In the field of high-temperature flue gas filtration, the choice of filter media directly determines the operational stability, emission compliance, and total life-cycle cost of the dust removal system. Continuous operating temperature, instantaneous temperature resistance, chemical corrosion resistance, hydrolysis resistance, oxidation resistance, thermal shrinkage rate, and price—each dimension requires a trade-off based on specific operating conditions. No single filter media is universally applicable; only by making the correct selection based on the specific characteristics of the flue gas can the optimal balance between performance and economy be achieved.
I. Performance Analysis of Six Typical Organic Fiber Filter Media
Polyphenylene sulfide fiber is one of the most widely used high-temperature filter media in the field of flue gas filtration in coal-fired power plants. Its continuous operating temperature is 190℃, and it can withstand instantaneous temperatures of 210℃. PPS’s outstanding advantages lie in its excellent acid and alkali resistance and hydrolysis resistance, exhibiting stability in sulfur-containing flue gas environments. Simultaneously, PPS fiber is relatively affordable, offering high cost-effectiveness, making it one of the preferred filter media for large-scale thermal power projects.
However, PPS has a significant drawback: poor oxidation resistance. When the oxygen content in the flue gas exceeds 14% and the temperature approaches its upper limit, the sulfur atoms in the PPS molecular chain react with oxygen, causing the fibers to become brittle and lose strength. Therefore, in high-oxygen conditions such as circulating fluidized bed boilers, the service life of PPS filter media may be significantly shortened.
Applicable scenarios: Coal-fired power plants, waste incineration power generation (requiring oxygen content control), biomass boilers.
Polytetrafluoroethylene (PTFE)
Polytetrafluoroethylene fiber, commonly known as Teflon, is the organic fiber material with the best chemical corrosion resistance. Its continuous operating temperature can reach 260℃, and its instantaneous temperature resistance is 300℃. PTFE is virtually unaffected by any acid or alkali media, exhibiting unparalleled stability in highly corrosive flue gas environments.
Another advantage of PTFE is its extremely low surface energy, possessing natural hydrophobic and oleophobic properties, making it difficult for dust to adhere and providing excellent dust removal performance. However, PTFE fiber is the most expensive of all organic filter media, which limits its widespread application in large-scale projects to some extent. Furthermore, pure PTFE filter media has relatively low mechanical strength and usually needs to be used in combination with reinforcing materials such as glass fiber.
Applicable scenarios: Waste incineration, hazardous waste disposal, chemical exhaust gas, highly corrosive flue gas.
Polyimide fiber, best known by the trade name P84, is a high-performance filter media with a unique cross-sectional shape. Its continuous operating temperature is 230℃, and its instantaneous temperature resistance is 260℃. The most prominent feature of PI fiber is its trilobal cross-section, with a specific surface area much larger than that of conventional circular cross-section fibers. This structure gives PI fiber excellent dust capture capabilities, especially for fine particulate matter, where its filtration efficiency is significantly higher than other filter media.
The disadvantage of PI fiber is its poor resistance to hydrolysis. In environments with high moisture content in flue gas and where temperature fluctuations can lead to condensation, the imide rings in the PI molecular chain are prone to hydrolysis and ring-opening, resulting in a sharp decrease in fiber strength. Therefore, PI filter media is generally unsuitable for high-humidity flue gas environments.
Applicable Scenarios: Cement kiln tail, steel sintering, dust removal after dry flue gas desulfurization.
Meta-aramid fiber, trade name Nomex, is one of the earliest synthetic fibers used in high-temperature filtration. Its continuous operating temperature is 200℃, and its instantaneous temperature resistance is 240℃. PMIA fiber has excellent flame retardant properties and good mechanical properties, maintaining high mechanical strength even at high temperatures.
PMIA has acceptable tolerance to acidic media but is more sensitive to alkaline environments. In flue gas with high alkalinity, such as certain special industrial kilns or chemical tail gas, the long-term stability of PMIA filter media will be challenged. Furthermore, PMIA’s resistance to hydrolysis is better than PI but not as good as PPS.
Suitable Scenarios:Dust removal in steel plants, asphalt mixing plants, cement mills, and non-high humidity conditions.
Polysulfonamide fiber is a high-temperature filter media with relatively balanced performance, and its applications in industrial filtration have increased in recent years. Its continuous operating temperature can reach 250℃, and its instantaneous temperature resistance is 270℃, placing its temperature resistance between PTFE and PI. The most noteworthy advantage of PSA fiber is its low thermal shrinkage rate and good dimensional stability under long-term high-temperature operation, which is particularly important for products such as filter cartridges that require high dimensional accuracy.
PSA has better oxidation resistance than PPS and better hydrolysis resistance than PI, but its performance in these two dimensions is not top-tier, making it a “balanced” performer. In terms of price, PSA is in the mid-to-high range.
Suitable Scenarios:Cement industry, steel smelting, and general industrial kilns.
Polyacrylonitrile Pre-oxidized Fiber (PAN Pre-oxidized)
Polyacrylonitrile pre-oxidized fiber is a specially treated high-performance fiber whose temperature resistance significantly surpasses that of conventional organic fibers. PAN pre-oxidized fibers can operate continuously at temperatures exceeding 250℃ and are non-combustible—they do not burn in flames, only carbonize. This characteristic makes them uniquely valuable in applications with extremely high fire safety requirements.
PAN pre-oxidized fibers exhibit excellent thermal stability, showing almost no thermal shrinkage or oxidative degradation at high temperatures. However, their drawbacks are equally apparent: the fibers are relatively brittle, and their bending and abrasion resistance are inferior to other organic fibers. In conditions with frequent pulse cleaning, the mechanical life of PAN pre-oxidized filter media may be affected.
Applicable scenarios: Alternative to ultra-high temperature conditions, applications with special fire protection requirements, high-temperature gas-solid separation.
II. Composite Filter Media: A Solution that Compensates for Each Other
Single fibers cannot simultaneously meet all performance requirements; composite filter media have become an important direction for resolving this contradiction.
The combination of PPS and PTFE is a common approach in the ultra-low emission retrofitting of coal-fired power plants. PPS provides good cost-effectiveness and hydrolysis resistance, while the surface or blended PTFE enhances corrosion resistance and cleaning performance. This composite filter media significantly improves the tolerance to high-oxygen and high-sulfur flue gas while maintaining controllable costs.
The composite of PI and glass fiber balances filtration accuracy and structural stability. PI provides highly efficient fine particle capture, while the glass fiber skeleton enhances the filter media’s resistance to thermal shrinkage and mechanical strength. This combination is particularly suitable for cement kiln tail conditions with large temperature fluctuations and stringent emission requirements.
The composite of PSA and PTFE targets the balanced market. PSA provides good temperature resistance and dimensional stability, while PTFE enhances corrosion resistance and surface smoothness, resulting in a product with comprehensive performance.
At the TrennTech materials laboratory in Frankfurt, Germany, researchers have long been conducting performance tests on composite filter media with different fiber combinations. Through accelerated aging tests simulating real-world conditions, they provide data support for the structural design and formulation optimization of composite filter media.
The selection of high-temperature resistant organic fiber filter media is essentially a multi-objective optimization problem. A correct selection strategy begins with an accurate understanding of the operating conditions: Is the flue gas temperature steady-state or fluctuating? What are the highest and lowest temperatures? Does the flue gas contain high concentrations of oxygen, acidic gases, alkaline substances, or water vapor? Is the dust sticky, abrasive, or hygroscopic? …
Only by fully answering these questions can a scientific selection be made among various fibers and their composite combinations. With increasingly stringent environmental regulations and continuous advancements in industrial flue gas treatment technologies, the performance boundaries of high-temperature filter materials continue to expand. New fiber modification technologies, composite structure designs, and surface treatment processes are pushing the comprehensive performance of organic fiber filter media to new heights