Selection of air dust filter bags

1.2 Select according to filter material characteristics

1.2.1 Polyester

Polyester filter materials are usually used in low temperature occasions, and usually do not need to be coated. Only when the emission requirement is less than 30 mg/Nm3, or when the dust is very fine and the humidity is high, the coating is considered.

1.2.2 PTFE

Polytetrafluoroethylene (PTFE), also known as Teflon, is stretched into a strong microporous material with a pore size of 0.1 μm to 2.0 μm and a porosity greater than 80%. It has excellent chemical resistance. Sodium hydroxide and uranium pentafluoride, a strong corrosive agent in the atomic industry, will not corrode, and can withstand cold and heat. It can be used for a long time at -200 ℃ ~ 250 ℃, and has good electrical insulation and surface smoothness. . The PTFE filter material is often treated by technology such as film coating or acupuncture, so as to improve the dust removal efficiency and prolong the service life.

1.2.3 Glass fiber

Glass fiber has good high temperature resistance, tensile strength, acid and alkali resistance and hydrophobicity. However, under the existing scientific and technological conditions, the glass fiber has been subjected to good post-treatment and the application of film coating technology, so that its filtration performance is very good, and it has been widely used in foreign countries, especially in Europe and the United States.

1.2.4 P84

P84 filter bag is a filter material woven from fibers with excellent comprehensive properties developed by an Italian company. Its high temperature resistance is slightly inferior to glass fiber, and its acid and alkali resistance is good. However, due to its special fiber structure, it is usually not used with a film, so the filtration efficiency is not as good as that of a film-coated filter bag, and because of its high price, it is rarely used abroad, especially in the European and American markets.

1.3 Choose according to the nature of dusty gas

1.3.1 Gas temperature

Dust-laden gas temperature is an important factor in the selection of filter bags. Usually, the dust-containing gas less than 130 ℃ is called normal temperature gas, and the dust-containing gas greater than 130 ℃ is called high-temperature gas, so the filter bags can be divided into two categories: the normal temperature filter bags below 130 ℃ and those higher than 130 ℃. High temperature filter bag. To this end, the appropriate filter bag should be selected according to the flue gas temperature. In actual work, some people call 130-200 ℃ gas as medium-temperature gas, but the filter bag is mostly of high-temperature type.

The temperature resistance of the filter bag has two types: "continuous long-term use temperature" and "instantaneous short-term temperature". "Continuous long-term use temperature" refers to the long-term temperature at which the filter bag can be applied and continuously operated, and the filter bag should be selected at this temperature. "Instantaneous short-term temperature" refers to the maximum temperature that the filter bag is not allowed to exceed 10 minutes a day. If the time is too long, the filter bag will soften and deform.

1.3.2 Gas humidity

Dust-containing gas is divided into three states according to relative humidity: dry gas when the relative humidity is below 30%, general state when the relative humidity is between 30% and 80%, and high-humidity gas when the relative humidity of the gas is above 80%. For high-humidity gas, when it is in a high temperature state, especially when the dust-containing gas contains SO2, condensation will occur when the gas is cooled. Not only will this foul and plug the surface of the filter bag, but it will also corrode the materials of construction, so special attention is required.

For moisture-containing gas, the following points should be paid attention to when selecting filter bags:

(1) Moisture-containing gas makes the dust captured on the surface of the filter bag wet and bonded, especially for water-absorbing, deliquescence and wet dust, which will cause the bag to stick. For this reason, filter bags with smooth surface and long fibers such as nylon and glass fiber should be used, and the filter bags should be impregnated with silicone oil and fluorocarbon resin, or acrylic acid and polytetrafluoroethylene should be used on the surface of the filter bags. and other substances for coating treatment. The plastic sintered board and film-coated material have excellent moisture resistance and easy cleaning performance, and should be the first choice for high-humidity gas.

(2) When high temperature and high humidity exist at the same time, it will affect the temperature resistance of the filter bag, especially for materials with poor hydrolysis stability such as nylon, polyester, and imide, which should be avoided as much as possible.

(3) For moisture-containing gas, circular filter bags should be used in the design of dust removal filter bags, and flat filter bags and diamond-shaped filter bags (except plastic sintered plates) with complex shapes and very compact arrangements should not be used as much as possible.

(4) The inlet temperature of the dust-laden gas in the dust collector should be 10-30 °C higher than the dew point temperature of the gas.