The main factors affecting the service life of dust bag filters

In industrial smoke removal, due to the differences in the characteristics of steel, cement, power generation, waste incineration and other industries and the company's own different working conditions, the following factors that affect the service life of the dust bag filters need to be considered.

1) Smoke volume and wind speed

When the smoke and dust enters the dust collector, the dust with a large diameter falls or falls off under the interception of the filter bag due to the difference in dust diameter and weight, and the dust with a small particle size generates kinetic energy under the action of the wind speed. When the dust is trapped by the bag filter and is collected on the cloth bag, the kinetic energy is converted to zero, which will inevitably cause impact on the bag filter; under the action of kinetic energy, the dust will constantly flush the bag filter. If the smoke contains large amount of dust and the wind speed of filtration is high, bag filters will withstand thousands of times friction and erosion, and the surface fiber of the bag filters can not withstand the erosion and fall off, damaging filtration efficiency of the bag filters. Therefore, when the dust content and wind speed are high, the wear resistance of the needle felt must be considered.

2) Size of smoke particle

The dust particles in the coal-fired flue gas, like the blades, hit the surface of the bag filter under the action of the high-speed air flow. Because of their different particle sizes, the impact force on the dust filter bag is not the same, and the dust also contains a large number of acidic substances and alkaline substances. Their diameter is very small, when intercepted by the cloth bag, it still cannot fall off due to the influence of the filtration wind speed, and it remains on the surface of the filter material or enters the inside of the fiber. When combined with water vapor, it will be stuck to the filter bag and lead to chemical change of the filter material to cause corrosion. Therefore, the particle size distribution of the dust is a necessary consideration when selecting the filter materials.

3) Chemical composition of gases and smoke

In industrial dust removal, the smoke generated from coal combustion contains acid gases mainly composed of CO, CO2, NO2, and SO2. This part produces a chemical reaction with the water vapor in the smoke to generate strong acid, which is corrosive. The higher the temperature of working conditions, the faster the chemical corrosion. Therefore, the chemical composition and content of the smoke is one of the essential elements in the analysis of operating conditions.

The solid dust and the moisture in the smoke stick to the surface of the filter bag after binding, or remain inside the fiber and block the filtration hole, which will greatly affect the service life of the filter bag.

4) Continuous working temperature and extreme temperature

Working temperature is one of the important indicators for the use of filter materials, and the temperature determines the service life. Filters can be divided according to the withstanding temperature: ambient temperature filter material (less than 150 °C), medium temperature filter material (150 °C -180 °C), high temperature filter material (160 °C -300 °C). The filter material can only prolong its service life at the best use temperature. If the temperature is too high, the chemical properties of the filter material will be lost. In particular, filter materials with low flame retardancy will easily cause fire. However, when the temperature is too low, there will be condensation and corrosion of the filter materials and the service life of will be greatly shortened.

5) Water content and working temperature

If the filter material is below the working temperature, the service life of the filter material will not be reduced. However, if the water vapor content in the working environment is too high and the temperature of the exhaust gas is too low, the service life will be seriously affected. Such as PE filter material, the working temperature is 130-150 degrees, but the smoke temperature of the steel pipe factory is only 70-90 degrees, and the humidity is very high. Because the temperature is just at the dew point, the water vapor will be condensed into liquid water.The mixture of water and smoke is solidified on the surface of the PE filter bag and corrodes the filter material, which not only affects the filtration accuracy of the PE filter bag, but also shortens the service life of the filter material by 80% to 90%. Under this working condition, it is necessary to effectively increase the temperature of the smoke, and install insulation measures for the pipeline and the dust collector.

6) Air flow of dust cleaning

Air flow of dust cleaning also affects the life of the filter bag. When the filter bag is used for a period of time, the surface of the filter bag will be covered with a layer of smoke particle compound, and it is necessary to clean the bag filter. If the distribution and the direction of the air flow of the dust cleaning are unreasonable, it will cause direct impact on the surface of the bag. The surface of the filter bag is not evenly stressed, and the surface that is subjected to the pressure of the air flow will wear or break even faster. Dust bag filters work under these conditions for a long period of time, resulting in a significant reduction in the service life of the entire bag filter. Our common solution is to install the Venturi tube above the keel of the bag filter, which plays a guiding role in dust cleaning air flow, so that the vertical air flow bag filters can be cleaned to avoid direct flushing of the surface of the bag filters.