How to distinguish the Dust collector "blockage bag" and "burning bag"

When the bag is operated in the dust collector, the filter performance is often lost or partially lost for one reason or another, and the actual service life of the bag is greatly shortened as expected, so that the maintenance and operation cost of the factory is greatly increased. “blockage bag” and “burning bag” are typical problems. Although there is only one word difference between them, the causes and solutions of the faults are very different.

Dust collector "blockage bag"

What is a "blockage bag"?

“blockage bag” is the process of coagulation, adhesion or knotting of dust on the filter surface of filter bag or filter material in the condition of high humidity or oily substance contacting with filter material during long-term operation or shutdown of dust bag. The shell cannot be effectively removed by the online cleaning system, resulting in a significant increase in running resistance.

The harm of "blockage bag"?

After the dust bag is wrapped, the dust is densely covered on the surface of the filter bag, so that the effective filtration area of the filter material is greatly reduced, the air permeability of the filter material is drastically decreased, the running resistance becomes high, and the load of the induced draft fan is increased, resulting in energy. The consumption is rising, and even the exhaust fan can be overwhelmed and unable to operate. At the same time, the pressure drop of the dust bag is high, so that the online cleaning system is frequently cleaned, which not only consumes a large amount of compressed air, but also causes serious loss of mechanical strength of the filter material, and the service life is greatly shortened.

The reason for the formation of "blockage bag":

1. Condensation blockage bag

Under normal circumstances, the operating temperature requirement of the bag filter must be higher than the acid dew point temperature of 25 ° C or more, which is safe for the bag. This is mainly to avoid the occurrence of condensation. When the operating temperature is lower than the dew point, liquid water is formed, and the liquid water is mixed with the dust and collected on the surface of the filter bag to form blockage bag.

Second, pulsed clean air is one of the possible causes of condensation. The compressed air temperature is generally much lower than the operating temperature of the precipitator. At the moment of the pulse, the low temperature compressed air will rapidly lower the temperature of the upper part of the filter bag. When it is lower than the dew point temperature, condensation will appear on the outer surface of the filter bag at the part.

In addition, the air leakage rate of the precipitator is also a possible cause of condensation. The air leakage rate of the general dust collector is about 1% to 2%. However, as the running time increases, the air leakage rate will increase. If it is in the cold winter, the problem becomes bigger. The higher the air leakage rate, the greater the influence on the local temperature in the dust collector, and the risk of the bag in the leaking portion of the leaking portion is higher and higher.

2. Adhesive blockage bag

Mainly because the dust adhesion is relatively large, although no condensation occurs, the dust still adheres to the surface of the fiber, and the online cleaning system cannot remove it. The reason for the adhesive blockage bag may be due to the following conditions.

(1) The viscosity of the dust itself is relatively large, and when it is in contact with the filter fiber, the intermolecular force is relatively strong. For example, oily particles, ammonium sulfate formed by denitrification, and limestone used for desulfurization.

(2) Although some dusts are not sticky, they are easily deliquescent. When they are trapped on the surface of the fiber, they absorb moisture from the air and form a solution on the surface of the fiber.

(3) Some dust adhesion may not be strong, but it can absorb the moisture in the flue gas and carry out the chemical process of recrystallization, to generate new hydraulic substances or crystals, and the formed "crust" covers the filter material. surface. For example: cement clinker, desulfurization products, Calcium sulfate.

(4) Even if the dust itself is not sticky, if the dust particles are fine and the water content of the dust is relatively large, the dust is easily adsorbed evenly on the surface of the filter material to form a layer of “floating ash”, and the adhesion is not very strong. But it is difficult to remove. The longer the running time, the thicker the “gray”. This may happen in general coal-fired power plants, especially for filter bags longer than 6 meters.

3. Operation errors

(1) The pre-spraying is not carried out as required, so that the oil mist in the ignition directly invades the filter material, resulting in blockage bag.

(2) When the switch is turned on (especially before a long shutdown), the cleaning operation is not performed according to the correct procedure.

(3) The filter bag is not properly treated and remedied when there is an accident such as a pipe burst during operation.

Solution of "blockage bag"

1. Strictly control the operating temperature to prevent condensation.

To prevent the bag filter from dewing the bag, it is necessary to keep the temperature of the process gas above its dew point of 25 ° C to 35 ° C. When the dust collector is used to treat high temperature and high humidity gas, a temperature detection alarm device should be installed at the entrance for monitoring, and thermal insulation materials such as rock wool should be installed outside the casing for heat preservation.

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

The dust collector must be tightly sealed and the air leakage rate is less than 3%. Welding quality is critical during the installation of the equipment. All welding must be carried out in accordance with the relevant specifications and standards. After the welding is completed, the phosphors are used for leak inspection, and the leaks must be re-welded. The inspection door of the dust collector must be sealed with rubber strips and checked frequently. Carefully inspect the unloader and flange to seal. Reducing the air leakage of the dust collector can effectively protect the filter bag, avoid the occurrence of blockage bag, and ensure the smooth running of the equipment under low resistance.

3. Perform the correct power on/off operation.

During the startup and shutdown process (especially for long time shutdown), the program operation should be carried out in strict accordance with the instructions of the switch machine. For example, before the dust removal system stops running, the wet gas in the dust collector must be completely discharged and replaced with dry air. To prevent condensation, that is, after the production equipment has stopped running, the dust removal fan should be extended for a period of time before it stops.

Dust collector "burning bag"

In addition to the high temperature burnout of the bag filter, the damage of sparks in the flue gas to the bag of the dust collector is also quite serious, such as coke oven, drying kiln, chain furnace, cupola, electric furnace, blast furnace, mixed iron furnace, etc. in the production process. There will be a large number of sparks entering the smoke. If the sparks is not treated in time, especially when the dust layer on the surface of the filter bag is thin, sparks will burn the filter bag and form an irregular round hole. When the dust layer on the surface of the filter bag is thin, sparks will not directly burn through the filter bag, and a deep color baking mark will be formed on the surface of the filter bag.

Reasons for "burning bags":

1. High temperature burnt dust bag

High temperature damage to the dust bag is fatal. For example, in a pulverized coal drying kiln, since the pulverized coal particles are very fine and particularly sticky after drying, the cleaning is not ideal, so that a large amount of dried coal powder remains on the surface of the filter bag, and the dried coal powder has a very low ignition point. When the high-temperature flue gas enters the dust collector, it will quickly ignite the coal powder on the surface of the filter bag, causing the dust bag and the dust-removing skeleton of the entire dust collector to be completely burned.

2. Sparks burns through the dust bag

In addition to the high temperature burnout, the damage of sparks in the flue gas to the dust bag is also very serious. In the production process, such as coke oven, drying kiln, chain furnace, cupola, electric furnace, blast furnace, mixed iron furnace, etc., a large number of sparks will be mixed into the flue gas, such as the treatment of sparks is not timely, especially the dust layer on the surface of the dust filter bag. When it is thin, sparks will burn the dust bag and form an irregular round hole. However, when the dust layer on the surface of the dust bag is thick, sparks will not directly burn the dust bag, which will cause a deep color baking sparks on the surface of the dust bag.

3. High temperature shrink dust bag

Another kind of damage of high temperature flue gas to dust bag is high temperature shrinkage. Although the temperature of each filter material is different, when the flue gas temperature exceeds its use temperature, if the warp shrinkage rate is too large, the dust bag will be in length. The size in the direction is shortened, and the bottom of the dust bag is held against the skeleton and damaged by force. If the latitudinal heat shrinkage of the dust bag is too large, the dust bag will become smaller in the radial direction, and the dust bag will be tightly hung on the skeleton, and even the skeleton cannot be extracted. Therefore, the dust bag is always under stress, causing the filter bag to shrink, deform, become brittle, accelerate the strength loss, and shorten the life of the filter bag. Since the filter bag is tightly hung on the skeleton after being deformed, the filter bag is difficult to be deformed during the cleaning, which is not favorable for the spray cleaning, resulting in high resistance of the filter bag.

4. Ash bucket dust storage heat burning dust bag

After the high-temperature dust is collected into the ash bucket, if it cannot be discharged in time, the dust will accumulate in the ash bucket for a long time, causing the temperature inside the ash bucket to rise continuously. The dust-removing cloth bag will become brittle and hard under long-term baking at high temperature. Burnt, especially the flammable substances contained in the dust, will burn in the ash hopper, thus burning the dust bag.

Solution of "burning bag"

If it is necessary to cool the exhaust gas, when using the cooling method, pay attention to the humidity of the air and whether it contains acid and alkali components. At the same time, try to ensure that the temperature of the exhaust gas treated by the dust collector is higher than the dew point and avoid water droplets directly entering the filter bag.

In order to prevent sparks from entering the dust collector and causing the filter bag to be burnt, pretreatment methods may be used. For example, a protective layer may be pre-coated on the surface of the filter bag, and kaolin, limestone powder or the like may be used. At the same time, it is necessary to prevent unburned carbonaceous materials from being burned in the dust collector.

There are many reasons for the “blockage bag” and “burning bag” of the dust collector filter bag. Therefore, in the daily operation and maintenance process, care should be taken to avoid these situations. Regularly replace the powder layer on the surface of the filter bag and avoid this from the source. Two types of failures. If it has already occurred, relevant emergency treatment should be carried out in time to avoid further deterioration.