Simple and easy to remember vertical grinding parameter derivationDate: 2019-07-01 Views:
Vertical mill is widely used in the grinding of cement raw materials. As a complete machine, it consists of a motor, a reducer, a grinding device consisting of grinding disc grinding rolls, and a classifier. Due to its unique structure, it integrates powder grinding and powder selection. Compared with ordinary tube grinding, it can save about 30% of electricity, and the investment is small and the floor space is small.
During operation, the motor drives the grinding disc through the reducer. When the material falls through the center feeding tube to the grinding disc through the feeding device, the grinding roller presses the material through the hydraulic cylinder and the grinding roller under the action of the high-pressure oil, and the grinding disc is pressed. Driven around the fixed axis to rotate. The material is ground under the action of rolling, shearing, granules and friction. Under the action of centrifugal force, it moves to the periphery of the grinding disc. When it reaches the wind ring, it is turned to the grinding disc by the high-speed airflow, and the large particles fall and re- Grinding; fine particles are brought into the classifier by the wind, and the unqualified coarse powder is returned to the grinding disc to continue grinding, and the qualified fine powder separator is separated into the warehouse. Due to the high temperature of the airflow from the wind ring, at around 200 °C, not only the material is dried, but also the fine powder is carried, so that the high-temperature exhaust gas at the kiln tail is utilized; not only the dust collection but also the energy is saved.
Compared to tube mills, vertical mills have many advantages:
First, the grinding uses the principle of crushing and squeezing the material bed, so that the material receives impact, rolling, shearing, friction and the like in the grinding. Under the action of centrifugal force, the material that has been crushed quickly leaves the hot air of the grinding disc and the wind ring, and the large particles are turned up to the grinding disc, and the fine powder is taken away, and the large particles that cannot be removed are taken out as the slag discharge. The residence time of the material in the mill is only a few minutes, which is several times the flow rate of the tube mill. Therefore, the grinding efficiency is high, and the power is saved compared to the tube mill.
Second, the drying ability is strong. It can directly use the hot air at the kiln tail to mix with the circulating air in the mill to dry the material in the mill, and the drying ability is strong, and the raw water with 8% of water can be dried.
Third, the practical range of material size is large. It is possible to allow 5% of the particle size of the grinding roller to enter the grinding mill for grinding.
Fourth, the vertical grinding has strong adaptability to materials, and even if the wearability is very different, it can grind satisfactory products through reasonable operation.
Fifth, the combination of grinding and powder selection, compact layout and small footprint, open-air operation, less investment. Sixth, low noise and less dust are beneficial to the protection of the environment.
Seventh, high efficiency, large output, easy to configure with the kiln stand-alone.
The biggest drawback is that it does not allow the entry of hard materials such as steel. The second is that the high-pressure oil station associated with it has higher requirements, otherwise it is a valve. The third is that some mills are difficult to overhaul and the degree of automation is also high. and many more.
Related parameters of vertical mill:
The rotation speed of the mill determines the residence time of the material on the grinding disc, and must be balanced with the grinding speed. Different types of mill speeds are different, but the centrifugal force requirements of the material are the same. The following is the calculation formula of the mill speed.
Where K is the coefficient, LM=58.5
RM=54.0 D is the diameter of the grinding disc (m) n is the grinding disc speed (per revolution)
Mill production capacity:
Raw material vertical grinding and grinding, the ability of which is determined by the smaller one, the grinding ability is related to roll pressure, easy grinding, particle size, mill specifications, and its grinding ability can be calculated by the following formula.
In the formula, when G is Taiwan, it is tons per hour.
D is the diameter of the grinding disc, in meters
K is the coefficient. LM=9.6 MPS=6.6
The drying capacity of the vertical mill is generally calculated by the manufacturers to obtain empirical data through experiments on raw materials.
The relationship between vertical mill production and fineness:
Vertical mill production is closely related to fineness and can be calculated by the following formula.
However, using the above formula is more troublesome. In fact, the amount of output growth is very related to the increase in fineness. For every 1% of the raw material, the percentage of the raw material is increased by three to four percent. For cement and pulverized coal, it is increased. 2% or so.
Mill roller pressure:
For the rolling of the grinding roller, it is not easy to calculate. Generally, the projected area of the grinding roller is used for calculation. Generally, the design of the eyebrow square meter is 800 kN.
Installed power of the mill:
Where K is a constant LM=72.5
N is the installed power (kW)
Several wind speeds of vertical mill:
The wind speed of the vertical mill is also one of the key parameters. Generally, the wind speed in the inner section of the mill is limited to 3 to 6 meters per second, the wind speed of the wind ring is 50 meters per second, the wind speed of the pipeline is not less than 20 meters per second, and the air volume is 0.5 to 0.8 kg. The finished product is considered as a cubic gas.
Concluding remarks: The calculation process of the parameters of the vertical mill is more complicated, and it is easy to remember after simplification. If you are not correct, please criticize and correct. Thank you!