Grinding Mill Research Articles

Mesoporous silicon nanoparticles covered with PEG molecules by mechanical grinding in aqueous suspensions

We propose a one-step procedure to stabilize mesoporous silicon nanoparticles in aqueous solutions by polyethylene glycol (PEG) coating during grinding in a planetary ball mill. The milling is done in aqueous medium that allows us to directly obtain the aqueous suspension of PEGylated nanoparticles. The prepared nanoparticles are investigated by means of the scanning electron microscopy, energy dispersive X-ray spectroscopy, low-temperature nitrogen sorption, dynamic light scattering, Fourier transform infrared spectroscopy, Raman and photoluminescence spectroscopy, which reveal the nanoparticle size of 50–100 nm, preservation of the nanocrystallinity and mesopores. The PEGylated nanoparticles are found to be stable in aqueous solution for at least 24 h. The proposed PEGylation method can be used to control the physical properties and stability of mesoporous silicon nanoparticles for biomedical applications.

Features of determining the specific surface area of powdered quartz-containing systems

Introduction. Mineral raw materials, mechanically dispersed to a fine-grained condition, contribute to the effective use of the energy potential in the course of the structuring of composite materials. An important parameter, characterizing the dispersion ability and allowing to evaluate the ability of the system to transform is the specific surface of the substance. The experimental value of the specific surface depends on the measurement method and may differ for the same solids when different methods are applied. The purpose of the work is to study the morphological features of the surface of powdered quartz-containing systems having varying degrees of dispersion. The work represents the experimental identification of specific surface.
 Materials and methods. Filtration and adsorption methods were used to identify the specific surface of a mechanically activated sample of polymineral sand. Fine powders of sand were obtained by dry grinding in a planetary ball mill. The analysis of the obtained results was conducted taking into account the surface tension values of the powders as the characteristics of the surface energy of a surface area unit.
 Results. It is found that dimensions of the specific surface identified using the gas filtration method are smaller than those obtained using the nitrogen adsorption method. The authors have identified a linear functional dependence between the ratio of dispersion and polarization components of the surface tension and the ratio of specific surfaces obtained using different methods for one sample of sand.
 Conclusions. Despite a difference in the values obtained for the same material sample, specific surface area indicators, identified using different methods, allow to evaluate the extent of the surface maturity, the availability of active centres, and the energy potential of mineral powders. The ratio of specific surfaces can be used as a criterion for the rational choice of the operating parameters of mechanical activation of quartz-containing powder systems to increase the energy potential of the surface.

An Observer to Detect Infrequently-Occurring Disturbances in Grinding Operations

Changes in ore properties create challenges for the control and optimization of comminution operations because they are generally difficult to measure in real time and have significant impacts on the grinding process and downstream operations. The effectiveness of a multi-model observer to detect and estimate step changes in the particle size distribution of the ore feed to a semi-autogenous grinding (SAG) mill using noisy measurements of the product particle size, is evaluated using a simulation model of the process. The observer maintains multiple hypotheses about the disturbance until their likelihood given the measurements can be determined and used to estimate the disturbance and the true process output. The results demonstrate that the multi-model observer has lower overall estimation errors than a single Kalman filter because it responds to changes in the output quickly without a compromised sensitivity to noise during steady-state. Real-time estimation of changes in ore feed properties in grinding operations could have significant benefits, however, more work is needed to characterize these disturbances, to determine if the process and disturbance models can be identified in practice, and to estimate the potential benefits.

Controlling a Grinding Mill Circuit using Constrained Model Predictive Static Programming

A constrained Model Predictive Static Programming (MPSP) method is implemented in simulation to a single-stage grinding mill circuit model. The results are compared to a constrained Nonlinear Model Predictive Control (NMPC) method. Both the constrained MPSP and NMPC controllers were able to track the desired output set-points without exceeding any constraints. The comparison shows that the constrained MPSP has a faster computational time than that of the NMPC controller with similar performance. Therefore, constrained MPSP shows promise as a model-based controller for large processes where computational time limits the use of NMPC.

A Comparative Technique for Performance Evaluation of Hammer Mill and Disk Mill in Yam Flour Processing

Grinding (Particle size reduction) of biomass is an age-long operation that is performed during the preparation process of certain food products. Among the grinding mill machines mostly used for this operation are hammer mill and disk mill. Being that the nature of biomass affects the performance and choice of grinding-mill machine to be adopted, it is imperative to compare and select appropriate grinding mill machine that is efficient and effective. In this paper, a comparative technique to evaluate and select appropriate grinding mill machine for particle size reduction of dried white yam (Dioscorea rotundata) is proposed. Hammer mill and disk mill machines were selected for consideration. Two white yam species (Benue and Delta Yam) were prepared into dried chips and ground using the selected mills. Among the attribute (performance parameters) considered are crushing time, particle size distribution and energy consumed. A measure of performance (Index I) based on the comparative technique was formulated and used in evaluating the performance of the two mills. In the hammer mill, index I recorded 2721.2 and 3719.82 par/kWh for Benue Yam chips at screen size 4 and 6 mm, respectively, while 2647.89 and 3472.01 par/kWh was recorded for Delta yam chips at screen size 4 and 6 mm, respectively. Index I values for the Disk mill were 2536.25 and 2433.42 par/kWh at 1.2 mm clearance distance for Benue Yam chips and Delta Yam chips, respectively. The results indicated that hammer mill performed better overall than the disk mill. The comparative technique was found suitable in the evaluation of the performance of the mills. It is recommended that hammer mill be adopted.

Quantitative reversible one pot interconversion of three crystalline polymorphs by ball mill grinding

We demonstrate here using a disulfide system the first example of reversible, selective, and quantitative transformation between three crystalline polymorphs by ball mill grinding.

Performance and Blood Profile of Grower West African Dwarf (WAD) Bucks Fed Graded Levels of Toasted Baobab (<i>Adansonia digitata</i>) Seed Meal

An experiment was conducted to evaluate the performance and blood parameters of West African Dwarf (WAD) bucks fed graded levels of toasted baobab seed meal for 84 days. Baobab seeds were washed, sun-dried and toasted uniformly using a cast iron pan. The toasted baobab seeds were crushed with a roller mill grinding machine to make baobab seed meal (BSM). The BSM was included at 0%, 25%, 50% and 75% levels in diets 1, 2, 3 and 4 respectively to replace soybean. Each treatment was replicated four times in a completely randomized design. Uncoagulated blood samples were collected from WAD bucks at the end of the 84 days’ feeding trial and analysed for packed cell volume (PCV), haemoglobin concentrate (Hb), red blood cells (RBC) and white blood cells (WBC). The mean corpuscular haemoglobin volume (MCV), mean corpuscular haemoglobin (MCH), platelets, neutrophils, lymphocytes, monocytes, eosinophils, and basophils were calculated using PCV, RBC and Hb. The blood meant for serological analysis was centrifuged at 1000 G for 10 minutes, after which the serum was separated and used for determining serum total protein (Tp), albumin, serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT). The inclusion of baobab seed meal up to 50% in the experimental diet did not have any negative effect on the performance of the goats and did not pose any health challenge to the animals during the study period.

Optimisation of solids concentration in wet rod mill grinding of limestone ore through modelling and simulation

Optimisation of solids concentration in wet rod mill grinding of limestone ore through modelling and simulation

Optimisation of solids concentration in wet rod mill grinding of limestone ore through modelling and simulation

Optimisation of solids concentration in wet rod mill grinding of limestone ore through modelling and simulation

Creation of electrically conductive composite ceramics based on facing tiles with the addition of SiC

In the article, the creation of electrically conductive composite ceramics based on facing tiles with the addition of SiC with specified electrodynamics’ characteristics was considered.
 To obtain a press powder, the raw materials in a predetermined amount were weighed, 10, 20 and 30 % silicon carbide were added and subjected to wet grinding in a ball mill. The resulting slip was dried in a drying oven and passed through a № 05 sieve. The finished press powder for facing ceramics with SiC, moistened to 8 %, was weighed and poured into a mold for pressing, the pressure force was 18—20 MPa. The resulting green was dried in a drying oven. The semi-finished product was burned in a sillite furnace at a firing temperature of 1120—1140 °C with a holding at a maximum temperature of 5—10 minutes. The chemical composition of obtained press powder and the technological scheme for obtaining samples were presented.
 The obtained data shown that the best sample was facing ceramics with 30 % SiC, which had the following properties: water absorption — 5.9 %, open porosity — 12.5 %, apparent density — 2.13 g/cm2, resistivity — 0.43 ⋅10-6 Ohm ⋅m. The obtained X-ray diffraction pattern indicated the presence of silicon carbide in the sample after firing, which was confirmed by the data on the study of specific volumetric resistance of the studied ceramics and the obtained practical results.

Development and study of the properties of a ceramic-matrix composite material for the production of ultra-thin large-format ceramic granite slabs

The article analyzes the advantages and disadvantages of large-format ultra-thin ceramic granite slabs, shows the need and identifies ways to increase their strength. The composition of the ceramic matrix has been developed, provides the maximum level of sintering (W ≤ 0.5 %) in accordance with the requirements for ceramic plates of class ВІа, and the choice of the reinforcing filler has also been substantiated. It has been experimentally established that mullite-silica fibers have a positive effect on the physical and mechanical properties of the slabs, which makes it possible to reduce their thickness by three times, and therefore significantly reduce the weight of products. The fractional composition of the grinding products of mullitesilica fibers was determined depending on the grinding conditions, and the influence of the quantitative and qualitative characteristics of the reinforcing filler on the main properties that determine the quality of ceramic granite slabs was investigated. The conditions for the formation of densely sintered composite materials with a complex of high-performance properties have been determined. It was shown the possibility of increasing the samples bending strength up to 57 MPa by introducing 4 wt. % of finely dispersed mullitesilica fibers, most of which (~ 60 %) have a length up to 45 microns, which is achieved by 3 min grinding in a planetary mill at a speed of 300 rpm. The structural-phase features of the samples obtained under the high-speed firing conditions, which consist in the increased amount of the mullite phase formation in the presence of mullite-silica fibers, have been established. The latter not only reinforce the ceramic matrix, but also act as a precursor of new mullite formations, the crystals of which, in the presence of a melt, acquire an isometric shape and contribute to an increase in the products strength. The research results indicate the promising obtain large-format ultra-thin ceramic granite slabs using composite materials technology. The combination of excellent technical qualities, large dimensions, and reduced slabs thickness opens up the new possibilities for using composite ceramic granite in design of furniture and large rooms due to the possibility of creating a continuous seamless coating and a significant reduction in the products weight.

Utilization of Waste Glass Powder as a Filler in Epoxy Resin Based Composite

This work focuses on the preparation of a high-quality glass powder from broken household waste glass. The expected glass powder prepared from household waste must show a high amount of silicon dioxide with fine particle size. The processing technique used in this work is coarse grinding and high-speed vibratory milling under a variety of conditions to get the best quality of glass powder. The particle size and particle size distribution were examined by using DLS technique. The chemical composition was examined by EDX together with FT-IR and XRF spectroscopies. The morphology of all glass powders was investigated by SEM. The results showed that the wide range of particle size distribution occurred in all milling conditions, which approximately ranged from 1 to 10 µm, and the 4 h-milling time showed the smallest particle size of glass powder. The chemical analysis showed that the glass powder was rich in silica which contained about 67% of SiO2. After that, the various ratios of the glass powder/epoxy resin composites were formed by using the traditional casting method. The physical, mechanical and electrical properties were investigated for all composites. The results showed that the Hv value of the glass powder/epoxy resin composites exhibited a much higher value than that of pure epoxy resin. For the electrical properties, after added 1 wt% of glass powder into the matrix, the εr and R significantly increased. The Eb value of the composite prepared from waste glass powder showed no significant difference from the composite prepared from commercial SiO2. So, it can say that the waste glass powder can be used as a filler in the epoxy resin-based composite as well as the commercial SiO2 powder for the electrical insulting application.

Using Solid Catalysts in Disulfide-Based Dynamic Combinatorial Solution- and Mechanochemistry.

It was shown for the first time that solid amines can act as catalysts for disulfide-based dynamic combinatorial chemistry (DCC) by ball mill grinding. The mechanochemical equilibrium for the two disulfide reactions studied was reached within 1-3 h using ten different amine catalysts. This contrasts with the weeks to months to achieve solution equilibrium for most solid amine catalysts at 2 %mol mol-1 concentration in a 2 mMolar disulfide dynamic combinatorial library in a suitable solvent. The final mechanochemical equilibrium was independent of the catalyst used but varied with other ball mill grinding factors such as the presence of traces of solvent. The different efficiencies of the amines tested were discussed.

RETRACTED: Experimental Study of Operational Parameters on Product Size Distribution of Tumbling Mill

To assess the effects of the mill operating parameters such as mill speed, ball filling, slurry concentration and slurry filling on grinding process and size distribution of mill product, it was endeavored to build a pilot model with smaller size than the mill. For this aim, a pilot mill with 1 m × 0.5 m was implemented. There are 15 lifters with 50 mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60 mm diameter, 40% of the balls with 40 mm diameter and 20% of the balls with 25 mm diameter) was used as grinding media with 10%, 15%, 20% and 25% of the total volume of the mill. The experiments were carried out at 60%, 70%, 80% and 90% of the critical speed. The feed of the mill is copper ore with the size smaller than 25.4 mm, which d80 and d50 of them are 12.7 and 8 mm, respectively and slurries with 40%, 50%, 60%, 70% and 80% of solid and the slurry filling between 0.5 and 2.5. The results showed that the best grinding and grading occurs at 70–80% of the critical speed and ball filling of 20–25%. Optimized grinding was observed when the slurry volume is 1–1.5 times of the ball bed voidage volume and the slurry concentration is between 60% and 70%. The mill grinding mechanism in this work is a combination of both impact and abrasion mechanisms.

The Effect of Grinding Media on Mineral Breakage Properties of Magnetite Ores

The breakage and liberation of minerals are the key to fluidized mining for minerals. In the ball milling process, steel balls function as not only a grinding action implementer but also energy carrier to determine the breakage behavior of ores and the production capacity of the mill. When ground products present a much coarse or much fine particle size distribution, the separation process will suffer, resulting in inefficient recovery of useful minerals. Optimal control of the particle size distribution of the products is therefore essential, but the complexity and randomness of ball mill grinding make it difficult to determine the appropriate ball size. To solve the problem in the precise measurement of grinding ball diameters, this paper carried out magnetite grinding experiments with grinding balls of different diameters under the same grinding conditions to study the influence pattern of steel ball diameters on the particle break behavior, the particle size distribution of ground products, and the mineral liberation degree distribution. The research proposed on the matching relation between the ball size and the quality of ground products is essential for improving the ground product quality and reducing energy consumption.

Experimental studies of in-line gasification of mechanically activated coal fuel

The 1 MW experimental stand was modernized with a scroll swirler and a crushed fuel supply system. Comparative data on combustion and gasification of coal fuel crushed in high-stress mills - disintegrator, vibrocentrifugal and hammer mill - at a stand with a thermal power of 1 MW were obtained. The experiments used coal of the Kuznetsk Basin, grade D, with technical characteristics: Wr, % = 5.4; Ar, %=22.3; Vr, % = 32.3; Qsr, MJ/kg = 20.0. Elemental analysis showed that: Cr, %=54.6; Hr, % = 4.1; Nr, % = 1.3; Sr, % = 0.5; Or = 11.8. In experiments with grinding coal on a disintegrator mill, the value of H2 = 4.5 vol.% and CO = 9.4 vol.%, when grinding in a vibro-centrifugal mill, the values of H2 = 0.6 vol.% and CO = 5.8 vol.%, when grinding in a hammer mill, the values of H2 = 0.3 vol.% and CO = 2.8 vol.%. When studying the combustion of mechanochemically treated coal samples, it was found that, all other things being equal, the gasification parameters, namely, the gas concentration and the distribution of temperature zones, depend strongly on the type of equipment used for processing. In particular, processing to approximately the same degree of fineness in mechanical mills-activators with constrained impact and in free impact mills (disintegrators) resulted in different flame parameters.

Tobacco stalk lignocellulosic nanofibers characterization for pharmaceutical applications

Lignocellulosic nanofibers derived from tobacco stalk can have countless applications in polymers composites, textile, cosmetics, and pharmaceuticals. Thus, it is important to evaluate biomass characteristics such as the presence of nicotine. In this study, nanofibers were obtained by mechanical fibrillation while cellulose content (0.5 and 2.0%) and drying methods were varied. Nanofibers were characterized by thin layer chromatography, 1H NMR, morphological analysis, α-cellulose content, Fourier transform infrared spectroscopy, X-ray diffraction and thermal analysis. Results demonstrate the absence of nicotine in tobacco stalk. The grinding mill process was efficient to produce by freeze-drying, nanofibers with fiber’s mean diameter of ~30 nm. Solid concentrations can influence the diameter of obtained fibers. Thermal stability increased and crystallinity decreased when alkali treatment was applied. The characterization techniques applied enable the evaluation of tobacco stalk and expanded its application to pharmaceutics.

Investigation of the influence of the pattern of a disc mill set on the process of obtaining powdered pulp

On the market of pulp and paper products, new requests for more narrowly targeted products appear every year. To stay competitive in the market, manufacturers need to use not only traditional types of fibrous materials, but also use with excellent characteristics from the usual cellulose. The article discusses the role of the knife process of pulp grinding. A method for producing powdered cellulose with preliminary grinding in a disk mill is proposed. The paper-forming properties of the pulp and the degree of polymerization of powdered cellulose, depending on the degree of grinding, are given.

Experimental characterization of chalcopyrite ball mill grinding processes in batch and continuous flow processing modes to reduce energy consumption

A mineralogy, rheology, and energy consumption-based experimental characterization of chalcopyrite ball mill grinding processes, in both batch and continuous flow processing modes, is carried out in this work. Accordingly, chalcopyrite ore samples are initially characterized in terms of mineralogical composition, particle size distribution, grindability characteristics, and work index. Next, a rheological characterization of actual and lab-created chalcopyrite mineral-slurries is performed. Finally, an energy consumption-based characterization of several chalcopyrite ball mill grinding processes is performed. The results from the initial mineralogical characterization indicate ore samples featuring 5% chalcopyrite. These results also highlight that 80% of the particles present in the chalcopyrite head ore have a diameter smaller than 1386 μm. In addition, they indicate that the Bond ball mill work index is equal to 15.3 kWh/ton, which corresponds to a mineral with the presence of chalcopyrite. The rheological characterization related results indicate that all actual and lab-created mineral-slurries exhibit a shear thinning rheological behavior. These results also show that, because of the higher number of particle interactions, the slurries’ apparent viscosity increases with the increase in their solids content. Finally, the energy consumption-based characterization results emphasize that energy consumption is more significantly affected by mill speed than by slurry solids content. Indeed, for the same percentage of mass passing through a 200 mesh, it is found that the specific grinding energy decreases with both the increase in slurry solids concentration and the decrease in mill speed. The results obtained in this work are consistent with findings made in previous studies.

Solution combustion assisted synthesis of ultra-magnetically soft LiZnTiMn ferrite ceramics

Wide practical application and increasing functional requirements for high-frequency ceramics lead to the active search for novel multicomponent ferrites and their synthesis technique. In this paper, a solution-combustion-assisted approach was proposed and realized for the successful production of ultra-magnetically soft LiZnTiMn-ferrite ceramics with advanced electromagnetic performance. Preceramic nanopowders of Li0.28Zn0.16Ti0.41Mn0.10Fe2.05O4 with spinel structure were synthesized via glycine-nitrate combustion at variable Ox/Red ratios (φ = 0.5, 1.0 and 1.5) followed by stabilizing quenching (600 °C, 2 h) and vibrating mill grinding. LiZnTiMn-ferrite-based fine ceramics were produced then using PVA binding (1 wt%), isostatic pressing (400 МPа) and Bi2O3-assisted (0.3 wt%) isothermal sintering (980 °C, 8 h) techniques. As result, a series of LiZnTiMn-ferrite ceramic samples were obtained and their structure was examined in detail using XRD, SEM, EDXS, AAS and ASA methods. It was shown that the Ox/Red ratio of the initial reaction solution is an efficient parameter affecting both crystallite size (26–38 nm) /crystallinity degree (up to 91%) of preceramic LiZnTiMn-ferrite powders and grain size (2.7–9.8 µm) / grain size distribution of resulting fine ceramics. Based on the results of vibration magnetometry it was found that ceramics samples possess the ultra-magnetically soft behavior with Hc = 0.61–0.89 Oe, Mr = 3.62–5.13 emu/g and Ms = 67.23–78.70 emu/g depending on the initial Ox/Red ratio. Besides, results of resonator analysis (100 Hz - 1000 kHz) demonstrate that the dielectric constant of the samples strongly depends on the average grain size and reaches its maximum value (~ 6.4⸱10–4) at 100 Hz for the stoichiometric Ox/Red ratio (φ = 1.0) of reagents, wherein the linewidths of ferromagnetic resonance and resonance of spin waves practically unchanged and are in ranges of 327–344 and 1.43–1.45 Oe, respectively. Thus, it was found that the solution combustion synthesis, adapted for fine ceramics production, provides controlling morphological and structural parameters of the pre-ceramic powders through Ox/Red ratio of initial reagents and as consequence, allows variable magnetic and dielectric characteristics of the resulting ceramic products. Developed ceramic materials can be promising for use as a basis for modern radio-electronic devices of both civil and military use.