What is a Filter Bag?
Filter bags are a common element in dust collection systems. The system uses a fan or blower to pressure or vacuum (suck) air across the filter bag’s media.
The bag’s material type and micron rating determines how well it will filter. It’s important to know the differences between them.
A high performance bag is a bag that can be continuously cleaned without shutting down the system. These are typically needle felt, nonwoven or spun bonded filters.
Reduces Particles and Microorganisms
Filter bags are used to reduce the amount of contaminant in a liquid stream. They can be found in many industries such as oil and gas, pharmaceutical manufacturing, and paint and coatings production. In these applications, filtering is used to remove impurities that can damage equipment or lead to quality defects in the final product.
Filtration is accomplished using a fan or blower to pressure (push) or vacuum (suck) the dirty air through the filter bag’s media. The dirty side of the bag intercepts, filters, and compacts the dirty air stream gases while the clean side comes into contact with the clean air flow to release dust as it passes through the filter.
In order to maintain optimum performance, filter bags must be periodically cleaned to regenerate the permeability of the media. Cleaning the bag with a high velocity of air or a cyclone system will remove the compacted dust cake from the media, and it is then ready for the next cycle.
Filter bags are available in a variety of materials and pore size ratings for different contaminant removal. Felt filter bags are economical and can be used in coarser less critical filtration applications. Needlefelt and meltblown filter bag felt bags offer higher dirt holding capacity and are washable. Polypropylene bags offer greater strength and can be used in high temperature and corrosive environments. Filter bags made of ePTFE fibers and a PTFE membrane provide maximum emissions protection, high temperature resistance, and cake release.
Flow Rates
Bag filter systems provide user friendly, cost effective solutions for a broad range of surface and depth filtration applications. With a variety of single and multi-bag filter housings that hold up to 14 filter bags, Envirogen is able to supply solutions for a wide range of flow rates. Flow rates are based on using Nominal Rated Filter Bags and can vary based on source water quality, particle size, and application.
The rate at which a fluid flows through the filter is determined by its viscosity, temperature, and pressure drop across the bag. It is also dependent on the size of the pores in the filter media. A more porous filter material will allow a larger amount of liquid to pass through, but it may be less effective in trapping unwanted particles and microorganisms.
Liquid bag filters are used to filter a variety of liquids, including acids, solvents and chemicals. They are also used for the filtration of steam and water in boilers, furnaces, and other industrial heating and cooling processes.
The flow rate of baghouse dust collectors is a significant factor in selecting the proper filter type and size for a particular job. Different manufacturers offer a number of different filter materials, each with unique temperature limits and chemical resistance capabilities. It is important to select a filter that can handle the operating conditions and environmental factors for optimal performance and longevity.
Durability
Bag filters can be made of a variety of materials depending on the needs of your application. The material of the filter is crucial to its performance, lifespan and compatibility with various fluids. Whether it’s the adaptability of polyester and polypropylene, the elasticity of PTFE or aramid, or the cost-effectiveness of glass fiber and nylon, selecting the right material will play a critical role in the success of your filtering system.
Abrasion Resistant – Many grain dusts are highly abrasive and can quickly wear out conventional sewn bags. Pleated filters with spun bound polyester media and shortened element length can provide better abrasion resistance. This extends the life of the filter and reduces costly downtime associated with frequent filter change outs.
Corrosion Resistant – Stainless steel filtration bags are a good choice for applications that require high corrosion resistance. They are able to withstand temperatures up to 480, and can maintain a higher replacement pressure difference than other types of bag filters.
Cotton filter bags are also very durable and demonstrate a long service life. They can handle a large number of dust particle sizes without wearing out, even in abrasive environments with high concentrations of particulate. They can also withstand high air flow rates and are often used in vibrating dust collectors, ensuring efficient air quality control and minimizing emissions.
Environmentally Friendly
Unlike other filter systems that use membranes or carbon filters, which require more maintenance and are usually limited in flow rates, bag filtration is quick, simple and cost-effective. It can be used to filter both water and air. In the case of water, a secondary, more precise cartridge or membrane filter is also often required to remove the suspended solids from the water supply.
A fan or blower will either pressure (push) Underground garage drainage membrane or vacuum (suck) the air across the filter bag’s media. The dirty side of the media intercepts, filters, and compacts the dirty air stream gases, while the clean side makes contact with the clean air stream gas.
The filtration process is achieved by using a polytetrafluoroethylene (PTFE) membrane bonded to the surface of the traditional filter medium. This eliminates the need for a primary dust cake, enabling higher filtration efficiencies and longer service life.
Conventional woven filter bags are made from a variety of materials including needle felts, carded nonwovens, meltblown fibers and spun bonded webs. They can be graded with pore volumes ranging from 70-90%, and may be stitched or seamless.
The annual replacement of conventional woven dust filter bags generates a large quantity of industrial waste, polluting the environment and wasting resources. In this context, meta-aramid has become a popular choice for flue gas filtration due to its thermal stability, resistance to chemical corrosion and mechanical properties. However, meta-aramid has a disadvantage in that it is very difficult to degrade when treated as solid waste.