Modification of C1 cylinder of preheater to improve service life of impeller of high temperature fan

Date: 2019-06-24 Views:

The impeller wear of high temperature fan at the end of kiln has been very serious. When the kiln system runs normally for about a month, the impeller center of high temperature fan at the end of kiln is seriously worn out in V shape, and even worn through. Due to the influence of the air pulling capacity of high temperature fan, the output of kiln system will also decrease sharply. Therefore, in view of the serious wear and short service cycle of high temperature fan impeller, our company appointed various professional and technical personnel to follow up and investigate, collect all aspects of data, and finally solve the serious problem of high temperature fan impeller wear.

1. Problems in operation


After the exhaust gas from Φ 6 m C1 cylinder is blocked by high temperature butterfly valve, 70% ≤ 80% of the high temperature gas enters the high temperature fan and 20% ≤ 30% of the high temperature gas enters the high temperature fan directly into the high temperature fan. The exhaust gas discharged by the high temperature fan is used by raw material mill and coal mill. High temperature fan model: 3200DIBB50, flow rate: 1 ≤ 150 × 000 m ~ 3 ·h, full pressure: 8 000 Pa, working temperature: 275 ℃ (< 450 ℃), gas dust concentration: < 80 g / m ~ 3. For a high temperature fan impeller with a service cycle of only about 1 month, see figure 1.

2. Analysis of the reason


The serious wear of impeller is mainly due to the high dust concentration of the gas entering the high temperature fan, which is beyond the allowable dust concentration range, and the high speed and high temperature dust gas scours the impeller running at high speed.

The relationship between the wear amount F of the centrifugal fan impeller and the gas dust concentration C and the velocity V: F = CV n (n is the speed index), the wear amount of the impeller is directly proportional to the dust concentration of the gas, and the larger the dust concentration, the higher the number and frequency of the solid particles in the unit time impact the wall surface of the impeller blade, The greater the abrasion of the impeller blades, the greater the wear amount of the impeller and the n-th power of the gas movement speed, the greater the velocity, the greater the centrifugal force and the kinetic energy of the dust particles, the greater the impact on the impeller, and the more severe the wear.
When the feeding amount of the raw material is 530t/ h, the dust concentration and the air volume at the outlet of the C1-barrel outlet are measured. The result of the measurement is that the gas flow rate is 908-002 m3/ h, the dust concentration in the working condition is 57.01 g/ m3, and the dust concentration of the conversion is 129.1 g/ Nm3. It can be seen from the calibration results that the dust concentration of the gas in the actual operation is much higher than that of the fan's rated allowable dust concentration value of 80 g/ Nm3, which shows that the high dust concentration of the inlet fan gas is a direct cause of the serious wear of the fan impeller.

3. Solution


In order to fundamentally solve the problem of impeller wear of high temperature fan, we must first solve the problem of high dust concentration of high temperature fan. The inlet gas of high temperature fan comes from the outlet of C1 cylinder, and the high dust concentration at the outlet of C1 cylinder is directly caused by the low separation efficiency of C1 cylinder. According to the raw feed quantity, the outlet exhaust gas flow rate of C1 cylinder and the dust concentration of the gas, the separation efficiency of C1 cylinder is calculated to be 89.24%. This data is much lower than the C1 cylinder separation efficiency required in the design code is not less than 94%. The most effective way to increase the separation efficiency of cyclone cylinder is to increase the length of cyclone cylinder. According to the experience, the height of the inner cylinder is about whirlwind. The height of the tuyere is 1.3 times 1.5 times higher than that of the tuyere. The height of the inlet of the C1 tube in our company is 3 090 mm,C1, the length of the inner tube is 4 ≤ 160 mm, which is 1.35 times of the height of the inlet, which is within a reasonable range, but considering the low separation efficiency of the C1 tube at present, it is adopted to increase the height of the C1 inner tube to improve the separation efficiency.

It is determined that the original height of C1 inner cylinder is increased by 700 mm, to 4 ≤ 860 mm, which is 1.57 times of the inlet height. Due to the ultra-low resistance of the preheater system and the natural rotation length is still within a reasonable range, it is considered that this scheme is feasible.

4 Post-adjustment effect

4.1 variation of dust concentration at the inlet of high temperature fan


the dust concentration of the inlet of the high-temperature fan is tested before the technical improvement of the C1 inner cylinder, and two times are detected under the condition that the feeding amount of the kiln is 520 t/ h, the rotating speed of the high-temperature fan is 765r/ min, the opening degree of the hot air baffle of the power generation is 10 percent, The dust concentration of the inlet of the high-temperature fan is 34.07 g/ m3 and 35.23 g/ m3. The dust concentration of the inlet of the high-temperature fan after the transformation of the inner cylinder of the high-temperature fan is detected 4 times. The result of the test is 24.19 g/ m3 under the condition that the feeding amount of the kiln is 520 t/ h, the rotating speed of the high-temperature fan is 765r/ min, the opening degree of the hot air baffle of the power generation is 10%, 23.19 g/ m3, 25.36 g/ m3, 24.53 g/ m3. It can be seen that the dust concentration in the inlet of the fan after the technical improvement is obviously reduced as compared with the prior modification.

4.2 Change of outlet pressure of C1 cylinder


It can be seen that the outlet pressure of the C1-barrel after the transformation is slightly greater than that before the modification, for example, when the feeding amount is 530 t/ h, the outlet pressure before the modification of the C1-barrel is about -3,988 Pa after the modification, and the pressure of the outlet of the C1-barrel before and after the transformation can be seen, and after the modification, the outlet pressure is about -3,988 Pa, and after the modification, the outlet pressure is-4.099 Pa, The outlet pressure after the transformation is greater than about 110 Pa before the modification.


4.3 variation of current of high temperature fan


The statistical data in Table 2 are the operation data of 10 days before and 10 days after revamping of kiln system. It can be seen that the current of high temperature fan is basically the same when the amount of feed is the same, and there is no obvious change trend through the observation of the current of returning ash back into kiln and homogenizing reservoir by central control. The impeller of high temperature fan was checked after 6 months of revamping. It was found that the wear of impeller of high temperature fan was improved after the transformation of C1 inner cylinder, and the wear amount was obviously reduced compared with that before revamping.

5 Summary


After revamping the system and using the high temperature fan for 6 months, the impeller wear is also quite small, which completely solves the impeller wear problem caused by the large gas dust content at the outlet of C1 cylinder, and eliminates the problem of the decrease of drawing air volume and the low output of the firing system caused by the impeller wear, which lays a solid foundation for the high yield operation of the kiln.

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