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How to choose the dust collector filter bag?

Time: 2018-01-29

Dust filter bag can be called the heart of the dust collector, filter bag selection is crucial, it directly affects the dust removal effect, dust filter bag fabric and design should pursue efficient filtration, easy to dust stripping and durable effect. Selection of filter bags should be selected from the following aspects: gas temperature, humidity and chemical; particle size; dust concentration; filter wind speed; cleaning methods and other factors considered.


Filter bag selection principle

And precautions

filter bag is generally based on the nature of dust-laden gases, the nature of the dust and dust cleaning methods of different options filter bag, the choice should follow the following principles:

filter bag performance should meet the general conditions of production and dust removal process and special requirements.

In the above premise, the filter bag should be as long as possible to choose long life, it is because the long service life not only can save operating costs, but also to meet the long-term gas emissions requirements.

filter filter bag selection should be a comprehensive comparison of various sorts should not be used in a so-called "good" filter bag to adapt to a variety of working conditions.

In the nature of gas, dust and cleaning methods, should seize the main factors to choose filter bag, such as high temperature gas, corrosive gases, combustible dust and so on.


According to dusty gas

Nature choice

gas temperature. Dust gas temperature is an important factor in filter bag selection. Usually less than 130 dust gas called room temperature gas, dust gas is greater than 130 called high temperature gas, so the filter bags can be divided into two categories: the normal temperature filter bag and high temperature filter bag. Therefore, the appropriate filter bag should be selected according to the flue gas temperature. Some people called 130-170 temperature, but the filter bag and more high-temperature type.

The temperature of the bag has "continuous long-term use temperature" "instant short-term temperature" two. "Continuous long-term use temperature" refers to the filter bag can be applied to the continuous operation of the long-term temperature, the temperature should be used to filter bag. "Instantaneous short-term temperature" refers to the maximum daily temperature of the filter bag is not allowed more than 10min, the time is too long, the bag will soften the deformation.

gas humidity. Dust gas is divided into three states according to the relative humidity: when the relative humidity is below 30%, it is dry gas, which is easy to generate static electricity. Like the high-humidity gas, the dust is easy to attach and difficult to clean. Relative humidity of 30% to 80% for the general state, the best working condition of the precipitator. When the relative humidity of gas is above 80%, it is high-humidity gas. When the high-humidity gas is in the high temperature state, especially the gas containing SO3 in the dust-containing gas will cause condensation. This will not only make the bag surface fouling, clogging, but also corrosion of structural materials, dust removal device, filter bag, etc. caused serious damage, it is necessary to pay special attention to the selection of wet gas bag should pay attention to the following points:

1) Moist air causes the dust trapped on the surface of the filter bag to be wet-bonded, especially for water-absorbing, deliquescent and wetting dusts that cause the bagging. This should be used such as nylon and glass fiber surface smooth, long fiber, easy to clean the filter bag, and the bag should be used silicone oil, fluorocarbon resin invasion treatment, or in the bag surface using acrylic, polytetrafluoroethylene Substance such as coating. Molded board and film material has excellent moisture resistance and easy to clean performance. But as the first choice of high humidity gas should be waterproof oil dust bag.



2) When the high temperature and high humidity will affect the temperature resistance of the filter bag, especially for cotton, polyester, imide and other hydrolytic stability of the material is even more so, should be avoided as much as possible.

3) It is advisable to adopt a circular filter bag for the design of the filter bag with moisture contained in the wet gas. Try not to use the flat filter bag and the diamond filter bag (except the plastic burning board) with complicated shapes and shapes.

4) dust collector dust inlet temperature should be higher than the gas dew point temperature above 30 , in order to avoid paste bag.

5) Gas chemistry. In a variety of kiln exhaust gas and chemical waste, often contain acid, alkali, oxidants, organic solvents and other chemical composition, and often by temperature, humidity and other factors affect the cross. This selection of dust filter bag should be considered thoroughly, so as to avoid unnecessary losses.

Polyester fiber has good temperature resistance and chemical resistance at normal temperature, but its chemical resistance is worse under high temperature conditions. Polyphenylene sulfide fiber has good performance of high temperature resistance and acid and alkali corrosion resistance, suitable for coal-fired flue gas dust removal, but the antioxidant capacity is poor, although the polyimide fiber can make up for its deficiencies, but the hydrolytic stability is not ideal. As the "plastic king" PTFE fiber has the best chemical resistance, but the price is more expensive. In the selection of media, we must base on the chemical composition of dust-laden gas, seize the ingredients, to seize the main factors for consideration.


According to the choice of dust properties

dust wettability and adhesion. Dust wettability, wettability through the formation of capillary action between dust particles to complete, and the atomic chain of dust, the state and the surface tension of liquid and other factors, can be used to characterize the wetting angle. Usually less than 60 degrees called hydrophilic, more than 90 degrees are called hydrophobic. Hygroscopic dust in its humidity increases, the cohesion of the particles, the viscous force increases, the mobility, charge decreases, the adhesion to the surface of the bag over time, cleaning failure, dust cake knot.

Some dust such as CaO, CaCl2, KCL, MgCL2, NaCO3 after moisture absorption further chemical reaction, the nature and morphology have changed, called the deliquescence. After deliquescence, the dust capped the filter bag surface, which is the most taboo filter bag.

For wettability, deliquescence of dust, filter media should pay attention to the choice of filter material smooth, non-cashmere and gift of water, of which plastic film covered plastic bag as the best.

Wetting strong dust many strong adhesion, in fact, and sticky inseparable link. If the filter bag adhesion is too small, will lose the ability to capture dust, and adhesion is too large and cause dust cohesion, cleaning difficulties.

For the strong adhesion of dust should also use the filament non-woven fabric filter bag, or the surface singeing, calendaring, mirror-processing needle felt filter bag, impregnation, coating, coating technology should make full use of. Speaking from the material on the dust bag nylon, fiberglass better than other varieties.




dust flammability and chargeability. Some dust may burn or explode in the air if sparks are exposed to certain concentrations. Combustibility of dust and its particle size, composition, concentration, heat of combustion and burning rate and other factors. The smaller the particle size, the larger the surface area, the easier it ignites. An important condition of dust explosion is airtightness. In this space, the lower limit of its explosion concentration is generally tens to hundreds of grams per cubic meter. The higher the heat of combustion and the burning speed of dust, the greater its explosive power.

Dust combustion or explosion sources of fire are usually caused by friction sparks, electrostatic sparks, glowing particles, etc., of which the charge-end is the most damaging. This is because the chemical fiber filter is because the chemical fiber filter is usually easy to charge, if the dust is very easy to produce sparks while charging, so for flammable and easily charged dust such as pulverized coal, coke powder, alumina powder and magnesium Powder, etc., should choose flame retardant filter and antistatic dust bag.

Generally believed that the oxygen index greater than 30 fibers mixed with conductive fibers, the filter material in the longitudinal direction or have conductive properties, the resistance is less than 1 * 109 ohms. Commonly used conductive fibers are stainless steel fibers and modified (charcoal) chemical fibers. Compared with the former two, the conductivity is stable and reliable, while the latter is easy to decline after a certain period of time. The amount of conductive fiber mixed is about 2% ~ 5% of the basic fiber.

dust flow and friction. Dust flow and friction strong, it will directly wear bags, reducing service life. Surface roughness, irregular diamond particles than the spherical surface of the abrasive wear 10 times larger. Dust particles with a particle size of about 90 microns have the highest wear and tear, while when the particle size is reduced to 5 to 10 microns, the wear is very weak. Abrasion and airflow velocity of 2 to 30000 square and the grain of 1.5 is proportional to the square, therefore, the air flow velocity and its uniformity must be strictly controlled. In the common dust, aluminum powder, silicon powder, coke powder, carbon powder, sintered ore, etc. belong to high wear dust. Wear-resistant dust should be used for good wear-resistant filter bag.

Dust filter bag wear parts and forms varied, according to experience, filter bag wear in the lower part, it is because the upper filter filter bag speed is low, the concentration of gas dust is small. In order to prevent the lower part of the filter bag worn, the design should limit the rate of air flow in the lower part of the bag.

For the strong wear of dust, filter bag should pay attention to three points:

chemical fiber is better than glass fiber, expanded glass fiber is better than ordinary glass, fine, short, curly fiber is better than coarse, long, smooth fiber.

felt material should be acupuncture way to strengthen the interwoven between fibers, the fabric satin fabric optimal, brushed fabric surface is to improve the wear resistance measures, but the felt, satin fabric and fleece Bag will increase the resistance value.

For ordinary filter surface coating, calendering and other post-treatment can also improve the wear resistance. For glass fiber filter bags, silicone oil, graphite, PTFE resin treatment can improve the wear-resistant folding. However, the membrane filter for abrasive conditions, the film will wear too early to lose the role of film.