Rotation Speed Of Mill Research Articles

Mass finishing of additively manufactured AISI 316L using pecan nutshells as sustainable abrasive media

Abrasive processes represent the main methods for obtaining high-quality surface finish in metal parts. As one main characteristic, these processes have a relatively high consumption of energy per material volume removed, as well as many inputs, such as abrasive tools and equipment, and, consequently, a high associated environmental impact. Additive manufacturing is becoming a competitive method to produce customized parts, but the surface finish is often not good enough for the application, and post-processing is needed. In this work, a mass finishing process using a planetary mill with abrasive media made of sustainable materials (pecan nutshells) was used on AISI 316L stainless steel samples manufactured by selective laser melting (SLM). The main goal was to perform a multicriteria analysis of the sample surface before and after post-processing. Through the analysis, it could be observed that the nutshell abrasive media has results close to those of traditional ceramic media. The increase in the rotation speed of the planetary mill, increase of finishing time, and use of abrasive pastes can further increase the effectiveness of the process.

The influence of mechanochemical activation on the rheological properties and strength development of geopolymer

To address the significant carbon emissions caused by the cement industry and its contribution to the greenhouse effect, there is an urgent need for new construction materials that can substantially reduce the use of traditional Portland cement. Alkali-activated binders, known for their excellent performance and lower carbon footprint, have emerged as a promising alternative. Despite the numerous advantages of geopolymers, their practical application is hindered by challenges in processability required for construction techniques, such as pumping, spreading, and forming. This study focuses on enhancing the rheological properties of geopolymers through mechanochemical activation and exploring the modification mechanisms involved. Slag and fly ash raw materials were processed under different ball milling conditions, specifically varying ball milling rotation speed (BR) and ball milling time (BT). The mechanical properties, workability, and rheological behavior of geopolymer specimens were evaluated to identify the optimal milling parameters affecting these properties. Detailed analysis using XRD, SEM, and heat of hydration tests elucidated the phase composition, microstructural evolution, and thermal characteristics of mechanochemically modified geopolymers, providing insights into the fundamental mechanisms of mechanochemical activation modification. The results indicate a significant correlation between ball milling parameters and the rheological properties of geopolymers. The optimal milling regime was identified as grinding at a speed of 70r/min for 50 min. This specific milling condition imparts ideal properties to the geopolymer, including moderate yield stress (34.353 Pa), low plastic viscosity (0.452 Pa s), good thixotropy, and high 28d strength (53.28 MPa), without any significant shear thickening behavior.

Effect of Grinding Conditions on Clinker Grinding Efficiency: Ball Size, Mill Rotation Speed, and Feed Rate

The production of cement, an essential material in civil engineering, requires a substantial energy input, with a significant portion of this energy consumed during the grinding stage. This study addresses the gap in the literature concerning the collective impact of key parameters, including ball size, feed rate, and mill speed, on grinding efficiency. Nine spherical balls, ranging from 15–65 mm, were utilized in six distinct distributions, alongside varying feed rates and mill speeds. ANOVA, Taguchi, and regression analyses were employed to explore their influence on grinding efficiency and cement properties. The findings revealed that ball size variation significantly affects grinding performance, with smaller diameter balls yielding higher efficiency due to increased abrasion and fine formation. Conversely, elevating mill speed generally diminishes grinding efficiency, particularly at speeds approaching 90% of the critical speed, impacting ball shoulder and foot angles. Moreover, increasing the feed rate affects the grinding performance differently based on ball distribution, with finer distributions experiencing adverse effects. Signal-to-noise ratios facilitated determining the optimal control factor levels to minimize energy consumption. Quadratic regression models exhibited strong predictive capabilities for energy consumption in grinding. Ultimately, the optimal grinding performance was achieved with Bond-type ball distribution No. 6, considering ball size, mill speed, and feed-rate interactions, albeit with considerations regarding grinding time and energy efficiency.

Preparation of Cementitious Materials from Mechanochemically Modified Copper Smelting Slag Compounded with High-Aluminum Fly Ash.

Copper smelting slag discharged from mining and high-aluminum fly ash generated during the combustion of coal for energy production are two typical bulk solid wastes, which are necessary to carry out harmless and resourceful treatment. This research proposed an eco-friendly and economical method for the co-consumption of copper smelting slag and high-aluminum fly ash. Cementitious materials were compounded with copper smelting slag and high-aluminum fly ash as the main materials were successfully prepared, with a 28-d compressive strength up to 31.22 MPa, and the heavy metal leaching toxicity was below the limits of the relevant standards. The optimum mechanical properties of the cementitious materials were obtained by altering the material proportion, ball mill rotation speed, and CaO dosage. Under the combined effect of mechanical ball milling at a suitable speed and chemical activation with a certain alkali concentration, the prepared cementitious materials had an initial activation. The pastes of the cementitious materials generated a gel system during the subsequent hydration process. The two steps together improved the mechanical strength of the cured products. The preparation was simple to operate and offered a high stability of heavy metals. The heavy metal contaminants were kept at a low content throughout the process from raw materials to the prepared cured specimens, which was suitable for application in practical environmental remediation projects and could provide effective solutions for ecological environment construction.

Pengaruh Putaran Mill Jar Pada Proses Penghalusan Serbuk Keramik Alumina dengan Alat Horizontal Ball Mill

Powder technology is one of the most frequently used alumina manufacturing processes. The powder must be made as small as possible because the mechanical strength of the ceramic is inversely proportional to the size of the powder. Powder grinding can be done using a horizontal ball mill. Ball mill is equipment that functions to grind powdered material with the help of grinding balls inside it. The purpose of this study was to determine the effect of variations in the rotational speed of the mill jar on the quality of alumina powder products at room temperature. The research method used is the experimental method by testing the alumina powder material with variations in the rotation speed of the mill jar 100 rpm, 125 rpm, 150 rpm, 175 rpm, 200 rpm, 225 rpm and 250 rpm. The results of the study showed that variations in the rotational speed of the mill jar affected the size of the alumina powder which was ground using a ball mill. The best mill jar rotation speed from this test was 150 rpm, resulting in a sub-micron size percentage of 8.0% and a reduction in the size of alumina powder from 70.28 µm to 44.07 µm.

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.

Enhanced Degradation of Decabromodiphenyl Ether via Synergetic Assisted Mechanochemical Process with Lithium Cobalt Oxide and Iron

The removal of decabromodiphenyl ether (BDE 209), as a typical persistent organic pollutant (POP), is of worldwide concern. Mechanochemical (MC) processes are promising methods to degrade environmental pollutants, most of which use a single grinding reagent. The performance of MC processes with co-milling agents still needs to be further verified. In this study, an efficient MC treatment with combined utilization of lithium cobalt oxide (LiCoO2) and iron (Fe) as co-milling reagents for BDE 209 degradation was investigated. The synchronous action of LiCoO2 and Fe with a LiCoO2/Fe/Br molar ratio of 1.5:1.67:1 and a ball-to-powder ratio of 100:1 led to almost thorough-paced abatement and debromination of BDE 209 within 180 min using a ball milling rotation speed of 600 rpm. The reduction in particle sizes and the destruction of crystal structure in mixture powders with the increase in milling time induced the enhanced degradation of BDE 209, as characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The X-ray photoelectron spectroscopy (XPS) characterization showed that the valence state of Co was converted from Co(III) to Co(II), and Fe(0) was changed to Fe(III) when treated with an MC process. This indicated that the reductive debromination of BDE 209 by Fe and the following oxidative degradation of debrominated products by LiCoO2 were integrated in a concerted way. It proved the removal of BDE 209 via an MC treatment. The full breakage of C-Br and C-O bonds in BDE 209 was confirmed by Fourier transform-infrared spectrometry (FT-IR) spectra, and a possible abatement pathway was also proposed based on the identified intermediate products using gas chromatography–mass spectrometry (GC-MS). These obtained results indicated that a combination of LiCoO2 and Fe as co-milling reagents is promising in the MC treatment of toxic halogenated pollutants like BDE 209.

Exploring the effects of a new lifter design and ball mill speed on grinding performance and particle behaviour: A comparative analysis

Ball mills are the leading grinding equipment in the mineral processing industry. Balls are the primary component in the grinding of materials. Lifters lift these balls to the shoulder position before cataracts them to the toe position. Almost all classical theories do not consider the lifter's geometry in calculating the energy consumption of ball mills and focus only on the fill level of the charge, the lifter dimensions, their number, and the mill's rotational speed. To improve the ball mill's performance, a new shape of the lifters was proposed in the present research work. Simulation through the EDEM software and the discrete element method (DEM) was used to predict the particle behaviour and conduct a comparative study on the influence of the lifter geometry and ball mill rotational speed on torque, power draw, and kinetic energy. The validation of our results is evaluated by a confrontation of the experimental tests of discontinuous grinding with a 573 x 160 cm of Bian. The results show that using helical lifters has a more significant effect on the grinding efficiency, the torque, and the power draw of the ball mill. They decrease the wear rate of liners and lifters when mill speeds are extremely high (90%, 100%).

Optimization of the SAG Grinding Process Using Statistical Analysis and Machine Learning: A Case Study of the Chilean Copper Mining Industry.

Considering the continuous increase in production costs and resource optimization, more than a strategic objective has become imperative in the copper mining industry. In the search to improve the efficiency in the use of resources, the present work develops models of a semi-autogenous grinding (SAG) mill using statistical analysis and machine learning (ML) techniques (regression, decision trees, and artificial neural networks). The hypotheses studied aim to improve the process's productive indicators, such as production and energy consumption. The simulation of the digital model captures an increase in production of 4.42% as a function of mineral fragmentation, while there is potential to increase production by decreasing the mill rotational speed, which has a decrease in energy consumption of 7.62% for all linear age configurations. Considering the performance of machine learning in the adjustment of complex models such as SAG grinding, the application of these tools in the mineral processing industry has the potential to increase the efficiency of these processes, either by improving production indicators or by saving energy consumption. Finally, the incorporation of these techniques in the aggregate management of processes such as the Mine to Mill paradigm, or the development of models that consider the uncertainty of the explanatory variables, could further increase the performance of productive indicators at the industrial scale.

Effect of Ball Milling Technology on Properties of Refractory Waste

With the popularization of "sponge city" in the whole country, the use of permeable bricks is increasing every year. Although the raw materials required for the preparation of permeable bricks are widely sourced, there are few reports on the process of using refractory waste to prepare permeable bricks. It is the ball milling process of refractory waste. The effects of ball milling time, ball mill rotation speed, and ball-to-material ratio on the properties of refractory waste were mainly studied. Through the experimental results and analysis, the following conclusions can be drawn: with the increase of ball milling time, ball milling speed and ball-to-material ratio, the particle size of refractory waste powder gradually decreases. Through research, it is concluded that the optimal ball milling time is 4h, the ball milling speed is 100r/min, and the ball-to-material ratio is 2:1.

Grain size and phonon thermal conductivity of sintered bulk undoped lead telluride compacts processed via mechanical grinding and alloying

This study focused on investigating the influence of processing undoped, dense lead telluride (PbTe) either via mechanical grinding (MG) or mechanical alloying (MA), based on the milling rotation speed (1.5–3.0 Hz), followed by hot pressing (HP) on the grain size and phonon thermal conductivity (κphonon). The samples prepared via MG-HP were single-phased, had high relative densities (>99%), and exhibited uniform morphologies. For a milling rate of 2.5 Hz, the minimum κphonon of MG-HP was 0.90 W m−1 K−1 and the average grain size was 0.47 μm. Furthermore, the grains produced by MG-HP and milled at 2.5 Hz comprised subgrains with a size of approximately 50 nm. The samples prepared using MA-HP showed higher theoretical relative densities. For a milling rate of 2.0 Hz, the minimum κphonon of MA-HP was 1.36 W m−1 K−1 and the average grain size was 0.52 μm. The electrical conductivity and Seebeck coefficient of MG-HP and MA-HP were similar to those of the p-type doped materials. Thus, the MG-HP process is an appropriate method for producing undoped PbTe with a high Seebeck coefficient and a low κphonon.

Extremum seeking control for optimization of an open-loop grinding mill using grind curves

A semi-autogenous grinding mill is simulated with gradient and non-gradient based extremum seeking controllers to maximize the mill performance using grind curves. Grind curves map the essential performance measures of a grinding mill to the mill load and rotational speed. The curves vary with the changes in the feed ore characteristic but show generic parabolic features with extremums. The extremum seeking controllers search along the unknown input–output map to steer the process towards an unknown optimum. In this study, a classical perturbation-based method, a time-varying parameter estimation-based method and the Nelder–Mead simplex method are employed as extremum seeking control (ESC) methods to search along the grind curves to either optimize the mill throughput or grind by means of manipulating the mill feed or rotational speed. The proposed extremum seeking controller could reduce the need for a plant operator to manually select the optimal operating conditions that maximize the performance measures of a grinding mill. Since the controller is agnostic to the process model, the grinding mill can be optimized without the need for a detailed process model. The simulated results show that the extremum seeking controllers steer the mill operating conditions toward the steady-state optimum and can be used to satisfy operational objectives. However, the slow grinding mill dynamics result in a long convergence rate when the initial conditions are far from the optimal operating conditions.

Optimization of the Ball Mill Lifter Shapes and Rotational Speed by Investigating the Dataset of Their Effects on Particle Size Decreasing and Electrical Power Consumption

Optimization of the Ball Mill Lifter Shapes and Rotational Speed by Investigating the Dataset of Their Effects on Particle Size Decreasing and Electrical Power Consumption

Effect of Silica on Pyrene-Contaminated Soil Subjected to Mechanochemical Remediation

Soil contaminated by polycyclic aromatic hydrocarbons (PAHs) is a common problem in the world. Mechanochemical treatment is a promising technology for remediation of PAH-contaminated soil. This study investigated the feasibility of pyrene degradation with silica by mechanochemical remediation. The effects of ball milling time and rotation speed on the removal efficiency of pyrene in soil were also studied. When the milling time was 3 h and the rotation speed was 500 rpm, the removal efficiency of pyrene in soil was over 98%. The intermediate products detected by gas chromatography–mass spectrometry proved that the hydrogenation reaction and the destruction of benzene rings occurred in the milling process. Both graphite and amorphous carbon were detected by Raman spectra. The main degradation pathway and mechanism of pyrene by mechanochemical treatment should be the destruction of benzene rings caused by free radicals and further carbonization.

Determining an appropriate range for the number of cuboid lifters in ball mills using DEM

The number of lifters in the liner of ball mills and the mill rotation speed are among the most significant factors affecting the behavior of grinding charge (balls) and their motion trajectory, and consequently, the comminution mechanism in these mills. In this research, in order to find a suitable range for the number of lifters in the liner of ball mills, the DEM method is utilized. Initially, a pilot-scale ball mill with dimensions of 2.0 m × 1.11 m without any lifter is simulated. Afterwards, by adding, respectively, 1, 2, 4, 8, 16, 20, 26, 30, and 32 cuboid lifter(s) with dimensions of 2 m × 5 cm × 5 cm, nine other separate simulations are performed. The influences of the number of cuboid lifters on the two new factors introduced here, namely ‘head height’ (HH) and ‘impact zone length’ (IZL) at various mill speeds, that is, 70% and 80% of its critical speed (CS) are investigated. The results indicate that in order to find a suitable range for the number of lifters in the liner of ball mills, it is necessary to consider these two parameters simultaneously as the criteria for selecting the appropriate range, That is, liners that simultaneously produce both a higher HH and a greater IZL are more suitable for use in the industry. The results also demonstrate that the suitable range for the number of cuboid lifters in the liner of ball mills is between 16 and 32, which field research on the ball mills of three different plants in the industry confirms the accuracy of the results obtained in this research. Unlike the previous research works, it has now been shown that the number of ball mill lifters does not only depend on the diameter of the mill but also depends on the width, height, angle of the lifter, and generally on the type of lifter.

Development of agomelatine nanocomposite formulations by wet media milling

Nanocrystal formulations of the BCS class II agomelatine, were developed by wet media milling. The most suitable stabilizer was identified and effects of process and formulation variables on the nanocrystal size and ζ-potential were evaluated employing a Box-Behnken experimental design. The optimized nanosuspensions were dried and subsequently evaluated for redispersibility and physicochemical properties. Computational simulation of solid state properties was applied to rationalize crystal fracture. It was found that low viscosity hydroxypropylcellulose with sodium dodecyl sulfate is the most suitable stabilizer. Stabilizer concentration exerts a statistically significant effect on particle size, which depends on the mill's rotation speed. The milling process induces a polymorphic transition to form II, which could affect size reduction kinetics. The solidified nanosuspensions’ redispersibility is deteriorating progressively with storage time, with only minor differences between drying methods, retaining enhanced dissolution rate. Crystal lattice simulations suggest high mechanical anisotropy of form I crystals, which could be an additional reason for fast particle size reduction prior to the polymorphic transformation. Wet media milling, combined with a suitable drying method, can be an efficient technique for the production of stable nanocrystals of agomelatine. Particle informatics methods can enhance our understanding of the mechanisms responsible for agomelatine's nanocomminution.

AG/SAG mill acoustic emissions characterisation under different operating conditions

Towards the development of an improved and more efficient online monitoring system in an industrial AG/SAG grinding mill, the present study employs a laboratory-based AG/SAG mill and acoustic sensor to investigate the acoustic characteristics of different mill operating conditions. Specifically, mill operating conditions such as empty mill, individual charge compositions and their combinations, together with different lifter heights and mill speeds were studied. The results showed remarkable acoustic emission in ball only load and reduced in order of ball-water, ball-rock, rock-ball-water, rock only, rock-water, water only and no load. Water and rock showed minor and major dampening effects on the mill acoustic emission, respectively, in the presence of steel balls. Generally, mill rotational speed, charge load as well as lifter height variations reflected well in the mill noise emission. This study supports the use of mill acoustic sensing technique to understand different grinding conditions in AG/SAG mills for improved and continuous process monitoring, energy-efficient milling, and enhanced optimisation.

Mechanochemical and microwave treatment of precipitated zirconium dioxide and study of its physical\u2013chemical, thermal and photocatalytic properties

The effects of the microwave treatment (MWT) and mechanochemical treatment (MChT) on the structure and physicochemical properties of precipitated zirconium oxide were investigated. The obtained materials were characterized using the N2 adsorption/desorption, thermogravimetry (TG, DTG, DTA), XRD and UV–Vis/DRS methods. Photocatalytic properties of the samples were also studied as regards the rhodamine B (RhB) degradation in the aqueous solution. The results show that the microwave and MChT, differing in mill rotation speed, temperature or treatment media, causes significant changes in the porous structure of the obtained samples. In most samples, the specific surface area increase was observed. The DTA and XRD results showed the formation of crystalline structure during MWT. As follows from the investigations, each way of modification results in the shift of the absorption edge toward higher wavelength values and causes photocatalytic degradation of RhB under UV irradiation and makes the obtained materials effective photocatalysts in the visible region.

The influence of the rotation frequency of a planetary ball mill on the limiting value of the specific surface area of the WC and Co nanopowders

An increase in the hardness and wear resistance of WC-Co alloys with a decrease in the grain diameter of WC and Co makes it relevant to search for methods for producing powders with a maximum specific surface area (SSA). SSA growth is limited even when milling powders of WC and Co in the most high-energy mills. Effect of increasing the rotation speed of a planetary ball mill on the limiting value of the SSA of obtained nano sized WC and Co powders is studied. According to the developed model, an increase in the rotational speed of the mill leads to an increase in the limiting value of SSA if the cause is particle hardening. If the cause is coalescence, an increase in frequency leads to a decrease in the limiting value of the SSA. It was determined that the limiting value of SSA of WC particles increases from 1.0⋅108 m2/m3 to 2.2⋅108 m2/m3 (Sauter average diameter decreases from 60 to 27 nm) with increase of mill rotation frequencies from 2.5 to 4.2 rps due to a decrease in the volume of “indestructible” particles. And the limiting value of SSA of WC particles decreases from 2.2⋅108 m2/m3 to 1.1⋅108 m2/m3 (Sauter average diameter increases from 26 to 55 nm) with increase of mill rotation frequencies from 5 to 6.7 rps due to the increase of the coalescence rate. The experiment showed that the limiting value of SSA for Co powder decreases from 1.0⋅108 m2/m3 to 1.1⋅106 m2/m3 with increasing of the rotational speed of the mill from 2.5 rps to 6.7 rps (Sauter average diameter increases from 60 to 5450 nm) due to the increase of the coalescence rate. Studies have shown that the growth of SSA of WC grains is limited by a certain value (11.5 nm).

Modeling and prediction of wear rate of grinding media in mineral processing industry using multiple kernel support vector machine

In this study, we investigates the application of three powerful kernel-based supervised learning algorithms to develop a global model of the wear rate of grinding media based on the input factors such as pH, solid percentage, throughout, charge weight of balls, rotation speed of mill and grinding time. It is found that there is a trade-off between the training and testing error when a single kernel function is used and therefore these methods cannot provide the generalization capability. However, this problem is solved utilizing the multiple kernel learning frameworks for support vector machine in which the kernel function was expressed as a combination of basis kernel functions. It is distinguished that compared to the single kernel and ANN-based techniques, the use of multiple kernel support vector machines benefit from a higher degree of correctness and generalization ability for prediction of wear rate of grinding media. Meanwhile, the findings indicate that in this state, the values of R2 are achieved 0.99417 and 0.993 for training and testing datasets, respectively.