Precautions for the operation of bag filter(two)

2022-03-25 09:58

4. Precautions for stopping work

When the bag filter stops running, in addition to cleaning the dust thoroughly, the following issues should also be paid attention to:

(1) Moisture condensation often occurs in the bag room, which is caused by the moisture-containing gas, especially the gas generated by combustion, after cooling. Therefore, before the system is cooled, the moisture-containing gas should be discharged and replaced with dry air. That is, after the process equipment stops running, the exhaust fan of the bag filter should run for a period of time before it stops running.

(2) During the long-term shutdown period, pay full attention to the cleaning and rust prevention of the fan to prevent dust and rain from entering the bearing (pay attention to the moisture-proof of the motor). Before stopping the operation, the ash accumulation in the ash hopper should be removed. The cleaning mechanism and driving part should be fully oiled.

⑶ During the period when the bag filter is out of operation, regular short-term operation (dry operation) is the best maintenance method to ensure the normal operation of the dust removal system.

5 Maintenance

5.1 Always check the operation of control valves, electromagnetic pulse valves and timers.

The failure of the rubber diaphragm of the pulse valve is a common fault, which directly affects the cleaning effect. The equipment belongs to the external filter type, and the bag is equipped with a skeleton. It is necessary to check whether the parts fixing the filter bag are loose and whether the tension of the filter bag is appropriate. Whether the support frame is smooth to prevent wear of the filter bag. Compressed air is used for cleaning. Therefore, it is required to remove oil mist and water droplets, and the oil-water separator must be cleaned frequently to prevent the failure of the moving mechanism and the blockage of the filter bag.

5.2 Prevent condensation

In use, it is necessary to prevent the gas from cooling below the dew point in the bag chamber, especially when using the bag filter under negative pressure. Since the outer shell often leaks air, the temperature of the gas in the bag room is lower than the dew point, and the filter bag will be damp, so that the dust is not loosely attached to the filter bag, but sticky to the filter bag, blocking the fabric holes, causing clear The ash fails, so that the pressure drop of the dust collector is too large, and it cannot continue to operate.

To prevent condensation, the temperature of the gas in the dust collector and its system must be kept 25-35°C higher than its dew point (for example, the dew point temperature of the kiln-milling machine is 58°C, and the operating temperature should be above 90°C). To ensure the good use of the filter bag. , the measures are as follows:

⑴ Increase the raw material storage shed. In cement production, the water content of various raw materials, fuels and mixtures varies. If they are placed in a fixed shed to prevent rain, the water content of the material can be greatly reduced, which is an effective measure to reduce the water content of the material. This situation is relatively common in cement plants in southern my country, but some of the material sheds are too small, and some are not. Therefore, it is difficult to use the bag filter.

(2) Reduce air leakage. The air leakage in the gap of the dust collector body should be controlled below 3.5%. In the dust collector system, the air leakage of the process equipment, such as the closed ash discharge valve at the discharge port of the ball mill, the air leakage of the closed ash discharge valve under the dust collector, and the pipe flange connection, etc., are often ignored by the maintenance and management personnel. Therefore, , increasing the unnecessary air leakage and worsening the operating conditions of the bag filter.

(3) The dust-laden gas should be evenly distributed in the dust collector to prevent eddy currents from appearing in the corners, which will reduce the amount of gas passing here and cause local low temperature to cause condensation problems.

⑷ Do a good job of heat preservation and rain protection for dust collectors, pipes and other related places. Practice has proved that good insulation measures can make the temperature difference between the inlet and outlet of the bag filter very small, which is an effective measure to prevent condensation.

⑸ Take appropriate heating measures. If a far-infrared electric heater or electric heater is installed in the dust collector, or a radiator is added in the bag room, the flue gas temperature of the main engine can be appropriately increased.

⑹ Strengthen the temperature monitoring of the dust collector and the dust removal system, so as to grasp the operating conditions of the bag filter and prevent condensation.

5.3 Prevention of burning and explosion

The exhaust gas discharged from the rotary kiln end of the cement plant and the exhaust gas discharged from the coal mill preparation contains combustible substances such as CO and coal dust. Under the conditions of its content, dust concentration and certain temperature, a combustion explosion accident will occur, not only burning the dust removal equipment , also affects the normal operation of the production host, so necessary precautions must be taken, mainly including:

(1) To prevent the accumulation of combustible substances and combustible gases (CO, etc.) in the pipes and bag chambers of the bag filter, special attention should be paid to coal dust.

(2) Strengthen the control of the inlet temperature of the bag filter.

⑶ The bag filter is equipped with explosion-proof valve to ensure safe use.

5.4 Preventing the reduction of dust removal efficiency

(1) Block the air leakage, especially the air leakage of the ash discharge port of the dust collector. Because there is a large amount of slowly falling dust in the ash hopper of the dust collector, the countercurrent upward leakage air flow causes the falling dust to fly twice and circulate for many times, so the air leakage from the ash discharge port can make the dust concentration in the dust collector double. The dust concentration is higher than that of the intake air, which deteriorates the working conditions of the bag filter and affects the dust removal efficiency of the bag filter.

(2) Prevent short circuit of airflow inside the dust collector. Because of the high dust concentration in the dust source gas (such as 20 g/m3), even if only 1% of the gas escapes from a short circuit, it will exceed the emission standard. Dust-laden gas escapes directly from certain gaps without passing through the filter bag. This situation is not allowed. Therefore, attention should be paid during design, installation and maintenance.

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