Simulation of wet ball milling of iron ore at Carajas, Brazil (original) (raw)
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Mining, Metallurgy & Exploration, 2020
Iron ores obtained from different sources differ in their chemical and physical properties. These variations make the process of grinding a difficult task. The work carried out in this context focuses on three different samples of iron ore, viz., high silica high alumina, low silica high alumina, and low silica low alumina. The grinding process for all the three iron ores is carried out individually in Bond's ball mill and the total retention time taken by each iron ore sample is calculated. The present investigation focuses on utilizing the calculated retention time of the iron ore as a standard grinding reference time to the laboratory ball mill for optimizing the grinding time of each ore. The desired P 80 (150 μm) with an acceptable range of hematite liberation (> 75%) was obtained in the laboratory ball mill after reducing 6 min from the total retention time taken in the Bond ball mill.
THE EFFECTS OF PROCESS VARIABLES ON THE GRINDING OF IRON ORE
Grinding is the highest energy consumer in all the unit processes of mineral beneficiation. The performance of grinding mills depends on many operating factors among which are the time of grinding, mill speed, grinding media–to-ore ratio, and filling ratio. These factors affect the fraction of energy from the total energy drawn by the mill system utilized in material size reduction. These variables were investigated in regard to the Itakpe iron ore. A representative sample of 10.5kg of the iron ore was collected and milled, taking appropriate quantities to study the process variables; the effect of grinding time, fraction of mill critical speed, media-to-ore ratio and mill filling. The results of the analyses clearly shows that using a sieve of +180µm and its bottom -180µm, the best time for grinding 0.5kg of Itakpe iron ore with 3kg of grinding media and a mill speed of 92 rpm is 8 minutes, yielding 17.10% fines and 82.90% coarse., 0.8 mill critical speed measured 15.20% fines and 84.80% coarse. Grinding media-to-ore ratio of 3:0.5kg gave 21.00% fines, 79.00% coarse and mill filling is 3kg:1kg of media and iron ore liberating 15.00% fines and 85.00% coarse. KEYWORDS: Critical speed, Communition, Mill Filling, Grinding Media, Mill Speed, Beneficiation.
Study of the effect of the mineral feed size distribution on a ball mill using mathematical modeling
Iranian Journal of Chemistry & Chemical Engineering-international English Edition, 2020
In this paper, the effect of the feed size distribution was studied for a ball mill. Copper ore of 0.5% was tested using batch-grinding tests. Samples were carried out using three reconstructed feed size distributions in an experimental ball mill. The size distribution was reconstructed using the double Weibull formula, and modeled using the selection and breakage functions. Copper ore samples were grinding up to 15 min. A monosize (-19+12.5), coarse (-19+6.3 mm), medium (-4.75+0.6 mm), and fine (+0.425-0.038 mm) particle size distributions were tested. The 0.32 m diameter test mill was run at 38% volume loading and at Nc (critical speed) of 68% (50.85 rpm). Breakage rate parameters were calculated and simulated for each size distribution in an industrial mill. The results show that the change in the feed size distribution has an impact on the grinding kinetics. The curves show that the mono size fraction has the highest specific rate of breakage. It is also important to note that, ...
Investigation on Iron Ore Grinding based on Particle Size Distribution and Liberation
Transactions of the Indian Institute of Metals, 2020
In the iron and steel industry, the production of narrow particle size distribution (PSD) for pellet feed making with acceptable liberation of valuables from the iron ore is very difficult. This study has been carried out to achieve desired pellet feed with narrow PSD and maximum liberation of hematite from the iron ore. The iron ores have been collected from three different sources (mines in Karnataka state) and milled. The iron ores and the blend feed samples were analyzed in the Optical Microscope (OM) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) to understand the PSD and percentage of hematite liberation. The new approach is adapted to identify the retention time (RT) of the iron ore in the mill, and the total RT taken for the blend sample in the Bond's ball mill is considered as the reference grinding time for milling in the Laboratory Ball Mill (LBM). The desired narrow PSD (-150/? 10 lm) with acceptable hematite liberation is achieved at an optimal grinding time of 7 min in the LBM.
Investigating grinding mechanisms and scaling criteria in a ball mill by dimensional analysis
Advanced Powder Technology
A dimensional analysis of the ball mill process is carried out through the Buckingham-Pi method. The dimensionless quantities identified are discussed and used in order to suggest scaling criteria for ball mills. The flowability and the particle size distribution of an alumina powder ground in laboratory ball mills of various dimensions are compared in order to discuss the influence and the relevance of each dimensionless numbers. Some geometrical, kinetics and dynamic similitudes are highlighted both theoretically and experimentally. In particular, the conservation of the Froude number and the fragmentation number lead to relevant scaling criteria for mills of 1, 2 and 7 L inner volumes. The importance of the ratio between the pebble size and the vessel diameter is also discussed. Finally, the preponderance of the fragmentation number over the number of revolutions of the vessel is interpreted in terms of particle fragmentation mechanisms.
Study of Iron Ore Mixtures Behavior in the Grinding Pelletizing Process
Mineral Processing and Extractive Metallurgy Review, 2016
The main unit operations of pelletizing process are grinding, filtering, pressing, pelletizing, and firing. Grinding, the first operation in the process, is a crucial step for the subsequent operations. Three iron ore mixtures with different grindability index (low, medium, and high) were used in order to verify the influence in the operational parameters such as production rate, discharge density, and pump pressure. Through Design of Experiments (DOE), nine experiments over each iron ore mixture were done, varying the minimum and maximum grinding operational parameters. Independent variables (responses) were the specific surface area or Blaine index (BI) and the particle size (PS), which were measured by the automatic PS analyzer system (PSI). The main objectives of this study are to know the behavior of iron ore mixtures with different grindability indexes in the industrial plant and develop a regression model that can be used for real-time measurement of PS and BI for different grindability indexes in the industrial operations. The results showed satisfactory correlations between the factors and responses.
A Review of the Grinding Media in Ball Mills for Mineral Processing
Minerals
The ball mill is a rotating cylindrical vessel with grinding media inside, which is responsible for breaking the ore particles. Grinding media play an important role in the comminution of mineral ores in these mills. This work reviews the application of balls in mineral processing as a function of the materials used to manufacture them and the mass loss, as influenced by three basic wear mechanisms: impact, abrasion, and corrosion. The effect of grinding media geometries and density on the mill performance was also reviewed to determine what the research has recommended as the most suitable grinding media for different grinding applications. Although considerable work has been carried out in that area, the influence of grinding media shape on the liberation of minerals, as well as the effect of various mill conditions on the performance of mixed grinding media shapes, are still poorly understood. Thus, the review opens up opportunities for further research to improve the grinding pr...
Modelling fine grinding in a fluidized bed opposed jet mill: Part I: Batch grinding kinetics
1999
A methodology for characterising grinding kinetics is developed based on a new criterion, 'the residual fraction' to represent the performance of a grinding process. This is applied to pseudo-batch grinding of hydrargillite in a fluidised bed opposed jet mill Alpine 100 AFG. It appears to give an adequate representation and a simple mathematical expression for the change in particle size distribution with time. Approximate values of breakage and selection matrices are then calculated on the basis of previous studies, showing that the breakage function is not normalisable over the whole range of particle size. These results are used to propose a fragmentation mechanism for hydrargillite which includes cleavage of the larger particles and destructive breakage of the fine particles.
Exploring ball size distribution in coal grinding mills
Tube mills use steel balls as grinding media. Due to wear in the abrasive environment it is necessary to charge new balls periodically to maintain a steady balanced ball charge in the mill. The amount and ball size distribution in this charge, as well as the frequency with which new balls are added to the mill, have significant effects on the mill capacity and the milling efficiency. Small balls are effective in grinding fine particles in the load, whereas large balls are required to deal with large particles of coal or stone contaminant. The steady state ball size distribution in the mill depends on the top-up policy. The effect of the ball size distribution on the milling rate of coal has been measured as a function of ball size distribution. The change in ball size distribution as affected by wear and ball top-up policy has been modelled. From this a best ball top-up policy can be recommended that will ensure a close approximation to the desired steady-state ball size distribution that gives the required PF size distribution for the selected mill demand.
Variables affecting the fine grinding of minerals using stirred mills
Minerals Engineering, 2003
Base metal resources are becoming more fine-grained and refractory and minerals separation processes require these ores to be milled to increasingly finer sizes. To cope with very fine grinding to below a P 80 of approximately 15 lm stirred milling technology has been adopted from other industries. Neither this technology, nor the basic concepts of fine grinding, are well understood by the minerals processing industry. Laboratory studies were therefore carried out in order to investigate fine milling using different types of stirred mills. The variables analysed were stirrer speed, grinding media type and size, slurry solids content as well as the feed and product size. The results of the testwork have shown that all of these variables affect the grinding efficiency. The ratio of media size to material size was found to be of particular significance. The results were also analysed using the stress intensity approach and the optimum stress intensity ranges for the most efficient grinding were determined. Application of the results for process optimisation in the industrial size units is also discussed in this paper.