Cause analysis and solution of dust filter bag paste bag

The reason for the "paste bag" of dust filter bag

1. Condensation paste bag

In general, the operating temperature of the bag filter must be 25°C higher than the acid dew point temperature, and it is safer to operate for the bag filter. This is mainly to avoid the occurrence of condensation. When the operating temperature is lower than the dew point, liquid water will form. The liquid water and dust will mix and gather on the surface of the dust filter bag to form a paste bag.

Secondly, the compressed air for pulse cleaning is also one of the possible causes of condensation. The compressed air temperature is generally far lower than the operating temperature of the dust collector. At the moment of pulse, the low-temperature compressed air will rapidly reduce the temperature of the upper part of the dust filter bag. When it is lower than the dew point temperature, it will cause condensation on the outer surface of the part.

In addition, the air leakage rate of the dust collector is also a possible factor causing condensation. Generally, the air leakage rate of the dust collector is about 1% to 3%. But with the extension of running time, the air leakage rate will increase. If it is in the north, where the winter is severely cold, the problem becomes greater. The higher the air leakage rate, the greater the impact on the local temperature in the dust collector, and the higher the risk that the dust filter bag in the leaked part will stick to the bag due to condensation.

2. Adhesive paste bag

Mainly refers to that due to the relatively high adhesion of dust, although no condensation occurs, the dust still adheres to the surface of the fiber, and the online dust removal system cannot remove it. The reason for the adhesive paste bag may come from the following situations.

(1) The dust itself is relatively viscous, and when it comes in contact with the filter fiber, the intermolecular force is relatively strong. Such as oily particles, ammonium sulfate produced by denitration, nitrate lime used for desulfurization, etc.

(2) Although some dust is not sticky, it is easy to deliquesce. When it is trapped on the surface of the fiber, it will absorb moisture in the air and form a solution on the surface of the fiber.

(3) Some dusts may not have strong adhesion, but they can absorb the moisture in the flue gas and carry out the chemical process of recrystallization, forming new hydraulic substances or crystals, and the formed "crust" covers the filter material. Surfaces, such as: cement clinker, desulfurization products, calcium sulfate.

(4) Even if the dust itself is not sticky, if the dust particles are finer and the water content of the dust is relatively large, the dust can easily be uniformly adsorbed on the surface of the filter material, forming a layer of "floating dust", and the adhesion is not very strong. But it is difficult to remove. The longer the running time, the thicker the "floating ash". This situation may occur in general coal-fired power plants, especially for dust filter bags with a length of more than 6 meters.

3 Operation errors lead to paste bag

(1) Pre-spraying is not carried out as required, so that the oil mist during ignition will directly penetrate into the dust filter bag, resulting in a paste bag.

(2) When the machine is switched on and off, especially before the machine is shut down for a long time, the dust removal operation is not carried out according to the correct procedure.

(3) In case of accidents such as tube bursts in the boiler during operation, the dust filter bag was not properly handled and remedially operated.

The solution of dust filter bag "paste bag"

1. Strictly control the operating temperature to prevent condensation

To prevent the bag-type dust filter bag from condensing, the temperature of the processing gas must be 25℃～35℃ higher than its dew point. When the dust collector is used to process high-temperature and high-humidity gas, a temperature detection and alarm device should be installed at the entrance for monitoring, and thermal insulation materials such as rock wool should be installed outside the shell for insulation.

2. Do a good job of sealing the dust collector body

The dust collector must be strictly sealed, and the air leakage rate is less than 3%. During the equipment installation process, welding quality is of paramount importance. All welding must be carried out in accordance with the corresponding specifications and standards. After the welding is completed, fluorescent powder is used for leakage inspection, and the leakage must be re-welded. The inspection door of the dust collector must be sealed with rubber strips and checked and replaced frequently. Check each unloader and flange carefully to make a good seal. Reducing the air leakage of the dust collector can effectively protect the cloth bag, avoid the occurrence of dust filter bag sticking, and ensure the smooth operation of the equipment under low resistance.

3. Perform correct switch operation

During the start-up and shutdown process (especially long-term shutdown), strictly follow the power-on and turn-off guidelines for procedural operations. For example, before the dust removal system stops running, the wet air in the dust collector must be completely discharged and replaced with dry air. Prevent condensation, that is, after the production equipment stops running, the dust removal fan should run for a period of time before stopping.