Laboratory Ball Mill Research Articles

Geopolymerisation of Mechanically Activated Lignite and Brown Coal Fly Ash

Geopolymers have been synthesized from mechanically activated lignite and brown coal y ash. Mechanical activation of y ash has been carried out using laboratory ball mill. To determine the structural changes in both, the y ash and the resulted geopolymer, Fourier transform infrared spectroscopy measurements were performed. Isothermal conduction calorimetry method was applied to study the geopolymerisation reactions in mechanically non-activated (raw) and activated y ash samples. The isothermal conduction calorimetry results showed similar peak intensity for mechanically activated (5 30 min) y ash samples. However, the intensity of peak for 120 min milled brown coal y ash was the highest. The compressive strength of the specimen was found to be dependent on the grinding residence time as well as composition/type of y ash.

Dynamic image based shape analysis of hard and lignite coal particles ground by laboratory ball and gyro mills

A new real-time 3D dynamic image analysis system was used to measure the particle shapes of different type of coal samples (lignite and hard coals) ground by different mills (ball and gyro mills). Shape factors such as circularity, ellipse aspect ratio (EAR), bounding rectangle aspect ratio (BRAR) and Feret aspect ratio (FAR) described the results. At least 6400 particles were measured for each mill product indicating the accuracy of the results achieved with 99% statistical significance. Although experiments were performed on different ranked coal samples, there is a clear difference in the particle shapes generated by the grinding methods tested. Results indicated that the ball mill ground particles had the highest aspect ratios (EAR, BRAR, and FAR) with the lowest circularity. However, the gyro mill produced particles with highest circularity along with the lowest aspect ratios. Thus ball milled particles had the highest elongated particles with the lowest rounded particles. On the other hand, gyro mill products included the highest rounded particles and the lowest elongated particles. This relative difference in shape was attributed to the difference in grinding action involved in the ball and gyro mills. Results will find applications in various coal characterization, preparation, and utilization processes.

Effect of Grinding Time of Mill Scale on the Physicochemical Properties of Produced Briquettes and Its Reduction via Hydrogen

This study deals with the grinding of mill scale in a laboratory ball mill for different milling time then briquetted by using 2% molasses as a binder and investigates the effect of grinding of mill scale for different time on the physicochemical properties and the reduction degree of the mill scale briquettes via hydrogen. Diffusion process control equation was applied and the energy of activation was calculated = 28.33 kJ/mole.

The Effect of Ball Media with Different Diameters on Grinding Kinetics of Cassiterite-Polymetallic Sulphides

To investigate the effects of grinding media size on the grinding kinetics of cassiterite-polymetallic sulfide ores, the ball grinding media with diameters of 25mm, 30mm, 35mm and 40mm were studied in a laboratory ball mill. The results showed that the coarse and fine particles obeyed the first-order grinding kinetics laws in the process of grinding and the ball grinding media with 35mm diameter had a significant advantage on grinding up the coarse particles and controlling the generation of fine particles, which could provide theoretical guidance for practical production so that the grinding effects would be improved effectively and the problem of cassiterite over-grinding would also be settled very well.

Efficient Fuel Pretreatment: Simultaneous Torrefaction and Grinding of Biomass

Combining torrefaction and grinding of biomass in one reactor may be an attractive fuel pretreatment process. A combined laboratory torrefaction and ball mill reactor has been constructed for studies of the influence of temperature and residence time on the product yields and particle size reductions of Danish wheat straw, spruce chips, and pine chips. On the basis of initial experiments, which evaluated the influence of reactor mass loading, gas flow, and grinding ball size and material, a standard experimental procedure was developed. The particle size reduction capability of the torrefaction process has been evaluated by the relative change in d50, and this method was compared to the Hardgrove grindability index (HGI), showing reasonably similar results. Significant differences in torrefaction behavior have been observed for straw and spruce chips torrefied at 270–330 °C. Torrefaction of straw for 90 min yielded a higher mass loss (27–60 wt %) and relative size reduction (59–95%) compared with spruce (mass loss of 10–56 wt % and size reduction of 20–60%). The two types of biomass investigated differ with respect to hemicellulose type, lignocellulosic composition, particle morphology, and ash composition, where straw has a higher alkali content. This and other studies indicate that the large difference in the alkali contents of the biomasses is the main cause for the observed difference in torrefaction characteristics. Experiments with separate particle heating and grinding showed a swift grinding of the torrefied biomass. This implies that the rate-limiting step in the laboratory reactor is the heat transfer and not the grinding process. Large pine particles (8–16 mm) showed a slightly higher mass loss than 4–8 and <4 mm particles. This could be the consequence of exothermic reactions in the particle core, which locally increase the temperature and conversion.

Influence of Cow Bone Particle Size Distribution on the Mechanical Properties of Cow Bone-Reinforced Polyester Composites

This work was carried out to investigate the influence of cow bone particle size distribution on the mechanical properties of polyester matrix composites in order to consider the suitability of the materials as biomaterials. Cow bone was procured from an abattoir, washed with water, and sun-dried for 4 weeks after which it was crushed with a sledge hammer and was further pulverized with laboratory ball mill. Sieve size analysis was carried out on the pulverized bone where it was sieved into three different sizes of 75, 106, and 300 μm sieve sizes. Composite materials were developed by casting them into tensile and flexural tests moulds using predetermined proportions of 2, 4, 6, and 8%. The samples after curing were striped from the moulds and were allowed to be further cured at room temperature for 3 weeks before tensile and flexural tests were performed on them. Both tensile and flexural strength were highly enhanced by 8 wt% from 75 μm while toughness was highly enhanced by 6 and 8 wt% from 300 μm. This shows that fine particles lead to improved strength while coarse particles lead to improved toughness. The results show that these materials are structurally compatible and are being developed from animal fibre based particle; it is expected to also aid the compatibility with the surface conditions as biomaterials.

Effect of deep cryogenic treatment on the microstructure and wear performance of Cr–Mn–Cu white cast iron grinding media

The phase transformation and grinding wear behavior of Cr–Mn–Cu white cast irons subjected to destabilization treatment followed by air cooling or deep cryogenic treatment were studied as a part of the development program of substitute alloys for existing costly wear resistant alloys. The microstructural evolution during heat treatment and the consequent improvement in grinding wear performance were evaluated with optical and scanning electron microscopy, X-ray diffraction analysis, bulk hardness, impact toughness and corrosion rate measurements, laboratory ball mill grinding wear test etc. The deep cryogenic treatment has a significant effect in minimizing the retained austenite content and converts it to martensite embedded with fine M7C3 alloy carbides. The cumulative wear losses in cryotreated alloys are lesser than those with conventionally destabilized alloys followed by air cooling both in wet and dry grinding conditions. The cryotreated Cr–Mn–Cu irons exhibit comparable wear performance to high chromium irons.

A comparison of the reactivity of activated and non-activated olivine with CO2

This study compares the reactivity of as-received and mechanically activated olivine (Mg0.93Fe0.07)2SiO4 (collected from Åheim, Norway) with carbon dioxide at ambient temperature (~25°C) and 60bar in the absence of any organic or inorganic additives. Mechanical activation (30min) was performed in a laboratory ball mill. Mineral carbonation (6h) was performed in a high-pressure laboratory reactor. Various instrumental techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal analysis (TA) and scanning electron microscopy (SEM) were used to characterise solid products before and after carbonation as well as before and after filtration. Structural, surface and morphological changes of mechanically activated olivine resulted in an increased reactivity. The presence of amorphous magnesium carbonate in the form of hydromagnesite ((MgCO3)4·Mg(OH)2·4H2O) has been confirmed.

Comparisons of Dry Grinding Kinetics of Lignite, Bituminous Coal, and Petroleum Coke

The objective of this study was to analyze dry grinding kinetics of three different solid fuels in terms of selection and breakage distribution functions values using a batch laboratory ball mill. For this purpose, first, standard Bond grindability tests were made for three different fuel samples. Second, experiments were carried out with eight different mono-sizes between 1.7 and 0.106 mm formed by a √2 sieve series fraction. Then, parameters of Si and B i,j equations were determined from the size distributions at different grinding times. Finally, the kinetic model parameters (Si , aT , α, γ, β, and φ j ) were compared for three different fuel samples, and the relationship between proximate analysis values (ash, moisture, etc.) with the Bond grindability value (Gbg ) and breakage parameters were examined. From the results of the test, the validity of the relationships between Bond grindability and proximate analysis has been not confirmed with good correlation coefficients. The reason for this negative result could be attributed to a difference of the geological origin of solid fuels. However, relationships between breakage parameters of grinding kinetic and proximate analysis values of solid fuel samples were obtained for γ value. Additionally, it was found that the bituminous coal was easier to grind than lignite and petroleum coke, taking into account the quite different values of the model parameters. However, petroleum coke was given finer than other fuel in respect to finer size fraction.

Mechanical activation of chemically activated high phosphorous slag content cement

Abstract Increase of specific surface area by mechanical activation accelerates hydration reactions of cements and results in higher compressive strengths. The compressive strength development of chemically activated high phosphorous slag content cement at different Blaine finenesses has been investigated. Mixes of phosphorous slag (80 wt.%), Portland cement (14 wt.%), and compound chemical activator (6 wt.%) were prepared at different Blaine finenesses using a laboratory ball mill. Compressive strengths of mortar specimens cured in lime-saturated water were measured at different curing times. Results show that increasing fineness to 450 m2/kg, provides the possibility of achieving high 28-day compressive strengths up to almost 93 MPa. Complementary measurements confirmed that increasing fineness results in significant reductions in the amount of water absorption and the total open pore volume of mortar specimens. The simultaneous application of both chemical and mechanical activations, therefore, provides complementary improving effects in the quality of high phosphorous slag content cements.

Application of response surface methodology for modeling of ball mills in copper sulphide ore grinding

Abstract Modeling of some parameters of wet ball milling system of copper sulphide ore was performed in this study. A three level Box–Bhenken design combining a response surface methodology (RSM) with quadratic model was employed for modeling of key operating parameters of ball mills. Grinding experiments were designed and executed by a laboratory ball mill, considering ball size, ball charge and solid content as variables. Grinding tests were performed changing these three variables (ball size, ball charge and solid content) in the range of 20–40 mm, 20–40% and 65–80% respectively. Product 80% passing size (d80) was defined as process response. A quadratic model was developed to demonstrate the effect of each parameter and its interaction with d80 of product. Predicted values of response obtained using model equation were in good agreement with the experimental values (R2 value of 0.994 for d80). Finer d80 was achieved using greater ball charges with smaller ball sizes. More favorable results were also obtained at the center of solid content level. Results suggest that RSM could be efficiently applied for modeling of ball milling system of some copper sulphide ores.

A Study of the Effect of Mineral Particle Shapes on Breakage Rate in Ball Mill Using DEM

In order to investigative the effect of mineral particle shapes to breakage rate of ore, basing on discrete element method, comparative grinding experiments were performed separately in a laboratory ball mill under the same conditions of mass and feed by using regular tetrahedron, parallelepiped and sphere as models of mineral particle. This study shows that ore grain shapes have a great influence on breakage rate due to different impact energies in ball mill.

The effect of processing parameters on energy consumption of ball mill refiner for chocolate

A laboratory ball mill consisting of vertical cylinder, equipped with a rotating shaft with arms, and filled with steel balls as a grinding medium has been used in the experiments. The aim of the study was to examine the effect of agitator shaft speed and amount of grinding media (steel balls) on power requirements and energy consumption of a ball mill. With constant mass of the steel balls (20 kg, 30 kg and 40 kg), the agitator shaft speed was increased from 10% to 100% of the maximum speed which corresponds to a speed of 50 rpm. The power consumption (W) was recorded upon which milling energy consumption (J/kg) has been calculated. The results were statistically analyzed using ANOVA. The increase of the agitator shaft speed, in steps of 10% to the maximum speed of 50 rpm, led to a statistically significant increase in milling energy consumption. At low agitator shaft speed (10%), increase in the mass of the steel balls had no influence on the power requirements. Power requirements for the grinding runs using 30 kg and 40 kg are similar and higher compared to power requirement in trial with 20 kg, as agitator shaft speed increases from 20% to 70%. At high agitator shaft speeds (?80%), increase in steel balls mass led to the significant increase in power requirements of the ball mill.

The Effect of Microwave Treatment on Dry Grinding Kinetics of Iron Ore

The effect of microwave treatment on the grinding kinetics of an iron ore was assessed using mono-sized materials of −2.360 + 2.0 mm, −1.400 + 1.180 mm, −1.0 + 0.850 mm, and −0.355 + 0.300 mm as feed. Microwave-treated samples were kept in a multimode microwave oven with 1100 W input power. The grinding tests were conducted using a laboratory ball mill under identical conditions to allow a comparative analysis of the results. The specific rates of breakage (Si) and cumulative breakage distribution function (Bi,j) values, as grinding breakage parameters, were determined for those size fractions of untreated and microwave-treated feeds. It was determined that breakage of iron ore followed a first-order behavior for fine feed sizes and deviated from first order for coarse feed size. The specific rate of breakage parameters of untreated iron ore was compared with microwave-treated iron ore under the same experimental conditions and it was found that microwave-treated materials break faster than untreated in terms of the Si and A values. Breakage parameters showed that treated materials produce more coarse material than untreated material in terms of the γ value of Bi,j.

Dispersion of crystalline powder materials in gaseous media of different chemical compositions

The process of grinding of rutile and barite crystalline powders in a laboratory ball mill in different types of gaseous media (air, nitrogen, helium) has been investigated. Comparative evaluations of the intensity of the dispersion of these minerals have been performed and the particle sizes of powders obtained in different modes of their dispersion have been measured. A sharp increase in the intensity of this process in the helium medium as compared to the air and nitrogen media has been revealed and ultrafine-grained particles of barite powders have been obtained. The results of the performed investigations have demonstrated that the helium medium can be recommended for producing nanoparticles of powder materials in modern types of ball and bead mills with a drastic decrease in the time and energy consumptions required for their preparation.

Characterization and Use of Egyptian Nubian Sandstone in the Ceramic Tile Industry

Egyptian ball clay quarried in the Aswan area in Upper Egypt contains up to 10% Nubian sandstone. This inclusion causes problems in clay grinding when used in ceramic industries. In the present paper, Nubian sandstone was characterized for mineralogical and chemical compositions using XRD and XRF respectively. Its grinding characteristics were then established using a laboratory ball mill where stone was ground for time periods ranging from 60 to 150 min at speeds ranging from 40 to 90 rpm. The cumulative analysis and specific surface area were determined for all samples. It was found that while an increase in either time or speed favoured higher fineness, the effect of rotating speed was more pronounced than that of grinding time. The findings were then applied to the production of ceramic tiles. It was found that crushed sandstone could be crushed and ground with ball clay without impairing the grinding characteristics of the latter or affecting the composition of the final body.

Impact of Swelling Indices of Sokoto Clays on the Moulding Properties of the Clays in Sand Mixtures

The Impact of Swelling Indices of Sokoto Clays on the Moulding Properties of the Clays in Sand Mixtures was investi- gated. Four clays (labeled A, B, C, D) from different locations in Sokoto state of Nigeria were sampled. The sampling method was that for each deposit five samples were taken at different positions and then mixed together. At the labora- tory they were washed to remove organic matter and then dried at 110°C in the oven. A laboratory ball mill was used to grind the dried clays. Each of the clay was then sampled for the determination of its swelling index. The determination of the moulding properties of the clays then followed. Only green compression strength, dry compression strength and green permeability, moulding properties were determined. The analysis of the result revealed that clay B has the highest green and dry strength values it had the highest green compression strength of 71.7 KN/m2 and the highest dry com- pression strength of 3225.75 KN/m2. Clay B also has the highest swelling index of 60% and very high degree of expan- siveness when compared to the other three clays. Clay B was followed by clay A with swelling index of 25%; the clay has high green and dry compression strength and a moderate degree of expansiveness. The inability of clay D with swelling index of 40% to be the next clay to clay B which has the highest swelling index of 60% among the four clays in terms of good moulding properties is an indication that high swelling index does not always mean good moulding properties in clay binders.

Computer Simulation of Product Size Distribution of a Laboratory Ball Mill

In this study, a computer simulation of a suitable matrix notation of the Broadbent and Callcott grinding model was written. First, a chromite sample was ground in the laboratory type batch ball mill at different grinding times, with different particle size distributions and different capacities. Second, elements of the matrix for computer simulation were found and a “milling matrix” was formed. Third, particle size distributions were predicted by computer simulation for the whole test. Finally, a relationship between the computer simulation predicted by dates and experimental results was established, with a good correlation within the limits of mean error values.

Performance of ground clay brick in ASR-affected concrete: Effects on expansion, mechanical properties and ASR gel chemistry

The effects of ground clay brick (GCB) on alkali-silica reaction (ASR) expansion as well as on mechanical properties of ASR-affected concrete are investigated. Crushed red clay brick originated from demolished masonry was ground in a laboratory ball mill and replaced for portland cement at levels of 15% and 25% by weight in concrete mixes produced with alkali reactive sand. ASR expansion, compressive strength , flexural strength , and modulus of elasticity of the concrete mixes were evaluated. Effect of GCB on ASR gel chemistry was also studied on Pyrex glass-paste specimens using SEM/EDS (scanning electron microscope equipped with energy dispersive X-ray spectroscopy). The results indicate that GCB effectively reduces ASR expansion in concrete: associated cracking and loss on mechanical properties are also significantly reduced. SEM study suggests that GCB alters alkali silica gel chemistry thus resulting in a less expansive product.

Investigation of breakage behavior of different mineralogical and morphological characteristic pumices

Theobjectiveofthisstudyistoanalyzedrygrind- ing behavior of four different pumices in terms of Bond grindabilityvalue,selectionandbreakageparametersvalues. Forthispurpose,firstly,Bondgrindabilitytestweremadefor four pumices. Then, eight different mono-size fractions for each of pumices were carried out between 1.7 and 0.106mm formed by a √ 2 sieve series, and ground batch wise in a laboratory ball mill for determination of breakage parame- ters. Finally, Si and Bi, j equations were determined from the size distributions at different grinding times, and the model parameters (Si , aT ,α , γ , βand φ j) were compared for four different pumice samples.