Filter Bags For Flue Gas & Dust Collection

A baghouse filter is an air pollution control device that removes particulates or dust from flue gas or exhaust air in industrial applications. It is widely used in industries such as power plants, steel mills, cement plants, and chemical production to ensure cleaner emissions.

Filter bags are the core component of baghouse filters. They capture fine dust and particulate matter from the airflow passing through the system. The material of the bag filters dust while allowing clean air to pass through. Over time, dust accumulates on the surface of the bag and needs to be cleaned or replaced to maintain efficiency.

When the flue gas or dust-laden air enters the baghouse, the filter bags trap the dust particles on their surface. The clean air passes through the fabric, while the dust accumulates on the outside. Periodically, the system cleans the bags (either using reverse air, shaking, or pulse-jet cleaning) to remove the dust layer and maintain performance.

Filter bags can be made from a variety of materials, depending on the application and temperature. Common materials include:

Polyester (PE): General-purpose material used in moderate temperature and dust conditions.

Polypropylene (PP): Resistant to chemical attack and moisture.

Nomex (Aramid): Heat-resistant, ideal for high-temperature applications (up to 204°C/400°F).

PTFE (Teflon): Excellent chemical resistance and can handle extreme temperatures (up to 260°C/500°F).

Fiberglass: High-temperature resistant but more fragile and prone to abrasion.

PPS (Polyphenylene Sulfide): Resistant to acids and alkalis, often used in coal-fired boilers or waste incineration.

There are several types of filter bags based on their use and cleaning mechanisms:

Shaker Bags: Used in shaking-type baghouse filters, these bags are cleaned by mechanical shaking, which dislodges the dust.

Reverse Air Bags: In reverse air systems, low-pressure air is blown into the bag to dislodge the dust.

Pulse Jet Bags: These are cleaned by a high-pressure burst of air (pulse jet) that knocks the dust off the bag.

There are three common cleaning methods:

Shaking: Mechanical shaking knocks dust from the bag’s surface.

Reverse Air: Airflow is temporarily reversed, causing dust to fall off.

Pulse Jet Cleaning: A brief pulse of compressed air blows into the bag, creating a shock wave that removes dust from the surface.

When choosing the right filter bag, consider the following:

Particle size and dust type: Fine vs. coarse dust requires different filter materials.

Temperature: Ensure the filter bag material can withstand the operating temperature.

Chemical composition of the dust: Certain materials resist acids, alkalis, or solvents better.

Moisture content: Humid conditions may require different filter materials.

Air-to-cloth ratio: The volume of air passing through the filter bag per square meter of fabric should align with design specifications.

The air-to-cloth ratio (or filter ratio) is the amount of air that passes through a unit area of filter material. It’s crucial to ensure efficient filtration while maintaining a manageable pressure drop. A high air-to-cloth ratio can lead to quicker wear and tear on the bags, while a low ratio might lead to inefficient filtration or overloading the system.

The lifespan of filter bags depends on several factors, such as the type of dust being filtered, the cleaning mechanism, temperature, and frequency of operation. Under normal conditions, filter bags may last anywhere between 1 to 5 years. Bags in more severe conditions (high temperatures or abrasive dust) may need replacement sooner.

Regular inspections can help determine the right time to replace filter bags. Indicators that bags need replacing include:

Increased pressure drop: Higher resistance to airflow suggests the filter is clogged.

Bag wear or damage: Physical damage, such as holes or tears, can lead to inefficient filtration.

Excessive dust emissions: When bags no longer perform effectively, dust will pass through.

Filter bags generally cannot be reused after they have been clogged or damaged. However, in some systems, bags can be cleaned and reconditioned multiple times using the right techniques before needing replacement. Cleaning methods include washing, reverse air cleaning, and pulse jet cleaning.

Common reasons for filter bag failure include:

Overheating: Using the wrong material for high-temperature conditions.

Chemical degradation: Exposure to harsh chemicals that degrade the bag material.

Abrasion: High-velocity airflow or abrasive dust particles can cause holes or wear over time.

Improper cleaning: Inefficient cleaning can cause the dust layer to harden or “cake,” making it difficult for air to pass through.

Regular inspections: Look for signs of wear, holes, or excessive dust buildup.

Proper cleaning: Ensure the baghouse cleaning system is functioning efficiently.

Appropriate material selection: Choose the correct filter bag material for your specific operating conditions.

Monitor system parameters: Keep an eye on pressure drop, dust emissions, and airflow to catch problems early.

Baghouse filters are used across a wide range of industries, including:

Cement and concrete manufacturing
Steel mills and foundries
Power generation plants
Pharmaceutical manufacturing
Food processing
Waste incineration
Chemical processing
Mining and quarrying

Yes, filter bags are highly efficient at capturing fine dust and particulate matter, helping industries comply with environmental regulations and reduce harmful emissions into the atmosphere.