Dust filter bag selection
Choose according to the properties of dust gas
Gas temperature. Dust gas temperature is an important factor in the selection of filter bag. Generally, dust-containing gas less than 130℃ is called normal temperature gas, and dust-containing gas greater than 130℃ is called high temperature gas. Therefore, filter bags can be divided into two categories: normal temperature filter bag and high temperature filter bag. Therefore, appropriate filter bags should be selected according to the flue gas temperature. Some people put 130-170℃ call medium temperature gas, but filter bag more choose high temperature type.
The temperature tolerance of filter bag has two kinds: "continuous long-term service temperature" and "instantaneous short-term temperature". "Continuous long-term service temperature" refers to the long-term temperature at which the filter bag can be used for continuous operation, and the filter bag shall be selected at this temperature. "Instantaneous short-term temperature" refers to the maximum temperature of the filter bag that is not allowed to exceed 10min per day. If the temperature is too long, the filter bag will be softened and deformed.
(2) gas humidity. Dust-containing gas is divided into three states according to the relative humidity: when the relative humidity is less than 30%, it is a dry gas, easy to generate electrostatic, and like high-humidity gas, dust is easy to adhere and difficult to clear ash. The relative humidity is in the general condition of 30% ~ 80%, and the dust collector is in the best working condition. When the relative humidity of the gas is above 80%, it is considered as high humidity gas. When the high humidity gas is in the high temperature state, especially when the dust gas contains SO3, the phenomenon of condensation will occur in the gas cooling. This will not only cause fouling and blockage on the surface of filter bag, but also corrode structural materials and cause serious damage to dust removal device and filter bag. Therefore, special attention should be paid to the following points when selecting filter bag with wet gas:
1) the wet gas will moisten and bond the dust collected on the surface of the filter bag, especially the hygroscopicity, deliquescence and wetting dust, which will cause the pasting of the bag. For this reason, filter bags with smooth surface, long fiber and easy ash removal, such as polyamide and glass fiber, should be selected, and should be impregnated with silicone oil and fluorocarbon resin, or coated with acrylic acid, polytetrafluoroethylene and other materials on the surface of filter bags. Plastic burning board and film coated materials have excellent wet resistance and easy to clean ash. But as a high humidity gas preferred should be waterproof oil - proof dust - removal cloth bag.
2) when high temperature and high humidity exist simultaneously, the temperature resistance of filter bag will be affected, especially for materials with poor hydrolysis stability, such as cotton fiber, polyester, imide, etc., which should be avoided as far as possible.
3) circular filter bag should be used for dedusting filter bag with wet gas, and flat and diamond filter bag with complicated shape and compact arrangement should not be used as far as possible (except plastic burning board).
4) the inlet temperature of the dust containing gas of the dust collector should be above 30℃ above the dew-point temperature of the gas to avoid bagging.
5) chemical properties of gases. In various furnace exhaust gas and chemical waste gas, often contain acid, alkali, oxidant, organic solvent and other chemical components, and often by temperature, humidity and other factors of the cross influence. Therefore, the selection of dust filter bag should be considered, so as to avoid unnecessary losses.
Polyester fiber has good temperature and chemical resistance at room temperature, but at high temperature, chemical resistance is poor. Polyphenylene sulfide fiber has good properties of resisting high temperature and acid and alkali corrosion, and is suitable for dust removal of coal-burning flue gas. Teflon, the "king of plastics", has the best chemical resistance but is expensive. In the selection of filter material, must be based on the chemical composition of dust gas, grasp the composition, grasp the main factors, comprehensive consideration.