Classification criteria and working principle of iron ore ball mill

The ball mill is an important part of the beneficiation equipment. However, in the actual situation, many people know little about the classification principle and working principle of the ball mill. This article gives a brief introduction to the classification and working principle of ball mills for reference by manufacturers.

First, the classification of ball mill

1, according to the ratio of the length and diameter of the cylinder classification

(1) When the aspect ratio of the short mill is 2 or less, it is a short mill or a short ball mill. It is generally a single bin, used for rough grinding or first-grade grinding, and can also be used in series with 2-3 ball mills.

(2) Medium and long mills with a length-to-diameter ratio of medium to long mills around 3.

(3) Long mill long bar It is a long mill or pipe mill when it is 4 or more. In the long and long mills, the interior is generally divided into 2-4 bins. Used more in cement long.

2, according to the shape of the grinding medium loaded into the grinding

(1) Ball Mill The grinding medium that is loaded is mainly steel balls or steel sections. This type of ball mill is most commonly used.

(2) The rod grinder is loaded with a steel bar having a diameter of 50-100 mm as a grinding medium. Rod mill barrel length and diameter ratio is generally 1.5-2.

(3) Baseball Mill This ball mill usually has 2-4 bins. In the first chamber, a cylindrical steel rod is used as a grinding medium, and each subsequent chamber is loaded into a steel ball or a steel section. The ratio of length to diameter of the baseball mill should be about 5, the ratio of the length of the bin to the effective diameter of the mill should be between 1.2-1.5, and the length of the rod should be about 100mm shorter than the rodhouse, in order to facilitate the parallel arrangement of the steel bars and prevent crossover and Awkward sticks.

(4) The grinding media loaded in the gravel grinding are gravel, pebbles, porcelain balls, and the like. With granite, porcelain liner. For white or colored cement and ceramic production.

3, according to unloading classification

(1) The material to be milled by the tail unloading mill is fed from one end of the mill and discharged from the other end and is called a tail dump mill.

(2) The materials to be milled in the unloading mill are fed from both ends of the mill and discharged from the middle of the mill barrel, which is called a unloading mill. This type of mill is equivalent to two billiard mills used in parallel, so that the equipment is compact and simplifies the process. According to the discharge method of the tail dump mill, there are a variety of types such as a lattice discharge, an overflow discharge, a peripheral discharge, and a wind discharge. The reducer drives the hollow shaft of the discharge end of the mill and drives the grinding body to rotate. The deceleration and the output shaft are in line with the center line of the mill.

(2) Edge-drive mill The motor drives a large gear fixed on the discharge end cylinder to drive the rotation of the mill barrel through a speed reducer.

5, other classifications

According to the process operation can be divided into dry mill, wet mill, intermittent mill and continuous mill. Compared with the gap mill, the continuous mill has a high output, a low power consumption per unit weight of the product, a high degree of mechanization, and a small number of operators. However, investment in infrastructure investment is large and operation and maintenance are more complicated. Intermittent mills are rarely used today and are often used as laboratory lab mills.

Second, the principle of ball mill:

The ball mill is mainly composed of a cylindrical body, an end cap, a bearing, and a gear ring and the like. A steel ball or a steel rod with a diameter of 25-150 mm is loaded into the cylinder body and is called a grinding jig. The amount of the ball mill is the whole barrel body. There are 25%-50% of the volume. Both ends of the cylinder body have end caps. The end caps are connected with the end flanges of the cylinder body by screws. The middle part of the end caps has a hole, which is called a hollow journal. The hollow journal is supported on the bearing, and the cylinder body can rotate. A large gear ring is also fixed on the barrel. In the drive system, the motor drives the large gear ring and the barrel through a coupling, a speed reducer, and a pinion, and slowly rotates. When the cylinder rotates, the grinding medium rises to a certain height along with the wall of the cylinder, and then it drops down or drops down under the parabola. Since the end cap has a hollow journal, the material is fed into the cylinder from the left hollow journal and gradually Diffusion and movement to the right, when the material moves from left to right, the rotating cylinder brings the steel ball to a certain height and falls to break the material, and a part of the steel ball grinds the material when the cylinder is in leaking state. The entire moving process is also the process of material crushing.

A ball mill is provided with a grid plate at the right end (discharging end), and the grid plate has a plurality of scallops with a width of 7-20 mm, generally 7-8 mm, and the material can enter the grid plate and the end cap through the boring hole. In the space between them, the material is then lifted upward by the lifting plate 2, and the material slides down the taper block to the right to the hollow journal and then exits the machine by the hollow journal.

The other way is that the air discharge ball mill adopts discharge, and the material enters the ball mill from the feed port. As the mill rotates, the grinding mill (steel ball) impacts and grinds the material, and the material is from the left end of the mill ( The import) gradually moves to the right end, which is the process of crushing and grinding the material during the movement. It is connected to the air duct at the outlet end of the ball mill, followed by the inlet of the separator, wind separator, dust collector and fan in the piping system. When the wind system drives, the ball mill body is also in a negative pressure operation. When the grinding material becomes loose with the rotation of the mill, and the wind enters the pipe system from the discharge port, the coarse particles are separated by the powder separator and then sent to the inlet of the ball mill. The fine powder is separated and recovered by the separator. It is discharged into the atmosphere by fans.