Filter Bags Are Selected According To The Nature Of Dust Gas

- Nov 21, 2019-

Filter bags are selected according to the nature of dust gas


(1) gas temperature. Dust gas temperature is an important factor in selection of filter bag. Usually less than 130℃ dusty gas called normal temperature gas, more than 130℃ dusty gas called high temperature gas, so the filter bag can be divided into two categories: normal temperature filter bag and high temperature filter bag. Therefore, suitable filter bags should be selected according to the flue gas temperature. Some people put 130-170℃ called medium temperature gas, but the filter bag choice of high temperature type.


The temperature resistance of the filter bag can be divided into "continuous long-term service temperature" and "instantaneous short-term temperature". "Continuous long-term service temperature" refers to the applicable and continuous long-term operating temperature of the filter bag, and the filter bag should be selected at this temperature. "Instantaneous short-term temperature" means that the maximum temperature of the filter bag is not allowed to exceed 10min per day. If the time is too long, the filter bag will be softened and deformed.


(2) 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 and easy to generate static electricity. Like high humidity gas, dust is easy to adhere to and difficult to remove ash. Relative humidity in 30% ~ 80% for the general state, dust collector working state is the best. When the relative humidity of the gas is above 80%, it is high humidity gas. When the high humidity gas is at high temperature, especially when SO3 is contained in the dust gas, condensation will occur when the gas is cooled. This will not only scale and block the surface of the filter bag, but also corrode the structural materials, causing serious damage to the dust removal device and filter bag, etc. Therefore, special attention should be paid to the following points when selecting the filter bag for the wet gas:


1) the wet gas makes the dust collected on the surface of the filter bag wetting and bonding, especially for the water absorption, moisture and wetting dust, which will cause the paste bag. To this end should choose nylon and glass fiber, such as smooth surface, long fiber, easy to clean ash filter bag, and it is appropriate to use silicone oil, fluorocarbon resin impregnation treatment, or use acrylic acid, polytetrafluoroethylene and other substances on the surface of the filter bag coating treatment. Plastic-fired plate and coated materials have excellent moisture resistance and easy ash removal performance. But as the first choice of high humidity gas should be waterproof and oil-proof dust bag.  


2) when high temperature and high humidity exist at the same time, the temperature resistance of the filter bag will be affected, especially for materials with poor hydrolysis stability such as nylon, polyester, and linamide, which should be avoided as far as possible.


3) circular filter bag should be adopted in the design of dedusting filter bag for wet gas, and flat filter bag and diamond filter bag with complicated shape and very compact layout should be avoided as far as possible (except plastic burning plate).


4) the inlet temperature of dust-containing gas of the dust collector should be higher than 30℃ above the dew-point temperature of gas to avoid paste bags.


5) chemical properties of gas. In all kinds of furnace exhaust 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 impact. For this reason, the selection of dust filter bag should be considered, so as not to cause unnecessary losses.


Polyester fiber has good resistance to temperature and chemistry at room temperature, but has poor resistance to chemistry at high temperature. Polyphenylene sulfide fiber has good resistance to high temperature and acid and alkali corrosion, and is suitable for dust removal of coal flue gas. However, its antioxidant capacity is poor. Although polyimide fiber can make up for its deficiency, its hydrolysis stability is not ideal. As the "king of plastics" polytetrafluoroethylene fiber has the best chemical resistance, but the price is more expensive. In the selection of filter materials, must be based on the chemical composition of dust gas, grasp the composition, grasp the main factors, for comprehensive consideration.

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