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.

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.

Study on heat transfer behavior and thermal breakage characteristic of the charge in ball mills

Ball mill is the widely used comminution device for the size reduction of iron ore particles, yet the underlying mechanisms of heat transfer and thermal breakage inside the mills heretofore are not deeply understood. Therefore, the Discrete element method was carried out to study the effect of operating parameters on charge temperature, and the batch grinding experiments of iron ores were conducted to verify the heating temperatures using a laboratory ball mill. Results show that increasing mill speed will result in the charge temperature increasing initially and then decreasing. The temperature fields of the charge and load behavior remain approximately the same for the different ball filling. The main findings of this study are that the heating temperature can contribute to enhancing the breakage behavior of iron ore particles, and correspondingly the optimal feed sizes for different heating temperatures are determined to be 2.48 mm, 2.63 mm, 2.78 mm, and 3.59 mm, respectively.

Grinding Kinetics Study of Tungsten Ore

The European Commission (EC) maintains the consideration of tungsten as a critical raw material for the European industry, being the comminution stage of tungsten-bearing minerals an essential step in the tungsten concentration process. Comminution operations involve approximately 3–4% of worldwide energy consumption; therefore, grinding optimization should be a priority. In this study, the grinding behavior of tungsten ore from Barruecopardo Mine (Salamanca, Spain) is analyzed. A protocol based on Austin’s methodology and PBM is developed in order to study the influence of operational and geometallurgical variables on grinding kinetics. In addition to the kinetic parameters, the breakage probability (Si) and breakage function (Bij) is determined. The selection function was formulated for the Barruecopardo Mine with respect to the mill speed.

Kinetics of Dry-Batch Grinding in a Laboratory-Scale Ball Mill of Sn–Ta–Nb Minerals from the Penouta Mine (Spain)

The optimization of processing plants is one of the main concerns in the mining industry, since the comminution stage, a fundamental operation, accounts for up to 70% of total energy consumption. The aim of this study was to determine the effects that ball size and mill speed exert on the milling kinetics over a wide range of particle sizes. This was done through dry milling and batch grinding tests performed on two samples from the Penouta Sn–Ta–Nb mine (Galicia, Spain), and following Austin methodology. In addition, the relationships amongst Sn, Ta and Nb content, as metals of interest, the specific rate of breakage Si, the kinetic parameters, and the operational conditions were studied through X-Ray fluorescence (XRF) techniques. The results show that, overall, the specific rate of breakage Si decreases with decreasing feed particle size and increasing ball size for most of the tested conditions. A selection function, αT, was formulated on the basis of the ball size for both Penouta mine samples. Finally, it was found that there does exist a direct relationship amongst Sn, Ta and Nb content, as metals of interest, in the milling product, the specific rate of breakage Si and the operational–mineralogical variables of ball size, mill speed and feed particle size.

Operation Analysis of a SAG Mill under Different Conditions Based on DEM and Breakage Energy Method

As one of the machines widely used in mining, a semi-autogenous grinding (SAG) mill can significantly improve the roughing efficiency of rock. But the SAG mill still faces the obstacles of significant energy consumption and empirical operation parameters. In order to obtain the optimal operation parameters of a SAG mill, in this paper, the discrete element method (DEM) is used to simulate the breakage process of the particles by controlling three parameters, i.e., the mill speed ratio, the mill fill level ratio, and the steel ball ratio. This method simulates the particles size, mill power, and qualified particles quality of crushed particle, which reveal the grinding strength and energy consumption of the SAG mill. In this paper, the grinding changes of a SAG mill under different parameter conditions are explored. Firstly, an experiment on the influence of a single parameter change on the mill’s operation is set up, and then the influence of three parameter changes on the mill’s operation is analyzed. These changes are characterized by particle size and mill power. Simulation results under the ∅5250 × 500 mm mill model show that the mill operates with the optimal effect when the mill is under the condition of 80% critical speed and 15% fill level; the power of the mill does not increase linearly with an increase in the mill speed ratio, but will decrease after 85% of the critical speed, and finally increase again; the optimal steel ball ratio in the SAG mill depends on the simulation time (mill actual working time) and the limitation of the rated power. The mill speed, fill level ratio, and steel ball ratio can significantly affect mill operation, and our conclusions can provide a reference for an actual situation.

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 1m × 0.5m was implemented. There are 15 lifters with 50mm height and face angle of 30˚. In the present work, the combination of the balls (40% of the balls with 60mm diameter, 40% of the balls with 40mm diameter and 20% of the balls with 25mm 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.

Understanding milling tandem control

Considerable work has been done over the years to automatically control the operation of the milling tandem. Control can be achieved by utilising relatively simple algorithms. Chute-level control, added-water rate control and speed and torque control of each mill drive are the main elements of the control system. Factory rate control can be achieved by controlling the prepared cane level in the chute of the first mill and controlling the first-mill speed to a set point that may vary depending on factory capacity constraints. Added water rate should vary with the objective of maintaining a relatively constant ratio to the cane-fibre rate, with a potential advantage to extraction by increasing further when pol in cane is high. For rate, performance and protection, the speed of and torque on each milling unit drive should be controlled.

Effect of the operating parameter and grinding media on the wear properties of lifter in ball mills

The wear of lifter in ball mill directly affects the grinding efficiency and economic cost. However, how to evaluate the variation of wear process and predict the wear distribution of lifter is poorly developed. To this end, a laboratory-scale ball mill was used to evaluate the variation of wear process of the lifter in different milling conditions of mill speed, ball filling, grinding media size and shape. Besides, a wear prediction method was used to compare and validate the experimental results. The experimental results showed that the Abbott-Firestone curve can evaluate the lifter surface topography. The wear rate of the lifter specimen is increased first and then decreased with mill speed and grinding media size. Increasing ball filling will increase the wear rate, and the grinding media shape of ball has a maximum wear rate. The wear characteristics of the lifter specimen are consisting of impact pit, indentation, plastic deformation and scratch. Furthermore, the discrete element method (DEM) simulation showed that the wear behavior on the upper surface is higher than that on the side surface of the lifter. The DEM simulation with Archard wear model is an effective tool to investigate the wear distribution on the lifter, which is in good consistent with the wear behavior measured by the experiment.