About the cooling of large cement mills and raw material grinding hot spots

Date: 2019-07-09 Views:

The cement mill differs from the original due to the difference in the grinding material. The cement mill is generally high in temperature due to the clinker (especially in summer), and the hot spot is the grinding head spindle and the main reducer bush; the original (for the drying type) is the hot air of the kiln tail humidification tower. Drying heat source, the hot point is the sliding bearing bush (grinding head) and the main reducer bearing bush.

In response to the above heating points, we have adopted different cooling measures and received good results, which improved the operating temperature of cement mills and original spindles in summer.

1. Cooling of the cement mill heating point

The cement mill model of our factory is Ф4 m×13 m ball mill, power 2 800 kW, using central drive, main reducer JS140-A, its thin oil station model is XYZ-350, heat exchange area is 21 m2; mill main The model of the thin oil station equipped with the bearing oil station is XGO-A2.5/40, and the heat exchange area is 5 m2. Due to the influence of external temperature in summer, the temperature of the grinding spindle and the bearing speed of the main reducer are often around 60-62 °C, and the normal temperature range normally controlled is <60 °C (the grinding head spindle is 5-6 lower than the grinding tail). °C).

Such high temperatures pose a hidden danger to the normal production of the mill. To this end, we have taken measures to increase the cooling area of ​​the thin oil station (that is, the different types of tube-type coolers on the string) to achieve effective control of the temperature of the grinding spindle and the bearing temperature of the main reducer.

1.1 cooling measures

Next to the cement mill main reducer thin oil station and the grinding tail spindle tile oil station cooler, one row of tube coolers are connected in series. The technical parameters are shown in Table 1, and the installation arrangement is shown in Figure 1. In order to achieve effective control, a plurality of valves are designed to achieve temperature control of different seasons and different heating temperatures. That is: the outside temperature is low in winter, the valves 1, 2, 3, 4 are closed, the lubricating oil in the thin oil station does not need a cooler, and the valves 5 and 6 are directly taken to reach the lubrication point; in summer, the external temperature is high, and the valve is closed. 6, the lubricating oil needs to be fully cooled by two coolers (ie, valves 1, 2, 3, 4 open); spring and autumn temperatures are more suitable, only one cooler is needed (close the valves 5, 3, 4, only open the valve 1 2, 6) will meet the requirements.

1.2 improved effect

Since the cooling device of the cement mill oil station has been improved in series since 2004, the temperature control of the hot spot is relatively easy. Even in the hot summer, the heating temperature of each lubrication point is below the safe value. The JS140-A reducer for cement grinding has two bearings, 10 bearing bushes, 12 temperature measuring points, and two temperature measuring points for the grinding spindle. The temperature comparison before and after the improvement is shown in Table 2.

2. Cooling of the original hot spot

Our factory used the original Ф 4.6 m × (3 + 10) m drying in the unloading, the middle with the sliding support, the main reducer model used is JS150-B, the center drive, power 3 550 kW. For the hot sliding bearing bush and the main reducer bearing bush, we adopted the air-cooled sliding shoe and the water-cooled thin oil station, which also achieved the purpose of cooling.

2.1 Cooling of the original sliding bearing bush

With compressed air, the inner surface of the air-cooled shoe can effectively reduce the temperature of the sliding bearing bush. The air-cooling device is shown in Figure 2. It is welded to a "C" frame with a 25 mm steel tube and attached to the outer seal of the shoe.

The "C" shaped frame encases the shoe along the outer edge of the mill barrel. At the two ends of the frame, along the inner width of the shoe, there are four small holes of Ф8 mm, and the positions of the small holes are directly opposite the shoes. One end of the frame is connected to the compressed air duct and is provided with a valve to control the air volume.

When the original sliding temperature reaches 60 °C, the valve is opened to cool the shoe, and the opening degree of the valve is adjusted to an appropriate level according to the temperature of the sliding bearing bush. In the hot summer, the device can be kept open, so that the maximum temperature measurement point of the shoe is controlled at 55-57 °C.

2.2 Cooling of the original main reducer bush

The original main reducer JS150-B has a large body and a large heat dissipation area. The main reducer is in operation, only the individual bearing bushes have a high temperature phenomenon, and for the cooling thereof, a water-cooled thin oil station is adopted.

2.2.1 Cooling measures for the main reducer bush

Use the heating hole of the XPZ-400P thin oil station to cool down. The heating device equipped with the thin oil station (see Fig. 3a) is very characteristic and belongs to a sheathed heating device. The heating wire of the heater is in a closed sleeve and is not in direct contact with the lubricating oil. We used this special device to remove the heater and then make the water inlet and outlet pipes (see Figure 3b) for water cooling. Among them, the length of the inlet pipe is longer, 50 mm from the bottom edge of the sleeve, and the outlet pipe is designed to be shorter, and the length is controlled to 100 mm. The inlet pipe and the outlet pipe are welded to the flange at the same time. The size of the flange is the same as that of the heater. It is fastened with 6 M6×30 mm hexagon socket bolts. Before tightening the bolt, pad the bottom of the flange. A 2 mm rubber pad is provided to prevent the flange from leaking. Finally, the water pipes are connected by a rubber tube, and the joints of the rubber tubes are fastened with a wire, as shown in Fig. 4.

2.2.2 Precautions

It should be noted that the original design of the thin oil station pipelines are all seamless steel tubes, flange joints, argon arc welding, so that no leakage. However, for safety reasons, the water pressure test of the heater jacket should be carried out before the water cooling, and the water pressure test at 0.4 MPa should not have water seepage. After the cooling water is passed, the water pressure is controlled to be less than 0.2 MPa. In winter, the heating device should be restored, and the sheath should be air-dried before recovery. After the inner hole of the sheath is dried, the heating wire is fastened.

2.2.3 Water cooling effect

The thin oil station has 6 juxtaposed HRY sheathed electric heaters. The jacket size is Ф110mm×1200mm. After changing to a water cooling device, it is equivalent to adding a surface area of ​​2.54 m2 to the inside of the thin oil station. Device. In the summer of 2005, we first tested on the #1 line, and the cooling effect was very obvious. In the summer of 2006, we extended it to the #2 line. The original main reducer is the same as the cement mill main reducer. There are two bearings, 10 bushes and 12 temperature measuring points. The temperature of the test points of the main reducer before and after the improvement is also shown in Table 2.

3, the conclusion

(1) The cooling of large cement mills and raw lubrication hot spots is very important in production. If the cooling measures are not timely, it will not only affect the normal operation of the mill, but also may cause burnt tiles.

(2) Summer is the peak season of production and sales. The cement mill operation rate is relatively high, the supply of cement is in short supply, and the cooling of the main shaft is very important. Our measures of using a series cooler are more appropriate, and the investment is only about 20,000 yuan. Compared with the cement grinding rate, the original grinding rate is lower, and the temperature of the grinding material is not high. The air cooling and water cooling oil station can meet the cooling requirements. Of course, it is also possible to use a series cooler to cool down.

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