Operational experience of vertical roller millBecause of the many advantages of vertical roller mill, cement mill has become the first choice. However, in practice, there are still many problems worth noting, especially the author describes some operational experience.1. Operation points

1.1 Stable Beds: to maintain stability and bed material, which is grinding roller grinding bed basis, the normal operation of the key. Material thickness can be adjusted to adjust the height of retaining ring material, a suitable thickness and their relationship with the correspondence between the vertical roller mill output should be in the debugging stage of the first to find out. Lower fuel layer thick grinding efficiency, material layer is too thin will cause vibration. Such as roll up, then fine powder generated much thinner material layer; roll reduction, disc material thicker, more appropriate to return the materials, material layer thickening. vertical roller mill speed increase, increase in internal circulation, material layer thickness, reducing the wind speed, reducing the inner loop, material layer thinning. Under normal operation by the vertical roller mill feed roller bed thickness after compaction should not be less than 40 ~ 50ram.

1.2 Control of grinding pressure: the pressure is affecting the grinding mill output, power mill grinding efficiency and the main factor. vertical roller mill is to impose by means of the material bed crushing pressure and the pressure to increase production increased, but reached a certain critical value does not change, the pressure increase followed by a increase in power, resulting in unit power consumption increase, so the appropriate roll to production and energy consumption both. This value depends on material properties, particle size and volume of feed. In the test production grinding to find the right pressure and wind pressure can form a reasonable good internal circulation, so that the material layer disc proper, stable, high grinding efficiency. In the production process, when the wind area of a certain ring, the wind speed from the wind decide. Production capacity with the correspondence between, to ensure the grinding effect.

1.3 The guarantee of the grinding temperature: vertical roller mill is drying and grinding system, the ground temperature is a measure of whether the normal drying operation comprehensive index. In order to ensure good drying of raw materials, the grinding of materials is less than 0.5% moisture, the general control of mill outlet temperature at 90 ~ C or so. If the temperature is too low then finished water, causing the efficiency of grinding efficiency and reduce the separator, dust collection system may cause condensation; If too high, humidity is not enough that gas cooling, dust collection will also affect the results.

1.4 Control of a reasonable wind speed: grinding materials driven mainly by air circulation. Reasonable speed to form a good inner loop, so that the material layer disc proper, stable, high grinding efficiency. But the wind is wind speed decisions, and the volume of feed air flow is associated, such as feeding large, air volume to be large; and vice versa decreases. Fan air flow resistance by the impact of the system can be adjusted by adjusting the fan valve. Mill drop, into the vertical roller mill vacuum, a vacuum can reflect the amount of wind vertical roller mill size. Pressure drop, said negative pressure large wind velocity, air volume; the other hand the small amount of the corresponding wind speed. The stability of these parameters indicated that the air flow on the stability, thus ensuring the stability of the material bed.

1.5 Degree of control of the raw material: Raw fine degree of speed by the separator, the system air volume, the vertical roller mill load density. Change in air volume and load situation, you can manually change the speed to adjust the fineness adjustment increase or decrease when the maximum of 2r/min, had led the General Assembly to increase vertical roller mill vibration or tripping.

2. Exception handling

2.1 vertical roller mill vibration is too large:

(1) Feed uneven, when the mixture into the vertical roller mill over the powder, the vertical roller mill's loading rate, leading to the vertical roller mill on the thin material, and even disc direct contact with the roller, resulting in mechanical milling; when into the vertical roller mill multi-material mixture materials for the block, the resulting pressure grinding roll instability, resulting in mechanical milling. The solution is to stabilize the particle size of materials into the vertical roller mill, the appropriate adjustment of feed rate or reduce the grinding pressure, the assurance required under the premise of the fineness of materials, appropriate to reduce the classifier speed.

(2) Metal piece into the vertical roller mill, check the metal detectors, magnetic separators are working correctly.

(3) Damage caused by the kiln exhaust fan vibration or grinding of the kiln exhaust gas pressure were high, instability and the dust concentration within the high temperature wear Ambassador to increased vertical roller mill capacity, and you should increase the cycle of throttle opening degree increase into the grinding cycle of throttle to raise the vertical roller mill of the population vacuum, so that vertical roller mill running balance.

2.2 vertical roller mill capacity is too low:Possible causes are:

(1) Feed rate is low;

(2) The grinding pressure is low;

(3) Product fineness too fine;

(4) Low air volume system.

The solution to increase the feed rate or increasing the grinding pressure, lower separator speed, increase the amount of exhaust system. Instead vertical roller mill capacity is too high, the solution the opposite.

2.3 Feed shortage: When they find enough feed storage materials should be shut down, at this time if it continues to grind out the danger of conveying availability should feed vertical roller mill equipment and feeding, otherwise it would Beds thinning occurred rumble noise, causing gear damage.

2.4 Vertical roller mill pressure too: At this point should be immediately reduced feeding observed pressure indicating device.

Check the possible causes:

(1) Feeding device failure, feeding too much;

(2) The Department of nozzle ring vertical roller mill block;

(3) Air volume is too low or unstable;

(4) Separator adjusted through the fine details.

Pressure difference is too small because:

(1) Feed rate so low feed interrupt;

(2) The fineness of the product is too thick.

2.5 Tensioning system pressure drop:

Should check:

(1) Duct leaks;

(2) Pressure relief valve is fail safe;

(3) The oil pump is working;

(4) Pressure switch is abnormal.

If, after checking the equipment in good condition, then re-start the pump working, close the pump after the pressure is still normal, you do not stop, otherwise stop.

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