Effect Of Milling Speed Research Articles

Size reduction performance evaluation of HPGR/ball mill and HPGR/stirred mill for PGE bearing chromite ore

In the present study, size reduction experiments were performed on High-Pressure Grinding Rolls (HPGR), ball mill and stirred mill of PGE bearing chromite ore. The performance of HPGR was evaluated in two stages of size reduction to reduce energy consumption. In the first stage of HPGR, the effect of operating variables such as the gap between the rolls, roll speed, and specific pressing force on product size (P80) and energy consumption (ECS) was investigated. The process to get the smallest product size was optimized within the experimental range of investigation. The crushed product of HPGR was subjected to grinding in the second stage in a ball mill and stirred mill. The effect of mill speed, grinding time, and ball size on the performance of the ball mill was investigated and the product was further investigated in the second stage. A comparative analysis of the ball mill and stirred mill performance and energy consumption at different grinding time intervals was also performed. It was found that the ball mill consumed 54.67 kWh/t energy to reduce the F80 feed size of 722.2 µm to P80 product size of 275.4 µm while stirred mill consumed 32.45 kWh/t of energy to produce the product size of 235.6 µm. It also showed that stirred mill produced finer product than the ball mill at around 40% lesser consumption of energy. It can be concluded that the HPGR-Stirred mill combination was a more energy-efficient grinding circuit than the HPGR-Ball mill combination for PGE bearing chromite ore.

Effects of Mill Speed and Air Classifier Speed on Performance of an Industrial Ball Mill

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.

Advanced comminution modelling: Part 2 - Mills

This second part paper explores rock breakage mechanisms, the life cycle of rocks in mills and the strong influence of end walls on charge motion within mills. We present recent advances in particle-based modelling of mills for comminution focused around wear and the effect of slurry and slurry phase grinding. Three mill scenarios are considered:1.Media flow and the resulting wear evolution of the belly and end wall liners and the resulting change in mill performance for a full industrial scale dry ball mill (modelled using DEM)2.Axial slurry transport and mixing in a wet overflow industrial scale ball mill (modelled using fully coupled DEM and SPH)3.Effect of mill speed on slurry and solid charge motion and the resulting grinding of fine particles in a 1.8 m diameter wet Hardinge pilot mill (modelled using fully coupled DEM and SPH with advection-diffusion-population balance equations solved for the slurry size distribution for each SPH particle)These demonstrate the nature and level of fidelity that is now possible to include in particle-scale comminution models. They provide insights into the critical importance of curtain flows generated by the end walls of tumbling mills, on wear behaviour on liners, on the structure of slurry pools and mill discharge and on the adverse effect on grinding of increasing mill speed.

Effect of mill speed and slurry filling on the charge dynamics by an instrumented ball

In the ball mill, the motion of charge is a complex system, especially under wet grinding. It is difficult to measure the charge physical quantities and hard to validate the correctness of charge motion simulation. To this end, an instrumented ball which is capable of measuring the charge physical quantities was designed. The laboratory ball mill was lined with 12 pieces of trapezium lifters and filled with Jb = 25% grinding balls. An iron ore was used to prepare the slurry at 50% solid concentration by mass. A series of tests were carried out to investigate the charge dynamics at different mill speeds and slurry filling. The average rotational kinetic energy, average applied force and mill power were measured and analyzed. The results showed that the average rotational kinetic energy increases with mill speed, whereas the average applied force first increases and then decreases. The average rotational kinetic energy and applied force first increases and then decreases by the increase in slurry filling. Furthermore, there exists a slurry filling U = U* that the mill power has a maximum value.

Effects of Mill Speed on Kinetic Breakage Parameters of Four Different Particulate Pumices

In this study, the effect of mill speed was investigated on different particulate pumice samples at batch grinding conditions based on a kinetic model. For this purpose, S i and B i,j equations were determined from the size distributions at different grinding times, and the model parameters (S i , a T , α, γ, and φ j ) were compared for three different mill speed (fraction of mill critical speed; 65%, 75%, and 85%). The effect of fraction of mill critical speed (φc) on the grinding for model parameter a T found to be different for four different pumices. Additionally, in this study it was found that optimum grinding occurs at φc = 85% for all pumice samples, in contrast to the 75% of critical speed of the ball mill.

The effect of milling speed on the structural properties of mechanically alloyed Fe–45%Ni powders

FeNi-based alloy powders are interesting in their applications as soft magnetic materials with low coercivity and high permeability. Their magnetic properties are closely related to their microstructure and particle size. In this study, nanocrystalline Fe–45%Ni alloy powders were prepared using a planetary ball mill. The effects of ball milling speed (the vial rotation speed ( ω) and the disc rotation speed ( Ω)) on the microstructure and particle size of Fe–45%Ni alloy powders have been studied. The face-centered-cubic (FCC) γ-(Fe, Ni) solid solution phase was identified by X-ray diffraction (XRD). The lattice parameter, lattice strain, grain size and quantitative amount of γ-(Fe, Ni) phase have been estimated from Rietveld's powder structure refinement analysis of XRD data. The powder morphology and particle size were examined using scanning electron microscopy (SEM). The results showed that the FCC γ-(Fe, Ni) phase could be observed completely at the vial rotation speed of 350 rpm and the milling time of 24 h. We also found that the higher milling speed leads to higher milling energy, larger lattice parameter, larger particle size and lower grain size of the investigated system.

English

Ammonium perchlorate has been pulverised by an impact mill (air classifier mill) to study the influence of different operating parameters, viz., effect of mill speed, classifier speed, feed rate, and damper opening (suction rate) on the particle size. Further based on the different grinding parameters, an empirical equation has been developed and used for the prediction of particle size. The experimental results indicate that the values are very close to the predicted ones. In addition, particle size distribution has also been studied by applying different model equations and it has been found that Rosin-Rammler model is the most suitable model for this operation.

The effect of mill speed on kinetic breakage parameters of clinker and limestone

In this study, the effect of mill speed was investigated on the limestone and the clinker samples of Göltaş Cement Factory (Isparta, Turkey) at batch grinding conditions based on a kinetic model. For this purpose, first, six different monosize fractions were carried out between 0.850 and 0.106 mm formed by a two-sieve series. Then, S i and B i,j equations were determined from the size distributions at different grinding times, and the model parameters ( S i, a T, α, γ, and φ j) were compared for five different mill speed (fractional of mill critical speed; 55%, 65%, 75%, 85%, and 95%). The effect of the fraction of mill critical speed ( φ c) on the grinding for model parameter a T was found to be different for two different samples: a T=0.0344 exp(0.00301 φ c) for clinker and a T=0.0225 exp(0.06183 φ c) for limestone. Additionally, it was found in this study that optimum grinding occurs at φ c=85%, in contrast to the 70% of critical speed of the ball mill in the cement factory.

Effects of mill speed and filling on the behaviour of the load in a rotary grinding mill: Liddell, K S; Moys, M H J S Afr Inst Min MetallV88, N2, Feb 1988, P49–57

The dynamics of the ball load within a wet-grinding mill are examined, using measurements of torque and load position, The test equipment provided an accurate torque measurement, and the toe and shoulder positions of the load were measured by the use of a conductivity probe mounted in the mill shell. Both the variables tested-mill filling and rotational speed-influence the position of the load, and hence the torque, and have interactive effects on both the torque and the load position, An increase in mill speed and filling causes the torque to increase to a maximum value, after which further increases in speed or filling cause the torque to decrease. The position of the load toe is influenced only by the filling up to speeds of approximately 80 per cent of critical, whereas the speed and filling both cause the load shoulder to rise as their magnitudes are increased, The power drawn by the mill is predicted by the use of published equations, and these values are compared with the measured power draw.