Selection of Dust Filter Material 1-Gas Chemical Characteristics

The dust filter bag is the core part of the bag filter. The performance and quality of the filter material of the dust bag directly affect the performance and operation of the dust collector. When selecting the dust filter material, the physical and chemical properties of dust-containing gas and dust, such as gas composition and temperature must be considered. , Humidity, dust particle size, density, concentration, cohesiveness, abrasiveness, flammability, etc. The choice of dust removal filter is also related to the dust removal method of the dust collector. This article describes in detail how to choose dust removal according to the characteristics of dust-containing gas Filter material.

 Dust filter materials are mostly made of fibers, each of which has different physical and chemical properties. It is impossible to have completely excellent performance in adapting to temperature, humidity, and chemical resistance. Therefore, the selection of dust removal filter materials must fully grasp the characteristics of dust-containing gas, and carefully select reasonable selections according to the conditions that various fibers are adapted to. The following table shows the temperature resistance of commonly used fibers and the ranking of their main physical and chemical properties for reference when choosing.

1. Selection of dust removal filter material-temperature of dust-containing gas

 The temperature of the dust-containing gas is the primary factor in the selection of the dust removal filter. The table lists the temperature of various materials for continuous and long-term use, as well as the upper limit temperature of the instantaneous use that is allowed due to equipment and management reasons. According to the continuous use temperature (dry state), the dust removal filter material is divided into 3 categories: lower than 130°C is normal temperature filter material; 130-200°C is medium temperature filter material; higher than 200°C is high temperature filter material, usually according to the continuous use temperature. To determine the dust removal filter material, for working conditions where the gas temperature is constantly fluctuating, a material with a slightly larger safety factor should be selected. The continuous use temperature of the selected dust removal filter material should not be lower than the upper limit of the temperature fluctuation range. There are two options for high-temperature flue gas, namely, direct selection of high-temperature filter material, or cooling measures followed by selection of room temperature filter material. It is advisable to determine the solution and the corresponding type of dust removal filter material after technical and economic analysis and comparison.

2. Selection of dust removal filter material-humidity of dusty gas

 The humidity of dust-containing gas indicates how much water vapor is contained in the gas, and is usually characterized by the volume percentage of water vapor or relative humidity of the dust-containing gas. In the field of ventilation and dust removal, when the volume percentage is greater than 8% or the relative humidity exceeds 80%, it is called wet dusty gas. For the wet dusty gas, the following points should be paid attention to in the selection of dust removal filter material and system design:

⑴The wet dust-containing gas makes the dust collected on the surface of the dust removal cloth bag wet and condense, especially the water-absorbent and slippery dust, which can cause the paste bag. For this reason, a dust-removing filter material with a smooth surface and a fiber material suitable for cleaning should be selected. , And it is advisable to use silicone oil and fluorocarbon resin impregnation treatment for the dust removal filter material. At present, the most common application in the industry is the use of PTFE emulsion for impregnation treatment. In addition, the newly developed PTFE covering filter material also has excellent moisture resistance and easy dust cleaning performance.

⑵When high temperature and high humidity coexist, it will affect the temperature resistance of the dust removal filter material, especially for materials with poor hydrolysis stability such as polyamide (nylon), polyester (polyester) and imide (aramid). The following table lists the commonly used temperature values in dry and wet conditions in the continuous use temperature column, which should be selected as appropriate during design.

⑶ Circular filter bags should be used in the design of dust removal cloth bags for wet dusty gas, and flat cloth bags with complex shapes and compact layout should not be used as far as possible.

⑷When designing the system working condition for wet dusty gas, the selected working condition temperature of the dust collector should be 10 to 20℃ higher than the gas dew point temperature. For this, high temperature gas (hot air) can be mixed, and the dust collector box can be heated. Measures such as heat preservation.

3. Selection of dust removal filter material-corrosiveness of dust-containing gas

Generally, the chemical gas and various kiln flue gas often contain acid, alkali, oxidant, organic solvent and other chemical components. The chemical resistance of different fibers is different. Table 1 lists the order of pros and cons of various fiber-pushing inorganic acids, organic acids, alkalis, oxidants, and organic solvents.

 The chemical resistance of the dust filter material is often affected by multiple factors such as temperature and humidity. For example, the polyester fiber filter material that is widely used now has good mechanical properties and acid and alkali resistance at room temperature. It is very sensitive to water vapor at high temperature, and is prone to hydrolysis, which greatly reduces the strength: polypropylene fiber has more comprehensive chemical resistance, but it will be significantly deteriorated under working conditions above 80°C; aramid fiber is more Polyester fiber has higher temperature resistance, but poor chemical resistance under high temperature conditions; PPS fiber has good high temperature resistance and acid and alkali corrosion resistance. It is suitable for dust removal from coal-fired boiler flue gas, but has better antioxidant capacity. Poor, it can only be used when the O2 content is less than or equal to 10%; P84 has better oxidation resistance than PPS, but its hydrolytic stability is not ideal; as the "Plastic King" PTFE fiber has strong chemical resistance Sex, but the strength is lower and the price is higher. When selecting materials, it is necessary to grasp the main factors according to the chemical composition of the dust-containing gas, comprehensively compare, and choose the best choice.

4. Selection of dust removal filter material-flammability and explosiveness containing raw gas

Some of the flue gas produced during metal smelting and chemical production contains hydrogen, carbon monoxide, methane, propane and acetylene and other combustible gases, or contains coal dust and combustible dust such as magnesium and aluminum. It is used in light industry, food processing and other industries. The production tail gas contains flammable organic dust. When they are mixed with oxygen and air into other combustion-supporting gases, and their concentration reaches a certain range, they will explode when they encounter a fire source. For this, a flame-retardant anti-static dust removal filter material should be selected.