cc-Py) consisting of grinding media, chalcocite and pyrite with different surface area ratios of pyrite to chalcocite (Py/Cc) to reflect the practical nature. The electrochemical studies found that chalcocite acted as a cathode in the galvanic system in the absence of pyrite, but it was switched to an anode after the addition of pyrite at Py/Cc = 1. An increase in pyrite surface area not only further anodised grinding media and chalcocite, but also increased the galvanic interaction and the oxidation of anodic materials. This nature of galvanic interactions was found to impact the pulp chemistry after grinding and also the mineral flotation behaviour. A greater pyrite surface area caused a more reducing pulp condition and higher chalcocite oxidation, both promoting copper activation on pyrite and then pyrite flotation. This study identified a high amount of pyrite recovered in copper mineral flotation at a high pyrite feed grade and suggested solving this problem by altering the cathodic role of pyrite.

Processing of kaolin micro-composite functional fillers for enhancing the near-IR reflective performance of polyurethane resin coatings

Polyurethane (PU) resin products meant for protective coatings are chemically composed of two-phase microstructures; soft ‘polyols’ and hard ‘diisocyanates and chain extenders’. For durable high-performance specialty PU coatings, their surface heat reflectance property is to be enhanced; otherwise, the absorption of solar heat energy eventually generates heat build-up that finally induces microstructural changes and chemical degradation. Hence, in this work, an attempt is made to improve the poor IR reflectance property of PU resin by incorporating kaolin micro-composite functional fillers. In this study, kaolin delamination was first carried out using alumina and zirconia milling media. Delaminated kaolin was treated with colloidal oxides, SiO2, Al2O3, and TiO2, to produce kaolin micro-composite fillers. The filler effect, chemical interaction, heat build-up, scratch resistance, and hydrophobic properties were examined, and results were presented. The study confirmed that when Al2O3-modified kaolin micro-composites improved the scratch resistance, the incorporation of 10 mass% mixed oxide kaolin micro-composite fillers enhanced the NIR reflecting property of PU coats from 4% to 53%. A facile strategy to enhance the solar heat shielding property of PU top coats for obtaining long-life durable protective coatings is presented in this work.

Electromechanical coupling characteristics analysis of vertical stirred mill based on ECS-MBD-DEM

This paper focuses on the start-up and steady-state operation stages of a vertical stirred mill, and the electromechanical coupling characteristics are thoroughly investigated based on the ECS-MBD-DEM coupling method. Firstly, according to the driving and working principles of the vertical stirred mill, the electrical control system (ECS) and multibody dynamics (MBD) model of the vertical stirred mill are separately established. Subsequently, a discrete element method (DEM) model is developed for the grinding media inside the mill. On this basis, the ECS-MBD-DEM coupling model of the vertical stirred mill is constructed, and its feasibility is validated through experiments. Then, the pitch, screw diameter, grinding media filling, and mill rotation speed of the helical agitator are considered as influential factors, with average value and coefficient of variation used as evaluation indicators for the level and fluctuation of changes. The load torque and current amplitude during the start-up and steady-state stages of the vertical stirred mill are analysed separately based on the ECS-MBD-DEM coupling method. The results indicate that the pitch, screw diameter, and grinding media filling have a significant effect on the average value of load torque. The screw diameter, grinding media filling, and mill rotation speed significantly influence the coefficient of variation of the load torque. The mill speed has a significant effect on the average value and coefficient of variation of the current amplitude. Finally, the cumulative volume velocity difference is proposed as an evaluation indicator for the grinding efficiency in the annular region, and the impact of influential factors on it is discussed, the results show that the grinding media filling and mill speed have a significant impact on the cumulative volume velocity difference.

Control of Non-Ferrous Metal-Sulfide Minerals’ Flotation via Pulp Potential

Studies on the dependence of the technological results of non-ferrous sulfide ore (copper—arsenic-bearing and non-arsenic-bearing—lead–zinc, and polymetallic) flotation on the pulp potential Eh are reviewed. Findings on the relation of Eh and collectorless flotation are presented. Changes in the pulp potential due to different gas applications and various reagent additions are considered. The influence of the grinding medium on the pulp Eh and hence on the flotation results is presented through various examples. The relation between the oxidation–reduction potential and reagent effects is exhibited and explained. pH–Eh ranges of different minerals’ flotation, as recorded in various studies, are summarized and visualized jointly for all mentioned ores. It is concluded that the pulp Eh value, considered together with the pH value, is a useful means for flotation selection controlling and deserves further research, especially under industrial conditions. Some problems and difficulties in using pulp Eh for flotation control are discussed.

Evaluate the Depression of High-Concentration Pyrite in Copper Flotation by High-Chromium Grinding Media

ABSTRACT The copper (Cu) concentrators have to process high-pyrite-content ores due to rapid depletion of high-grade ores and a high demand for Cu by clean energy technologies. However, depressing high-concentration pyrite in copper flotation is challenging presently. For the first time, this study evaluated 30 wt% Cr steel, a type of high-chromium (HiCr) steel grinding media, which can effectively produce a high Cu concentrate grade in processing low-concentration pyrite ores, in treating 25% pyrite in a Cu feed at 1.7% Cu in comparison with treating 5% pyrite in a Cu feed at the same Cu grade. Flotation tests showed decreased Cu grade and Cu recovery as pyrite feed grade increased from 5% to 25%, which was attributed to the changed galvanic interaction between grinding media and sulfide minerals, supported by ethylene diamine-tetra acetic acid disodium extraction, pulp chemistry measurements, and electrochemical studies. As pyrite feed grade increased from 5% to 25%, the anodic role of 30 wt% Cr steel did not change, but the anodic role of chalcopyrite and the cathodic role of pyrite were enhanced, promoting chalcopyrite oxidation while retarding pyrite oxidation, both of which facilitated copper activation on pyrite and subsequent pyrite flotation. This study also compared 30 wt% Cr steel and traditional forged steel in depressing 25% pyrite in the feed, and forged steel poorly depressed pyrite due to a strong anodic role of forged steel and a strong cathodic role of pyrite during the galvanic interaction leading to strong copper activation on pyrite. This study points to a direction how to depress high-concentration pyrite in copper flotation.

Effect on Fine Particles Output Characteristics of Ceramic Ball Grinding

Steel balls as traditional grinding media are prone to excessive fines generation and high energy consumption. Therefore, in light of this problem, the authors investigated another media—ceramic balls based on the output characteristics of fine particles. This study discusses the effect of ceramic balls on the change of the particle size distribution, zero-order output characteristics, micro-strain, and collision energy in ground products. The results showed that for −10 μm particle size, ceramic balls have a smaller production rate than steel balls. In addition, when the filling rate of ceramic balls is 40%, the yield of −10 μm is reduced compared to steel balls. Therefore, ceramic balls greatly reduced the overgeneration of fines. Additionally, the micro-strain rate of ceramic ball grinding with time is 67% lower than that of steel ball grinding. Furthermore, ceramic balls cannot only mitigate excessive fines generation but also effectively reduce energy consumption.

INFLUENCE OF YAG CERAMIC POWDERS GRINDING CONDITIONS OF ON THE PROPERTIES OF OPTICAL CERAMICS

In this study, the changes in the morphology and degree of agglomeration of both precursor powders and ceramic YAG powders under varying grinding conditions was considered. The effect of these parameters on the optical properties and structure of the ceramics was assessed. The YAG precursor powders were obtained through chemical co-precipitation. The morphology, size of agglomerates, and crystallites was evaluated using scanning electron microscopy, laser diffraction analysis, X-ray phase analysis, and Brunauer–Emmett–Teller gas adsorption. It was found that milling the YAG precursor powders allows for a reduction in the degree of agglomeration of the ceramic powders. It was discovered that optimal modes can be achieved at a mass ratio of grinding balls to precursor powder of 6.75/1 and a ratio of the mass of the grinding medium to the mass of the precursor powder of 4.5/1. These modes provide the necessary granulometric characteristics and the highest monodispersity. Therefore, it has been demonstrated that the use of an additional milling stage for powders synthesized by chemical precipitation, along with the selection of milling modes, can improve the properties of YAG optical ceramics.

A Review of the Grinding Media in Ball Mills for Mineral Processing

The ball mill is a rotating cylindrical vessel with grinding media inside, which is responsible for breaking the ore particles. Grinding media play an important role in the comminution of mineral ores in these mills. This work reviews the application of balls in mineral processing as a function of the materials used to manufacture them and the mass loss, as influenced by three basic wear mechanisms: impact, abrasion, and corrosion. The effect of grinding media geometries and density on the mill performance was also reviewed to determine what the research has recommended as the most suitable grinding media for different grinding applications. Although considerable work has been carried out in that area, the influence of grinding media shape on the liberation of minerals, as well as the effect of various mill conditions on the performance of mixed grinding media shapes, are still poorly understood. Thus, the review opens up opportunities for further research to improve the grinding processes, especially considering that even a slight improvement in the process efficiency significantly reduces the production costs.

Simulation of Particle Breakage in Vibration Mill Based on Tavares Model

In this paper, discrete element simulation software EDEM and Tavares crushing model were used to carry out numerical simulation research on the motion characteristics and crushing characteristics of materials in the MZ100 vibration mill during the grinding process. The influence of material characteristics, shape characteristics and filling rate of grinding media, vibration frequency, and amplitude of vibration mill on the efficiency and effect of vibration mill was analyzed. The factors affecting the distribution characteristics of the rotary center of mass and the low-energy region of the grinding medium in the grinding cavity are discussed. The extreme inflection point of the crushing efficiency of the grinding material in the grinding cavity with respect to the increase of the excitation frequency is obtained. In order to improve the grinding efficiency and reduce the low energy zone, the optimum process parameters of eccentric vibration grinding were discussed, which provided theoretical guidance for the efficient crushing of grinding materials.

High-temperature oxidation of ZrB<sub>2</sub>–SiC–La<sub>2</sub>O<sub>3</sub> ceramic material produced via spark plasma sintering

The study investigated the influence of La2O3 addition on the oxidation properties of composite ceramics with a composition of 80 vol. % ZrB2 and 20 vol. % SiC. The source materials utilized in this study included zirconium diboride (DPTP Vega LLC., Russia), grade 63C silicon carbide (Volzhsky Abrasive Works JSC, Russia), and lanthanum hydroxide concentrate (Solikamsk Magnesium Plant JSC, Russia), with the following elemental content (wt. %): La – 54.2, Nd – 4.3, Pr – 2.8, and trace amounts of other elements (<0.1). The La2O3 content in the charge varied between 0, 2 and 5 vol. %. The powders were mixed in a planetary mill with ethyl alcohol as the medium for 2 h, using a grinding media to powder ratio of 3:1. Consolidation of the powders was achieved through spark plasma sintering at 1700 °С, applying a pressing pressure of 30 MPa. The heating rate was 50 °С/min, and the isothermal holding time was 5 min. Oxidation was carried out in air at 1200 °С and the total oxidation time was 20 h. Oxidation experiments were conducted in air at 1200 °С, with a total oxidation time of 20 h. It was observed that the most significant weight gain occurred within the first 2–4 h of testing. Specimens containing 5 vol. % La2O3 exhibited the smallest weight gain after 20 h of exposure. Regardless of the presence of La2O3 , silicon carbide was found to be the first material to undergo oxidation. In specimens without La2O3 addition, the oxidized layer mainly consisted of silicon monoxide and dioxide. In contrast, specimens with La2O3 exhibited a predominantly oxidized layer composed of ZrSiO4 and ZrO2 . The study revealed that the introduction of La2O3 intensified the formation of zircon, which subsequently slowed down the oxidation processes in the material.

Mechanical activation mechanism of cassiterite based on copper-based grinding media

During grinding, the abrasion and corrosion of the grinding media generate metal ions, thereby affecting mineral flotation separation. In this study, the mechanical activation mechanism of cassiterite by copper-based media was investigated via grinding and micro-flotation experiments, inductively coupled plasma optical emission spectroscopy (ICP-OES), solution chemistry calculations, X-ray photoelectron spectroscopy (XPS) and Density functional theory (DFT). Compared with ceramic medium, copper-based medium enhanced the grinding technical efficiency of cassiterite and improved the flotation recovery. Mechanism study revealed that the increase Cu ions content in the pulp of cassiterite grinding products was the main contributor to the mechanical activation of cassiterite by copper-based grinding media, and the main forms of Cu in the solution were Cu2+, Cu(OH)+ and Cu(OH)2. XPS results demonstrated that the Cu components adsorbed on the surface of cassiterite as Cu(II) and Cu–O groups. Meanwhile, DFT calculation results shown that the Cu components were spontaneously adsorbed on the surface of cassiterite (110) in the following order: CuOH+ < Cu(OH)2 < Cu2+. Therefore, the adsorption capacity of BHA increased. These results indicate an improvement in the flotation behavior of cassiterite mechanically activated by copper-based grinding media.