PTFE needle-punched felt filter bag: Analysis and application guide for high-performance filter bags

1. Overview and technical principles of PTFE needle-punched felt filter bag

Polytetrafluoroethylene (PTFE) is a high-performance polymer material with a unique molecular structure. The PTFE molecular chain consists of the main chain of carbon atoms and the side groups of fluorine atoms, forming a stable linear polymer structure. This special molecular configuration gives PTFE materials a range of superior product properties:

 

Chemical stability: PTFE is almost not eroded by any strong acids, strong alkalis and organic solvents, including extreme chemical environments such as aqua regia and hydrofluoric acid.

Thermal stability: can be used for a long time within the temperature range of -200℃ to 260℃, and the temperature resistance can reach 300℃ in a short time

Surface characteristics: Extremely low surface energy (18.5mN/m) makes it excellent non-stick and hydrophobic

Electrical performance: Excellent dielectric performance, volume resistivity up to 10¹⁸Ω·cm

Mechanical properties: good wear resistance and bending fatigue resistance, extremely low friction coefficient

 

• Manufacturing technology of PTFE needle felt

PTFE needle-punching felt filter bag is a nonwoven filter material formed by entangling PTFE fibers with each other through a three-dimensional needle-punching process. The manufacturing process mainly includes the following key steps:

 

Fiber preparation: PTFE resin is made into continuous fibers with a diameter of 3-20μm by paste extrusion and stretching process.

Mesh laying: Use air-flow or mechanical mesh laying to form the fiber mesh layer

Needle-punch reinforcement: Use a barbed needle to penetrate and entangle the fibers up and down to form a three-dimensional three-dimensional structure

Heat setting treatment: hot rolling or hot air treatment at a temperature slightly lower than the melting point of PTFE to improve dimensional stability

Surface treatment: Perform post-organization processes such as burning, calendering, coating or film composite according to application requirements

This unique manufacturing process enables PTFE needle felt to have high porosity (70-85%) and controllable pore size distribution, enabling high efficiency and low resistance filtration performance.

 

• Comparison between PTFE needle felt and traditional filter material

Compared with traditional polyester, acrylic, PPS and other filter materials, PTFE needle felt has obvious advantages in multiple performance dimensions:

Performance indicators	PTFE needle felt	Polyester filter material	PPS filter material	Glass fiber
Continuous use temperature	260℃	130℃	190℃	280℃
Acid resistance	Excellent	Moderate	Good	Poor
Alkali resistance	Excellent	Good	Poor	Extremely poor
Abrasion resistance	Excellent	Good	Moderate	Poor
Service life	3-5 years	1-2 years	2-3 years	6-12 months
Filtration accuracy	0.1-10μm	5-30μm	3-15μm	1-5μm

2. Advantages and performance characteristics of PTFE needle felt filter bags

Excellent chemical corrosion resistance

The advantage of PTFE needle felt filter bags is its chemical stability. Since the bond energy of the carbon-fluorine bond in the PTFE molecule is as high as 485kJ/mol, and the steric hindrance effect of the fluorine atom forms a "shielding protection" for the carbon chain, it can resist almost all chemical media encountered in industrial environments:

Acid corrosion environment: can withstand strong acids such as concentrated sulfuric acid (98%), nitric acid (68%), hydrochloric acid (37%), and hydrofluoric acid (40%)

Alkali corrosion environment: resistant to strong alkaline solutions such as sodium hydroxide (50%) and potassium hydroxide

Organic solvents: completely inert to organic solvents such as benzene, acetone, and carbon tetrachloride

Oxidizing environment: can resist the erosion of strong oxidants such as ozone and hydrogen peroxide

This feature makes PTFE filter bags an irreplaceable choice in highly corrosive flue gas treatment occasions such as chemical industry, electroplating, and pickling.

 

Excellent thermal stability

PTFE needle felt filter bags have a wide operating temperature range and can meet various high-temperature flue gas filtration needs:

Long-term temperature resistance: can be used continuously in the range of -200℃ to 260℃

Short-term peak temperature: can withstand instantaneous high temperature shock of 300℃

Heat shrinkage rate: heat shrinkage rate <1% at 260℃, excellent dimensional stability

Heat aging resistance: strength retention rate >90% after aging for 1000 hours at 200℃

This thermal stability makes it particularly suitable for high-temperature flue gas purification systems such as steel sintering, cement kilns, and garbage incineration, avoiding deformation or failure of filter bags caused by temperature fluctuations.

 

Excellent filtration performance

PTFE needle felt filter bags achieve efficient particle capture through precisely controlled fiber structure and surface characteristics:

Surface filtration mechanism: After surface treatment, a microporous membrane can be formed on the surface of the filter material to achieve surface filtration

Cleaning performance: The extremely low surface energy makes dust easy to peel off and maintains a low residual resistance

Air permeability: The initial air permeability is maintained in a reasonable range of 8-15cm³/(cm²·s)

Actual engineering data shows that the dust removal system using PTFE needle felt filter bags can stably control the outlet dust concentration within the standard range to meet emission requirements.

 

Long service life

The durability of PTFE needle felt filter bags is significantly better than other types of filter materials-

Abrasion resistance: Taber wear test shows that its wear resistance is 3-5 times that of conventional filter materials

Anti-hydrolysis: Excellent strength retention rate under high temperature and high humidity environment

Fatigue resistance: Can withstand more than 5 million pulse cleaning cycles

Anti-condensation: The hydrophobic surface can prevent the problem of hardening caused by condensation of water vapor

3. Application fields of PTFE needle felt filter bag

• Power industry application

In the flue gas purification system of coal-fired power plants, PTFE needle felt filter bags show unique advantages:

Coping with high sulfur coal combustion: tolerate corrosion of acid gases such as SO₂ and SO₃

Adapt to SCR denitrification: Resisting ammonium corrosion caused by ammonia escape

Mercury emission control: can be used as a capture medium after activated carbon injection

Ultra-low emission transformation: Meet the particulate matter emission limit of <10mg/m³

The application case of a 1000MW unit electric bag composite dust collector shows that after three years of operation, the resistance of the PTFE filter bag remains below 800Pa, and the emission concentration is stable at around 3mg/m³.

 

• Iron and Steel Metallurgy Industry

The high-temperature and high-humidity dust-containing flue gas generated by sintering heads, converters, electric furnaces and other processes during the steel production process poses severe challenges to the filter material:

Dust removal from the sintering machine head: treatment temperature is 80-150℃, containing corrosive gases such as SO₂, HF, etc.

Converter gas purification: Reducible environment that withstands high temperatures above 200℃

Hot rolling finishing mill: captures abrasive particles such as iron oxide sheets

Blast furnace gas dry dust removal: maintain stable filtration performance under high pressure conditions

The practice of a large steel joint enterprise shows that after using PTFE base cloth composite filter bags, the service life will be extended from the original 18 months to more than 48 months.

 

• Chemical industry application

The complex component flue gas generated during chemical production requires filter materials of special materials:

Sulfuric acid production: Treatment of high-temperature furnace gas containing SO₂ and SO₃

Titanium dioxide production: Resistance to the combined corrosion of concentrated sulfuric acid and chlorine

Pesticide production: filtering process exhaust gas containing organic solvents and corrosive media

Fluorine Chemicals: The only filter material option that can withstand HF gas corrosion

In a converter post-dust removal system with an annual output of 300,000 tons of sulfuric acid, the PTFE filter bag has not been corroded and damaged for five consecutive years, and the system resistance remains stable.

 

• Waste incineration power generation

The flue gas composition generated by incineration of urban domestic waste is complex and changeable:

Acid gases: corrosive components such as HCl, SOx, NOx, etc.

Heavy metals: toxic metal vapors such as Pb, Cd, Hg

Dioxin: Highly efficient filtration is required to prevent resynthesis

Humidity change: Treat humid smoke with moisture content of more than 30%

Operation data from a waste incineration plant in Shanghai shows that PTFE coated filter bags can control the dioxin emission concentration below 0.05ng TEQ/m³, which is far stricter than the national standard limit.

 

• Cement industry application

High temperature and high concentration dust treatment in various process links of cement production:

Kiln head and kiln tail: treat high-temperature flue gas above 300℃

Coal mill system: high-precision filtration under explosion-proof requirements

Raw material preparation: capture of high concentration of raw material dust

Cement grinding: Emission control of ultrafine cement particles

The cement kiln head bag dust collector using PTFE needle felt filter bags can be stably maintained below 10mg/m³, and the equipment resistance is <1000Pa.

 

4. Guidelines for the use and maintenance of PTFE needle felt filter bags

Key points for filter bag selection

The following key parameters are required to consider when choosing a suitable PTFE needle felt filter bag:

Gram weight selection: 450-550g/m² is used conventionally, and can be increased to 600-800g/m² in high abrasion situations

Thickness control: generally 1.8-2.5mm, too thick will affect breathability

Surface treatment: different treatment methods such as standard, rinsing, calendering, and coating

Base fabric configuration: pure PTFE base fabric or composite structure with other high-temperature resistant fibers

Sewing process: wire selection (PTFE or PPS suture), needle distance control (8-12 stitches/inch)

 

Installation precautions

Correct installation is crucial to ensuring the performance of the filter bag:

Pretensioning treatment: Apply appropriate tension during installation (usually 15-25N/bar)

Centering adjustment: Make sure the filter bag is concentric with the cage bone, with a deviation of <5mm

Sealing inspection: The contact surface between the flower panel and the bag mouth must be 100% sealed

Anti-wear measures: The cage bone surface is smooth and burrless, and spray protective layer if necessary

Installation order: Follow the principle of "from inside to outside, from bottom to top"

 

Running parameter control

Optimized operating parameters can extend the service life of the filter bag:

Temperature control: Try to control it below 200℃ to avoid exceeding the limit temperature of 260℃.

Humidity management: operation at 15-20℃ above the dew point temperature of the flue gas

Filtration wind speed: It is recommended to maintain a net filtering wind speed of 0.8-1.2m/min

Cleaning strength: pulse pressure 0.2-0.4MPa, cleaning cycle optimization adjustment

Pressure difference monitoring: During normal operation, the pressure difference should be controlled between 800-1200Pa.

 

Key points of daily maintenance

System maintenance is very important to ensure long-term performance:

Regular inspection: Check the fixation and surface status of the filter bag every month

Resistance monitoring: record the system resistance trend and detect abnormalities in a timely manner

Bag breaking detection: using fluorescent powder detection or online monitoring technology

Spare parts management: maintain a 5-10% product rate and store it in the same batch

Fault analysis: Establish filter bag failure analysis files and improve operational strategies

 

Frequently Asked Questions and Solutions

Common problems and countermeasures in the use of PTFE needle felt filter bags:

Problem phenomenon	Possible cause	Solution
Early damage of filter bag	Burrs on cage frame, improper installation	Check the finish of cage frame, standard installation
Resistance rises too fast	Insufficient cleaning, bag sticking	Optimize cleaning parameters, check flue gas dew point
Elevated emission concentration	Broken filter bag, seal failure	Fluorescence detection, replace damaged filter bag
Wear on the bottom of the filter bag	Uneven airflow distribution	Adjust the diversion device and check the ash hopper for ash unloading
Overall embrittlement of the filter bag	Long-term over-temperature operation	Strictly control the flue gas temperature

 

5. Sustainable development trends

The green development direction of PTFE needle felt filter bag:

Recycling: Establish a PTFE material recycling system for used filter bags

Energy saving and consumption reduction: Develop a lower resistance filter structure to reduce system energy consumption

Long-life design: extend service life through material modification and reduce solid waste generation

Clean production: Optimize manufacturing processes to reduce energy consumption and waste emissions

Full life cycle assessment: Establish a comprehensive environmental assessment system from raw materials to waste