There are many factors that affect the quality of the mill when using the Vertical roller mill. Some factors are uncontrollable. We can't do anything, but some factors are controllable, even faults caused by mistakes in the operation of the staff, so we must avoid it! Today, the SBM heavy machine is going to introduce to you, what our operators need to pay attention to when controlling the Vertical roller mill!
Vibration is a common condition in the work of roller mills. Reasonable vibration is allowed, but if the vibration is too large, it will cause mechanical damage to the disc and the grinding roller, as well as damage to the accessory equipment and measuring instruments. The uneven thickness of the material layer is the main reason for the vibration. Other reasons are: there are large metal objects in the grinding; the grinding pressure is too large; the wear parts are damaged; the accumulator gas pressure is not equal; the grinding and ventilation are insufficient.
In operation, the vibration should be strictly controlled within the allowable range to create a prerequisite for stable operation.
Another important factor in the stable operation of the Vertical roller mill is the stability of the bed. The material layer is stable, and the air volume, wind pressure and feed amount can be stabilized. Otherwise, the thickness of the layer should be maintained by adjusting the air volume and the feed amount. If the adjustment is not timely, it will cause vibrations to increase, motor load rises or system trips. Theoretically, the thickness of the layer should be 2% ± 20 mm of the diameter of the grinding roller, and the diameter of the vertical grinding roller is 3000 mm, so 60 ± 20 mm is a suitable thickness of the layer. In addition, the thickness of the preferred layer depends primarily on the quality of the raw materials such as water content, particle size, particle distribution and grindability.
At the beginning of the operation, in order to find a good layer thickness, the height of the retaining ring is adjusted. Under the condition that the height of the retaining ring is constant, one of the important conditions for stabilizing the thickness of the layer is that the feeding size and particle size are reasonable. If the average particle size of the feed is too small or too much fine powder, the layer will become thinner; if the average particle size is too large or the bulk material is too much, the layer will become thicker and the mill load will increase. The material layer can be stabilized by adjusting parameters such as water spray amount, grinding pressure, circulating air volume and number of revolutions of the classifier. Water spray is a prerequisite for the formation of a solid bed. The proper grinding pressure is a condition for maintaining the stability of the bed. The internal ventilation is a means to ensure the fineness and moisture of the raw meal.
The pressure difference is the pressure loss at the wind ring and is one of the important control parameters. Since the influence of the wind on the Vertical roller mill is large, the pressure difference is kept constant and the running state of the mill is good. The pressure difference is still a mirror of the grinding condition. The operator can observe the pressure difference by observing the pressure difference, and judge the material, the material, the wind, the wind, the grinding efficiency and so on. Moreover, with the change of the feeding amount, the magnitude of the grinding ventilation and the stable value of the differential pressure are also different. In the ordinary operation, attention should be paid to observation and attention to accumulate experience.
If the pressure difference is too large, it means that the internal friction is large and the internal circulation is large. At this time, the material reduction measures should be taken to increase the ventilation volume, increase the water spray, stabilize the material layer, and temporarily reduce the number of rotations of the powder separator. The fine powder accumulated in the mill is discharged out of the mill, and the pressure difference is restored to normal, and then the parameters are appropriately restored to avoid the phenomenon of over-grinding, and the occurrence of grinding and jumping and full-grinding accidents due to vibration is prevented. If the pressure difference is too small, it means that the material in the grinding is too small, the polishing layer will be thinned quickly, causing the vibration to increase. Therefore, the material should be added immediately, and the water spray should be added to form a stable layer.
The power of the Vertical roller mill is determined by the pressure applied by the grinding roller to the grinding disc and the relevant design parameters. If there is too much material on the grinding disc and the grinding pressure is not kept up, the grinding efficiency is low and the grinding power consumption is large; if the grinding pressure is too large It will also increase the grinding power, which will adversely affect the equipment.
Supplying hot air into the mill is the need to dry the material and lift the material. The temperature of the gas at the exit of the mill is an important factor to measure the operating condition of the mill. Overheating will cause internal mechanical damage; if it is too low, it will not achieve the purpose of drying. According to the operating experience of SBM heavy machine for many years, the mill outlet temperature is well controlled at around 95 °C. If the outlet temperature is high, open the circulating fan baffle or open the cold air baffle properly; if the outlet temperature is low, increase the hot air supply amount to ensure that the raw water does not exceed the standard.
The fineness of the product is mainly adjusted by the speed of the powder selection machine. The number of revolutions is large and the product is fine; the number of revolutions is small and the product is thick. The amount of air used in the mill also has a great influence on the fineness of the product.
Whether the Vertical roller mill output is properly calibrated or not is important for stable operation and full use of its advantages of energy saving and cost reduction. While increasing production, the operator should pay attention to the appropriate increase of parameters such as hot air, grinding ventilation, grinding pressure, and water spray to ensure stable pressure difference.