What is a filter bag?

Structure and Shape

• Filter bags are typically cylindrical in shape, which provides a large surface area for filtration and allows for efficient capture of particles. They can also come in other shapes such as rectangular or conical, depending on the specific application3.

Materials Used

• Polyester: It has good chemical resistance, high tensile strength, and is suitable for filtering a wide range of liquids and gases. It can withstand moderate temperatures and is often used in industrial applications1.
• Polypropylene: This material is known for its excellent resistance to alkalis and acids, as well as its good abrasion resistance. It is commonly used in applications where the filtered medium is corrosive or contains abrasive particles. However, its maximum operating temperature is relatively low2.
• Nylon: Nylon filter bags have high strength and 耐磨性. They are often used in applications where fine particle filtration is required, such as in the food and beverage industry or in some pharmaceutical processes.
• Fiberglass: Fiberglass filter bags can withstand high temperatures, making them suitable for applications in industries such as steel, cement, and power generation. They are used to filter hot gases and dust particles at elevated temperatures2.
• PTFE (Polytetrafluoroethylene): PTFE is a synthetic polymer that offers excellent chemical resistance and a very low coefficient of friction. PTFE-coated or PTFE-based filter bags are often used in applications where the filtered material is sticky or prone to caking, as the low friction surface helps to prevent the buildup of particles2.

Working Principle

• Liquid Filtration: In liquid filtration systems, the liquid to be filtered enters the filter bag from the inside. As the liquid passes through the fabric of the bag, solid particles are trapped inside the bag, while the filtered liquid exits through the pores of the fabric. The filtration process is based on the principle of physical separation, where the size of the pores in the fabric determines the size of the particles that can be captured1.
• Gas Filtration: For gas filtration, dirty air or gas enters the filter bag, either from the inside or the outside depending on the design of the filtration system. The filter bag prevents solid debris, dust particles, and other contaminants from passing through while allowing the clean gas to pass through the fabric and exit the system. The collected dust particles accumulate on the surface of the bag and are usually removed periodically through a cleaning process2.

Applications

• Industrial Dust Collection: In factories and industrial plants, filter bags are used in dust collection systems to capture airborne dust and particulate matter. This helps to maintain a clean and safe working environment, prevent pollution, and protect the health of workers23.
• Water Treatment: Filter bags are employed in water treatment plants to remove sediment, sand, rust, and other impurities from water sources. They are used in both municipal water treatment and in industrial water treatment processes to ensure the quality of the treated water3.
• Chemical Processing: Industries involved in chemical manufacturing use filter bags to separate solids from liquids during chemical reactions, purification processes, and product recovery. This helps to ensure the purity and quality of the chemical products3.
• Pharmaceuticals: In the pharmaceutical industry, filter bags are used to filter out contaminants and impurities from pharmaceutical solutions and suspensions, ensuring the safety and quality of drugs and medical products3.