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Effects of operating parameters on the efficiency of dry stirred milling

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Abstract

Stirred media milling is an industrially accepted efficient grinding method for fine and coarse particles. The stirred mills can be operated both in vertical and horizontal configurations and the selection depending on the process variables. Successful operation of horizontal stirred milling (i.e. IsaMill) in wet applications encouraged the studies in dry applications. In this study, series of dry grinding tests were performed in a prototype horizontal stirred mill (42 L) to investigate the effects of operating parameters such as stirrer speed, feed rate, media filling and ball size on grinding considering the degree of size reduction and the energy consumption. The test results have shown that the stirrer speed, the media size and the media filling are directly proportional and the feed rate is inversely proportional with the specific energy consumption. Besides, energy savings up to 27% were achieved by adjusting the milling conditions properly (suitable media size) and the size reduction values (F50/P50) were between 1.05 and 2.42.

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... Jayasundara, Yang and Yu [19] investigated the effects of using different media sizes in a horizontal mill computationally, but each charge was a single size. This is just one example of a series of studies that have observed the effects of different-sized media within horizontal setups [20][21][22][23][24]. Cho et al. [8] took this one step further by comparing a monodispersed experimental mill with simulated binary and three-size bead distribution ratios. ...
... Different sizes can also be added to the virgin media to aid this. Wear profiles and correlations can be generated [62][63][64][65], with Altun et al. [20] being one such example in the mining industry. ...
... As you add smaller media, they segregate toward the bottom of the mill, and with more being able to fit into the same volume as the larger size, reduce the number within the pin region. The greater attrition coming from smaller media [4] will also cause more wear on the lower attritor pins, as demonstrated by Altun et al. [20] who observed 2.5 times the amount of wear on the bottom pins of a HIGMill compared to the top ones. This becomes more extreme when higher size ratios are considered because the smaller size takes up a lower overall volume despite being kept in constant numerical proportions. ...
Article
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Most industrial vertical stirred mills contain a non-uniform set of grinding media sizes. However, this fact is often ignored in simulations, which mostly use monodispersed media. The paper explores the fundamental dynamics of vertical mills when using multiple sizes of grinding media, by using DEM simulation. Our results suggest that by including both large and small media, one may be able to optimise its performance in several manners. The energy going into the contacts can be increased by including a second size, leading to more effective grinding. Including smaller media can also reduce the power draw of the mill, increasing the efficiency and sustainability of the mill. Finally, the natural segregation between different sizes creates different types of collision which grind different particle sizes more effectively. Segregation leads to smaller media at the bottom, so continuous processes can be optimised for fine grinding by feeding from the top, where the larger media are. This further enables control of the resulting product specifications.
... Among the reported literature, the vertical stirred mills were found to be more realistic option (Radziszewski and Allen 2014). The energy savings in the stirred mills are due to smaller media which stirs at a high velocity rather than cascading and cataracting movements that are common in conventional tumbling mills (Altun, Benzer, and Enderle 2013). There is a significant difference in the frequency distribution of energy intensities for the stirred and conventional ball mills. ...
... Stirrer speed mainly increases the probability of media to particle impact/attrition by creating high energy strength environment in the grinding chamber (Altun, Benzer, and Enderle 2013;Eswaraiah et al. 2015). The increase in stirrer speed increases the stress intensity in the mill, influences the interaction between grinding media and slurry, and it is an important operating variable in the stirred mill operation (Hasan 2016). ...
... It was observed that higher stirrer speed consumes higher energy to reduce the desired product particle size. The observation made regarding the product size (P 80 ) and the energy consumption (E CS ) is consistent and concurring with the reported literature (Zheng, Harris, and Somasundaran 1996;Jankovic 2003;He, Wang, and Forssberg 2004;Pilevneli et al. 2004;Altun, Benzer, and Enderle 2013;Eswaraiah et al. 2015;Hasan et al. 2017). In the present study, stirrer speed played a significant role in grinding of chromite bearing PGE minerals. ...
Article
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The depletion of high-grade ores has forced the utilization of low-grade ores. The small liberation sizes in the low-grade ores require fine grinding which is an energy intensive operation. In the present study, low-grade chromite ore bearing platinum group of elements (PGE) was used as an experimental material. The previous study concluded the liberation size of around 1–50 µm for chromite ore bearing PGE minerals. Therefore, the target product size for grinding was kept below 50 µm. The wet fine grinding experiments were performed in a vertical stirred mill. Four significant operating variables stirrer speed, grinding time, feed size, and solids concentration were investigated for their effect on the performance of stirred mills. The performance of the mill was assessed in terms of achieving small product size at lower energy consumption. The detailed investigations were carried out according to popularly adopted methods of statistical design of experiment. The results revealed that stirrer speed, grinding time, and feed size played crucial role on the performance of stirred mill. Mathematical correlations were developed for predicting product size and energy consumption. The models developed were then optimized using quadratic programing to minimize the combination of product size and energy consumption.
... [5,6]) and horizontal (e.g. [7,8]) designs. First studies underline that dry stirred media milling is very different in comparison to wet stirred milling, i.e. as comparably moderate stirrer tip speeds [7,9] and lower bead filling ratios [7,10] are favorable for a high energy utilization. ...
... [7,8]) designs. First studies underline that dry stirred media milling is very different in comparison to wet stirred milling, i.e. as comparably moderate stirrer tip speeds [7,9] and lower bead filling ratios [7,10] are favorable for a high energy utilization. However, due to the difficult process control of fine grinding processes in dry stirred media mills, this development is still in an early to intermediate stage. ...
... [7,8]) designs. First studies underline that dry stirred media milling is very different in comparison to wet stirred milling, i.e. as comparably moderate stirrer tip speeds [7,9] and lower bead filling ratios [7,10] are favorable for a high energy utilization. However, due to the difficult process control of fine grinding processes in dry stirred media mills, this development is still in an early to intermediate stage. ...
Article
The demand on minerals with increasing product fineness is currently rising in many industrial applications. Especially in dry grinding processes, fine powders are difficult to produce and to handle. Particle-particle attractive forces, which become more decisive with decreasing particle size, lead to a higher extent of agglomeration, material adherences and a more cohesive flow behavior. As a consequence, dry fine grinding processes demand large quantities of energy due to the amount of applied energy that is dissipated into heat. Current approaches for improving the energy efficiency mainly cover the improvement of a) machine equipment and b) the material behavior. The main focus of this study was to investigate both aspects within one single study: On the one hand, dry fine grinding of limestone was investigated in a dry operated stirred media mill, which is a promising and emerging option for dry fine grinding applications. On the other hand, the impact of the particle stabilization by liquid grinding aids on the grinding performance was evaluated. It was demonstrated that the grinding mechanism inside the mill depends on both the mill parameters as well as the powder flow behavior. Therefore, it is of crucial importance to adjust the mill parameters to the applied grinding aid when it comes to dry fine grinding in media mills.
... Stirred mills are used in fine and ultrafine grinding where the liberation occurs at very fine sizes. [11][12][13][14][15][16][17] The stirred media mills are introduced in different process industries due to their higher energy efficiency and capability to produce finer products. These mills have been used over the years to improve the energy efficiency in the fine grinding zone that may lead to energy saving of the overall comminution process. ...
... Stirrer speed mainly increases the probability of media to particle impact by creating a high stress-energy environment that increases the stress intensity within the grinding chamber. [11,14] It was observed that with the increase in stirring speed from 450 to 850 rpm, the energy consumption increased from 9.75 to 15.6 kWh/t, as shown in Fig. 7a. The resulting trend is well matched with the reported literature. ...
Article
Full-text available
Platinum group of elements (PGE) mineral is a valuable resource for platinum and other elements. Grinding experiments were conducted in a laboratory-scale stirred mill on a low-grade PGE bearing chromite ore. High-Pressure Grinding Rolls (HPGR) product of −1 mm was used as feed material to the stirred mill experiments. A four-factor (stirrer speed, grinding time, pulp density, and media filling) and a five-level Central Composite Design matrix (CCD) was applied to investigate the stirred mill performance in coarse grinding. The stirred mill grinding efficiency was evaluated based on the particle size distribution and energy consumption. The experimental results showed that the stirrer speed, grinding time, and media filling significantly affect the product size and energy consumption. Pulp density had little influence on the process responses. 3D response surface plots were also discussed in detail to better understand the process variables. A finer size product of 274.7 µm (reduction ratio of 2.63) was achieved at optimal conditions of the stirred mill with an expense of 26.01 kWh/t energy. The results stated that good performance was obtained with the coarser feed size in the stirred mill.
... The ultra-fine grinding (UFG) mills consume a much higher installed power per mill unit volume (Altun et al., 2013). On the other hand, they use a finer media size (i.e., 2-3 mm) than the conventional tumbler mills, which typically require 12 to 100 mm grinding media. ...
... A significant saving of 33% can be achieved by increasing the grinding media size from +40/-210 to +420/-850 µm. According to Altun et al. (2013), the grinding media size plays a vital role in grinding operations, and its proper selection can positively impact energy efficiency. Likewise, unsuitable grinding media sizes might dramatically increase the power draw (Jayasundara et al., 2012). ...
Article
This study investigated ultra-fine coal grinding performance of four low- to moderate-cost grinding media in a laboratory stirred mill. Kinetic grinding tests showed that silica beads generated the finest product size with a P80 of 5.9 μm from a feed size of 24.4 μm while having a specific energy (SE) input of 309 kWh/ton. Nonetheless, the least energy consumption of 109 kWh/ton was achieved by alumina beads; however, yielding a coarser product size of 15.5 μm. In addition, test results indicate that optimizing media sizes, solids concentration, and using viscosity modifiers enhance coal ultra-fine grinding performance. Under the optimized testing conditions, a P80 of 2.7 μm was produced with a corresponding SE input of 270 kWh/ton using silica beads ranging from 420 to 850 μm and a dispersant dosage of 14 kg/ton. Moreover, the mathematical models generated based on population balance modeling provided an accurate forecast of the particle-size distribution.
... Stirred milling technology is suitable for re-processing coarse-and fine-grained mining waste as it uses an attrition mechanism to grind the material (Altun et al., 2013;Wills and Finch, 2016;Napier-Munn et al., 1996), removing hydrophilic surfaces and reducing particle size. Stirred milling technology is also attractive as it is more energy efficient, has lower capital costs, and has a smaller footprint than conventional tumbling ball mills (Altun et al., 2013;Gupta and Yan, 2016). ...
... Stirred milling technology is suitable for re-processing coarse-and fine-grained mining waste as it uses an attrition mechanism to grind the material (Altun et al., 2013;Wills and Finch, 2016;Napier-Munn et al., 1996), removing hydrophilic surfaces and reducing particle size. Stirred milling technology is also attractive as it is more energy efficient, has lower capital costs, and has a smaller footprint than conventional tumbling ball mills (Altun et al., 2013;Gupta and Yan, 2016). ...
Article
Demand for technologies delivering renewable energy and improving energy efficiencies are set to increase with the worldwide movement towards low carbon economies. Many of these technologies are reliant on “critical metals”: metals considered both important to society and vulnerable to supply disruption. Significant concentrations of critical metals have reported to mining and processing wastes over time; thus, an opportunity exists to meet critical metal demand through re-processing of these wastes. Mining and processing wastes have significantly different properties to run of mine ores. This means that while the overall mineral processing sequence for mining and processing wastes is the same as run of mine ore, the best technologies to achieve the liberation, separation, and concentration of critical metals is different. There are a range of innovative technologies that can be used to liberate and separate critical metals from mining and processing waste. Mineral liberation can be achieved using stirred milling, which breaks up particles and removes hydrophilic surface that can prevent particle flotation. Particle separation based on size can be achieved using semi-inverted cyclones and hybrid classification technologies. Separation of minerals from gangue can be achieved using flotation, with fluidised bed reactors and reactor-separator induced air reactors being suitable for coarse and fine particles, respectively. Gravity concentration using counter flow fluidised bed separators is also suitable for separating minerals from gangue. This review provides an overview of these technologies, as well as an introduction to the sequence of events when undertaking mineral processing, for an audience not specialised in this discipline. However, extraction of any metal value from tailings is contingent on detailed mineralogical characterisation. Three case studies are presented to demonstrate the analysis that is necessary as a crucial first step towards valorisation. Ultimately, implementation of these technologies to extract critical metals from mining and processing wastes will not only aid in meeting future critical metal demand but is essential for achieving a sustainable circular mining system with near-zero waste.
... Many parameters may influence the outcomes of dry grinding in stirred media mills. It is possible to classify such parameters as the mill's design properties (e.g., impeller types, the features of impeller arms, the length/diameter ratio of the mill, the orientation of the shaft), vertical [6][7][8] or horizontal [9][10][11][12] and operating parameters (e.g., grinding time [7,[13][14][15], stirrer speed [6,9,13,[15][16][17][18], media loading, type and size [13,19,20], grinding type. The information obtained from these studies shows that dry stirred media mills are still in an early to intermediate stage of development. ...
... Many parameters may influence the outcomes of dry grinding in stirred media mills. It is possible to classify such parameters as the mill's design properties (e.g., impeller types, the features of impeller arms, the length/diameter ratio of the mill, the orientation of the shaft), vertical [6][7][8] or horizontal [9][10][11][12] and operating parameters (e.g., grinding time [7,[13][14][15], stirrer speed [6,9,13,[15][16][17][18], media loading, type and size [13,19,20], grinding type. The information obtained from these studies shows that dry stirred media mills are still in an early to intermediate stage of development. ...
Article
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The optimization of the operating parameters of a stirred media mill in the dry grinding of calcite was investigated. A three-level Box-Behnken design was used for the purpose of examining the impact of four independent factors, the stirrer speed (SS), grinding time (GT), media filling ratio (MFR), and solid mass fraction (SMF), on the product particle size (d50). For the purpose of establishing an empirical correlation between operating parameters and responses, a series of experiments were carried out. Variance analysis showed a reasonably good value for d50 (R2 = 0.965). According to the software solutions, the optimum conditions for minimizing the d50 size were found to be 573 rpm stirrer speed, 11.18 min grinding time, 63% media filling ratio, and 11.52% solid mass fraction, with 3.78 µm for the d50 size. To verify the improvement of grinding, verification tests were performed using the above-mentioned optimum conditions and the average d50 size and standard deviation were found to be 3.83 µm and 0.025, respectively. The average d50 value obtained was smaller than those obtained in the 27 tests. Furthermore, when the optimum result obtained from the experiments was compared with the result obtained using the software, a 22% energy saving was achieved. The impacts of grinding on the structural characteristics of calcite particles were characterized by XRD analysis. XRD measurements indicated that no change was observed in the peak areas of ground calcite specimens compared to the untreated calcite specimen.
... The higher tip speed and the smaller ball size of horizontal mills make them more energy efficient over the vertical configurations (Gao et al., 2002;Clark, 2007). Furthermore, due to the higher start-up torque of vertical stirred media mills have scale-up problems (Altun et al., 2013). According to Molls and Hornle (1972) more than 40 parameters of influence were identified in the case of stirred media mill. ...
... In the field of cementitious materials several recently published paper deal with the mechanical activation of clinker and the production of microcement in stirred media mill (Altun et al., 2013(Altun et al., , 2014(Altun et al., , 2015Mucsi et al., 2013). Altun et al. (2014Altun et al. ( , 2015 studied three types of grinding aids (TEA-based and TIPA-based) on the grinding results of dry stirred milling of cement. ...
Article
Comminution in stirred media mills is a frequently applied top-down method towards the production of micron- and submicron particles. However, due to the high energy density, this type of mill is appropriate for mechanical activation (MA) as well. Despite the vast field of mechanochemistry which encompasses an increase in reactivity by mechanical energy input, there is only limited publication on stirred media mill-based MA until now. The main focus of this paper is the short introduction of MA and review of the above field related to the mentioned mill type. It can be identified as a general conclusion that this recently introduced mill is not yet applied in a wide range in MA compared to other high energy density mills (HEM) like planetary ball mill or vibratory mill which have been used since long time. However, the results published on the mechanical activation in stirred media mill seems very promising which is forecasted the increase of publication in number in the future. The basis for this lies in its high energy density (3…10 times higher than other HEM), the ability of continuous operation, high number of operating parameters (circumferential velocity, ball size, material, wet or dry state, drying in the mill, …) makes it a well controllable method for the manufacture of high value added products such as advanced materials or various composites.
... It is also seen in Figure 3 that size reduction became insignificant at higher stirrer speeds (1120, 1400 rpm) due to the inefficiency of the grinding operation. This result agrees with those of Fadhel and Frances [22] and Altun et al. [23] who reported that the excess energy that is transformed into heat at higher stirrer speeds stops the grinding process. The change in the stirrer speed and d50 versus the width of particle size distribution (d90/d10) is illustrated in Figure 4. Accordingly, the width of particle size distribution (d90/d10) decreased with increasing stirrer speed. ...
... It is also shown in the figure that, as the ball filling ratio is increased, the specific surface area became larger as expected. Altun et al. [23] found that a change in the ball filling ratio from 30% to 60% ...
Article
This study focused on ultra-fine grinding of calcite powder (CaCO3) using a vertical stirred ball mill. The influences of various operating parameters such as stirrer speed (rpm), ball filling ratio (J), powder filling ratio (fc), solid ratio (wt.%) and grinding time were studied under wet conditions. The experiments were carried out in a batch mode of operation. The experimental results were evaluated based upon product size (d50), specific surface area (m2/g) and width of particle size distribution. As a result of this work, the optimum grinding test conditions were found to be 840 rpm for stirrer speed, 0.70 for ball filling ratio, 0.100 for powder filling ratio, 50% for solid ratio and 20 min for grinding time. It was also observed that stirrer speed, ball filling ratio and grinding time were directly proportional whereas powder filling ratio and solid ratio were inversely proportional to product fineness and specific surface area. The width of particle size distribution decreased with decreasing product size for all grinding conditions.
... Similar result was observed by Fadhel and Frances (2001), they concluded that higher stirrer speeds did not make an evident difference in terms of size reduction (median size) due to the inefficient grinding conditions. Altun et al. (2013) also indicated that the change in stirrer speed from 8.67 to 9.76 m/s increased the temperature of the mill chamber 75 0 C to 90 0 C which affected the material load directly. Therefore, they recommended mills to be operated at an energy level that was just enough to break the particles because the excess energy transformed into heat reduced the efficiency of grinding. ...
... This dominated the design of stirrer and shaft. On the other hand, in horizontal mills, many stirrers are available to stir the settled load thus scale-up procedure was easier compared to vertical mills (Altun et al., 2013). It is also shown that, the two mill orientations appeared to have similar trends and optimum stress intensity ranges. ...
... Crystallite size and lattice strain had little effect on the particles if the grinding time was too short or if the particle size was above submicron range. Silica ground in the oscillating mill had undergone mechanochemical effects although the particle size was not in the submicron range [9,10]. There has been some previous research into mercury adsorption using mechanochemical modified fly ash. ...
... The diameter corresponding to 10% volume fraction is represented as D 10 . The diameter corresponding to 50% and 90% volume fraction are represented as D 50 and D 90 , respectively. ...
Article
Power plant coal fly ash was modified for mercury adsorption. The fly ash was subjected to mechanochemical ball milling and bromide compounds were added. The results show that mercury capture capacity increased with increasing grinding time, up to 50 min. Grinding over 50 min did not lead to further improvements. Results from the mercury adsorption test show that the mechanochemical processing technique coupled with the addition of bromide compounds improves mercury adsorption performance for fly ash. Both physical and chemical factors contribute to the improvements in capture performance. Increasing the grinding time produced smaller particles with higher surface area. As a result, more unburned carbon was exposed, which resulted in better mercury adsorption. Thermal gravimetric analysis of modified fly ash shows combustion peak temperatures shift towards lower temperatures with increased grinding time. This result indicates that mechanical treatment increased the thermal activity of fly ash. As a result of this study, the first on-line modified fly ash unit was installed on site at a 300 MW coal fired power plant in China.
... Due to higher energy efficiency and the ability to produce the extremely fine size of the product, stirred media mills are frequently used to grind fine or ultra-fine particles in many industrial applications such as pharmaceutical, cosmetic, paints and paper manufacture. [1][2][3][4] Compared to the traditional tumbling ball mills, stirred media mills use an agitator to mix the feeding material and the grinding beads. Instead of the impact force, the shear force caused by the attrition is the main breakage mechanism for stirred media mills. ...
... [8] In the last decades, some research has identified that the grinding efficiency is influenced by some important technical parameters such as specific energy, tip speed, grinding media, design of grinder, impeller geometries and solid mass concentration. [1,[9][10][11] Also, some research investigated some other factors such as process methods (e.g. circulated process) and size of grinding mill. ...
Article
Full-text available
This paper evaluates the effects of operating parameters on fine particle grinding process with a vertically stirred media mill. The effects are investigated through size reduction under different operating conditions by changing solids content, tip speed and the configuration of the impeller. Solids content at 65% (w/w) is demonstrated to be more efficient than 75% (w/w). The maximum difference in product size(D80) is about 2μm. Velocity maps are described at tip speeds of 5.23m/s, 6.54m/s and 9.81m/s by Positron Emission Particle Tracking (PEPT). The lower tip speed saves the specific energy 50-100kWh/t. Over energy input 100-300kWh/t, D80 of product is reduced 1-2μm by replacing standard impeller with new types of impeller.
... In this paper, we use DEM modelling to understand media motion within the operation of a full scale industrial Isamill. These mills are used dry for processes such as grinding of cement, an example of which is the Netzche Ankamill (Altun et al., 2013(Altun et al., , 2014. The media behaviour is also indicative of the performance of the wet Isamills. ...
... Jayasundara et al. (2010) showed that for high fill levels in a laboratory scale mill there is significant energy dissipation which does not contribute to grinding and they proposed that there is an optimal fill level below 90% that is the most energy efficient. Conversely, Altun et al. (2013) indicated that maximum media fill levels are generally recommended for the best grinding performance in industrial scale horizontally stirred mills. The largest reasonable operating range for fill levels of the M10000 Isamill appears to be from 70% to 90% with a most common operating level of 80%, so this is the range investigated in this study. ...
Article
Full-text available
The Isamill is a horizontal stirred media mill used for fine and ultrafine grinding. Discrete Element Method (DEM) simulation has been used in this paper to study the behaviour of the media and the collisional environment in a full industrial scale Isamill. The DEM modelling has been able to provide a general understanding of the force balances that control the mill performance and the quantitative variation of key performance measures such as power draw and peak collision energy with changes in mill operating parameters and media properties. The key factor controlling the behaviour of the media and mill performance is the force balance on the media adjacent to the rotating discs of the impellor. Gravity and any applied axial pressure gradient play a critical role by providing a restoring force that presses the media bed against the discs which enables energy transfer from the discs to the adjacent media. Three important aspects of the media flow are identified with the holes in the discs playing a critical role in media transport and generating high speeds media jets in the upper half of the mill.
... Furthermore, the existing studies in this area are still in the early to intermediate stages. Researchers have concentrated on operating parameters in dry stirred milling [5,6,8,9], grinding aids [7,[10][11][12][13][14] and design parameters [15,16], while only a few papers have covered stress model analysis [16][17][18]. Current studies on dry milling report encouraging results, and it is necessary to increase the number of such studies and understand the parameters that are studied comprehensively. ...
... For the activation milling a dry horizontal agitator bead mill from Netzsch Trockenmahltechnik was used for this study. This type of mill has been developed in recent years and various variables and modes of operation influencing the results are tested and scientifically evaluated [13] [14]. Dry agitator bead mills are already used sporadically in the building materials industry, so far exclusively for fine grinding. ...
Article
The hydraulic binder Celitement is produced by a mechanochemical activation of an X‐ray amorphous CSH phase. This process step not only chemically activates the material, but also reduces its specific surface area. Thus, both strength and workability of Celitement based systems can be controlled. In this paper the effect of the duration of the activation milling on chemical and microstructural changes of Celitement is focused. Therefore ATR‐FTIR Spectroscopy, Thermogravimetry, Heatflow Calorimetry, Scanning Electron Microscopy and BET (N 2 ) specific surface area measurements are used aside classical experiments on the flow spread and compressive strength of Celitement based mortars. As a result, it is shown that micro structural changes and chemical activation occur already at the beginning of the activation milling and significantly influence the practical performance of mortars.
... Stirred ball mills have been utilized efficiently for fine and ultra-fine grinding of numerous materials due to their simple operation, ease of construction, energy conservation, and increased grinding rate compared with other fine grinding machines (Altun et al., 2013;Bilir and Halil, 2022;Cayirli and Gokcen, 2021;Choi et al., 2010;Gao and Forssberg, 1995;Kwade, 1999;Rácz and Csőke, 2016;Zheng et al., 1996). Therefore, the dry grinding of muscovite in a stirred ball mill might be advantageous in terms of water and energy consumption and in improving the properties of muscovite mentioned above; furthermore, it will also contribute to the literature. ...
Article
This paper investigates the production of a micronized muscovite to a target product size of d50~15 µm with a minimum energy consumption to suit the product requirements of the paint industry by a dry grinding process in a laboratory-scale vertical stirred ball mill. A series of batch dry grinding tests were conducted without and with two commonly used industrial liquid grinding aids, ethylene glycol (EG, C2H6O2) and triethanolamine (TEA, C6H15NO3). The results were evaluated based on particle size distribution (PSD), specific energy consumption, span value, and aspect ratio. The results showed that using liquid grinding aids resulted in a finer PSD, lower specific energy consumption, a narrower size distribution, lower span values, and a higher aspect ratio, which meant better delamination and improved grinding efficiency to that of no grinding aid. The interaction between grinding aids and ground muscovite surfaces was investigated by Fourier Transform Infrared Spectroscopy (FTIR). FTIR measurements revealed that EG and TEA were physically adsorbed on muscovite surfaces. Scanning Electron Microscopy (SEM) was also employed to determine differences between ground muscovite surfaces with and without grinding aids. SEM images indicated that grinding aids could prevent the agglomeration of ground muscovite particles while improving delamination. Adding grinding aids led to a decrease in muscovite agglomeration and an improvement in lamination owing to the adsorption of grinding aids on the particle surfaces.
... Therefore, the mill type, as well as the feed size and strength of the material to be ground should be considered for energy consumption in grinding, which aims to decrease particle size and increase the surface area [3]. In this context in the last several decades, stirred mills have been commonly used for fine grinding in several industries such as minerals, ceramics, pharmaceuticals, chemicals, cosmetics, paints, and papers because they have higher energy efficiency than ball milling, and the ability to produce fine products [2,[4][5][6][7]. Moreover, it is well known that stirred mills provide a remarkable improvement in energy savings due to the small size of the grinding media and the ability to mix at higher speeds [8], with higher media loading compared to ball milling when finer particles are desired [9][10][11][12]. ...
Article
Full-text available
Since the particle size, shape, specific surface area, and purity of the ground calcium carbonate (GCC) decide its usability in the paper, paint, and plastic industries, the effect of grinding is important. However, the effect of stirred and ball mill grinding on the particle shape of GCC by dynamic image analysis (DIA) is still lacking in the literature. Therefore, the aim of this study is to compare the aspect ratio at the same fineness (d97 = 50 μm) and evaluate other properties such as color, and surface area of GCC particles by stirred and ball mill grindings. DIA results showed that particles produced by the ball mill had higher aspect ratio values than those by the stirred mill. This was attributed to the impact, and attrition breakage modes produced by the ball and stirred mill, respectively. This conclusion is supported by XRD and SEM. Finally, the results related to physical properties such as aspect ratio, surface area, and whiteness are discussed depending on the usage area of GCC.
... The stirring speed creates a high energy strength environment in the grinding chamber, increasing the probability of the grinding media impact and attrition of the particles. As the stirring speed increases, the stress intensity inside the mill chamber also increases, which seriously affects the interaction between the grinding media and the material to be ground [18,[22][23]. Grinding experiments were performed as a function of stirring speed (400, 500, 600, 700, 800 rpm) while grinding time was kept constant as 30 min. The effect of the stirring speed on the particle size distribution of the bentonite and Ec was given in Figure 5. ...
Article
Full-text available
In this study, a pin-type vertical stirred media mill was used to perform the dry grinding of bentonite. Grinding time and stirring speed were investigated for effect on the particle size distribution and energy consumption (Ec), while ball charge and bentonite charge were kept constant as 60% and 40%, respectively. It was observed that raw bentonites could be ultra-fine dry ground using vertical stirred media mills for the potential dry uses of bentonites. The experimental results revealed that a ground bentonite product having a d80 value of about 10 µm was obtained with 128.1 kWh/ton energy consumption. Optimum operational parameters were selected as 60% ball charge, 40% bentonite charge, 600 rpm stirring speed, and 20 min grinding time. Öz Bu çalışmada bentonitin kuru öğütülmesi için pim tipi dikey karıştırma ortamlı değirmen kullanıldı. Tane boyutu dağılımına ve enerji tüketimine (Ec) etkisi için öğütme süresi ve karıştırma hızı araştırılırken bilye ve bentonit şarj oranı sırasıyla %60 ve %40 olarak sabit tutuldu. Bentonitlerin potansiyel kuru kullanımları için ham bentonitlerin dikey karıştırmalı öğütücüler kullanılarak ultra ince kuru öğütülebildiği gözlemlendi. Deneysel sonuçlar, 128.1 kWh/ton enerji tüketimi ile yaklaşık 10 µm d80 değerine sahip öğütülmüş bentonit ürününün elde edildiğini ortaya koydu. Optimum çalışma parametreleri %60 bilye şarjı, %40 bentonit şarjı, 600 rpm karıştırma hızı ve 20 dk öğütme süresi olarak seçildi.
... The stirring speed creates a high energy strength environment in the grinding chamber, increasing the probability of the grinding media impact and attrition of the particles. As the stirring speed increases, the stress intensity inside the mill chamber also increases, which seriously affects the interaction between the grinding media and the material to be ground [18,[22][23]. Grinding experiments were performed as a function of stirring speed (400, 500, 600, 700, 800 rpm) while grinding time was kept constant as 30 min. The effect of the stirring speed on the particle size distribution of the bentonite and Ec was given in Figure 5. ...
... Mineral işlemede yaş işlemler için, özellikle tekrar öğütme aşamasında serbestlik derecesini arttırmak için veya yüzey temizleme amacıyla ince öğütme teknolojisi kullanılmaktadır (Jankovic, 2000;Gao vd., 2002;Taylor vd., 2020;Cleary vd., 2015). Son araştırmalar çimento öğütme devrelerindeki uygulamasına odaklanmıştır ve buna bağlı olarak son yıllarda kuru karıştırmalı değirmenler üzerine artan sayıda araştırma yürütülmüştür (Pilevneli vd., 2004;Altun, 2013;Çayırlı, 2017;Prziwara vd., 2018). Bilya, öğütme verimliliği ve işletme maliyetleri üzerindeki önemli etkisi nedeniyle öğütme operasyonlarının hayati bir parçasıdır. ...
Article
Nowadays, it is desired to use water resources more efficiently due to environmental factors. In this context, the importance of dry stirred mills is increasing day by day. In ball mills, grinding performance can be increased by using media with different sizes and choosing the appropriate grinding media size distribution. It is thought that a similar approach can be applied for dry-stirred mills. Thus, it is predicted that there may be effects on grinding performance and product quality. Although there has been an increasing amount of research on dry stirred mills lately, a missing point is the discussion of the effect of grinding media size distribution. Within the scope of the study, the effect of ball size distribution - a variable that directly affects the mill’s performance - on the grinding performance of the vertical dry stirred mill was investigated by batch grinding tests. For this purpose, the bi-modal and tri-modal compositions of the media sizes selected using the material size-ball size ratio values developed in the literature were mixed in different ratios for the vertical stirred mill. The data obtained from the tests performed at different stirrer speeds for calcite, clinker, and copper ores were evaluated in terms of energy, shape of the size distribution, and the obtained size reduction ratios. In addition, the effects of using different sized media distributions on media wear are discussed. It is thought that the findings obtained from the study will be beneficial on the dry stirred mill technology, which is expected to become increasingly widespread. Keywords: Grinding, Fine grinding, Stirred mill, Ball size optimization
... Ball size and interstitial filling ratio are among the variables that affect grinding efficiency. In general, increasing the ball size and decreasing the interstitial filling ratio increase the ground product's surface area (Altun, Benzer, and Enderle, 2013). However, depending on the total effect values in the ANOVA table, it can be interpreted that the effects of these two variables on the grinding efficiency are less important than the others. ...
Article
Full-text available
This study's aim is to investigate the wet and dry grindability of K-feldspar in a narrow grain size range in a stirred ball mill. In the evaluation of the grinding process, a full factorial design was used to observe the effects of the selected parameters on the dependent variable. On a narrow grain size range grinding, the parameter effects such as ball diameter, stirring speed, grinding time, and interstitial filling ratio were investigated. Experimental results showed that K-feldspar can be efficiently milled with a stirred ball mill in a narrow grain size range (1-10 microns).
... It can also produce fine-grained products with narrow particle size distributions after the grinding process by stirred mills (Gao and Forssberg, 1995, Zheng et al., 1996, Kwade and Schwedes, 1997, Kwade, 1999. In recent years, stirred ball mills are widely used for fine and ultrafine grinding processing in the ceramics, chemical, food, cement, paint, pharmaceutical, plastics and cosmetic industries (Jankovic et al., 2004, Altun et al., 2013, Ouattara and Frances, 2014, Toprak et al., 2014, Gokcen et al., 2015. Demand for stirred ball mills is increasing because of their ease of use, simple construction, high size reduction ratio, low energy consumption compared to other fine grinding machines and its suitability for modelling studies (Gao andForssberg, 1995, Zheng et al., 1996). ...
Article
Full-text available
Grinding aids are commonly used in grinding to disperse the material in the system effectively and to improve grinding performance. Most of the time, different grinding aids with varying dosages are tested in laboratory conditions by trial and error. A simple methodology is required to compare the results of different grinding aids and dosages in batch milling. In this study, the utilization of the modelling approach in comparing the effect of grinding aid types and dosages were aimed. In order to achieve this, an experimental program has been conducted using a laboratory-scale batch stirred ball mill. The empirical model developed using the Farazdaghi-Harris model offers a new approach to determine the effect of grinding aids on grinding performance.
... Bu konuda yapılan araştırmaların birçoğunda enerji ile boyut küçültme arasındaki ilişki belirlenmeye çalışılmış, böylece en az enerji ile en fazla boyut küçültmenin yolları araştırılmıştır. Bilindiği gibi öğütmede harcanan enerjinin bir kısmı doğrudan boyut küçültmede kullanılmakta, önemli bir bölümü ise faydalı bir iş (boyut küçültme) yapmadan ısı enerjisine ve sese dönüşerek kaybolmaktadır (Altun, Benzer, ve Enderle, 2013;Fadhel ve Frances, 2001;Gunda ve Moys, 2015;Kwade, Blecher, ve Schwedes, 1996). ...
Article
Full-text available
In this study, the use of olive pomace oil as a grinding aid was investigated in the grinding of calcite to dry micronized sizes in a laboratory scale stirred ball mill. For this purpose, in the first stage, different stress intensities were created and optimum grinding conditions were determined. In the second stage, the usability of olive pomace oil was investigated and compared with triethanolamine, a pure grinding aid. The experimental results were evaluated considering the amount of grinding aid, energy consumption, and particle size. According to the results obtained, the optimum stress intensity range was determined as approximately 1-2*10-3 Nm at 500 kJ/kg and 1000 kJ/kg energy levels. With the use of grinding aid (TEA and olive pomace oil), products with a particle size of 4 μm and finer sizes were produced at 2000 kJ/kg energy level. At advanced energy consumptions (1000 kJ/kg and 2000 kJ/kg), it was obtained similar particle sizes by the use of olive pomace oil compared to the TEA.
... The preparation of powder with typical specification and on an industrial scale could be challenging, as it demands understanding of effects of parametric variations on the powder quality. Altun et al., 2019 [8] investigated the effects of media, mill speed, feed rate and stirrer speed on the size reduction and power consumption on a customized horizontal mill. Previous studies showed that the ceramic waste was reduced into the particle size which is accomplished in the laboratory by crushing and grinding using a ball jar mill. ...
Article
Full-text available
Influences of Vacancies on the Electrical Resistivity Size effect of Nanocrystalline MetalTo maxim rehenihil inciur ma quo optatec toriat acera coratem nosam sequam resti bea conse nostior res il ipsaepuda debis seque dolor sitem velis am sit exerfer feribus sim facipie nisquia voluptium, ium et la voluptate sus alicipi tamus, sum a quae dita que et lias nonsendio occature venis des ex eum qui omnimpo ribere, sum facime maion rest et dion et re, occatur ibusam iur recum qui quatia nobitianis eium quos aborum conecti nvereic aestibus repudipsam fugia sunda dolorep ernatquam consendi sandae nullabo rectempore prat. Bea dit quis alignis este consero eium laut estrum adi ipsusdae nonestium num res velita dolum eum dus nempore cusci blab imporrumet ut et et reperuntis essitatenim sumquatet aut re dis maxime nimi, audae. 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Unt facerspe atque cus ani nem il eosae de vit eum receseque denihitium est volore aut ationsequae velibus am dit maximpere, ipienimi, officta sperum nos qui non comni re isciae ex eaquiassunt, cullabo rrorum, nectorrum lab iminus ium quatur, que laut quatem volorio. Iquia es aut lam rescit omnieni dis ad mincius cipsand ucillant ullibus, iuntio blat enisquidi ut volupti re et adis quatem ex eaquam doloria speriae ligendant quo volor sita volorrovid qui sequod qui consed erferum que ipsam hilignimodit vent quam quaerum rehent ut aliqui sit magnissin cus dis eturionse doloritione quistio. Rume nonsed eaqui te occum, veribust, ut undenti untotae sit faccupta et et quatist iations equiae ommoluptius. Hicimos erum nus ad utatios pres molor magnimus inimil ipid ut maios quas ma nulliquodis se dolupta estias sollaborum vellamCorepelicium ex et aut magnatur ad que pariatur? Influences of Vacancies on the Electrical Resistivity Size effect of Nanocrystalline MetalTo maxim rehenihil inciur ma quo optatec toriat acera coratem nosam sequam resti bea conse nostior res il ipsaepuda debis seque dolor sitem velis am sit exerfer feribus sim facipie nisquia voluptium, ium et la voluptate sus alicipi tamus, sum a quae dita que et lias nonsendio occature venis des ex eum qui omnimpo ribere, sum facime maion rest et dion et re, occatur ibusam iur recum qui quatia nobitianis eium quos aborum conecti nvereic aestibus repudipsam fugia sunda dolorep ernatquam consendi sandae nullabo rectempore prat. Bea dit quis alignis este consero eium laut estrum adi ipsusdae nonestium num res velita dolum eum dus nempore cusci blab imporrumet ut et et reperuntis essitatenim sumquatet aut re dis maxime nimi, audae. Luptios ad eossit Nowadays, ball mills are widely used in cement plants to grind clinker and gypsum to produce cement. The research focuses on the mill speed as well as air classifier speed effect on the two compartment Cement ball mill performance in terms of Blaine, Sulphur trioxide contents, mill power, mill residue and mill residence time. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the variation with the mill speed and the air classifier speed. Within the content of this work, sampling campaigns were organized around a cement grinding circuit and varying cement ball mill speed as well as an air classifier speed at various dosage feed rate. The fact that such an examination has not been made previously by using industrial data rather than lab scale makes this work unique. The fineness is measured in terms of Blaine number. Mill speed and air classifier speed were the investigating parameters. It was deduced that depending on the speed of mill and air classifier, their effects on Blaine, SO 3 , mill power and mill performance were varied, ultimately all of them improved the performance of grinding and classification operations. The rapid expansion of ceramic wastes in China has raised great many interests in their sustainable uses in building materials The micro ceramic powder can be taken as a supplementary cementitious material to replace cement up to 40% for tuning the microstructure and mechanical properties of blend cement materials. The Blaine quality dictates strength, setting time and overall performance of cement. Optimum performance of ball mill could potentially refine Blaine fineness, thereby improving the cement quality. This study investigates the effects of separator speed and mill speed on Blaine fineness, mill residue, consumed power. Five speed levels used in closed cycle grinding mill are 200, 400, 600, 800 and 1000 rpm. The capacities were determined to obtain product Blaine surface areas in the limits between 2000 cm 2 / gram and Variations in clinker feed rate, mill speed and separator speed could proportionally impact the grain quality of Blaine. When the separator speed is increased from 850 to 900 rpm the Blaine is increased from 2800 to 3000 cm 2 /g and mill residue decrease from 15 to 10 microns. Therefore, optimum parametric combination could reduce power consumption while improving the cement quality. Knowledge of effects of parametric variations on the quality of end product could be helpful for controlling product quality. Furthermore, proper grinding of clinker produces fine Blaine at first place and reduces the need for recycling of coarse grains.
... The preparation of powder with typical specification and on an industrial scale could be challenging, as it demands understanding of effects of parametric variations on the powder quality. Altun et al., 2019 [8] investigated the effects of media, mill speed, feed rate and stirrer speed on the size reduction and power consumption on a customized horizontal mill. Previous studies showed that the ceramic waste was reduced into the particle size which is accomplished in the laboratory by crushing and grinding using a ball jar mill. ...
Article
Full-text available
Nowadays, ball mills are widely used in cement plants to grind clinker and gypsum to produce cement. The research focuses on the mill speed as well as air classifier speed effect on the two compartment Cement ball mill performance in terms of Blaine, Sulphur trioxide contents, mill power, mill residue and mill residence time. Special importance was assigned to the study of the specific surface area and the surface area production rate, both during the variation with the mill speed and the air classifier speed. Within the content of this work, sampling campaigns were organized around a cement grinding circuit and varying cement ball mill speed as well as an air classifier speed at various dosage feed rate. The fact that such an examination has not been made previously by using industrial data rather than lab scale makes this work unique. The fineness is measured in terms of Blaine number. Mill speed and air classifier speed were the investigating parameters. It was deduced that depending on the speed of mill and air classifier, their effects on Blaine, SO3, mill power and mill performance were varied, ultimately all of them improved the performance of grinding and classification operations. The rapid expansion of ceramic wastes in China has raised great many interests in their sustainable uses in building materials The micro ceramic powder can be taken as a supplementary cementitious material to replace cement up to 40% for tuning the microstructure and mechanical properties of blend cement materials. The Blaine quality dictates strength, setting time and overall performance of cement. Optimum performance of ball mill could potentially refine Blaine fineness, thereby improving the cement quality. This study investigates the effects of separator speed and mill speed on Blaine fineness, mill residue, consumed power. Five speed levels used in closed cycle grinding mill are 200, 400, 600, 800 and 1000 rpm. The capacities were determined to obtain product Blaine surface areas in the limits between 2000 cm2 / gram and Variations in clinker feed rate, mill speed and separator speed could proportionally impact the grain quality of Blaine. When the separator speed is increased from 850 to 900 rpm the Blaine is increased from 2800 to 3000 cm2/g and mill residue decrease from 15 to 10 microns. Therefore, optimum parametric combination could reduce power consumption while improving the cement quality. Knowledge of effects of parametric variations on the quality of end product could be helpful for controlling product quality. Furthermore, proper grinding of clinker produces fine Blaine at first place and reduces the need for recycling of coarse grains.
... A similar finding was noted by Fadhel and Frances [15], who deduced that higher stirrer speeds did not provide sufficient differences considering particle sizes (size reduction) due to the inefficient grinding conditions. Altun et al. [16] also pointed out that the increase in stirrer speed from 8.67 to 9.76 m/s increased the temperature of the mill chamber from 75°C to 90°C which directly influenced the material filling. For this reason, they suggested that to break particles at an optimum grade (just enough), mills should be operated at a suitable energy level because of the reduction in the efficiency of grinding at which excess energy is transformed into heat. ...
Article
The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch type stirred mill. The experimental results were evaluated using stress intensity analysis. The performance was also compared in terms of mill orientation. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1*10−3 to 5*10−3 Nm at 750 and 1500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value. Additionally, to the best of the authors’ knowledge, this is the first study to compare mill orientation (vertical vs. horizontal) for the same mill and under the same test conditions.
... Öyle ki maksimum kırılma oranı 600 d/dk hızda ve %70 bilya doluluk oranında elde edilmiştir. Öğütücü ortam miktarındaki değişim, öğütücü ortam ile malzeme arasındaki oranı değiştirmekte ve bu etki ürün inceliğini de etkilemektedir [30]. Şekil 4(c)'den görüldüğü gibi maksimum karıştırma hızında, büyük çaplı bilyaların çoğunlukta olduğu yüksek seviyede (+1) maksimum kırılma oranı elde edilmiştir. ...
... Geleneksel bilyalı değirmenlerde optimum bir dönme hızı söz konusu iken, atritörlerde karıştırıcı kolların hızı ne kadar yüksek ise öğütme verimliliği de o kadar yüksek olmaktadır [15]. Karıştırma hızı arttıkça yüksek enerji yoğunluklu bir ortam oluşmakta, öğütücü ortam ile tane çarpışma olasılığı artmaktadır [16]. ...
... Stirred media mills can be either dry or wet. The operation of dry stirred media mills and the impact of material and process parameters have been the focus of many recent studies, for mills with both horizontal (Altun et al., 2013;Altun et al., 2014;Rácz and Csoke, 2016;Prziwara et al., 2018a) or vertical (Prziwara et al., 2018b) designs. An industrial challenge in dry stirred media milling is that the milling limit is approximately 1 μm. ...
Article
Wet comminution is an important process in the mineral processing industry. Modelling of wet comminution in stirred media mills requires the simultaneous modelling of grinding media, a moving internal stirrer, and slurry. In the present study, a novel approach for modelling the physical interactions between slurry, grinding media and mill structure in a stirred media mill is presented. The slurry is modelled with the particle finite element method (PFEM). The grinding media is modelled using the discrete element method (DEM) and the mill structure is modelled using the finite element method (FEM). The interactions between slurry, grinding media and mill structure are modelled by two-way couplings between the PFEM, the DEM and the FEM models. The coupled model of the present study is used to predict the motion of slurry and grinding media, and to calculate the power draw during wet comminution in a pilot scale horizontal stirred media mill. Furthermore, the model is used to compare a Newtonian and a non-Newtonian model of the slurry, where the non-Newtonian model is used to capture experimentally observed shear-thinning. The coupled PFEM-DEM-FEM model preserves the robustness and efficiency of each of the methods and it gives the possibility to use large time increments for the fluid, greatly reducing the computational expense. The coupled model of the present work provide information on the complex dynamics of slurry and grinding media. The numerical model is shown to be a useful tool for increasing the knowledge and understanding of wet comminution in stirred media mills.
... Sci. 2019, 9, 4816 2 of 23 ball mills [1][2][3][4]. The evaluation of the stress frequency and the stress energy requires information about the grinding media velocity and the grinding media motion inside the mill. ...
Article
Full-text available
Positron emission particle tracking (PEPT) was used to investigate the grinding media dynamics in a laboratory-scale attritor mill in the absence of powder. The grinding media motion was analysed as a function of the equipment’s typical operating parameters: impeller speed, impeller clearance and bead fill level. It was observed that the impeller speed had the strongest influence on the media motion. An increase of the impeller speed from 300 rpm to 600 rpm led to a change in the bead recirculation patterns with the increasing formation of well segregated upper and lower recirculation loops that fully developed at the maximum speed of 600 rpm. For a constant impeller speed, an increase of the bead loading did not majorly affect the bead velocity as remarked by minor changes on the flow field. For all the impeller clearance values, the occupancy plots revealed an inefficient dead region at the bottom of the attritor where the beads were moving at very low velocity. In this region the beads were tightly packed under their own weight and, furthermore, there was an absence of direct contact with the impeller arms. The depth of this region increased proportionally to the distance between the bottom of the impeller and the vessel base indicating that a minimum value of clearance should be set to optimise the lower recirculation pattern. For two experimental conditions, the data generated by PEPT measurements were utilised to set-up a friction-adjusted discrete element method (DEM) model. Here, the simulation results were qualitatively and quantitatively compared against the PEPT data by assessing the averaged velocity flow fields and the average velocity profiles at different radial locations inside the vessel. Given the intrinsic uncertainty of the PEPT measurements, the DEM model results were in considerably good agreement with the experimental results. The major discrepancy was observed close to the vessel wall where the simulations overpredicted the velocity by about 10%.
... Dry stirred media milling is a highly energy-efficient and promising technology that can be used to produce fine submicron ground materials, but there are still many problems to be solved in this area for wider industrial application. The operation of a horizontal dry stirred media mill was investigated by [1], found that increase of the stirrer speed produced finer material up to a point that further addition of energy was converted into heat causing decreased efficiency of the grinding operation, lower media fillings created inefficient grinding environments. Later in the same mill, the effects of chamber diameter and stirrer design on dry horizontal stirred mill performance was investigated [2], found that the larger gap between the stirrer edge and mill chamber performed more efficient grinding operation. ...
... The dry horizontal stirred media mill is a recent technology, and different research groups have focused on both understanding the operation and proving its benefits on different applications, i.e. cement, ground calcium carbonate, etc. (Altun et al., 2013;Altun et al., 2014;Racz and Csöke, 2016;. As such applications demand bigger size units, studies on the manufacturing of an industrial scale machine are still ongoing. ...
Article
This study aims to evaluate the use of different particle breakage characterization methodologies in modelling of a dry horizontal stirred media mill. Within the context, Hardgrove mill and drop weight tester were utilized on granulated blast furnace slag, coarse cement, finished cement, filter return and fly ash samples. As a result of the experimental works undertaken at different size intervals and energy levels, the appearance functions of each sample were calculated by using the correlation between specific comminution energy and t10 values or fines’ generation. Calculated appearance functions were inputted to the perfect mixing model and r/d values were back-calculated. In this regard, the feed and product data from the comminution tests of a pilot scale dry stirred mill was used. When the plots of r/d data were compared, it was found that both Hardgrove and impact bed breakage tests lead to having good agreement between the experimental and calculated product size distributions. Consequently, the later stage of the study focused on the development of a modelling for the dry stirred mill by using the breakage function from Hardgrove mill, which was found convenient and easier.
... Up to now various milling mechanisms, particularly in the field of attrition milling, have been developed and dry/wet stirred media mills can be count as one of them. Within the recent years, the developments in the dry operated horizontal stirred mill (Altun et al. 2013;Racz and Cs€ oke 2016;Prziwara et al. 2018) lead to the need for the model-related studies that is the step before the commercial use of the machine. Such models are required to carry out different simulation scenarios or flow sheets, which may convince the product manufacturers to utilize these machines. ...
Article
This paper aimed to investigate the applicability of impact bed breakage test for model fitting of continuous dry horizontal stirred mill. Initially, the breakage tests were performed for three types of materials at varying bed diameters, 2 cm, 3 cm, 4 cm, and 6 cm to find out the optimal bed geometry. The test results for the three materials showed that the bed height of 4 cm was optimal as the fines’ generation reached to a plateau and decided to be used in model fitting of the dry stirred mill. Afterward, cement material was processed within the dry stirred mill and samples were collected from feed and product ends when the steady-state conditions were established. The results of the grinding tests on cement material together with its breakage results obtained from 2 cm and 4 cm diameter beds were used in the model fitting of the mill by using perfect mixing approach. Accurate model fitting was obtained in case 4 cm diameter of bed was utilized and the predictions were in good agreement with the measured size distributions even if the operating conditions of the mill were changed.
... La quantité de billes a été fixée à 7.5 kg, ce qui représente 60% du volume total de la cuve. Ce taux de remplissage semble offrir la meilleure efficacité d'après la bibliographie [150]. De la même manière que dans le broyeur à boulets, la quantité de produit est déterminée de telle sorte que le produit en fin de broyage remplisse le volume interstitiel entre les billes, soit 739 ml équivalent à 1253 g de sable et 170 g de paille. ...
Thesis
Le broyage est une opération couramment réalisée dans de nombreux secteurs industriels. Malgré son apparente simplicité, le broyage met en jeu des phénomènes de fragmentation complexes dépendant à la fois des propriétés de la matière, des sollicitations mécaniques dans le broyeur, et de la dynamique des poudres au sein de celui-ci. Aujourd'hui l'évolution des technologies de broyage repose essentiellement sur un savoir-faire empirique et de nombreux efforts sont encore à déployer pour améliorer leur efficacité énergétique. Cette optimisation ne pourra être réalisé qu'en s'appuyant sur une connaissance fine des phénomènes mis en jeux à plusieurs échelles (échelle sub-particulaire, échelle de la particule, du lit de poudre et du procédé). L'objectif de ces travaux de thèse est de mettre en évidence les paramètres clés influençant les mécanismes de comminution et l'efficacité énergétique du broyage. Un modèle numérique de rupture de particules présentant des défauts sous forme de clivage a été mis en œuvre. Il a permis notamment d'analyser l'influence de la distribution spatiale des fissures sur la statistique des seuils de rupture en lien avec les chemins de fissures et la taille des fragments. A l'échelle du procédé, une étude expérimentale, réalisée au sein d'un broyeur de laboratoire, a permis de proposer un modèle énergétique s'inspirant de celui de Rittinger mais tenant compte des phénomènes d'agglomération. Ce modèle a ensuite été généralisé à différentes technologies de broyage à media broyant pour comparer leur efficacité énergétique lors du broyage de matières minérales, végétale ainsi qu'en condition de cobroyage.
... Bunlardan ilki yeni gelişen teknolojilerin üretim sürecine dahil edilmesidir. Bu bağlamda son yıllarda geniş uygulama alanı bulan karıştırmalı değirmenler [3,4], ön öğütme işleminde kullanılan yüksek basınçlı merdaneli presler [5] ve hem öğütme hem de sınıflandırma işlemini tek bir ekipmanda gerçekleştirebilen dik değirmenler [6] yeni devre akım şemalarında tercih edilebilmektedir. Ek olarak bu ekipmanlar, tesiste bulunan bazı akış kollarına adapte edilerek üretim miktarında artış sağlayabilmekte ve devrenin özgül enerji tüketimini düşürebilmektedir. ...
... Ball mill appears to be one of the few efficient technologies for fine and ultrafine milling of lignocellulosic biomasses and minerals ( Osawaru and Forssberg, 1992;Silva et al., 2012) and has been used in this study. In ball milling, the comminution efficiency and kinetics depend on the filling volume in the chamber ( Altun et al., 2013). For a same mass of material, the filling volume varies widely because of the difference in apparent densities of lignocellulosic biomasses and minerals. ...
... Stirred media mills are typically operated in wet mode, but dry mode mills have also been introduced by Altun et al. (2013) and Mucsi et al. (2013). The challenge in industrial dry grinding is the milling limit, which is currently in the region of one micrometre due to agglomeration. ...
Research
Full-text available
During the past decade submicron and nanoparticles have aroused a wide interest and gained new applications due to their high surface area and strength. Grinding with a wet stirred media mill is usually the last process step before the submicron or nanoparticles are added to an application, and the step where the final particle size distribution is achieved. Since stirred media milling is an energy-intensive process, energy efficiency should be optimized. This can be done by determining the optimum operational parameters for the mill and using the highest possible solids concentration. The solids concentration can be increased by controlling particle-particle interactions with stabilization chemicals, e.g. polymers. This thesis concerns parameters and grinding aids affecting the particle size distribution and suspension stability of the aqueous submicron grinding of calcium carbonate (CaCO3) and titanium dioxide (TiO2) in stirred media mills. TiO2 particles are aggregates produced via a bottom-up method, while CaCO3 are primary mineral particles produced by a top-down method. The most energy efficient grinding of TiO2 to a 300 nm particle size with the narrowest possible particle size distribution was obtained with the lowest stress energy, implying the smallest grinding medium size. It was observed that electrosteric stabilization with sodium polyacrylates was effective for TiO2, and sodium polyacrylate with a molecular weight of 12500 g/mol was found to be the most effective for reducing the viscosity of the suspension. As with TiO2, electrosteric stabilization with sodium polyacrylates was also found to be effective for CaCO3, but in this case sodium polyacrylate with a lower polydispersity index was more effective, showing a better stabilization potential in micron and submicron grinding and reducing the viscosity and particle size to a greater extent. Nanogrinding experiments were performed for a CaCO3 suspension with low PDI sodium polyacrylate and it was found to be possible to obtain a particle size of 26 nm, smaller than any size previously reported when grinding CaCO3.
Article
Full-text available
Mechanical activation of Ca/Mg silicates by grinding is a pre-treatment of some mineral carbonization processes. In this study, the mechanical activation of lizardite ore from a chromite beneficiation plant waste by grinding in a stirred media mill was studied. For grinding studies, grinding times of 10-20-30 min and stirring speeds of 600-800-1000-1200 rpm were the parameters investigated, while the ball charge rate was 60% and the ore charge rate was kept constant at 40%. This way, the effects of grinding time and stirring speed on particle size distribution and energy consumption were investigated. At the end of the grinding studies, the stirring speed was determined as 1200 rpm, and the grinding time was 10 min for the finer particle size distribution (d10: 2,7 µm, d50: 13,6 µm, d90: 57.6 µm) with less energy consumption (130.4 kWh/ton). FT-IR analyses proved that the samples were dehydroxylated by the milling process. As a result, according to the analysis performed after grinding, it can be said that the finer product obtained can be used in mineral carbonation processes.
Conference Paper
Full-text available
Mechanical activation of Ca/Mg silicates by grinding is a pre-treatment of some mineral carbonization processes. In this study, the mechanical activation of lizardite ore from a chromite beneficiation plant waste by grinding in a stirred media mill was studied. For grinding studies, grinding times of 10, 20, and 30 minutes and stirring speeds of 600, 800, 1000, and 1200 rpm were the parameters investigated, while the ball charge rate was 60% and the ore charge rate was kept constant as 40%. This way, the effects of grinding time and stirring speed on particle size distribution and energy consumption were investigated. At the end of the grinding studies, the stirring speed was determined as 1200 rpm, and the grinding time was 10 minutes for the finest particle size distribution. The particle size distribution data were determined as d10: 2, 7 μm, d50: 13, 6 μm, d90: 57.6. The energy consumption for the grinding process performed in these parameters was calculated as 130 kWh/ton.
Article
Full-text available
The present literature review explores the energy-efficient ultrafine grinding of particles using stirred mills. The review provides an overview of the different techniques for size reduction and the impact of energy requirements on the choice of stirred mills. It also discusses the factors, including the design, operating parameters, and feed material properties, influencing the grinding performance. The review concludes that stirred mills have significant potential for achieving the energy-efficient ultrafine grinding of particles. Stirred mills have unique designs and operations, which provide higher grinding efficiency, lower energy consumption, and reduced media consumption compared to traditional tumbling mills. The review highlights the advantages of stirred mills over conventional grinding methods and their potential to revolutionise industrial processes while lowering the environmental impacts.
Chapter
Comminuting raw materials are extensively utilized in various industries such as food, cosmetics, electronics, pharmaceutical, cement, recycling, and mineral processing. Bringing the input material to the desired size is one of the most energy-consuming and costly processes, consuming around 4% of the worldwide electricity production. This process can be performed in wet or dry mode. Comminution is mainly carried out for two reasons: final product preparation, according to the required size, and the liberation of valuable materials/minerals from their matrices.
Article
In the search for energy reduction potential, a large number of systems in the energy-intensive industrial sector of comminution are being investigated. In addition to the requirement for constant minimization of energy consumption, the demand for higher quality and fineness of the manufactured products is growing. These two requirements can usually only be met by new developments of milling equipment. Such a new development and the subsequent optimization of the process-determining parameters are presented here. The mill under investigation is a dry-operated agitated bead mill, whose design and mode of operation is based on a wet-operated bead mill. Five essential parameters for the plant operation of the dry agitator bead mill have been investigated: Besides filling level of the grinding media and circumferential speed of the agitator to achieve a reliable reference operation setup, particularly the number of agitators and the resulting distances between them, respectively, the wall distance of the agitator arms and the recirculation load in classifier-closed-loop operation. By adjusting the operating and geometry parameters, the specific energy consumption can be decreased from more than 150 kWh/t to about 80 kWh/t. Based on the findings of this work, the influence of individual parameters is shown and evaluated for the application under consideration. Thus, an optimal setup for the machine operation is defined.
Article
A grinding technology should consider the physical properties of the material, i.e., size, shape, which have effects on the product specifications, i.e., quality, strength or overall process efficiency. In this respect, this study aimed at evaluating the variations in the shape of product size distribution of a stirred media mill as the attention on this technology has been growing in the recent years. Within the scope of the research, series of grinding tests were performed at different operating conditions, i.e. bead size, bead type, tip speed, feed rate and mill design, with a laboratory scale continuously operated horizontal stirred media mill. The investigations proved that the use of coarser and denser beads as well as adjusting higher tip speeds resulted in obtaining narrower product size distribution for the same mean size. For a better understanding of the process, the stress energy and mean residence time evaluations were also undertaken. It was found that the stress energy and its normalization with the mean residence time are directly proportional to the slope of the distributions. As a conclusion, the dry stirred media mill is able to adjust the shape of the distribution, which may be beneficial regarding to the mechanical properties of the end products (cement manufacturing) or efficiency of the mineral beneficiation processes.
Article
A dry operated, horizontal stirred media mill was used for the fine grinding of limestone and compared in open and closed circuit modes. It was found that the choice of grinding aids as well as the stirrer tip speed are crucial for the mill operation, especially in terms of the grinding efficiency and the transport behavior through the mill. Independent of the process mode, both a too low and an excessive additive-induced flow behavior led to unfavorable stress conditions inside the mill, and thus, inefficient grinding. In the open circuit, especially high flowabilities turned out to be crucial, as thereby the stress conditions are negatively affected as a consequence of the material transport in combination with the overlapping impact of a mill- internal deflector wheel. Different important aspects were seen for the closed circuit grinding; especially when aiming for high finenesses or using high tip speeds, it is essential to ensure both a minimum flowability and a sufficient particle stabilization to ensure a fast removal of fine particles from the mill. High flowabilities in turn are not as critical during closed circuit grinding, but are accompanied by high material recirculations.
Article
The production capacity of the large-scale ball mill in the concentrator is a crucial factor affecting the subsequent separation and the economic benefits of the operation. The main aim of this study is to improve the processing capacity of the large-scale ball mill. Taking a Φ5.49 × 8.83 m ball mill as the research object, the reason for the low processing capacity of the ball mill was explored via process mineralogy, physicochemical analysis, workshop process investigation, and the power consumption method. Based on this framework, a series of laboratory grinding optimization tests were conducted and verified via industrial tests. The results show that the ore primarily contained hematite and magnetite, the disseminated particle size of magnetite was primarily a coarse-grained inlay that was easy to separate from gangue, while the disseminated particle size of hematite was primarily an uneven and medium-sized inlay, which increased the grinding difficulty. Under optimum conditions of +6.0 mm material suitable for a 100 mm ball diameter, −6.0 + 2.0 mm material suitable for an 80 mm ball diameter, −2.0 mm material suitable for a 70 mm ball diameter; medium ratio of Φ90 mm 34.62%, Φ70 mm 26.92%, Φ60 mm 23.08%, Φ40 mm 15.38%; filling ratio of 32%; material ball ratio of 1.0; rotation speed rate of 80%; and grinding concentration of 78%, the −0.074 mm content in the grinding product increased from 55.10% to 58.86% and the processing capacity of the ball mill increased from 310 to 320 t/h to 350 t/h. Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDS) micrograph analysis shows that the fineness of the ore and dissociation degree of useful minerals were apparently improved by optimizing the process and equipment.
Article
One of the most energy-intensive processes for producing submicron range calcite is stirred media mill. In the present work, numerous operating parameters such as solid mass fraction, grinding media size, media filling ratio, and grinding time have been investigated using a vertical type stirred media mill. The results are evaluated on the basis of mean particle size, specific surface area, and specific energy consumption. After conducting this study, optimum experimental conditions found to be as 70% media filling ratio, 25% solid mass fraction, 1 mm grinding media size, and 120 min grinding time. Besides, energy savings up to 22% were achieved with the choice of proper media size.
Article
Ground ultrafine and nano- materials are mainly produced by wet stirred media milling. The product related stress model can be used for the optimization of such grinding processes; the operational parameters can be related to the particle size or specific surface of the product. At the same time, for many materials dry grinding is required. During dry stirred media milling different problems arise, such as aggregation, agglomeration and particles sticking on the mill liners and on the grinding media. Consequently, the processes taking place in the mill and the effects of the operational parameters on the product properties are not as thoroughly known as in the case of wet stirred milling. In the present paper the application of the product related stress model for product dispersity control in dry batch stirred media milling is presented. Modifications of the models' main parameters such as stress intensity and stress number are introduced. The applications of the modified main parameters are presented for the optimization of the material and grinding media filling ratio, as well as functions for the characterization of the effect of the stress number and stress intensity on the product. With the introduced modifications, the product related stress model proved to be suitable for the characterization of dry batch stirred media milling.
Article
Full-text available
In this study, separator rejects of a closed circuit cement tube milling were dry ground in a 10-l pilot scale vertical stirred mill. Tests were done as open and closed circuit. The results were evaluated by size distributions, Blaine surface area of the products and the specific energy consumed during the tests. Mill capacity and the stirring speeds were the investigated parameters for the open circuit tests, whereas closed circuit tests were carried out at a constant stirring speed but variable discharge rate. Five speed levels used in the open circuit grinding tests are 200, 400, 600, 800 and 1000 rpm. The capacities were determined to obtain product Blaine surface areas in the limits between 2000 and 5000 cm2/g. Closed circuit tests have resulted in 87%, 182% and 452% circulating loads.
Article
Full-text available
Base metal resources are becoming more fine-grained and refractory and minerals separation processes require these ores to be milled to increasingly finer sizes. To cope with very fine grinding to below a P80 of approximately 15 μm stirred milling technology has been adopted from other industries. Neither this technology, nor the basic concepts of fine grinding, are well understood by the minerals processing industry. Laboratory studies were therefore carried out in order to investigate fine milling using different types of stirred mills. The variables analysed were stirrer speed, grinding media type and size, slurry solids content as well as the feed and product size. The results of the testwork have shown that all of these variables affect the grinding efficiency. The ratio of media size to material size was found to be of particular significance. The results were also analysed using the stress intensity approach and the optimum stress intensity ranges for the most efficient grinding were determined. Application of the results for process optimisation in the industrial size units is also discussed in this paper.
Article
With the test results presented in this paper, the range of application for stirred ball mills with an additional introduction of vibrations into the grinding chamber is defined in respect of the different sizes of grinding media that can be used. In this research, it could be established that grinding media < 2 mm are too small owing to the cushioning effect of the overall grinding media charge; grinding media > 5 mm, on the other hand, were found to be too large as they allowed only limited possibilities for contact between the material to be ground and the grinding media. For the grinding limestone as a starting material, with the median x50 = 22 μm and the characteristic particle size x97 = 94 μm, the economically viable range of grinding media diameters lies between dMK = 2.5 to 4 mm. With the use of grinding media of these sizes, favourable effects on comminution efficiency and the energy requirement can be recorded, especially in the initial phase of the grinding process.
Article
There has been a growing need in recent years to develop a more energy efficient grinding process. Fine grinding experiments have been conducted with a stirred ball mill (SAM-Sala Agitated Mill). The stirring is achieved by the rotation of a single vertical rotor equipped with protruding pins, which are made of solid tungsten carbide. Grinding media size (cylpebs), pulp density, rotor speed, media level and energy input have been identified as the most important parameters affecting fine grinding. The present paper discusses the influence of these parameters on fine grinding of a magnetite ore. The results show that for a given set of conditions (pulp density, energy input and rotor speed) qq 3mm balls are approximately 30% more efficient than 8mm qq cylpebs. There exists a particular combination of pulp density, grinding media level and rotor speed which optimises the grinding performance. Comparison of the stirred ball mill has been made with a conventional ball mill at the same energy input per ton of material and at three pulp densities. The comparison was made at optimum performance of both mills. 30-40% better fine grinding performance were obtained with the stirred ball mill.
Article
Powder technology is a rapidly expanding technology and nowhere more than in particle characterization. There has been an explosion of new particle measuring techniques in the past ten year particularly in the field of on-line measurement. One of the main aims of this book is to bring the reader up-to-date with current practices. One important area of interest is the improvements in on-line light scattering instruments and the introduction of ultrasonic on-line devices. Another is the introduction of on-line microscopy, which permits shape analysis in conjunction with particle sizing.Schools of powder technology are common in Europe and Japan but the importance of this subject has only recently been recognised in America with the emergence of the Particle Research Centre (PERC) at the University of Florida in Gainsville.
Article
The effect of media size and properties on milling efficiency, media wear, and power consumption will be discussed. A predictive model has been developed and was verified by analyzing results of laboratory trials in a mineral grinding application. Recent developments in high density media capabilities for a range of feed types and particle sizes will be presented.
Article
Improved concentrator economics can be achieved by the recovery of the valuable locked minerals discarded in the tailings streams due to their fine grain size. This can be achieved if improved comminution systems are used which are designed to liberate the valuable minerals at the fine grain sizes. The present improved performances of beneficiation processes using the fine and ultra-fine feed sizes has enabled this option to be considered. However, most comminution systems being operated are not effective or economic in grinding to below 45 microns. A move to a more suitable technology is required; the technology of the Stirred Media (SM) Mills. One example of a SM Mill is the ECC International Wet SM Mill. This SM Mill has been used successfully in the kaolin and calcium carbonate industries for over 25 years. The Mill has shown economic benefits with non-ferrous metals feeds. The need for a large and expensive development programme to result in a new, but industrially unproved, grinding Mill, can be eliminated, the transfer of a technology from one industrial sector to another.
Article
A study on the control of particle size distribution (PSD) of the ground carbonate product in stirred media mills (wet Drais stirred bead mill and dry Sala Agitated Mill) is presented in this paper. The results indicated that the slope of product size distribution can be controlled by altering some operating parameters, such as size of grinding media and tip or peripheral speed. The profile of product size distribution from the stirred media mills was found to follow most closely the Rosin-Rammler-Bennett (RRB) model.
Article
Refractory gold ores may be defined as those which yield low recoveries of gold when treated by the conventional grinding and cyanidation process. This refractory behaviour can vary from mild to severe with gold recoveries of 85% down to less than 30% [1].A common cause of refractoriness is encapsulation of fine gold within the matrix of sulphide minerals, particularly arsenopyrite and pyrite. The size and location of the gold within the sulphide matrix determines to a very large degree the nature of the process required for its liberation and recovery. Submicroscopic gold is liberated by destruction of the sulphide with processes based on the use of thermal, chemical or biological oxidation. If the encapsulated gold is coarser in size, ranging say, from 1 or 2 microns to approximately 20 microns, then liberation can also be achieved by ultra fine milling (UFM).The Western Australian goldfields, like many others, contain numerous orebodies which are refractory in their primary zones. The mineralogy of these ores shows great variation, as does the gold recovery by various processing options. [2] The ‘best’ process can only be chosen with confidence after a careful metallurgical evaluation programme based on good sampling, process mineralogy and testing various processing options; eg UFM, biological oxidation, pressure oxidation, roasting, etc., coupled with environmental and economic factors.For the past few years, Ammtec has been involved in numerous refractory gold projects. This paper presents some of the results from these process development programmes.
Article
Experimental investigations concerning the comminution of limestone in a stirred media mill have been carried out. The results show that the circumferential velocity of the stirrer discs as well as the density and the size of the grinding beads affect the specific energy consumption necessary to achieve the required product fineness. The influence of these three operating parameters on the comminution result can be fully described by the stress intensity of the grinding beads. Therefore, specific energy consumption and stress intensity of the grinding beads are the comprehensive influencing variables on the comminution of limestone in stirred media mills. It is expected that this relationship is also valid for the comminution of other materials in stirred media mills. For a fixed specific energy input, an optimum stress intensity exists, for which the finest product is achieved. With increasing specific energy input, and therefore increasing product fineness, the optimum stress intensity decreases. Since the specific energy is proportional to the product of stress intensity and stress frequency, the comminution result can also be correlated to the stress frequency and the stress intensity. With increasing stress intensity, the stress frequency required for a certain product fineness decreases.
Article
Experimental investigations on the wet batch comminution of an alumina hydrate in a stirred bead mill are presented. The influence of some operating parameters (mass solids concentration, initial size of particles, stirrer speed and beads size) on both the specific energy and the size distribution of the ground product is discussed. The existence of a limit fineness has been put in evidence and the conditions leading to a best efficiency of the process are defined.A quantitative characterization of the morphology of the fragmented particles has led to the identification of the fragmentation path occurring during the process. The analysis allows to interpret the evolution vs. time of the product size distributions characterized by a multimodal pattern.
Article
The attrition mill is a device for mechanically reducing solid particle size by intense agitation of a slurry of material being milled and coarse milling media. For example, in 10 hours of milling, specific surfaces of 40 and 25 m2/g were obtained for alumina and barite, corresponding to 38 and 56 nm equivalent spherical diameter, respectively. Size reduction rates for relatively coarse particles were first-order and increased linearly with power input to the mill. Optimum milling medium concentration corresponded to medium particles moving a distance of approximately 0.7 of their diameter before collision with another such particle. Power characteristics of the attrition mill were essentially the same as those of a radial flow turbine mixer. Laminar flow became disrupted at NRe ≈ 200, while turbulent flow was established at NRe > 8000. Slurries of fine powders exhibited the same linear power-average density dependence as single-phase liquids. However, a different dependence was observed with large particles.
Article
A large-scale continuous stirred media mill called the MaxxMill® system in dry mode was used to investigate the comminution characteristics. A limestone powder below 2 mm was used as a feed material. A statistical experimental design was prepared with the major influencing parameters of the MaxxMill®, such as rotational speed of stirrer, feed rate and bead size. The fineness of the ground products obtained under various conditions of the MaxxMill® and the corresponding energy utilisation have been evaluated and analysed. The results have been empirically correlated with the operating parameters. In addition, product size–energy input relations can be described empirically, independent of the parameters used.
Article
Grinding and energy input in stirred media mills are studied as functions of grinding time, stirring speed, media size and density, solid concentration, impeller and tank dimensions and design, and other relevant variables. Ground product size and surface area are determined with respect to the above variables. Changes in energy input and media/pulp rheological properties during grinding are described. The best conditions for grinding limestone in the laboratory stirred media mills have been identified. Equations for correlations involving power and modified Reynolds numbers have been established.
Article
A joined research project between the Technical University of Braunschweig and the Technical University of Mnchen investigates the possibilities for the production of stable product suspensions in a particle size range smaller than 100 nm. In this paper results for comminution of fused corundum showing the influence of the electrostatic stabilization at different pH-values on the grinding progress and the grinding media wear are presented. Furthermore, by means of experimental results the influence of the grinding media diameter and the stirrer tip speed is discussed.
Article
As a prerequisite to producing super-clean coal with any physical coal-cleaning process, such as microbubble flotation, the feed coal must be micronized to liberate finely disseminated mineral matter. The stirred ball mill is regarded as one of the most efficient devices for micronizing coal. Using a 13.4 cm batch mill, the optimum operating conditions have been determined in terms of media size, feed size and media type. The rate of breakage determined with monosized feeds are compared on the basis of specific energy consumption. It has been found that a 20:1 ball size/particle size ratio gives optimum grinding conditions.
Article
Stirred mills are primarily used for fine and ultra-fine grinding. They dominate these grinding applications because greater stress intensity can be delivered in stirred mills and they can achieve better energy efficiency than ball mills in fine and ultra-fine grinding. Investigations were conducted on whether the greater performance of stirred mills over ball mills in fine grinding can be extended to coarse grinding applications. Four different laboratory ball mills and stirred mills have been tested to grind seven ore samples with feed sizes ranging from 3.35 mm to 150 μm. A case study on full scale operations of a 2.6 MW IsaMill replacing the existing 4 MW regrind ball mill at Kumtor Gold Mine in Kyrgyzstan is also included. This paper summarizes the major findings from these investigations.
Article
Muscovite, wollastonite and kaolinite were wet attrition ground in a pilot-size stirred ball mill (continuous type) as well as a vibratory mill (batchIt is shown that the vibratory mill (SWECO) is much less efficient than the stirred mill (DRAIS), at least when 12-mm media are used in SWECO. This isThe highest performance of DRAIS is reached when using a low amount of polymer-type dispersant (0.35 g/100 g solids) and a low pulp density (12 wt.% so
Grinding Comparison Test of IsaMills with Tower Mills using Magnetite
  • L Clark
Clark, L., 2007. Grinding Comparison Test of IsaMills with Tower Mills using Magnetite. Xstrata Technology.
Modelling of the Performance of Stirred Media Mills in Regrinding Circuits
  • S Dikmen
Dikmen, S., 2008. Modelling of the Performance of Stirred Media Mills in Regrinding Circuits. Ph.D. Thesis, Hacettepe University, Ankara, Turkey.
IsaMill fine grinding technology and its industrial applications at Mt. Isa Mines
  • M Gao
  • M Young
  • P Allum
Gao, M., Young, M., Allum, P., 2002. IsaMill fine grinding technology and its industrial applications at Mt. Isa Mines. In: Proceedings of the 34th Annual Meeting of the Canadian Mineral Processors, Ottawa, Canada, pp. 171-188.
Mineral Comminution Circuits -Their Operation and Optimization
  • T J Napier-Munn
  • S Morrell
  • R D Morrison
  • T Kojovic
Napier-Munn, T.J., Morrell, S., Morrison, R.D., Kojovic, T., 1996. Mineral Comminution Circuits -Their Operation and Optimization. JKMRC Monograph Series in Mining and Mineral Processing, Brisbane, Australia.
A Detailed Study on Stirred Ball Mill Grinding
  • J L Sepulveda
Sepulveda, J.L., 1981. A Detailed Study on Stirred Ball Mill Grinding. Ph.D. Thesis, Department of Metallurgy and Metallurgical Engineering, The University of Utah, The USA.