In this chapter the motion of the particles constituting the charge of the mill will be considered it being assumed that there is no slip between the mill shell and the charge. There exists another type of motion in which the charge as a whole slips relative to the shell which gives rise to the phenomenon of surging but consideration of this type of motion will be deferred until a later chapter.Get A Quote
In this chapter the motion of the particles constituting the charge of the mill will be considered it being assumed that there is no slip between the mill shell and the charge. There exists another type of motion in which the charge as a whole slips relative to the shell which gives rise to the phenomenon of surging but consideration of this type of motion will be deferred until a later chapter.
A study from first principles of the behaviour of a mill charge is much simplified if the charge is imagined to be composed of rods instead of balls since by this means the complication of any axial motion of the balls is eliminated and the problem is reduced to one in two dimensions. Consider first the motion of a single rod of diameter d within a smooth shell of internal diameter D when the
shell rotates about a horizontal axis with an angulai velocity radians per second. In such a case the rod will lie near the lowest point of the mill as in Fig. 2.1 and will rotate at such speed that the peripheral speed of the rod is the same as that of the shell. Furthermore the displacement of the radius vector joining the centre of the mill and that of the rod would be such that the work done by reason of the couple formed by this displacement is equal to the energy dissipated in the distortion of the rod and shell at the line of contact.
If the speed of rotation of the mill is so low that the effects of centripetal acceleration may be neglected then the displacement of the centre of gravity of the charge will increase until either of two possible limiting conditions is reached these conditions being
By reference to Fig. 2.6 it is easily seen that if the trajectory is not to fall inside the shell the radius of curvature of the path e must be greater than R that is than that of the mill shell. Furthermore this must be true for from wherever the trajectory might start.
Mills usually operate in the range 65 - 82 of critical but values as high as 90 are sometimes used. A crucial parameter that defines the performance of a mill is the energy consumption. The power supplied to the mill is used primarily to lift the load medium and charge.
It transforms the mill rotation into charge motion and both profile and spacing must be carefully selected to suit each specific mill. When designing a shell lining Metso considers the type of grinding mill size and speed maintenance schedules safety impact levels
Oct 12 2017nbsp018332Ball mill is a fine grinder. A horizontal or vertical rotating cylinder which is filled partially with the balls of ceramics small rocks and balls made from stainless steel. The ball charge of a SAG mill is about 29 to 30. By friction and influence of tumbling balls inside rotating cylinder grinds the raw material to the required fineness.
Optimize performance and decrease disturbances in your mill. The Outotec MillSense mill charge sensor system provides on-line analysis of mill charge. The system measures the mills toe angle with a wireless sensor attached to the liner bolt. Together with Outotec39s advanced process controls the MillSense sensor system helps to stabilize and optimize grinding processes to ensure reliable operation and increased throughput.
Mill charge is calculated using on-line measurement of the toe position through strain gauge and acceleration sensors attached to a liner bolt on the mill shell. The sensor unit is powered by an inductive power source outside the mill shell and uses wireless technology to transfer data to the process control system. The sensor technology is based on robust direct contact measurement of the toe position and does not require calibration.
What is the effect of low ball full on grinding efficiencyOne of our clients is thinking of the future and has bought a ball mill that will be the right size someday but is very large now.I know what happens to mill power from adjustments to critical speed and balls charge. What I dont know is what happens to grinding efficiency as ball charge filling is lowered. For example does a grinding between two given sizes that takes 6 kWtonne at 40 full take 8 kWtonne or some other number at 20 full
The volume of grinding media in a mill is directly related to grinding efficiency. The higher the volume of grinding media the more effective the grind. Balls must be added to maintain the media load and mill power draw. The power draw increases as balls are added and decreases as media wears down add balls.
The main control on the power draw for a BM is the load of grinding media however adding water to the cyclone underflow can also be short term control of BM power.
Higher ball loads will result in finer grind but dont overcharge. If throughput of slurry to BM decreases the mill power draw will increase because balls grinding against balls are drawing more power finer grind.
I totally agree with you that the low charge rate directly affects the grinding efficiency but in here there is another thing we have that shouldnt be overlooked it is the power consumption at low charge rates below 20 the power consumption increase by 6-15 for the ball mills.
What are the dimensions of the ball mill you are looking at 40 ball charge is quite high unless you are looking at a small mill.
For grinding pyrite the behaviour of the 9 mm ball charge lies between the 3 mm and 6 mm ball charge data. For both mill feeds there is a difference in energy efficiency with the different ball sizes.
smaller mill the charge consisted of 16 balls . of three . The application of the method to industrial mills shows that a grinding mill operation could present an invariant behaviour that can .
Optimize grinding mill performance efficiency and availability to ensure you meet your plant39s operational targets. Outotec high-performance grinding mills use advanced simulation tools for the best possible process efficiency mechanical reliability and maintainability.
Choosing an appropriate grinding circuit configuration depends on your ore characteristics and mine plan. Outotec has extensive knowledge of comminution technologies and processes to ensure we provide the optimal solution for your needs.
Our state-of-the-art grinding process control solutions make it possible to stabilize adjust and improve your grinding results. These enhancing technologies accompany our grinding mills and make the grinding process more efficient which adds significant value to the whole concentration process. These technologies include on-line particle size analyzers for the feed and discharge Outotec RockSense and Outotec PSI particle size analyzers mill charge measurement tools Outotec MillSense and advanced process controls Outotec ACT.
Our unique Outotec TPL technology improves grinding process efficiency the primary grinding process can be intensified for hard ores and material transport can be improved for soft ores. TPL is an environmentally friendly technology used to achieve higher energy efficiency from the grinding mill. Better energy efficiency in the grinding process can also bring significant cost savings to your plant overall.
Mills 3 Ball charges Composition Calculator for 3 Chambers Mills 4 Modification of the Ball Charge after Sampling Analysis Calculator 5 Calculation of the Top Size Grinding Media 6 Ball Charges analysis calculator Weight and Surface of the Grinding Charges 7 Ball Charge Makeup Calculator 8 Ball Mill Simulation 9
Today we will learn about difference between sag mill vs ball mill. A mill is a machine by which solid or hard materials are broken into smaller pieces by means of grinding crushing or cutting. This commutation is an essential part of many processes. Various kinds of mills are there with which different material processing takes place.
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