Dust Collect Filter Bag Series

November 24,2021

Detailed Explanation of Basic Knowledge of Filter Material

(Part 1)

In order to achieve the goal of ultra-low emission of flue gas pollutants, a flue gas governance environmental protection island governance system came into being. It provides multiple technical routes through different combinations of configurations to meet the needs of different customers while achieving coordinated improvement of upstream and downstream pollutant governance effect.

The dust filter bag is the first step in the flue gas environmental protection island system, and it is also the key to the subsequent flue gas treatment. This article will explain in detail the basic knowledge of filter materials from three aspects: raw material selection, filter material production process, and main product characteristics and performance parameters.

Raw material selection

The dust filter bag is made of fiber as the raw material, which can be a single fiber or a mixture of multiple fibers. Generally, it can be divided into three categories: room temperature materials, high temperature organic materials and high temperature inorganic materials.

Normal temperature materials

1) Polypropylene fiber (Polypropylene filter felt)

Density 0.91g/cm3, melting point 150℃, breaking strength 3.4g/d, limiting oxygen index 19, thermoplastic fiber;

Filtration performance: can withstand an operating temperature of 80°C under dry conditions; an instantaneous use temperature of 100°C. It has good acid and alkali resistance, moisture resistance, and weak oxidation resistance.

2) Polyester fiber (Polyester filter felt)

Density 1.38g/cm3, melting point 256°C, breaking strength 5.5g/d, limiting oxygen index 22, thermoplastic fiber.

Filtration performance: it can withstand the operating temperature of 130°C under dry conditions; it will become hard when continuously working above 130°C; it will fade and become brittle. Poor hydrolysis resistance.

3) Acrylonitrile homopolymer fiber (acrylic filter felt)

The glass transition temperature of 1040C shows good resistance to organic solvents, oxidants, inorganic and organic acids when the temperature is lower than 1250C. Acrylonitrile homopolymer does not hydrolyze, so it can be used to replace polyester in low temperature, chemically corroded and humid places. The copolymer of acrylonitrile is not resistant to hydrolysis; thermoset fiber;

High temperature organic materials

1) PPS fiber (Polyphenylene sulfide filter felt)

The density is 1.38g/cm3, the breaking strength is 5.0g/d, and the limiting oxygen index is 34. It has the characteristics of heat resistance, chemical resistance and flame retardancy.

It can be used continuously at a temperature of 190℃, and the instantaneous temperature can reach 200℃; it has very good chemical resistance and is a fiber with strong acid and alkali resistance; its disadvantage is that the oxidation resistance is poor, and the higher the oxygen content, it is used the temperature will be lower.

2) Meta-aramid fiber (aramid filter felt)

The density is 1.3g/cm3, the breaking strength is 4.9g/d, and the limiting oxygen index is 29. It is a non-thermoplastic fiber. It will only be carbonized or decomposed into small molecules at high temperature such as 371℃;

It can withstand an operating temperature of 200°C under dry conditions; it is a hydrolyzable fiber, which will be quickly hydrolyzed and damaged when exposed to high temperature and organic chemical components and moisture; it can be applied under a moisture concentration of 10% and a weak acid and neutral environment Operating temperature of 190℃, especially afraid of SOX corrosion;

3) P84 fiber (PI polyimide filter felt)

The density is 1.40g/cm3, and the limiting oxygen index is 38. It is an irregular trilobe-shaped section, which increases the surface area for filtration; it has outstanding high and low temperature resistance, flame retardancy, electrical insulation and radiation resistance.

Filtration performance: It can be used continuously below 260℃, and the instantaneous temperature can reach 280℃ (accumulated less than 200 hours per year); it has a certain degree of hydrolysis;

4) PTFE fiber (Poly tetra fluoro ethylene ptfe filter felt)

Density 2.2g/cm3, melting point ~350℃, good thermal stability, chemical stability, insulation, lubricity, water resistance, etc.

Filtration performance: high temperature resistance, wide operating temperature range, can be used continuously at 260℃ (long-term continuous use at high temperature, the instantaneous temperature can reach 280℃; strong chemical stability, corrosion resistance; good self-lubrication, extremely low friction coefficient, very low filter wear Small; the surface tension of the PTFE membrane is very low, and it has good non-stickiness and water repellency.

5) PSA fiber (polysulfone psa filter felt)

(Polyphenylsulfone terephthalamide fiber) Except that the strength is slightly lower, the other properties are similar to aramid fiber, but it is significantly better than aramid fiber in flame resistance and thermal oxidative aging resistance. It is heated in 300 ℃ hot air for 100 hours, and it is strong The loss is less than 5%, and the limiting oxygen index exceeds 33; it also has good dyeability, electrical insulation, chemical resistance, and radiation resistance.

High-temperature inorganic materials

1) Glass fiber fabric (fiberglass filter felt);

The density is 2.54g/cm3, and the tensile strength of the original filament is 160～275kg/mm2. High temperature resistance, good dimensional stability, and high tensile strength at break. In terms of chemical resistance, except for hydrofluoric acid, high temperature and strong alkali, it is very stable to other media. The disadvantage of glass fiber is its poor bending resistance, and it is generally not used on oscillation or pulse systems.

Glass fiber can be used for long-term use under 260°C (medium alkali)/280°C without alkali), and the instantaneous temperature can reach 350°C;

2) High silica fiber/ceramic fiber (silica filter felt;