Mineral Processing
Sajad Kolahi; Mohammad Jahani Chegeni; Asghar Azizi
Abstract
In Part 2 of this research work, five types of liners, i.e. wave, step, step@, ship-lap, and ship-lap@, are examined. These liners all have similar connected lifters with different volumes. Their difference is in the width, height, and type of the lifter profile. All the five liner types, from 8 to 64 ...
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In Part 2 of this research work, five types of liners, i.e. wave, step, step@, ship-lap, and ship-lap@, are examined. These liners all have similar connected lifters with different volumes. Their difference is in the width, height, and type of the lifter profile. All the five liner types, from 8 to 64 lifters, are simulated using the Discrete Element Method (DEM). In this research work, for the first time, data from the sum of the kinetic and potential energies of individual balls (79,553 particles) are used to find the appropriate range for the number of lifters. In other words, the kinetic and potential energies of all particles within the system (inside the ball mill) are the basis for determining the appropriate number of lifters. The results suggest that for the wave liner, the appropriate range of the number of lifters is between 8 and 16, for the step, step@, and ship-lap liners; it is between 12 and 20, and for the ship-lap@ liner, it is between 8 and 20. In fact, using the data on the kinetic and potential energies of the balls inside the mill, it is possible to determine the appropriate range of the number of lifters, which is done for the first time in this study. In general, it is suggested that the data on the kinetic and potential energies of the balls can be used to determine the number of mill lifters, and unlike what has been done. So far, by other researchers, the number of mill lifters should not be determined solely by using its diameter or the dimensions of the lifters. Also the effect of mill-rotation direction on the values of kinetic and potential energies in step and ship-lap liners is investigated. It is shown that the step@ and ship-lap@ liners transfer more energy to the balls than the step and ship-lap liners, and have a suitable direction of rotation.
Mineral Processing
Mohammad Jahani Chegeni; Sajad Kolahi; Asghar Azizi
Abstract
Consumed energy is the most important issue and concern in industrial ball mills, and includes a major part of the costs of mineral processing plants. By using suitable liners and the optimal lifter count, the energy of the mill is properly transferred to the balls. In Part 1 of this research work, five ...
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Consumed energy is the most important issue and concern in industrial ball mills, and includes a major part of the costs of mineral processing plants. By using suitable liners and the optimal lifter count, the energy of the mill is properly transferred to the balls. In Part 1 of this research work, five types of liners, i.e. Lorain, Osborn, Rib, cuboid, and Hi-lo, are examined. These liners all have separate lifters with the same volume. Their difference is in the width, height, and type of lifter profile. First, all types of liners are simulated with four lifters using the Discrete Element Method (DEM). Then the lifter count is increased four by four to fill the entire wall of the mill with lifters. Based on this, Lorain liner from 4 to 24 lifters, Osborn liner from 4 to 120 lifters, Rib liner from 4 to 40 lifters, and cuboid and Hi-lo liners from 4 to 64 lifters are simulated. For the first time, the kinetic (KE) and potential (PE) energies as well as the sum of these two energies (TE) of all the balls are calculated, and compared in the entire duration of the simulation from 0–13s for all the liner types and lifter counts mentioned above. Finally, by using data related to KE, PE, and TE for each type of liner, the optimal lifter count is obtained. Accordingly, 16 to 20 lifters are recommended for the Lorain liner, 64 to 76 lifters for the Osborn liner, 24 to 32 lifters for the Rib liner, 44 lifters for the cuboid liner, and 36 to 44 lifters for the Hi-lo liner.
Mineral Processing
Ali Nikouei Mahani; Mohammad Karamoozian; Mohammad Jahani Chegeni; Mohammad Mahmoodi Meymand
Abstract
Generally, mineral processing plants generate a large quantity of waste in the form of fine particles. The flotation speed of mineral microbubbles by coarse bubbles is dramatically higher than that of individual particles. The advantage of microbubbles is due to the increase of binding efficiency of ...
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Generally, mineral processing plants generate a large quantity of waste in the form of fine particles. The flotation speed of mineral microbubbles by coarse bubbles is dramatically higher than that of individual particles. The advantage of microbubbles is due to the increase of binding efficiency of conventional bubbles with fine particles coated with microbubbles. Here, the focus is on reducing chemicals consumption and improving recovery. After preparing a representative sample, XRF, XRD, and mineralogical analyses were performed. Then 50 experiments were selected by experimental design using the response surface method (RSM), and in the form of central Composite design (CCD) by (design expert) DX 13 software. The interactions of collector consumption, frother agent, pH, particle size, and solid percentage were investigated, and 25 experiments using typical flotation and without nano-microbubbles and others with nano-microbubbles were conducted. The laboratory standard limit of the collector used in the pilot plant of the Sarcheshmeh Copper copper complex is 40 g/t (25 g/t of C7240 plus 15 g/t of Z11). Here, by consuming 20 g/t of collector in the absence of nanomicrobubbles, a recovery of 79.96% and in the presence of nanomicrobubbles, a recovery of 80.07% was obtained, that is a 50% reduction in collector consumption and a 0.11% increase in recovery was observed. Also the laboratory standard limit of frother used in the pilot plant of Sarcheshemeh Copper Complex is 30 g/t (15 g/t of MIBC plus 15 g/t of A65). Here, by using 10 g/t of frother in the absence of nanomicrobubbles, a recovery of 78.12%, and in the presence of nanomicrobubbles, a recovery of 82.05% was obtained. In other words, a decrease of 66.6% in the consumption of frother and an increase of 1.93% in recovery was observed.
Amir Mohammad Nasrollahzadeh Bafti; Mohammad Jahani Chegeni; Ahmad Moghooeinejad; Zahra Manafi
Abstract
Flotation is the most important method for processing sulfide copper ores. Due to the high cost and environmental hazards caused by the chemical reagents used in this process (collectors, frothers, pH regulators, depressants, etc.), the possibility of replacing all these reagents or at least some of ...
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Flotation is the most important method for processing sulfide copper ores. Due to the high cost and environmental hazards caused by the chemical reagents used in this process (collectors, frothers, pH regulators, depressants, etc.), the possibility of replacing all these reagents or at least some of them are of special importance through environmentally friendly methods such as bio-flotation using halophilic bacteria. These bacteria have the ability of growth and proliferation in salty media and relatively neutral pHs such as sea salty water. In this research work, the four types of halophilic bacteria Halobacillus sp., Alkalibacillus almallahensis, Marinobacter sp., and Alkalibacillus sp. are studied to replace frothers (MIBC and F7240), depressant (sodium metabisulfite), and pH regulator (lime) in sulfide copper flotation using a Denver laboratory flotation cell. The results obtained indicate that each of the four types of bacteria mentioned above along with collectors (gasoil, Z11, and C7240) as the only chemical reagents (bio-flotation + collector) can depress pyrite better than the bacteria-free mode (flotation + all chemical reagents). Iron recovery in tailings in the standard flotation test is 46.8%, which is, respectively, increased to 91.9%, 74.5%, 70.3%, and 76.9% using the halophilic bacteria of Halobacillus sp., Alkalibacillus almallahensis, Marinobacter sp., and Alkalibacillus sp. On the other hand, the recovery of chalcopyrite using the bio-flotation method is lower than its recovery using the flotation method. Copper recovery in the concentrate in the standard flotation test is 89.1%, which is reached to 58.8%, 71.4%, 62.5%, and 69.4%, respectively, using the above bacteria in the bio-flotation method.
Amirmohammad Nasrollahzadeh; Mohammad Jahani Chegeni; Ahmad Moghooeinejad; Zahra Manafi
Abstract
Due to the increasing consumption of lime in the flotation process to increase the pH of the system and create an alkaline environment, as well as its gradual increase in cost, the attention of researchers has been drawn to perform flotation operations in a neutral environment. Halophilic bacteria have ...
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Due to the increasing consumption of lime in the flotation process to increase the pH of the system and create an alkaline environment, as well as its gradual increase in cost, the attention of researchers has been drawn to perform flotation operations in a neutral environment. Halophilic bacteria have the potential to replace flotation reducers such as lime because flotation can be done with their help at neutral pH as well. Also, due to the buffer effect of sea water, which is the chosen medium for bio-flotation, the use of bio-flotation method reduces the use of drinking water, and also reduces the consumption of chemicals. In this research work, five types of halophilic bacteria are studied for pyrite bio-depression and chalcopyrite flotation. Bio-flotation experiments are conducted using Hallimond tubes, and the bacteria Halobacillus sp., Alkalibacillus almallahensis, and Alkalibacillus sp. had better performance in pyrite depression and chalcopyrite flotation than other bacteria. The recovery of pyrite depression when using them was 30.9, 30.3, and 34.0 %, respectively, and the recovery of chalcopyrite flotation by them was equal to 52.9, 68.6, and 55.7, respectively, which indicates the high selectivity of these bacteria in flotation. In addition to the above tests, the effect of the combination of these three types of bacteria on pyrite depression and chalcopyrite flotation was also studied. The results obtained indicate that in the combination (mix) test of all three types of bacteria (33.3% of each type), pyrite was depressed better than other tests, and its recovery was 27.5%, which was lower than the single bacteria tests. Also, the effect of the combination of these three types of bacteria on the flotation of chalcopyrite is investigated, and its recovery was 72.6%, which was higher than the single bacteria tests. On the other hand, considering that the recovery of chalcopyrite in the three-bacteria combination tests was is higher than the single-bacteria and two-bacteria tests, it can be concluded that the combination of all three bacteria can cause a better synergism and improve their performance in micro-flotation tests.
M. Jahani Chegeni; S. Kolahi
Abstract
The number of lifters in the liner of ball mills and the mill rotation speed are among the most significant factors affecting the behavior of grinding charge (balls) and their motion trajectory, and consequently, the comminution mechanism in these mills. In this research, in order to find a suitable ...
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The number of lifters in the liner of ball mills and the mill rotation speed are among the most significant factors affecting the behavior of grinding charge (balls) and their motion trajectory, and consequently, the comminution mechanism in these mills. In this research, in order to find a suitable range for the number of lifters in the liner of ball mills, the DEM method is utilized. Initially, a pilot-scale ball mill with dimensions of 2.0 m × 1.11 m without any lifter is simulated. Afterwards, by adding, respectively, 1, 2, 4, 8, 16, 20, 26, 30, and 32 cuboid lifter(s) with dimensions of 2 m × 5 cm × 5 cm, nine other separate simulations are performed. The influences of the number of cuboid lifters on the two new factors introduced here, namely ‘head height’ (HH) and ‘impact zone length’ (IZL) at various mill speeds, that is, 70% and 80% of its critical speed (CS) are investigated. The results indicate that in order to find a suitable range for the number of lifters in the liner of ball mills, it is necessary to consider these two parameters simultaneously as the criteria for selecting the appropriate range, That is, liners that simultaneously produce both a higher HH and a greater IZL are more suitable for use in the industry. The results also demonstrate that the suitable range for the number of cuboid lifters in the liner of ball mills is between 16 and 32, which field research on the ball mills of three different plants in the industry confirms the accuracy of the results obtained in this research. Unlike the previous research works, it has now been shown that the number of ball mill lifters does not only depend on the diameter of the mill but also depends on the width, height, angle of the lifter, and generally on the type of lifter.
Mineral Processing
S. Kolahi; M. Jahani Chegeni
Abstract
The number of lifters of mill shell liners, mill rotation speed, and filling percentage of grinding media are three of the most important parameters influencing the charge behavior and the trajectory of ball motion inside the SAG mills, and consequently, their performance. In this paper, the milling ...
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The number of lifters of mill shell liners, mill rotation speed, and filling percentage of grinding media are three of the most important parameters influencing the charge behavior and the trajectory of ball motion inside the SAG mills, and consequently, their performance. In this paper, the milling operation of pilot-scale SAG mills using the discrete element method (DEM) is investigated. First, a pilot-scale SAG mill with dimensions of 3.0 m × 1.5 m with no lifter is simulated. Then by adding, respectively, one, two, four, eight, sixteen, and thirty-two rectangle lifter(s), six other independent simulations are performed. The effects of the number of lifters on the two new parameters introduced by the authors, i.e. ‘head height’ and ‘impact zone length’ as well as on creation of cascading, cataracting, and centrifuging motions for balls at two different mill speeds, i.e. 70% and 80% of its critical speed (NC), are evaluated. Also in order to validate the simulation results, a laboratory-scale SAG mill is simulated. The results obtained indicate that the optimum number of lifters for pilot-scale SAG mills is between 16 and 32 lifters with medium thickness. Liners with the number of lifters in this range require less mill speed to create cataract motions. However, liners with the number of lifters less than this range require a higher mill speed. Also liners with the number of lifters beyond this range require less mill speed, and can cause centrifugal motions in the balls. Comparison of the simulations related to the laboratory-scale SAG mill with experimental results demonstrates a good agreement, which validates the DEM simulations and the software used.
Mineral Processing
M. Jahani Chegeni; S. Kolahi
Abstract
The shell liner type, rotation speed, and ball filling percent are the key factors influencing the charge behavior inside the SAG mills, and consequently, their performance. In this work, the milling operation of industrial SAG mills is investigated using the Discrete Element Method (DEM). First, an ...
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The shell liner type, rotation speed, and ball filling percent are the key factors influencing the charge behavior inside the SAG mills, and consequently, their performance. In this work, the milling operation of industrial SAG mills is investigated using the Discrete Element Method (DEM). First, an industrial SAG mill with dimensions of 9.50 m × 4.42 m that has a Smooth-type liner is simulated. Then by changing the liner types, i.e. Wave, Rib, Ship-lap, Lorain, Osborn, and Step liners, six other independent simulations are performed. In order to investigate the impact mechanism and improve the mill performance, two new parameters called ‘head height’ and ‘impact zone length’ are introduced. Then the effects of the mill shell liner type on those parameters at two different mill speeds, i.e. 70% and 80% of its critical speed (CS), are evaluated. Also for validation of the simulation results, a laboratory-scale SAG mill with dimensions of 57.3 cm × 16.0 cm is simulated. The results obtained indicate that the Osborn liner, due to the angularity of its lifters and their proper number and thickness, performs best because it increases both parameters more than the other liners. Thus this liner is recommended as the best and optimal liner in this research work and is suggested for installation inside the industrial SAG mills. Also the Wave liner, due to its specific geometrical shape and its wavy lifters as well as their low number and inadequate thickness, provides the lowest charge ‘head height’. Therefore, it is not recommended to install this liner inside the industrial SAG mills. Meanwhile, comparison of the simulations related to the laboratory-scale SAG mill with the experimental results demonstrates a good agreement that validates the DEM simulations and the software used.
Mineral Processing
M. Jahani Chegeni
Abstract
A deeper understanding of the milling operation of ball mills helps mineral processing engineers to control and optimize them, and therefore, reduce their consuming power. In this work, the milling operation of ball mills is investigated using two methods, i.e. DEM and combined DEM-SPH. First, a pilot ...
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A deeper understanding of the milling operation of ball mills helps mineral processing engineers to control and optimize them, and therefore, reduce their consuming power. In this work, the milling operation of ball mills is investigated using two methods, i.e. DEM and combined DEM-SPH. First, a pilot scale ball mill with no lifter is simulated by both methods. Then another pilot scale ball mill with eight rectangle lifters is simulated again by both methods. The effects of lifters on ball shoulder and toe points as well as on creation of cascading and cataracting movements for balls are studied by both methods. At the present time, there is not enough measured data available for dense slurries interacting with the coarse particulates available in the public domain that can be used adequately to validate these types of predictions. The results obtained indicated that fluid slurry in the mill lowered the charge shoulder by about 28 cm and 25 cm in the no-lifter and eight-lifter cases, respectively. However, it raised the charge toe by about 36 cm and 6 cm in the no-lifter and eight-lifter cases, respectively.
