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Operation details of vertical grinding

Date:2019-06-04 14:04     writer:cement editor     Views:


  Vertical mill is a device that grinds materials by relative rolling of a grinding disc. There are several main aspects to the impact of the normal operation of the vertical mill.

  1) The layer of the mill.

The proper thickness of the layer and the stable layer are the basis for the stable operation of the vertical mill. The material layer is too thick, the grinding efficiency is reduced, and when the pressure difference of the mill reaches the limit, the material will collapse, which will affect the main motor and the venting system; the material layer is too thin, the driving force of the mill increases, and the grinding roller both the disc and the hydraulic system are damaged.

  2) Vibration of the mill.

Excessive vibration of the mill not only directly causes mechanical damage, but also affects production and quality. The factors that cause vibration are: the basis of the mill, the grinding pressure, the thickness of the layer, the air volume and the air temperature, the accumulator pressure, the wear of the roller surface or the grinding disc, and the like.

  3) Grinding pressure:

Grinding pressure is the main factor affecting the quality of production. The grinding pressure is adjusted according to the amount of grinding machine feed, material size and easy grinding. In order to maintain a layer of material with a certain thickness on the grinding disc, reduce the vibration of the mill and ensure stable operation, the pressure of the grinding roller must be controlled. When the grinding pressure is increased, the grinding capacity of the mill is increased, but after reaching a certain point, it does not change. If the hydraulic cylinder setting pressure is too high, it will only increase the driving force and accelerate the wear of the components, and will not improve the grinding ability. This feature is like the working principle of a roller press.

  4) Mill outlet gas temperature.

When the temperature of the outlet gas of the mill is too low, the fluidity of the material will be deteriorated, and the qualified finished product cannot be extracted in time. When the pressure difference in the mill is too high, the material will collapse. The method of raising the temperature includes: increasing the suction of the mill, adjusting the fineness by the classifier, increasing the opening of the hot damper to reduce the opening of the circulating wind. These methods are also applicable to other types of raw material mills. However, if the temperature is too high (above 130), it will also cause damage to the equipment. The dividing wheel in the lower part of the cyclone will expand and become stuck, and the lubricating grease of the grinding roller will also be cracked. It is also disadvantageous for the tail dust bag.

  5) System air volume.

The system air volume must be matched with the feeding amount. The method of adjusting the air volume can generally be controlled by adjusting the power of the mill circulating fan or adjusting the opening degree of the kiln exhaust fan. The wind is going big. When the system air volume is too large, the internal pressure difference decreases, the main motor current decreases, the thickness of the material layer increases, the internal pressure difference increases, the main motor current increases, and the vibration of the mill increases.

  6) The amount of slag in the mill is excessive.

Feeding is large and satiety is a major cause. However, when the material is poor in wear ability, it will also slag. The size of the grinding material is large, the system air volume is insufficient, the grinding pressure is low, the system leaks air, the material layer is unstable, the material ring is low, and the roller surface or the grinding disc wears seriously, which will cause the grinding machine to slag more.

  7) The system operates safely.

When the raw material is running in the vertical mill, the drying heat source of the material comes from the hot gas at the kiln tail. Therefore, when the vertical mill is operated, the control of the inlet and outlet dampers should be balanced by the kiln mill. When the vertical mill inlet and outlet dampers are balanced, the system’s wind will be balanced and will not affect the pressure at the kiln end.

  8) Precautions for opening and stopping.

Before the grinding starts, it is necessary to stack enough material on the grinding disc so that when the grinding roller falls and grinds, it will not stop due to high vibration. However, the material layer should not be too high, otherwise the main motor current will be high when the roll is ground, which is unfavorable to the equipment. The air pressure at the nozzle ring before grinding is a key value for the observation level. The situation of each vertical mill is different and must be reasonably controlled according to circumstances. Try to increase the ventilation before stopping the machine to make the fine powder into the reservoir as much as possible if the fine powder is excessively rolled, the vibration of the mill is large.

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