Types Of Mills Research Articles

Comparison of breakage models in DEM in simulating impact on particle beds

The discrete element method (DEM) has proven to be a powerful tool to simulate processes involving particulate material. When simulating materials handling operations that lead to mechanical degradation as well as several types of crushers and mills, description of particle breakage inside the DEM environment becomes indispensable, since flow of solids, energy transfer and size reduction are deeply intertwined. However, breakage modeling in DEM is still in an earlier stage of development and comparatively limited work has been carried out demonstrating the validity and limitations of the various models pursued in the literature and already available in commercial DEM packages. The work analyzed particle breakage using three models available in commercial DEM simulation platforms: the bonded-particle model (BPM), the particle replacement model (PRM) and the fast-breakage model (FBM). These were initially calibrated on the basis of the distribution of breakage probabilities of individual 6.3–4.75 mm copper ore particles and, whenever possible, progeny size distributions. Breakage of particles in beds by impact by a falling steel ball is an interesting case for testing breakage models, besides an important microprocess in some comminution operations, since particles interact with each other and with the grinding medium. As such, the potential of the three models to describe size reduction was demonstrated through comparison of unconfined particle bed breakage experiments and simulations. The models demonstrated different abilities to describe the various aspects of breakage. The work then identified opportunities for improvement in each of the models.

Dry grinding in planetary ball mills: Evaluation of a stressing model

Planetary ball mills at laboratory scale are widely used for grinding and alloying processes. However, in contrast to other mill types, no applicable mechanistic model exists to describe the stressing conditions and their effect on particle breakage, so that processes are empirically evaluated so far. Within this study, the stressing conditions are determined by simulations based on the discrete element method including the contact model of Hertz and Mindlin. The contact model parameters are carefully calibrated by a series of experiments, so that it is finally possible to validate the simulation results by comparison of measured and calculated power values. The correlation of stressing conditions and breakage rates of alumina powder demonstrates the effect of stressing on breakage kinetics and breakage mechanism. It allows calculating the active mass in dependence on process parameters by an extension of Schönert’s active mass model.Altogether, the presented stressing model features analytical functions for the mill-related stressing conditions and highlights the importance of stressing intensity as process determining parameter, which defines the required number of material-related stressing events and the specific energy.

Agroindustrial performance of sugarcane varieties for panela in Antioquia, Colombia

En el municipio de San Carlos la agroindustria panelera es el sector agrícola más importante, en lo económico, en la generación de empleo y en la seguridad alimentaria. Las variedades de caña de azúcar obtenidas por Cenicaña representan alternativas de competitividad y productividad para el sector panelero de Colombia. La presente investigación evaluó agronómicamente y en rendimiento en trapiche tipo Cimpa, diez variedades de caña, en dos localidades del municipio de San Carlos, Antioquia, en un diseño de bloques completos al azar, con dos repeticiones. En cuatro surcos de seis metros de largo, se sembraron 10 yemas por surco. Con un promedio de tres ciclos de corte, las variables estudiadas fueron, toneladas de caña por hectárea, toneladas de panela por hectárea, rendimiento industrial (%) y calidad industrial. Las variedades CC 93-4418, CC 93-3817, CC 93-3895 y CC 92-2154 superaron en 40, 34, 30 y 21 toneladas de caña y 7, 6, 5 y 5 toneladas de panela, respectivamente, a los rendimientos obtenidos por el testigo Co 421. Los rendimientos industriales fluctuaron entre 11 y 13%, el testigo fue del 12%. Estas cuatro variedades presentan buenas características de pH, concentración de solidos solubles, sacarosa y azucares reductores. Estos resultados son replicables y asumibles para la mayoría de las de zonas productoras del departamento de Antioquia.

Symptoms of Respiratory Health Problems in Rice Mill Workers of Bangladesh

Background: Husking, Major and Automatic types of rice mills are small scale industry abundant in Bangladesh producing parboiled rice. A little information is available about the chronic respiratory health problems of the workers due their occupational exposure to the rice mill dust in Bangladesh.Objectives: To be aware of symptoms of chronic respiratory health problems in rice mill workers of Bangladesh.Materials and methods: This descriptive cross sectional study was carried out among 500 rice mill workers. Data were collected about the symptoms of chronic respiratory health problems by face to face interview with questionnaire. Physical examinations and lung function test were done.Results: Total 34.0% of workers complained suffering from the symptoms of chronic respiratory illness. Cough (18.0%), dyspnoea (10.0%), rhinitis (6.8%) and wheezing (5.8%) were the prevalent symptoms. No clinical sign of any respiratory disease was detected. The majority (69.0%) of the symptom sufferers worked in Parboiling and drying section (PBDS) of the mills and their duration of employment and suffering from symptoms were also short.Conclusion: Occupational respiratory health problem in rice mill workers in Bangladesh is not at remarkable level. Only symptomatic treatment is required to elude the problems at present but continuing in job health education, supervision and monitoring are essential for future.KYAMC Journal Vol. 7, No.-2, Jan 2017, Page 758-761

„Młyny ważne”, „młyny na wagach”. Przyczynek do genezy nazwy i konstrukcji

So far no satisfactory explanation has been provided in the Polish literature devoted to milling concerning the mills called scales mills or mills on scales. Th e attempts undertaken identified this kind of mills with watermills or, more often, mills on stilts. Th e author of the present article is of a different opinion as – on the basis of written sources – she identified those mills with the ones which were parallelly and simultaneously used with their medieval Latin names of molendinum pensile and molendinum pendens as well as the German name Panster Muhle , and which were characterized by a water wheel raised and lowered on chains or ropes, depending on the changing water level in rivers. The Polish name of such mills was derived by the author from the scales (counterbalance) stabilizing the water wheel in the desired position. At the same time, the author believes that such mills, as a whole or in part, were placed on stilts for obvious reasons but she also notices that other types of mills were raised on stilts too.

Research and Development Trend of Shape Control for Cold Rolling Strip

Shape is an important quality index of cold rolling strip. Up to now, many problems in the shape control domain have not been solved satisfactorily, and a review on the research progress in the shape control domain can help to seek new breakthrough directions. In the past 10 years, researches and applications of shape control models, shape control means, shape detection technology, and shape control system have achieved significant progress. In the aspect of shape control models, the researches in the past improve the accuracy, speed and robustness of the models. The intelligentization of shape control models should be strengthened in the future. In the aspect of the shape control means, the researches in the past focus on the roll optimization, mill type selection, process optimization, local strip shape control, edge drop control, and so on. In the future, more attention should be paid to the coordination control of both strip shape and other quality indexes, and the refinement of control objective should be strengthened. In the aspects of shape detection technology and shape control system, some new types of shape detection meters and shape control systems are developed and have successfully industrial applications. In the future, the standardization of shape detection technology and shape control system should be promoted to solve the problem of compatibility. In general, the four expected development trends of shape control for cold rolling strip in the future are intelligentization, coordination, refinement, and standardization. The proposed research provides new breakthrough directions for improving shape quality.

Optimal interface surface determination for multi-axis freeform surface machining with both roughing and finishing

In the current practice of multi-axis machining of freeform surfaces, the interface surface between the roughing and finishing process is simply an offset surface of the nominal surface. While there have already been attempts at minimizing the machining time by considering the kinematic capacities of the machine tool and/or the physical constraints such as the cutting force, they all target independently at either the finishing or the roughing process alone and are based on the simple premise of an offset interface surface. Conceivably, since the total machining time should count that of both roughing and finishing process and both of them crucially depend on the interface surface, it is natural to ask if, under the same kinematic capacities and the same physical constraints, there is a nontrivial interface surface whose corresponding total machining time will be the minimum among all the possible (infinite) choices of interface surfaces, and this is the motivation behind the work of this paper. Specifically, with respect to the specific type of iso-planar milling for both roughing and finishing, we present a practical algorithm for determining such an optimal interface surface for an arbitrary freeform surface. While the algorithm is proposed for iso-planar milling, it can be easily adapted to other types of milling strategy such as contour milling. Both computer simulation and physical cutting experiments of the proposed method have convincingly demonstrated its advantages over the traditional simple offset method.

Role of Sample Processing Strategies at the European Union National Reference Laboratories (NRLs) Concerning the Analysis of Pesticide Residues.

The guidance document SANTE 11945/2015 recommends that cereal samples be milled to a particle size preferably smaller than 1.0 mm and that extensive heating of the samples should be avoided. The aim of the present study was therefore to investigate the differences in milling procedures, obtained particle size distributions, and the resulting pesticide residue recovery when cereal samples were milled at the European Union National Reference Laboratories (NRLs) with their routine milling procedures. A total of 23 NRLs participated in the study. The oat and rye samples milled by each NRL were sent to the European Union Reference Laboratory on Cereals and Feedingstuff (EURL) for the determination of the particle size distribution and pesticide residue recovery. The results showed that the NRLs used several different brands and types of mills. Large variations in the particle size distributions and pesticide extraction efficiencies were observed even between samples milled by the same type of mill.

Stability of Pharmaceutical Cocrystal During Milling: A Case Study of 1:1 Caffeine–Glutaric Acid

Despite the rising interest in pharmaceutical cocrystals in the past decade, there is a lack of research on the solid processing of cocrystals downstream to crystallization. Mechanical stress induced by unit operations such as milling could affect the integrity of the material. The purpose of this study is to investigate the effect of milling on pharmaceutical cocrystals and to compare the performance of ball mill and jet mill, using caffeine–glutaric acid (1:1) cocrystal as the model compound. Our results show that ball milling induced polymorphic transformation from the stable Form II to the metastable Form I, whereas Form II remained intact after jet milling. Jet milling was found to be effective in reducing particle size, but ball milling was unable to reduce the particle size beyond a certain limit even with increasing milling intensity. The heating effect during ball milling was proposed as a possible explanation for the difference in the performance of the two types of mill. The local increase in t...

Mechanical Alloying and Sintering of Ni-Sn and Ni-Mg Powder Mixtures

Various intermetallics can be synthetized by mechanical alloying depending on alloy composition, type of mill, and milling parameters. This work discusses on the phase transformations during ball milling and subsequent sintering of Ni-Sn and Ni-Mg powder mixtures. The structural evaluation of as-milled and sintered samples was conducted by X-ray diffraction and scanning electron microscopy. Metastable phases were formed during milling of the Ni-Sn and Ni-Mg powder mixtures. The Ni3Sn and Ni3Sn2 compounds were produced after sintering from the as-milled Ni-25Sn and Ni-40Sn powders, respectively. Two-phase Ni2Mg+NiMg2 alloy was found after sintering of as-milled Ni-66Mg powders because the nominal Mg amount in starting powders was reduced due to its preferential cold welding during milling and/or evaporation during sintering.

Processing of Moringa leaves as natural source of nutrients by optimization of drying and grinding mechanism

AbstractIn this study, Moringa leaves were processed in two steps (1) drying and (2) grinding. In the first step, leaves were dried with different drying treatments including conventional, laboratory and advanced methods to optimize drying conditions in terms of maximum nutrients preservation and color quality. During the second step, leaves were ground with three different grinding mills including hammer, dry, and cutter mills to study the effect of grinding mechanism in combination with particles size and moisture content on the flowability of the powder. The flowability was measured using conventional and advanced methods including Carr Index and Cohesion Index. Oven drying at 50 °C was found to be the optimum conditions in terms of maximum nutrients and color preservation of Moringa leaves. The grinding mechanism having a substantial impact on the flowability of the powder produced in different types of mills. The effect of moisture content and particle size on Moringa leaves powder was also investigated and found that moisture content directly affects the flowability of Moringa leaves powder followed by particles size and shape. We have also noted powder sample prepared by the impact mechanism (hammer mill) with particle size 50 µm and moisture content 5% having appreciable flowability as compared to the samples processed by cutting (dry mill) and shattering (cutter mill) mechanisms. This study conveys an ultimate understanding regarding processing (drying and grinding) of Moringa leaves powder.Practical ApplicationsDried Moringa is restricted to use as dietary purposes because of its unpleasant taste, which becomes further bitter after drying procedure. Therefore, powder of Moringa leaves can be processed into different forms such as tablet, capsules and cereal formulations. For this purpose, a comprehensive study has been carried out to increase the understanding of drying and flow characteristics of Moringa (leaves and powder) using different drying and grinding mechanisms. The findings of this study regarding drying treatments, nutrients preservation, flowability and different grinding mechanisms can also be applied to other herbs and leaves. A correlation between Carr Index and Cohesion Index established successfully. This study will be helpful to conduct further research in food processing because Carr Index is simple and easy to measure as compared to Cohesion Index that requires both texture and powder flow analyzers.

Fine grinding: How mill type affects particle shape characteristics and mineral liberation

In minerals beneficiation applications, the main function of comminution circuits is to liberate valuable minerals to facilitate downstream separation processes such as flotation. Traditionally, design and optimisation of comminution circuits was based on the production of a target particle size distribution at an optimised throughput with consideration of energy efficiency and equipment wear rates. However, research in flotation and process mineralogy is leading to queries as to whether more should be demanded from the comminution circuit in terms of particle preparation. For example – if particle shape affects hydrophobicity, can mill operating conditions be adjusted to produce particles with shape characteristics which are more amenable to flotation? For this work UG2 ore (a South African platinum group mineral ore) was milled in a laboratory ball mill and stirred mill. To supplement the laboratory study, samples were taken from the fine grinding circuit of an operational UG2 concentrator. Automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry (Auto-SEM-EDS) was used for mineralogical and particle shape analysis of feed and product samples. Although the laboratory test work indicated a significant difference in product particle shape characteristics for the two mill types, the difference was not evident in the plant data.

Effect of design and operational parameters on particle morphology in ball mills

Different factors involving in grinding of ore cause various breakage mechanisms. These different mechanisms differ the morphology of ground particles. In this study, the effect of ball mill types, feed sizes, and ball surface area have been investigated on the morphology of ground quartz particles using MBL cruise optical microscope and Olympus E-510 camera. Measured two-dimensional particle projection was expressed mathematically such as circularity, roundness and aspect ratio by ImageJ software. >20,000 particles were morphologically measured for image analysis. Results show that circularity and roundness of ground particles are enhanced in an ordinary ball mill equipped with smooth liner (OBM). While higher aspect ratio of ground particles are achieved in cylindrical ball mill equipped with wavy liner (CBM). Consequently, the dominant breakage mechanism for OBM and CBM are abrasion and impact, respectively. Circularity and roundness values of coarse-grained ground particles are more than fine-grained particles. The increase of ball surface area causes the increase of circularity as well as roundness values and the decrease of aspect ratio value.

Effects of Different Mill Types on Ethanol Production Using Uncooked Dry‐Grind Fermentation and Characteristics of Residual Starch in Distiller's Dried Grains (DDG)

This study aimed to investigate impacts of milling methods on ethanol production using an uncooked dry‐grind (cold fermentation) process and characterize residual starch in the distiller's dried grains (DDG) coproduct. Four corn lines with different chemical compositions were ground with cyclone, ultra‐centrifugal, or hammer mills equipped with a screen of 0.5 mm opening and used for the cold fermentation process. Greater starch hydrolysis and ethanol yield were obtained from cyclone‐milled corn, resulting from larger damaged starch contents and smaller particle sizes of the ground corn. Corn grains and ground corn after five‐month storage showed less starch hydrolysis than the freshly ground counterpart. Residual starch (2.8–8.0%) with large proportions of intact amylopectin contents (up to 42.5%) was found in the DDG from all types of milling. The results suggested that the entrapment of starch granules in ground corn and a low activity of amylolytic enzymes at a high ethanol concentration were accountable for the remaining of starch in the DDG.

A unified analytical cutting force model for variable helix end mills

The paper proposes a unified analytical cutting force model based on a predictive machining theory for variable helix end mill considering cutter runout. The variable helix end mill is divided into a set of differential oblique elements along the axial direction. The cutting process of oblique element is based on the non-equidistant shear zone model and the equivalent plane method. The cutting forces of oblique element are modeled by shearing force components due to shearing at the shear zone and edge force components due to rubbing in the tertiary zone. In the primary shear zone, a modified Johnson-Cook model is introduced to account for the material size effect affected by varying instantaneous uncut chip thickness (IUCT) during milling process. In the tertiary zone, edge radius and the partial effective rake angle are included in the analytical model in order to take into account the rubbing effect precisely. The total instantaneous cutting forces are obtained by summing up the cutting forces acting oblique elements on all flutes. The unified analytical cutting force model is verified by experimental data using four different types of end mills, and a good agreement of the predicted and measured cutting forces shows that the proposed model is valid for variable helix end mills.

Scale-up of stirred media mills for fly ash grinding

AbstarctIn this study, fly ash was ground for use as a CO2 foam stabilizer. The investigated set of mills comprised 1 L and 10 L batch-type wet grinding stirred media mills. The employed grinding media was zirconia (ZrO2) beads with a density of 6 g/cc and mean diameter of 1.0 mm. Grinding experiments were conducted under different rotational speeds of the rotor. The investigated rotational speeds varied from 360 to 800 rpm for each type of mill. Based on the experimental results, a scale-up procedure related to the net specific grinding energy was developed, taking mill dimension into consideration. With the developed procedure, the D50 particle size could be estimated on the basis of operating conditions such as the rate of revolution and grinding time. Finally, this study investigated a scale-up procedure for stirred media mills, and the useful application of the function to predict mean particle size.

Analysis of the Cu-Al Milling Stages Through the Microstructure Evolution Studied by TEM and SEM

Fil: Giordana, Maria Florencia. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Comision Nacional de Energia Atomica. Centro Atomico Bariloche; Argentina

Secondary comminution of wood pellets in power plant and laboratory-scale mills

This study aims to determine the influence of mill type and pellet wood composition on particle size and shape of milled wood. The size and shape characteristics of pellets comminuted using power plant roller mills were compared with those obtained by using laboratory-scale roller- and hammer mills. A 2D dynamic imaging device was used for particle characterization. It was shown that mill type has a significant impact on particle size but an almost negligible effect on the shape of milled wood. Comminution in the pilot plant using a Loesche roller mill requires less energy than using a hammer mill, but generates a larger fraction of coarse particles. The laboratory-scale roller mill provides comparable results with the power plant roller mill with respect to particle size and shape.

Karbon Fiber Takviyeli Polimer Kompozitlerin Kenar Budama Değişkenlerinin Yüzey Kalitesine Etkisi

The main focus of this paper is to investigate the surface quality and machinability of the edge trimming process of carbon fiber reinforced polymer (CFRP) material. Measurement of transverse and longitudinal surface roughness and deformation behavior are carried out for different combinations of cutting speed, feed per tooth, tool type and milling type to evaluate the machined surface quality. Three different flutes (2,4,6) micro grain carbide end mill tools were used for vertical and inclined peripheral milling. Edge trimming experiments were conducted under different experimental parameters and their levels according to the Taguchi design of experiment method. The contribution ratio of parameters on machinability outputs has statistically analyzed by Analysis of Variance (ANOVA). According to machinability outputs such as surface roughness and deformation types, the inclined peripheral milling is more suitable than vertical peripheral milling. Edge trimming by vertical peripheral milling generates Type II delamination which consists of long uncut fibers protruding from the trimmed edges. Edge trimming by inclined milling generates Type I-II delamination which consists of short uncut fibers protruding from the trimmed edges and where plies have broken inwards in the same time. The transverse and longitudinal surface roughness and deformation decreased with increased number of teeth, cutting speed and decreased feed per tooth. The best machining quality was obtained when cutting at the highest level of cutting speed, lowest feed rate and 6 number of flute in inclined milling.

Optimum parameters for the production of porous ceramic materials

In this research, the effects of parameters such as sintering temperature, forming method, milling type and the content of alunite within kaolin were investigated for the production of porous ceramic material. For this purpose, kaolin samples with three different alunite contents, taken from the Balikesir-Sindirgi region of Turkey, were used. During the research, ball and jet mills were utilized to determine the effect of mill type onto the strength and porosity values of the porous body. Optimum milling times for the two mills were determined during this stage. Moreover, the effect of forming method onto the strength and porosity values of the porous bodies was investigated. For these tests, dry pressing and slip casting methods were employed. The samples formed were then sintered at a temperature range of 900 to 1300 °C. Consequently, the most optimum conditions for the production of the highest porosity ceramic material were determined.